@@ -1201,8 +1201,7 @@ vector_addrexcptn:
.long __fiq_svc @ e
.long __fiq_svc @ f
- .globl vector_fiq_offset
- .equ vector_fiq_offset, vector_fiq
+ .globl vector_fiq
.section .vectors, "ax", %progbits
.L__vectors_start:
@@ -165,19 +165,21 @@ SECTIONS
* only thing that matters is their relative offsets
*/
__vectors_start = .;
- .vectors 0 : AT(__vectors_start) {
+ .vectors 0xffff0000 : AT(__vectors_start) {
*(.vectors)
}
. = __vectors_start + SIZEOF(.vectors);
__vectors_end = .;
__stubs_start = .;
- .stubs 0x1000 : AT(__stubs_start) {
+ .stubs ADDR(.vectors) + 0x1000 : AT(__stubs_start) {
*(.stubs)
}
. = __stubs_start + SIZEOF(.stubs);
__stubs_end = .;
+ PROVIDE(vector_fiq_offset = vector_fiq - ADDR(.vectors));
+
INIT_TEXT_SECTION(8)
.exit.text : {
ARM_EXIT_KEEP(EXIT_TEXT)
Commit b9b32bf70f2f ("ARM: use linker magic for vectors and vector stubs") updated the linker script to emit the .vectors and .stubs sections into a VMA range that is zero based and disjoint from the normal static kernel region. The reason for that was that this way, the sections can be placed exactly 4 KB apart, while the payload of the .vectors section is only 32 bytes. Since the symbols that are part of the .stubs section are emitted into the kallsyms table, they appear with zero based addresses as well, e.g., 00001004 t vector_rst 00001020 t vector_irq 000010a0 t vector_dabt 00001120 t vector_pabt 000011a0 t vector_und 00001220 t vector_addrexcptn 00001240 t vector_fiq 00001240 T vector_fiq_offset As this confuses perf when it accesses the kallsyms tables, commit 7122c3e9154b ("scripts/link-vmlinux.sh: only filter kernel symbols for arm") implemented a somewhat ugly special case for ARM, where the value of CONFIG_PAGE_OFFSET is passed to scripts/kallsyms, and symbols whose addresses are below it are filtered out. Note that this special case only applies to CONFIG_XIP_KERNEL=n, not because the issue the patch addresses exists only in that case, but because finding a limit below which to apply the filtering is not entirely straightforward. Since the .vectors and .stubs sections contain position independent code that is never executed in place, we can emit it at its most likely runtime VMA (for more recent CPUs), which is 0xffff0000 for the vector table and 0xffff1000 for the stubs. Not only does this fix the perf issue with kallsyms, allowing us to drop the special case in scripts/kallsyms entirely, it also gives debuggers a more realistic view of the address space, and setting breakpoints or single stepping through code in the vector table or the stubs is more likely to work as expected on CPUs that use a high vector address. E.g., 00001240 A vector_fiq_offset ... c0c35000 T __init_begin c0c35000 T __vectors_start c0c35020 T __stubs_start c0c35020 T __vectors_end c0c352e0 T _sinittext c0c352e0 T __stubs_end ... ffff1004 t vector_rst ffff1020 t vector_irq ffff10a0 t vector_dabt ffff1120 t vector_pabt ffff11a0 t vector_und ffff1220 t vector_addrexcptn ffff1240 T vector_fiq (Note that vector_fiq_offset is now an absolute symbol, which kallsyms already ignores by default) The LMA footprint is identical with or without this change, only the VMAs are different: Before: Idx Name Size VMA LMA File off Algn ... 14 .notes 00000024 c0c34020 c0c34020 00a34020 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 15 .vectors 00000020 00000000 c0c35000 00a40000 2**1 CONTENTS, ALLOC, LOAD, READONLY, CODE 16 .stubs 000002c0 00001000 c0c35020 00a41000 2**5 CONTENTS, ALLOC, LOAD, READONLY, CODE 17 .init.text 0006b1b8 c0c352e0 c0c352e0 00a452e0 2**5 CONTENTS, ALLOC, LOAD, READONLY, CODE ... After: Idx Name Size VMA LMA File off Algn ... 14 .notes 00000024 c0c34020 c0c34020 00a34020 2**2 CONTENTS, ALLOC, LOAD, READONLY, CODE 15 .vectors 00000020 ffff0000 c0c35000 00a40000 2**1 CONTENTS, ALLOC, LOAD, READONLY, CODE 16 .stubs 000002c0 ffff1000 c0c35020 00a41000 2**5 CONTENTS, ALLOC, LOAD, READONLY, CODE 17 .init.text 0006b1b8 c0c352e0 c0c352e0 00a452e0 2**5 CONTENTS, ALLOC, LOAD, READONLY, CODE ... Acked-by: Nicolas Pitre <nico@linaro.org> Acked-by: Chris Brandt <chris.brandt@renesas.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm/kernel/entry-armv.S | 3 +-- arch/arm/kernel/vmlinux.lds.S | 6 ++++-- 2 files changed, 5 insertions(+), 4 deletions(-) -- 2.5.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel