| Message ID | 20240418201039.236867-7-gustavo.romero@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | Add another way to check tagged addresses on remote targets | expand |
On 4/18/24 21:10, Gustavo Romero wrote: > This commit adds a new packet, qIsAddressTagged, allowing GDB remote > targets to use it to query the stub if a given address is tagged. > > Currently, the memory tagging address check is done via a read query, > where the contents of /proc/<PID>/smaps is read and the flags are > inspected for memory tagging-related flags that indicate the address is > in a memory tagged region. > > This is not ideal, for example, for QEMU stub and other cases, such as > on bare-metal, where there is no notion of an OS file like 'smaps.' > Hence, the introduction of qIsAddressTagged packet allows checking > if an address is tagged in an agnostic way. > > The is_address_tagged target hook in remote.c attempts to use the > qIsAddressTagged packet first for checking if an address is tagged and > if the stub does not support such a packet (reply is empty) it falls > back to using the current mechanism that reads the contents of > /proc/<PID>/smaps via vFile requests. > > Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org> > --- > gdb/remote.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 75 insertions(+) > > diff --git a/gdb/remote.c b/gdb/remote.c > index cd271c4b493..3d034bb1ef8 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 for the qIsAddressTagged packet. */ > + PACKET_qIsAddressTagged, > + > PACKET_MAX > }; > > @@ -15535,6 +15538,50 @@ create_store_memtags_request (gdb::char_vector &packet, CORE_ADDR address, > strcpy (packet.data (), request.c_str ()); > } > > +static void > +create_is_address_tagged_request (gdbarch *gdbarch, gdb::char_vector &packet, > + CORE_ADDR address) > +{ > + int addr_size; > + std::string request; > + > + addr_size = gdbarch_addr_bit (gdbarch) / 8; > + request = string_printf ("qIsAddressTagged:%s", phex_nz (address, addr_size)); > + > + if (packet.size () < request.length () + 1) > + error (_("Contents too big for packet qIsAddressTagged.")); > + > + strcpy (packet.data (), request.c_str ()); > +} > + > +static bool > +check_is_address_tagged_reply (remote_target *remote, gdb::char_vector &packet, > + bool &tagged) > +{ > + gdb_assert (remote != nullptr); > + /* Check reply and disable qIsAddressTagged usage if it's not supported. */ > + packet_result result = remote->m_features.packet_ok (packet, > + PACKET_qIsAddressTagged); > + > + /* Return false on error (Exx), empty reply (packet not supported), or reply > + size doesn't match 2 hex digits. */ > + if ((result.status () != PACKET_OK) || (strlen (packet.data ()) != 2)) > + return false; > + > + gdb_byte reply; > + /* Convert only 2 hex digits, i.e. 1 byte in hex format. */ > + hex2bin (packet.data (), &reply, 1); > + > + if (reply == 0x00 || reply == 0x01) > + { > + tagged = !!reply; > + return true; > + } > + > + /* Invalid reply. */ > + return false; > +} > + > /* Implement the "fetch_memtags" target_ops method. */ > > bool > @@ -15581,6 +15628,31 @@ remote_target::store_memtags (CORE_ADDR address, size_t len, > bool > remote_target::is_address_tagged (gdbarch *gdbarch, CORE_ADDR address) > { > + /* Firstly, attempt to check the address using the qIsAddressTagged > + packet. */ > + if (m_features.packet_support (PACKET_qIsAddressTagged) != PACKET_DISABLE) > + { > + remote_target *remote = get_current_remote_target (); > + struct remote_state *rs = get_remote_state (); > + bool is_addr_tagged; > + > + create_is_address_tagged_request (gdbarch, rs->buf, address); > + > + putpkt (rs->buf); > + getpkt (&rs->buf); > + > + /* If qIsAddressTagged is not supported PACKET_qIsAddressTagged will be > + set to PACKET_DISABLE so no further attempt is made to check addresses > + using this packet and the fallback mechanism below will be used > + instead. Also, if the check fails due to an error (Exx reply) the > + fallback is used too. Otherwise, the qIsAddressTagged query succeeded > + and is_addr_tagged is valid. */ > + if (check_is_address_tagged_reply (remote, rs->buf, is_addr_tagged)) > + return is_addr_tagged; > + } > + > + /* Fallback to arch-specific method of checking whether an address is tagged > + in case check via qIsAddressTagged fails. */ > return gdbarch_tagged_address_p (gdbarch, address); > } > > @@ -16070,6 +16142,9 @@ 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_qIsAddressTagged, > + "qIsAddressTagged", "memory-tagging-address-check", 0); > + > /* Assert that we've registered "set remote foo-packet" commands > for all packet configs. */ > { Thanks, this is OK. Approved-By: Luis Machado <luis.machado@arm.com> Tested-By: Luis Machado <luis.machado@arm.com>
