| Message ID | 20240328224850.2785280-5-gustavo.romero@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | Add another way to check for MTE-tagged addresses on remote targets | expand |
Hello Gustavo, I started reviewing the patch series backwards... I'll provide comments on this patch first. Overall, it looks great. I just have some localised comments in a few places below. Also, for ease of review I suggest splitting this patch in two: - one that introduces the new check_memtag_addr target hook and converts the existing code to use it, - and another that adds a check_memtag_addr target hook implementation to the remote target. Gustavo Romero <gustavo.romero@linaro.org> writes: > This commit adds a new packet qMemTagAddrCheck allowing GDB remote > targets to use it to query gdbservers if a given address is tagged. > > It also adds a new GDB remote feature, 'memory-tagging-check-add+', > which must be advertised by the GDB servers to inform GDB they can reply > to address checks via the new qMemTagAddrCheck remote packet. You will need to document the remote protocol changes in gdb.texinfo, in the "Remote Serial Protocol" appendix. > Currently, this address check is done via a read query, where the > contents of /proc/<PID>/smaps is read and the flags in there are > inspected for MTE-related flags that indicate the address is in a tagged > memory region. > > This is not ideal, for example, on QEMU gdbstub and in other cases, > like in baremetal debugging, where there is no notion of any OS file > like smaps. Hence, qMemTagAddrCheck packet allows check addresses in > an OS-agnostic way. > > For supporting the new packet, a new target hook is introduced, > check_memtag_addr, which is used instead of the gdbarch_tagged_address_p > gdbarch hook in the upper layers (printcmd.c). > > The new target hook is then specialized per target, for remote.c, > aarch64-linux-nat.c, and corelow.c targets (the current targets that > are MTE-aware). > > The target hook in remote.c uses the qMemTagAddrCheck packet to check > an address if the server advertised the 'memory-tagging-check-add+' > feature, otherwise it falls back to using the current mechanism, i.e. it > reads the /proc/<PID>/smaps contents. > > In the aarch64-linux-nat.c and corelow.c the target hook uses the > gdbarch_tagged_address_p gdbarch hook, so there is no change regarding > how an address is checked in these targets. Just the > gdbarch_tagged_address_p signature is changed for convenience, since > target_check_memtag_addr takes the address to be checked as a CORE_ADDR > type. I agree that a CORE_ADDR argument is more convenient. > @@ -1071,6 +1073,12 @@ aarch64_linux_nat_target::store_memtags (CORE_ADDR address, size_t len, > return false; > } > > +bool > +aarch64_linux_nat_target::check_memtag_addr (CORE_ADDR address) > +{ > + return gdbarch_tagged_address_p (current_inferior ()->arch (), address); I think it's better to pass the gdbarch as an argument to the check_memtag_addr hook rather than getting it from current_inferior here, even if in practice your patch is equivalent to the existing code. The reason is that we are trying to move calls to current_* functions (which is global state in disguise) up the stack, so that most of GDB needs to reference only local state. Then if callers have a gdbarch available in their context they can pass it to the hook, or else they can use current_inferior ()->arch (). > @@ -1410,6 +1412,12 @@ core_target::fetch_memtags (CORE_ADDR address, size_t len, > return false; > } > > +bool > +core_target::check_memtag_addr (CORE_ADDR address) > +{ > + return gdbarch_tagged_address_p (current_inferior ()->arch (), address); Same comment here, of course. > diff --git a/gdb/printcmd.c b/gdb/printcmd.c > index ae4d640ccf2..c81c75afc5d 100644 > --- a/gdb/printcmd.c > +++ b/gdb/printcmd.c > @@ -1132,7 +1132,7 @@ do_examine (struct format_data fmt, struct gdbarch *gdbarch, CORE_ADDR addr) > = value_from_ulongest (builtin_type (gdbarch)->builtin_data_ptr, > tag_laddr); > > - if (gdbarch_tagged_address_p (current_inferior ()->arch (), v_addr)) > + if (target_check_memtag_addr (value_as_address(v_addr))) Missing space between "value_as_address" and the opening parens. Also, not a problem introduced by you, but I don't understand why the code uses the gdbarch from current_inferior if it was passed a gdbarch in the arguments. So I'd add a separate patch before this one to fix this code to use the gdbarch that was passed as a parameter. Then this patch can also pass it as a parameter to target_check_memtag_addr as I mentioned in an earlier comment. > { > /* Fetch the allocation tag. */ > struct value *tag > @@ -1289,7 +1289,7 @@ should_validate_memtags (struct value *value) > return false; > > /* We do. Check whether it includes any tags. */ > - return gdbarch_tagged_address_p (current_inferior ()->arch (), value); > + return target_check_memtag_addr (value_as_address(value)); Here there's no gdbarch available in context, but since there's only one caller to this function, it's easy to add the gdbarch parameter to it and make the caller pass it down. The caller does get it from current_inferior, so perhaps I'm being too pedantic here but IMHO it's worth it. Also, a space is missing before the opening