powerpc/64/signal: Fix regression in __kernel_sigtramp_rt64() semantics
Commit0138ba5783
("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 Now this semantics are no longer valid.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 of0138ba5783
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:0138ba5783
("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
This commit is contained in:
parent
66f0a9e058
commit
24321ac668
|
@ -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
|
||||
|
|
|
@ -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;
|
||||
|
|
Loading…
Reference in a new issue