diff options
| author |   Mark Rutland <mark.rutland@arm.com> | 2021-01-13 17:31:55 +0000 |
|---|---|---|
| committer |   Will Deacon <will@kernel.org> | 2021-01-20 12:47:54 +0000 |
| commit | 6106e1112cc69a367f495da2e66f13e2bca369fb (patch) | |
| tree | 3e6db60cef26810c7ebb7456a8795ccc67ecce5c /arch/arm64/kernel/entry.S | |
| parent | Linux 5.11-rc4 (diff) | |
| download | linux-dev-6106e1112cc69a367f495da2e66f13e2bca369fb.tar.xz linux-dev-6106e1112cc69a367f495da2e66f13e2bca369fb.zip | |
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/entry.S')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index c9bae73f2621..89fd3907816e 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -261,16 +261,16 @@ alternative_else_nop_endif stp lr, x21, [sp, #S_LR] /* - * In order to be able to dump the contents of struct pt_regs at the - * time the exception was taken (in case we attempt to walk the call - * stack later), chain it together with the stack frames. + * For exceptions from EL0, terminate the callchain here. + * For exceptions from EL1, create a synthetic frame record so the + * interrupted code shows up in the backtrace. */ .if \el == 0 - stp xzr, xzr, [sp, #S_STACKFRAME] + mov x29, xzr .else stp x29, x22, [sp, #S_STACKFRAME] - .endif add x29, sp, #S_STACKFRAME + .endif #ifdef CONFIG_ARM64_SW_TTBR0_PAN alternative_if_not ARM64_HAS_PAN |