parens. > } > > /* Helper for parsing arguments for print_command_1. */ > @@ -2946,9 +2946,10 @@ memory_tag_print_tag_command (const char *args, enum memtag_type tag_type) > flag, it is no use trying to access/manipulate its allocation tag. > > It is OK to manipulate the logical tag though. */ > + CORE_ADDR addr = value_as_address(val); Missing space before the opening parens. > if (tag_type == memtag_type::allocation > - && !gdbarch_tagged_address_p (arch, val)) > - show_addr_not_tagged (value_as_address (val)); > + && !target_check_memtag_addr(addr)) Missing space before the opening parens. > + show_addr_not_tagged (addr); > > value *tag_value = gdbarch_get_memtag (arch, val, tag_type); > std::string tag = gdbarch_memtag_to_string (arch, tag_value); > @@ -3104,8 +3105,9 @@ parse_set_allocation_tag_input (const char *args, struct value **val, > > /* If the address is not in a region memory mapped with a memory tagging > flag, it is no use trying to access/manipulate its allocation tag. */ > - if (!gdbarch_tagged_address_p (current_inferior ()->arch (), *val)) > - show_addr_not_tagged (value_as_address (*val)); > + CORE_ADDR addr = value_as_address (*val); > + if (!target_check_memtag_addr (addr)) > + show_addr_not_tagged (addr); This is another instance where I'd suggest making the caller pass gdbarch as an argument so that it can be used here, since this function only has one caller. > } > > /* Implement the "memory-tag set-allocation-tag" command. > @@ -3129,8 +3131,9 @@ memory_tag_set_allocation_tag_command (const char *args, int from_tty) > > /* If the address is not in a region memory mapped with a memory tagging > flag, it is no use trying to manipulate its allocation tag. */ > - if (!gdbarch_tagged_address_p (current_inferior ()->arch (), val)) { > - show_addr_not_tagged (value_as_address(val)); > + CORE_ADDR addr = value_as_address (val); > + if (!target_check_memtag_addr (addr)) { > + show_addr_not_tagged (addr); > } This is a preexisting issue in the code, but since you're touching it: the GNU style is to not use curly braces when there's only one statement in the if block. > @@ -15532,6 +15547,19 @@ create_store_memtags_request (gdb::char_vector &packet, CORE_ADDR address, > strcpy (packet.data (), request.c_str ()); > } > > +static void > +create_check_memtag_addr_request (gdb::char_vector &packet, CORE_ADDR address) > +{ > + int addr_size = gdbarch_addr_bit (current_inferior ()->arch()) / 8; > + > + std::string request = string_printf ("qMemTagAddrCheck:%s", phex_nz (address, addr_size)); > + > + if (packet.size () < request.length ()) There's an off-by-one error here: packet is expected to be null-terminated, but request.length doesn't count a terminating null byte so a "+ 1" needs to be added here. > + error (_("Contents too big for packet qMemTagAddrCheck.")); > + > + strcpy (packet.data (), request.c_str ()); > +} > + > /* Implement the "fetch_memtags" target_ops method. */ > > bool > @@ -15573,6 +15601,36 @@ remote_target::store_memtags (CORE_ADDR address, size_t len, > return packet_check_result (rs->buf).status () == PACKET_OK; > } > > +bool > +remote_target::check_memtag_addr (CORE_ADDR address) > +{ > + struct remote_state *rs = get_remote_state (); > + > + if (!m_features.remote_memory_tagging_check_addr_p ()) > + /* Fallback to reading /proc/<PID>/smaps for checking if an address is > + tagged or not. */ Currently this comment is accurate, but if some other architecture adds a gdbarch method that doesn't use /proc/<PID>/smaps then it won't be anymore. I suggest saying something like "Fallback to arch-specific method of checking whether an address is tagged". > + return gdbarch_tagged_address_p (current_inferior ()->arch (), address); > + > + create_check_memtag_addr_request (rs->buf, address); > + > + putpkt (rs->buf); > + getpkt (&rs->buf); > + > + /* Check if reply is OK. */ > + if ((packet_check_result (rs->buf).status () != PACKET_OK) || rs->buf.empty()) Missing space between "empty" and opening parens. But I don't understand why check whether buf is empty. Looking at remote_target::getpkt, it doesn't look like buf is ever emptied. > + return false; > + > + gdb_byte tagged_addr; > + /* Convert only 2 hex digits, i.e. 1 byte in hex format. */ > + hex2bin(rs->buf.data(), &tagged_addr , 1); Missing space between "hex2bin", "data" and the opening parens. > + if (tagged_addr) > + /* 01 means address is tagged. */ > + return true; > + else > + /* 00 means address is not tagged. */ > + return false; The above can be simplified to "return tagged_addr != 0". -- Thiago
Just one more suggestion that occurred to me later: Gustavo Romero <gustavo.romero@linaro.org> writes: > For supporting the new packet, a new target hook is introduced, > check_memtag_addr, which is used instead of the gdbarch_tagged_address_p > gdbarch hook in the upper layers (printcmd.c). "check_memtag_addr" is a bit vague: what does it check? This confused me a bit when I was reading the code with these patches applied. Alternatives I can think of are "is_addr_tagged", or "tagged_address_p". I'm not too fond of the "_p" suffix, but it has the advantage of being consistent with the existing gdbarch hook so it may be preferable in this case. Ah, one other thing that just occurred to me: I think this warrants an entry in gdb/NEWS. -- Thiago
