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authorMark Rutland <mark.rutland@arm.com>2021-01-13 20:31:55 +0300
committerWill Deacon <will@kernel.org>2021-01-20 15:47:54 +0300
commit6106e1112cc69a367f495da2e66f13e2bca369fb (patch)
tree3e6db60cef26810c7ebb7456a8795ccc67ecce5c /arch/arm64/kernel/stacktrace.c
parent19c329f6808995b142b3966301f217c831e7cf31 (diff)
downloadlinux-6106e1112cc69a367f495da2e66f13e2bca369fb.tar.xz
arm64: remove EL0 exception frame record
When entering an exception from EL0, the entry code creates a synthetic frame record with a NULL PC. This was used by the code introduced in commit: 7326749801396105 ("arm64: unwind: reference pt_regs via embedded stack frame") ... to discover exception entries on the stack and dump the associated pt_regs. Since the NULL PC was undesirable for the stacktrace, we added a special case to unwind_frame() to prevent the NULL PC from being logged. Since commit: a25ffd3a6302a678 ("arm64: traps: Don't print stack or raw PC/LR values in backtraces") ... we no longer try to dump the pt_regs as part of a stacktrace, and hence no longer need the synthetic exception record. This patch removes the synthetic exception record and the associated special case in unwind_frame(). Instead, EL0 exceptions set the FP to NULL, as is the case for other terminal records (e.g. when a kernel thread starts). The synthetic record for exceptions from EL1 is retrained as this has useful unwind information for the interrupted context. To make the terminal case a bit clearer, an explicit check is added to the start of unwind_frame(). This would otherwise be caught implicitly by the on_accessible_stack() checks. Reported-by: Mark Brown <broonie@kernel.org> Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20210113173155.43063-1-broonie@kernel.org Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/kernel/stacktrace.c')
-rw-r--r--arch/arm64/kernel/stacktrace.c13
1 files changed, 4 insertions, 9 deletions
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index fa56af1a59c3..0fb42129b469 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -44,6 +44,10 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
unsigned long fp = frame->fp;
struct stack_info info;
+ /* Terminal record; nothing to unwind */
+ if (!fp)
+ return -EINVAL;
+
if (fp & 0xf)
return -EINVAL;
@@ -104,15 +108,6 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
frame->pc = ptrauth_strip_insn_pac(frame->pc);
- /*
- * Frames created upon entry from EL0 have NULL FP and PC values, so
- * don't bother reporting these. Frames created by __noreturn functions
- * might have a valid FP even if PC is bogus, so only terminate where
- * both are NULL.
- */
- if (!frame->fp && !frame->pc)
- return -EINVAL;
-
return 0;
}
NOKPROBE_SYMBOL(unwind_frame);