diff --git a/gdb/remote.c b/gdb/remote.c index cd271c4b493..3d034bb1ef8 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 for the qIsAddressTagged packet. */ + PACKET_qIsAddressTagged, + PACKET_MAX }; @@ -15535,6 +15538,50 @@ create_store_memtags_request (gdb::char_vector &packet, CORE_ADDR address, strcpy (packet.data (), request.c_str ()); } +static void +create_is_address_tagged_request (gdbarch *gdbarch, gdb::char_vector &packet, + CORE_ADDR address) +{ + int addr_size; + std::string request; + + addr_size = gdbarch_addr_bit (gdbarch) / 8; + request = string_printf ("qIsAddressTagged:%s", phex_nz (address, addr_size)); + + if (packet.size () < request.length () + 1) + error (_("Contents too big for packet qIsAddressTagged.")); + + strcpy (packet.data (), request.c_str ()); +} + +static bool +check_is_address_tagged_reply (remote_target *remote, gdb::char_vector &packet, + bool &tagged) +{ + gdb_assert (remote != nullptr); + /* Check reply and disable qIsAddressTagged usage if it's not supported. */ + packet_result result = remote->m_features.packet_ok (packet, + PACKET_qIsAddressTagged); + + /* Return false on error (Exx), empty reply (packet not supported), or reply + size doesn't match 2 hex digits. */ + if ((result.status () != PACKET_OK) || (strlen (packet.data ()) != 2)) + return false; + + gdb_byte reply; + /* Convert only 2 hex digits, i.e. 1 byte in hex format. */ + hex2bin (packet.data (), &reply, 1); + + if (reply == 0x00 || reply == 0x01) + { + tagged = !!reply; + return true; + } + + /* Invalid reply. */ + return false; +} + /* Implement the "fetch_memtags" target_ops method. */ bool @@ -15581,6 +15628,31 @@ remote_target::store_memtags (CORE_ADDR address, size_t len, bool remote_target::is_address_tagged (gdbarch *gdbarch, CORE_ADDR address) { + /* Firstly, attempt to check the address using the qIsAddressTagged + packet. */ + if (m_features.packet_support (PACKET_qIsAddressTagged) != PACKET_DISABLE) + { + remote_target *remote = get_current_remote_target (); + struct remote_state *rs = get_remote_state (); + bool is_addr_tagged; + + create_is_address_tagged_request (gdbarch, rs->buf, address); + + putpkt (rs->buf); + getpkt (&rs->buf); + + /* If qIsAddressTagged is not supported PACKET_qIsAddressTagged will be + set to PACKET_DISABLE so no further attempt is made to check addresses + using this packet and the fallback mechanism below will be used + instead. Also, if the check fails due to an error (Exx reply) the + fallback is used too. Otherwise, the qIsAddressTagged query succeeded + and is_addr_tagged is valid. */ + if (check_is_address_tagged_reply (remote, rs->buf, is_addr_tagged)) + return is_addr_tagged; + } + + /* Fallback to arch-specific method of checking whether an address is tagged + in case check via qIsAddressTagged fails. */ return gdbarch_tagged_address_p (gdbarch, address); } @@ -16070,6 +16142,9 @@ 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_qIsAddressTagged, + "qIsAddressTagged", "memory-tagging-address-check", 0); + /* Assert that we've registered "set remote foo-packet" commands for all packet configs. */ {
This commit adds a new packet, qIsAddressTagged, allowing GDB remote targets to use it to query the stub if a given address is tagged. Currently, the memory tagging address check is done via a read query, where the contents of /proc/<PID>/smaps is read and the flags are inspected for memory tagging-related flags that indicate the address is in a memory tagged region. This is not ideal, for example, for QEMU stub and other cases, such as on bare-metal, where there is no notion of an OS file like 'smaps.' Hence, the introduction of qIsAddressTagged packet allows checking if an address is tagged in an agnostic way. The is_address_tagged target hook in remote.c attempts to use the qIsAddressTagged packet first for checking if an address is tagged and if the stub does not support such a packet (reply is empty) it falls back to using the current mechanism that reads the contents of /proc/<PID>/smaps via vFile requests. Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org> --- gdb/remote.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+)