On 3/30/24 03:08, Thiago Jung Bauermann wrote: > > Just one more suggestion that occurred to me later: > > Gustavo Romero <gustavo.romero@linaro.org> writes: > >> For supporting the new packet, a new target hook is introduced, >> check_memtag_addr, which is used instead of the gdbarch_tagged_address_p >> gdbarch hook in the upper layers (printcmd.c). > > "check_memtag_addr" is a bit vague: what does it check? This confused me > a bit when I was reading the code with these patches > applied. Alternatives I can think of are "is_addr_tagged", or > "tagged_address_p". That last bit seems more in line with the gdb terminology. A target took "tagged_address_p" or "target_is_address_tagged" should be a bit more clear. Plus we have precedent in the target hooks is_async_p, can_async_p, always_non_stop_p etc. > > I'm not too fond of the "_p" suffix, but it has the advantage of being > consistent with the existing gdbarch hook so it may be preferable in > this case. > > Ah, one other thing that just occurred to me: I think this warrants an > entry in gdb/NEWS. > > -- > Thiago
Hi Thiago, Luis On 4/3/24 11:04 AM, Luis Machado wrote: > On 3/30/24 03:08, Thiago Jung Bauermann wrote: >> >> Just one more suggestion that occurred to me later: >> >> Gustavo Romero <gustavo.romero@linaro.org> writes: >> >>> For supporting the new packet, a new target hook is introduced, >>> check_memtag_addr, which is used instead of the gdbarch_tagged_address_p >>> gdbarch hook in the upper layers (printcmd.c). >> >> "check_memtag_addr" is a bit vague: what does it check? This confused me >> a bit when I was reading the code with these patches >> applied. Alternatives I can think of are "is_addr_tagged", or >> "tagged_address_p". > > That last bit seems more in line with the gdb terminology. A target took "tagged_address_p" or "target_is_address_tagged" should be a bit more clear. > > Plus we have precedent in the target hooks is_async_p, can_async_p, always_non_stop_p etc. > >> >> I'm not too fond of the "_p" suffix, but it has the advantage of being >> consistent with the existing gdbarch hook so it may be preferable in >> this case. So, I really thought of something like the is_address_tagged at first, without the _p suffix because I thought this suffix would be present only in gdbarch hooks, not in the target hooks, but that seems not right, which is still a bit confusing to me tbh, because I have this in mind: /* MTE-specific settings and hooks. */ if (tdep->has_mte ()) { /* Register a hook for checking if an address is tagged or not. */ set_gdbarch_tagged_address_p (gdbarch, aarch64_linux_tagged_address_p); which I understand that functions with _p would be the functions to be set as the hooks for the gdbarch hooks only, using the set_gdbarch_* "API" functions. That, afaics, doesn't happen for the target hooks, like is_async_p, which is never explicitly set to any hook using a set_* function (so I'm also not fond of the _p in the is_async_p case too). Anyways, I'm going for "target_is_address_tagged", which I think is the clearest option and we all seem to agree on it :) Thanks! Cheers, Gustavo
Hi Thiago, Thanks a lot for the nice review. I think it helped a lot the series organization. On 3/29/24 8:35 PM, Thiago Jung Bauermann wrote: > > Hello Gustavo, > > I started reviewing the patch series backwards... > I'll provide comments on this patch first. > > Overall, it looks great. I just have some localised comments in a few > places below. > > Also, for ease of review I suggest splitting this patch in two: > > - one that introduces the new check_memtag_addr target hook and converts > the existing code to use it, > - and another that adds a check_memtag_addr target hook implementation > to the remote target. Done in v3. > Gustavo Romero <gustavo.romero@linaro.org> writes: > >> This commit adds a new packet qMemTagAddrCheck allowing GDB remote >> targets to use it to query gdbservers if a given address is tagged. >> >> It also adds a new GDB remote feature, 'memory-tagging-check-add+', >> which must be advertised by the GDB servers to inform GDB they can reply >> to address checks via the new qMemTagAddrCheck remote packet. > > You will need to document the remote protocol changes in gdb.texinfo, in > the "Remote Serial Protocol" appendix. Done in v3. >> Currently, this address check is done via a read query, where the >> contents of /proc/<PID>/smaps is read and the flags in there are >> inspected for MTE-related flags that indicate the address is in a tagged >> memory region. >> >> This is not ideal, for example, on QEMU gdbstub and in other cases, >> like in baremetal debugging, where there is no notion of any OS file >> like smaps. Hence, qMemTagAddrCheck packet allows check addresses in >> an OS-agnostic way. >> >> For supporting the new packet, a new target hook is introduced, >> check_memtag_addr, which is used instead of the gdbarch_tagged_address_p >> gdbarch hook in the upper layers (printcmd.c). >> >> The new target hook is then specialized per target, for remote.c, >> aarch64-linux-nat.c, and corelow.c targets (the current targets that >> are MTE-aware). >> >> The target hook in remote.c uses the qMemTagAddrCheck packet to check >> an address if the server advertised the 'memory-tagging-check-add+' >> feature, otherwise it falls back to using the current mechanism, i.e. it >> reads the /proc/<PID>/smaps contents. >> >> In the aarch64-linux-nat.c and corelow.c the target hook uses the >> gdbarch_tagged_address_p gdbarch hook, so there is no change regarding >> how an address is checked in these targets. Just the >> gdbarch_tagged_address_p signature is changed for convenience, since >> target_check_memtag_addr takes the address to be checked as a CORE_ADDR >> type. > > I agree that a CORE_ADDR argument is more convenient. > >> @@ -1071,6 +1073,12 @@ aarch64_linux_nat_target::store_memtags (CORE_ADDR address, size_t len, >> return false; >> } >> >> +bool >> +aarch64_linux_nat_target::check_memtag_addr (CORE_ADDR address) >> +{ >> + return gdbarch_tagged_address_p (current_inferior ()->arch (), address); > > I think it's better to pass the gdbarch as an argument to the > check_memtag_addr hook rather than getting it from current_inferior > here, even if in practice your patch is equivalent to the existing > code. > > The reason is that we are trying to move calls to current_* functions > (which is global state in disguise) up the stack, so that most of GDB > needs to reference only local state. > > Then if callers have a gdbarch available in their context they can pass > it to the hook, or else they can use current_inferior ()->arch (). > >> @@ -1410,6 +1412,12 @@ core_target::fetch_memtags (CORE_ADDR address, size_t len, >> return false; >> } >> >> +bool >> +core_target::check_memtag_addr (CORE_ADDR address) >> +{ >> + return gdbarch_tagged_address_p (current_inferior ()->arch (), address); > > Same comment here, of course. > >> diff --git a/gdb/printcmd.c b/gdb/printcmd.c >> index ae4d640ccf2..c81c75afc5d 100644 >> --- a/gdb/printcmd.c >> +++ b/gdb/printcmd.c >> @@ -1132,7 +1132,7 @@ do_examine (struct format_data fmt, struct gdbarch *gdbarch, CORE_ADDR addr) >> = value_from_ulongest (builtin_type (gdbarch)->builtin_data_ptr, >> tag_laddr); >> >> - if (gdbarch_tagged_address_p (current_inferior ()->arch (), v_addr)) >> + if (target_check_memtag_addr (value_as_address(v_addr))) > > Missing space between "value_as_address" and the opening parens. > > Also, not a problem introduced by you, but I don't understand why the code > uses the gdbarch from current_inferior if it was passed a gdbarch in the > arguments. > > So I'd add a separate patch before this one to fix this code to use the > gdbarch that was passed as a parameter. Then this patch can also pass it > as a parameter to target_check_memtag_addr as I mentioned in an earlier > comment. Done in v3 in commit "gdb: Use passed gdbarch instead of calling current_inferior". >> { >> /* Fetch the allocation tag. */ >> struct value *tag >> @@ -1289,7 +1289,7 @@ should_validate_memtags (struct value *value) >> return false; >> >> /* We do. Check whether it includes any tags. */ >> - return gdbarch_tagged_address_p (current_inferior ()->arch (), value); >> + return target_check_memtag_addr (value_as_address(value)); > > Here there's no gdbarch available in context, but since there's only one > caller to this function, it's easy to add the gdbarch parameter to it > and make the caller pass it down. The caller does get it from > current_inferior, so perhaps I'm being too pedantic here but IMHO it's > worth it. > > Also, a space is missing before the opening parens. > >> } >> >> /* Helper for parsing arguments for print_command_1. */ >> @@ -2946,9 +2946,10 @@ memory_tag_print_tag_command (const char *args, enum memtag_type tag_type) >> flag, it is no use trying to access/manipulate its allocation tag. >> >> It is OK to manipulate the logical tag though. */ >> + CORE_ADDR addr = value_as_address(val); > > Missing space before the opening parens. > >> if (tag_type == memtag_type::allocation >> - && !gdbarch_tagged_address_p (arch, val)) >> - show_addr_not_tagged (value_as_address (val)); >> + && !target_check_memtag_addr(addr)) > > Missing space before the opening parens. > >> + show_addr_not_tagged (addr); >> >> value *tag_value = gdbarch_get_memtag (arch, val, tag_type); >> std::string tag = gdbarch_memtag_to_string (arch, tag_value); >> @@ -3104,8 +3105,9 @@ parse_set_allocation_tag_input (const char *args, struct value **val, >> >> /* If the address is not in a region memory mapped with a memory tagging >> flag, it is no use trying to access/manipulate its allocation tag. */ >> - if (!gdbarch_tagged_address_p (current_inferior ()->arch (), *val)) >> - show_addr_not_tagged (value_as_address (*val)); >> + CORE_ADDR addr = value_as_address (*val); >> + if (!target_check_memtag_addr (addr)) >> + show_addr_not_tagged (addr); > > This is another instance where I'd suggest making the caller pass > gdbarch as an argument so that it can be used here, since this function > only has one caller. OK, done in v3. > >> } >> >> /* Implement the "memory-tag set-allocation-tag" command. >> @@ -3129,8 +3131,9 @@ memory_tag_set_allocation_tag_command (const char *args, int from_tty) >> >> /* If the address is not in a region memory mapped with a memory tagging >> flag, it is no use trying to manipulate its allocation tag. */ >> - if (!gdbarch_tagged_address_p (current_inferior ()->arch (), val)) { >> - show_addr_not_tagged (value_as_address(val)); >> + CORE_ADDR addr = value_as_address (val); >> + if (!target_check_memtag_addr (addr)) { >> + show_addr_not_tagged (addr); >> } > > This is a preexisting issue in the code, but since you're touching it: > the GNU style is to not use curly braces when there's only one statement > in the if block. > >> @@ -15532,6 +15547,19 @@ create_store_memtags_request (gdb::char_vector &packet, CORE_ADDR address, >> strcpy (packet.data (), request.c_str ()); >> } >> >> +static void >> +create_check_memtag_addr_request (gdb::char_vector &packet, CORE_ADDR address) >> +{ >> + int addr_size = gdbarch_addr_bit (current_inferior ()->arch()) / 8; >> + >> + std::string request = string_printf ("qMemTagAddrCheck:%s", phex_nz (address, addr_size)); >> + >> + if (packet.size () < request.length ()) > > There's an off-by-one error here: packet is expected to be > null-terminated, but request.length doesn't count a terminating null > byte so a "+ 1" needs to be added here. Good catch, thanks. Fixed in v3. >> + error (_("Contents too big for packet qMemTagAddrCheck.")); >> + >> + strcpy (packet.data (), request.c_str ()); >> +} >> + >> /* Implement the "fetch_memtags" target_ops method. */ >> >> bool >> @@ -15573,6 +15601,36 @@ remote_target::store_memtags (CORE_ADDR address, size_t len, >> return packet_check_result (rs->buf).status () == PACKET_OK; >> } >> >> +bool >> +remote_target::check_memtag_addr (CORE_ADDR address) >> +{ >> + struct remote_state *rs = get_remote_state (); >> + >> + if (!m_features.remote_memory_tagging_check_addr_p ()) >> + /* Fallback to reading /proc/<PID>/smaps for checking if an address is >> + tagged or not. */ > > Currently this comment is accurate, but if some other architecture adds > a gdbarch method that doesn't use /proc/<PID>/smaps then it won't be > anymore. > > I suggest saying something like "Fallback to arch-specific method of > checking whether an address is tagged". Done in v3. >> + return gdbarch_tagged_address_p (current_inferior ()->arch (), address); >> + >> + create_check_memtag_addr_request (rs->buf, address); >> + >> + putpkt (rs->buf); >> + getpkt (&rs->buf); >> + >> + /* Check if reply is OK. */ >> + if ((packet_check_result (rs->buf).status () != PACKET_OK) || rs->buf.empty()) > > Missing space between "empty" and opening parens. > > But I don't understand why check whether buf is empty. Looking at > remote_target::getpkt, it doesn't look like buf is ever emptied. I removed rs->buf.empty() in v3. >> + return false; >> + >> + gdb_byte tagged_addr; >> + /* Convert only 2 hex digits, i.e. 1 byte in hex format. */ >> + hex2bin(rs->buf.data(), &tagged_addr , 1); > > Missing space between "hex2bin", "data" and the opening parens. > >> + if (tagged_addr) >> + /* 01 means address is tagged. */ >> + return true; >> + else >> + /* 00 means address is not tagged. */ >> + return false; > > The above can be simplified to "return tagged_addr != 0". Done in v3. Cheers, Gustavo
diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c index 3face34ce79..1c64df6af41 100644 --- a/gdb/aarch64-linux-nat.c +++ b/gdb/aarch64-linux-nat.c @@ -110,6 +110,8 @@ class aarch64_linux_nat_target final /* Write allocation tags to memory via PTRACE. */ bool store_memtags (CORE_ADDR address, size_t len, const gdb::byte_vector &tags, int type) override; + /* Check if an address is tagged. */ + bool check_memtag_addr (CORE_ADDR address) override; }; static aarch64_linux_nat_target the_aarch64_linux_nat_target; @@ -1071,6 +1073,12 @@ aarch64_linux_nat_target::store_memtags (CORE_ADDR address, size_t len, return false; } +bool +aarch64_linux_nat_target::check_memtag_addr (CORE_ADDR address) +{ + return gdbarch_tagged_address_p (current_inferior ()->arch (), address); +} + void _initialize_aarch64_linux_nat (); void _initialize_aarch64_linux_nat () diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c index fc60e602748..2a47c3f0845 100644 --- a/gdb/aarch64-linux-tdep.c +++ b/gdb/aarch64-linux-tdep.c @@ -2451,17 +2451,15 @@ aarch64_mte_get_atag (CORE_ADDR address) /* Implement the tagged_address_p gdbarch method. */ static bool -aarch64_linux_tagged_address_p (struct gdbarch *gdbarch, struct value *address) +aarch64_linux_tagged_address_p (struct gdbarch *gdbarch, CORE_ADDR address) { - gdb_assert (address != nullptr); - - CORE_ADDR addr = value_as_address (address); + gdb_assert (address); /* Remove the top byte for the memory range check. */ - addr = gdbarch_remove_non_address_bits (gdbarch, addr); + address = gdbarch_remove_non_address_bits (gdbarch, address); /* Check if the page that contains ADDRESS is mapped with PROT_MTE. */ - if (!linux_address_in_memtag_page (addr)) + if (!linux_address_in_memtag_page (address)) return false; /* We have a valid tag in the top byte of the 64-bit address. */ diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c index 456bfe971ff..cb149c36bc9 100644 --- a/gdb/arch-utils.c +++ b/gdb/arch-utils.c @@ -102,7 +102,7 @@ default_memtag_to_string (struct gdbarch *gdbarch, struct value *tag) /* See arch-utils.h */ bool -default_tagged_address_p (struct gdbarch *gdbarch, struct value *address) +default_tagged_address_p (struct gdbarch *gdbarch, CORE_ADDR address) { /* By