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authorMark Rutland <mark.rutland@arm.com>2021-04-29 13:20:04 +0300
committerCatalin Marinas <catalin.marinas@arm.com>2021-04-30 20:30:45 +0300
commit8533d5bfad41e74b7dd80d292fd484913cdfb374 (patch)
treef4b0427bf323eea7321e1c71d7cf5479eebe23dc /arch/arm64
parent388708028e6937f3fc5fc19aeeb847f8970f489c (diff)
downloadlinux-8533d5bfad41e74b7dd80d292fd484913cdfb374.tar.xz
arm64: stacktrace: restore terminal records
We removed the terminal frame records in commit: 6106e1112cc69a36 ("arm64: remove EL0 exception frame record") ... on the assumption that as we no longer used them to find the pt_regs at exception boundaries, they were no longer necessary. However, Leo reports that as an unintended side-effect, this causes traces which cross secondary_start_kernel to terminate one entry too late, with a spurious "0" entry. There are a few ways we could sovle this, but as we're planning to use terminal records for RELIABLE_STACKTRACE, let's revert the logic change for now, keeping the update comments and accounting for the changes in commit: 3c02600144bdb0a1 ("arm64: stacktrace: Report when we reach the end of the stack") This is effectively a partial revert of commit: 6106e1112cc69a36 ("arm64: remove EL0 exception frame record") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Fixes: 6106e1112cc6 ("arm64: remove EL0 exception frame record") Reported-by: Leo Yan <leo.yan@linaro.org> Tested-by: Leo Yan <leo.yan@linaro.org> Cc: Will Deacon <will@kernel.org> Cc: Mark Brown <broonie@kernel.org> Cc: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> Link: https://lore.kernel.org/r/20210429104813.GA33550@C02TD0UTHF1T.local Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kernel/entry.S6
-rw-r--r--arch/arm64/kernel/stacktrace.c10
2 files changed, 9 insertions, 7 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 2df32a516ffe..806a39635482 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -283,16 +283,16 @@ alternative_else_nop_endif
stp lr, x21, [sp, #S_LR]
/*
- * For exceptions from EL0, terminate the callchain here.
+ * For exceptions from EL0, create a terminal frame record.
* For exceptions from EL1, create a synthetic frame record so the
* interrupted code shows up in the backtrace.
*/
.if \el == 0
- mov x29, xzr
+ stp xzr, xzr, [sp, #S_STACKFRAME]
.else
stp x29, x22, [sp, #S_STACKFRAME]
- add x29, sp, #S_STACKFRAME
.endif
+ add x29, sp, #S_STACKFRAME
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
alternative_if_not ARM64_HAS_PAN
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 2a1a7a281d34..c22706aa32a1 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -68,10 +68,6 @@ 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 -ENOENT;
-
if (fp & 0xf)
return -EINVAL;
@@ -132,6 +128,12 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
frame->pc = ptrauth_strip_insn_pac(frame->pc);
+ /*
+ * This is a terminal record, so we have finished unwinding.
+ */
+ if (!frame->fp && !frame->pc)
+ return -ENOENT;
+
return 0;
}
NOKPROBE_SYMBOL(unwind_frame);