diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2021-04-29 11:20:04 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2021-04-30 18:30:45 +0100 |
| commit | 8533d5bfad41e74b7dd80d292fd484913cdfb374 (patch) | |
| tree | f4b0427bf323eea7321e1c71d7cf5479eebe23dc | |
| parent | 388708028e6937f3fc5fc19aeeb847f8970f489c (diff) | |
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>
| -rw-r--r-- | arch/arm64/kernel/entry.S | 6 | ||||
| -rw-r--r-- | arch/arm64/kernel/stacktrace.c | 10 |
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); |