default, assume the address is untagged. */ return false; diff --git a/gdb/arch-utils.h b/gdb/arch-utils.h index 2dcd8f6dc53..467be40c688 100644 --- a/gdb/arch-utils.h +++ b/gdb/arch-utils.h @@ -141,7 +141,7 @@ extern std::string default_memtag_to_string (struct gdbarch *gdbarch, struct value *tag); /* Default implementation of gdbarch_tagged_address_p. */ -bool default_tagged_address_p (struct gdbarch *gdbarch, struct value *address); +bool default_tagged_address_p (struct gdbarch *gdbarch, CORE_ADDR address); /* Default implementation of gdbarch_memtag_matches_p. */ extern bool default_memtag_matches_p (struct gdbarch *gdbarch, diff --git a/gdb/corelow.c b/gdb/corelow.c index f4e8273d962..676738825fb 100644 --- a/gdb/corelow.c +++ b/gdb/corelow.c @@ -109,6 +109,8 @@ class core_target final : public process_stratum_target bool fetch_memtags (CORE_ADDR address, size_t len, gdb::byte_vector &tags, int type) override; + bool check_memtag_addr (CORE_ADDR address) override; + x86_xsave_layout fetch_x86_xsave_layout () override; /* A few helpers. */ @@ -1410,6 +1412,12 @@ core_target::fetch_memtags (CORE_ADDR address, size_t len, return false; } +bool +core_target::check_memtag_addr (CORE_ADDR address) +{ + return gdbarch_tagged_address_p (current_inferior ()->arch (), address); +} + /* Implementation of the "fetch_x86_xsave_layout" target_ops method. */ x86_xsave_layout diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h index ebcff80bb9e..63fab26987f 100644 --- a/gdb/gdbarch-gen.h +++ b/gdb/gdbarch-gen.h @@ -707,8 +707,8 @@ extern void set_gdbarch_memtag_to_string (struct gdbarch *gdbarch, gdbarch_memta /* Return true if ADDRESS contains a tag and false otherwise. ADDRESS must be either a pointer or a reference type. */ -typedef bool (gdbarch_tagged_address_p_ftype) (struct gdbarch *gdbarch, struct value *address); -extern bool gdbarch_tagged_address_p (struct gdbarch *gdbarch, struct value *address); +typedef bool (gdbarch_tagged_address_p_ftype) (struct gdbarch *gdbarch, CORE_ADDR address); +extern bool gdbarch_tagged_address_p (struct gdbarch *gdbarch, CORE_ADDR address); extern void set_gdbarch_tagged_address_p (struct gdbarch *gdbarch, gdbarch_tagged_address_p_ftype *tagged_address_p); /* Return true if the tag from ADDRESS matches the memory tag for that diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c index 9319571deba..2d92f604c49 100644 --- a/gdb/gdbarch.c +++ b/gdb/gdbarch.c @@ -3232,7 +3232,7 @@ set_gdbarch_memtag_to_string (struct gdbarch *gdbarch, } bool -gdbarch_tagged_address_p (struct gdbarch *gdbarch, struct value *address) +gdbarch_tagged_address_p (struct gdbarch *gdbarch, CORE_ADDR address) { gdb_assert (gdbarch != NULL); gdb_assert (gdbarch->tagged_address_p != NULL); diff --git a/gdb/gdbarch_components.py b/gdb/gdbarch_components.py index 7d913ade621..24e979431b6 100644 --- a/gdb/gdbarch_components.py +++ b/gdb/gdbarch_components.py @@ -1267,7 +1267,7 @@ must be either a pointer or a reference type. """, type="bool", name="tagged_address_p", - params=[("struct value *", "address")], + params=[("CORE_ADDR", "address")], predefault="default_tagged_address_p", invalid=False, ) diff --git a/gdb/printcmd.c b/gdb/printcmd.c index ae4d640ccf2..c81c75afc5d 100644 --- a/gdb/printcmd.c +++ b/gdb/printcmd.c @@ -1132,7 +1132,7 @@ do_examine (struct format_data fmt, struct gdbarch *gdbarch, CORE_ADDR addr) = value_from_ulongest (builtin_type (gdbarch)->builtin_data_ptr, tag_laddr); - if (gdbarch_tagged_address_p (current_inferior ()->arch (), v_addr)) + if (target_check_memtag_addr (value_as_address(v_addr))) { /* Fetch the allocation tag. */ struct value *tag @@ -1289,7 +1289,7 @@ should_validate_memtags (struct value *value) return false; /* We do. Check whether it includes any tags. */ - return gdbarch_tagged_address_p (current_inferior ()->arch (), value); + return target_check_memtag_addr (value_as_address(value)); } /* Helper for parsing arguments for print_command_1. */ @@ -2946,9 +2946,10 @@ memory_tag_print_tag_command (const char *args, enum memtag_type tag_type) flag, it is no use trying to access/manipulate its allocation tag. It is OK to manipulate the logical tag though. */ + CORE_ADDR addr = value_as_address(val); if (tag_type == memtag_type::allocation - && !gdbarch_tagged_address_p (arch, val)) - show_addr_not_tagged (value_as_address (val)); + && !target_check_memtag_addr(addr)) + show_addr_not_tagged (addr); value *tag_value = gdbarch_get_memtag (arch, val, tag_type); std::string tag = gdbarch_memtag_to_string (arch, tag_value); @@ -3104,8 +3105,9 @@ parse_set_allocation_tag_input (const char *args, struct value **val, /* If the address is not in a region memory mapped with a memory tagging flag, it is no use trying to access/manipulate its allocation tag. */ - if (!gdbarch_tagged_address_p (current_inferior ()->arch (), *val)) - show_addr_not_tagged (value_as_address (*val)); + CORE_ADDR addr = value_as_address (*val); + if (!target_check_memtag_addr (addr)) + show_addr_not_tagged (addr); } /* Implement the "memory-tag set-allocation-tag" command. @@ -3129,8 +3131,9 @@ memory_tag_set_allocation_tag_command (const char *args, int from_tty) /* If the address is not in a region memory mapped with a memory tagging flag, it is no use trying