diff options
| author | Raoni Fassina Firmino <raoni@linux.ibm.com> | 2021-02-01 17:05:05 -0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-02-02 22:14:41 +1100 |
| commit | 24321ac668e452a4942598533d267805f291fdc9 (patch) | |
| tree | 2c024465409db4444b46630af443bdcc5a8fa535 | |
| parent | 66f0a9e058fad50e569ad752be72e52701991fd5 (diff) | |
| download | lwn-24321ac668e452a4942598533d267805f291fdc9.tar.gz lwn-24321ac668e452a4942598533d267805f291fdc9.zip | |
powerpc/64/signal: Fix regression in __kernel_sigtramp_rt64() semantics
Commit 0138ba5783ae ("powerpc/64/signal: Balance return predictor
stack in signal trampoline") changed __kernel_sigtramp_rt64() VDSO and
trampoline code, and introduced a regression in the way glibc's
backtrace()[1] detects the signal-handler stack frame. Apart from the
practical implications, __kernel_sigtramp_rt64() was a VDSO function
with the semantics that it is a function you can call from userspace
to end a signal handling. Now this semantics are no longer valid.
I believe the aforementioned change affects all releases since 5.9.
This patch tries to fix both the semantics and practical aspect of
__kernel_sigtramp_rt64() returning it to the previous code, whilst
keeping the intended behaviour of 0138ba5783ae by adding a new symbol
to serve as the jump target from the kernel to the trampoline. Now the
trampoline has two parts, a new entry point and the old return point.
[1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2021-January/223194.html
Fixes: 0138ba5783ae ("powerpc/64/signal: Balance return predictor stack in signal trampoline")
Cc: stable@vger.kernel.org # v5.9+
Signed-off-by: Raoni Fassina Firmino <raoni@linux.ibm.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Minor tweaks to change log formatting, add stable tag]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210201200505.iz46ubcizipnkcxe@work-tp
| -rw-r--r-- | arch/powerpc/kernel/vdso64/sigtramp.S | 11 | ||||
| -rw-r--r-- | arch/powerpc/kernel/vdso64/vdso64.lds.S | 2 |
2 files changed, 11 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/vdso64/sigtramp.S b/arch/powerpc/kernel/vdso64/sigtramp.S index bbf68cd01088..2d4067561293 100644 --- a/arch/powerpc/kernel/vdso64/sigtramp.S +++ b/arch/powerpc/kernel/vdso64/sigtramp.S @@ -15,11 +15,20 @@ .text +/* + * __kernel_start_sigtramp_rt64 and __kernel_sigtramp_rt64 together + * are one function split in two parts. The kernel jumps to the former + * and the signal handler indirectly (by blr) returns to the latter. + * __kernel_sigtramp_rt64 needs to point to the return address so + * glibc can correctly identify the trampoline stack frame. + */ .balign 8 .balign IFETCH_ALIGN_BYTES -V_FUNCTION_BEGIN(__kernel_sigtramp_rt64) +V_FUNCTION_BEGIN(__kernel_start_sigtramp_rt64) .Lsigrt_start: bctrl /* call the handler */ +V_FUNCTION_END(__kernel_start_sigtramp_rt64) +V_FUNCTION_BEGIN(__kernel_sigtramp_rt64) addi r1, r1, __SIGNAL_FRAMESIZE li r0,__NR_rt_sigreturn sc diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S index 6164d1a1ba11..2f3c359cacd3 100644 --- a/arch/powerpc/kernel/vdso64/vdso64.lds.S +++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S @@ -131,4 +131,4 @@ VERSION /* * Make the sigreturn code visible to the kernel. */ -VDSO_sigtramp_rt64 = __kernel_sigtramp_rt64; +VDSO_sigtramp_rt64 = __kernel_start_sigtramp_rt64; |