to manipulate its allocation tag. */ - if (!gdbarch_tagged_address_p (current_inferior ()->arch (), val)) { - show_addr_not_tagged (value_as_address(val)); + CORE_ADDR addr = value_as_address (val); + if (!target_check_memtag_addr (addr)) { + show_addr_not_tagged (addr); } if (!gdbarch_set_memtags (current_inferior ()->arch (), val, length, tags, @@ -3158,12 +3161,12 @@ memory_tag_check_command (const char *args, int from_tty) struct value *val = process_print_command_args (args, &print_opts, true); gdbarch *arch = current_inferior ()->arch (); + CORE_ADDR addr = value_as_address (val); + /* If the address is not in a region memory mapped with a memory tagging flag, it is no use trying to access/manipulate its allocation tag. */ - if (!gdbarch_tagged_address_p (arch, val)) - show_addr_not_tagged (value_as_address (val)); - - CORE_ADDR addr = value_as_address (val); + if (!target_check_memtag_addr (addr)) + show_addr_not_tagged (addr); /* Check if the tag is valid. */ if (!gdbarch_memtag_matches_p (arch, val)) diff --git a/gdb/remote.c b/gdb/remote.c index e278711df7b..c5544d2e53c 100644 --- a/gdb/remote.c +++ b/gdb/remote.c @@ -337,6 +337,9 @@ enum { packets and the tag violation stop replies. */ PACKET_memory_tagging_feature, + /* Support checking if an address is tagged via qMemTagAddrCheck packet. */ + PACKET_memory_tagging_check_addr_feature, + PACKET_MAX }; @@ -758,6 +761,10 @@ struct remote_features bool remote_memory_tagging_p () const { return packet_support (PACKET_memory_tagging_feature) == PACKET_ENABLE; } + bool remote_memory_tagging_check_addr_p () const + { return packet_support (PACKET_memory_tagging_check_addr_feature) == + PACKET_ENABLE; } + /* Reset all packets back to "unknown support". Called when opening a new connection to a remote target. */ void reset_all_packet_configs_support (); @@ -1084,6 +1091,8 @@ class remote_target : public process_stratum_target bool store_memtags (CORE_ADDR address, size_t len, const gdb::byte_vector &tags, int type) override; + bool check_memtag_addr (CORE_ADDR address) override; + public: /* Remote specific methods. */ void remote_download_command_source (int num, ULONGEST addr, @@ -5762,6 +5771,8 @@ static const struct protocol_feature remote_protocol_features[] = { { "no-resumed", PACKET_DISABLE, remote_supported_packet, PACKET_no_resumed }, { "memory-tagging", PACKET_DISABLE, remote_supported_packet, PACKET_memory_tagging_feature }, + { "memory-tagging-check-addr", PACKET_DISABLE, remote_supported_packet, + PACKET_memory_tagging_check_addr_feature }, }; static char *remote_support_xml; @@ -5873,6 +5884,10 @@ remote_target::remote_query_supported () != AUTO_BOOLEAN_FALSE) remote_query_supported_append (&q, "memory-tagging+"); + if (m_features.packet_set_cmd_state (PACKET_memory_tagging_check_addr_feature) + != AUTO_BOOLEAN_FALSE) + remote_query_supported_append (&q, "memory-tagging-check-addr+"); + /* Keep this one last to work around a gdbserver <= 7.10 bug in the qSupported:xmlRegisters=i386 handling. */ if (remote_support_xml != NULL @@ -15532,6 +15547,19 @@ create_store_memtags_request (gdb::char_vector &packet, CORE_ADDR address, strcpy (packet.data (), request.c_str ()); } +static void +create_check_memtag_addr_request (gdb::char_vector &packet, CORE_ADDR address) +{ + int addr_size = gdbarch_addr_bit (current_inferior ()->arch()) / 8; + + std::string request = string_printf ("qMemTagAddrCheck:%s", phex_nz (address, addr_size)); + + if (packet.size () < request.length ()) + error (_("Contents too big for packet qMemTagAddrCheck.")); + + strcpy (packet.data (), request.c_str ()); +} + /* Implement the "fetch_memtags" target_ops method. */ bool @@ -15573,6 +15601,36 @@ remote_target::store_memtags (CORE_ADDR address, size_t len, return packet_check_result (rs->buf).status () == PACKET_OK; } +bool +remote_target::check_memtag_addr (CORE_ADDR address) +{ + struct remote_state *rs = get_remote_state (); + + if (!m_features.remote_memory_tagging_check_addr_p ()) + /* Fallback to reading /proc/<PID>/smaps for checking if an address is + tagged or not. */ + return gdbarch_tagged_address_p (current_inferior ()->arch (), address); + + create_check_memtag_addr_request (rs->buf, address); + + putpkt (rs->buf); + getpkt (&rs->buf); + + /* Check if reply is OK. */ + if ((packet_check_result (rs->buf).status () != PACKET_OK) || rs->buf.empty()) + return false; + + gdb_byte tagged_addr; + /* Convert only 2 hex digits, i.e. 1 byte in hex format. */ + hex2bin(rs->buf.data(), &tagged_addr , 1); + if (tagged_addr) + /* 01 means address is tagged. */ + return true; + else + /* 00 means address is not tagged. */ + return false; +} + /* Return true if remote target T is non-stop. */ bool @@ -16056,6 +16114,10 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL, add_packet_config_cmd (PACKET_memory_tagging_feature, "memory-tagging-feature", "memory-tagging-feature", 0); + add_packet_config_cmd (PACKET_memory_tagging_check_addr_feature, + "memory-tagging-check-addr-feature", + "memory-tagging-check-addr-feature", 0); + /* Assert that we've registered "set remote foo-packet" commands for all packet configs. */ { diff --git a/gdb/target-delegates.c b/gdb/target-delegates.c index 59ea70458ad..fbd9e3f65b4 100644 --- a/gdb/target-delegates.c +++ b/gdb/target-delegates.c @@ -197,6 +197,7 @@ struct dummy_target : public target_ops bool supports_memory_tagging () override; bool fetch_memtags (CORE_ADDR arg0, size_t arg1, gdb::byte_vector &arg2, int arg3) override; bool store_memtags (CORE_ADDR arg0, size_t arg1, const gdb::byte_vector &arg2, int arg3) override; + bool check_memtag_addr (CORE_ADDR arg0) override; x86_xsave_layout fetch_x86_xsave_layout () override; }; @@ -373,6 +374,7 @@ struct debug_target : public target_ops bool supports_memory_tagging () override; bool fetch_memtags (CORE_ADDR arg0, size_t arg1, gdb::byte_vector &arg2, int arg3) override; bool store_memtags (CORE_ADDR arg0, size_t arg1, const gdb::byte_vector &arg2, int arg3) override; + bool check_memtag_addr (CORE_ADDR arg0) override; x86_xsave_layout fetch_x86_xsave_layout () override; }; @@ -4562,6 +4564,32 @@ debug_target::store_memtags (CORE_ADDR arg0, size_t arg1, const gdb::byte_vector return result; } +bool +target_ops::check_memtag_addr (CORE_ADDR arg0) +{ + return this->beneath ()->check_memtag_addr (arg0); +} + +bool +dummy_target::check_memtag_addr (CORE_ADDR arg0) +{ + tcomplain (); +} + +bool +debug_target::check_memtag_addr (CORE_ADDR arg0) +{ + gdb_printf (gdb_stdlog, "-> %s->check_memtag_addr (...)\n", this->beneath ()->shortname ()); + bool result + = this->beneath ()->check_memtag_addr (arg0); + gdb_printf (gdb_stdlog, "<- %s->check_memtag_addr (", this->beneath ()->shortname ()); + target_debug_print_CORE_ADDR (arg0); + gdb_puts (") = ", gdb_stdlog); + target_debug_print_bool (result); + gdb_puts ("\n", gdb_stdlog); + return result; +} + x86_xsave_layout target_ops::fetch_x86_xsave_layout () { diff --git a/gdb/target.c b/gdb/target.c index 107a84b3ca1..938a0f76595 100644 --- a/gdb/target.c +++ b/gdb/target.c @@ -796,6 +796,12 @@ target_store_memtags (CORE_ADDR address, size_t len, return current_inferior ()->top_target ()->store_memtags (address, len, tags, type); } +bool +target_check_memtag_addr (CORE_ADDR address) +{ + return current_inferior ()->top_target ()->check_memtag_addr (address); +} + x86_xsave_layout target_fetch_x86_xsave_layout () { diff --git a/gdb/target.h b/gdb/target.h index c9eaff16346..bb64d32994e 100644 --- a/gdb/target.h +++ b/gdb/target.h @@ -1334,6 +1334,10 @@ struct target_ops const gdb::byte_vector &tags, int type) TARGET_DEFAULT_NORETURN (tcomplain ()); + /* Returns true if ADDRESS is tagged, otherwise returns false. */ + virtual bool check_memtag_addr (CORE_ADDR address) + TARGET_DEFAULT_NORETURN (tcomplain ()); + /* Return the x86 XSAVE extended state area layout. */ virtual x86_xsave_layout fetch_x86_xsave_layout () TARGET_DEFAULT_RETURN (x86_xsave_layout ()); @@ -2317,6 +2321,8 @@ extern bool target_fetch_memtags (CORE_ADDR address, size_t len, extern bool target_store_memtags (CORE_ADDR address, size_t len, const gdb::byte_vector &tags, int type); +extern bool target_check_memtag_addr (CORE_ADDR address); + extern x86_xsave_layout target_fetch_x86_xsave_layout (); /* Command logging facility. */
This commit adds a new packet qMemTagAddrCheck allowing GDB remote targets to use it to query gdbservers if a given address is tagged. It also adds a new GDB remote feature, 'memory-tagging-check-add+', which must be advertised by the GDB servers to inform GDB they can reply to address checks via the new qMemTagAddrCheck remote packet. Currently, this address check is done via a read query, where the contents of /proc/<PID>/smaps is read and the flags in there are inspected for MTE-related flags that indicate the address is in a tagged memory region. This is not ideal, for example, on QEMU gdbstub and in other cases, like in baremetal debugging, where there is no notion of any OS file like smaps. Hence, qMemTagAddrCheck packet allows check addresses in an OS-agnostic way. For supporting the new packet, a new target hook is introduced, check_memtag_addr, which is used instead of the gdbarch_tagged_address_p gdbarch hook in the upper layers (printcmd.c). The new target hook is then specialized per target, for remote.c, aarch64-linux-nat.c, and corelow.c targets (the current targets that are MTE-aware). The target hook in remote.c uses the qMemTagAddrCheck packet to check an address if the server advertised the 'memory-tagging-check-add+' feature, otherwise it falls back to using the current mechanism, i.e. it reads the /proc/<PID>/smaps contents. In the aarch64-linux-nat.c and corelow.c the target hook uses the gdbarch_tagged_address_p gdbarch hook, so there is no change regarding how an address is checked in these targets. Just the gdbarch_tagged_address_p signature is changed for convenience, since target_check_memtag_addr takes the address to be checked as a CORE_ADDR type. Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org> --- gdb/aarch64-linux-nat.c | 8 +++++ gdb/aarch64-linux-tdep.c | 10 +++---- gdb/arch-utils.c | 2 +- gdb/arch-utils.h | 2 +- gdb/corelow.c | 8 +++++ gdb/gdbarch-gen.h | 4 +-- gdb/gdbarch.c | 2 +- gdb/gdbarch_components.py | 2 +- gdb/printcmd.c | 27 +++++++++-------- gdb/remote.c | 62 +++++++++++++++++++++++++++++++++++++++ gdb/target-delegates.c | 28 ++++++++++++++++++ gdb/target.c | 6 ++++ gdb/target.h | 6 ++++ 13 files changed, 143 insertions(+), 24 deletions(-)