OpenE2K
/
glibc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

PowerPC64: Fix incorrect CFI in *context routines 

The context established by "makecontext" has a link register pointing
back to an error path within the makecontext routine.  This is currently
covered by the CFI FDE for makecontext itself, which is simply wrong
for the stack frame *inside* the context.  When trying to unwind (e.g.
doing a backtrace) in a routine inside a context created by makecontext,
this can lead to uninitialized stack slots being accessed, causing the
unwinder to crash in the worst case.

Similarly, during parts of the "setcontext" routine, when the stack
pointer has already been switched to point to the new context, the
address range is still covered by the CFI FDE for setcontext.  When
trying to unwind in that situation (e.g. backtrace from an async
signal handler for profiling), it is again possible that the unwinder
crashes.

Theses are all problems in existing code, but the changes in stack
frame layout appear to make the "worst case" much more likely in
the ELFv2 ABI context.  This causes regressions e.g. in the libgo
testsuite on ELFv2.

This patch fixes this by ending the makecontext/setcontext FDEs
before those problematic parts of the assembler, similar to what
is already done on other platforms.   This fixes the libgo
regression on ELFv2.
This commit is contained in:
Ulrich Weigand 2013-12-04 06:41:52 -06:00 committed by Adhemerval Zanella
parent 19e3372ba4
commit 5162e7dd96
3 changed files with 36 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
ChangeLog
View File

@ -1,3 +1,12 @@
2013-12-04 Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
* sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
(__makecontext): Fix incorrect CFI when backtracing out of
context created via makecontext.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/secontext.S
(__setcontext): Fix incorrect CFI during switch to new context.
(__novec_setcontext): Likewise.
2013-12-04 Ondřej Bílka <neleai@seznam.cz>
[BZ #4772]

9
sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
View File

@ -129,6 +129,10 @@ L(noparms):
the cpu link stack used to predict blr return addresses. */
bcl 20,31,L(gotexitcodeaddr);
/* End FDE now, because while executing on the context's stack
the unwind info would be wrong otherwise. */
cfi_endproc
/* This is the helper code which gets called if a function which
is registered with 'makecontext' returns. In this case we
have to install the context listed in the uc_link element of
@ -157,6 +161,11 @@ L(do_exit):
#endif
b L(do_exit)
/* Re-establish FDE for the rest of the actual makecontext routine. */
cfi_startproc
cfi_offset (lr, FRAME_LR_SAVE)
cfi_adjust_cfa_offset (128)
/* The address of the exit code is in the link register. Store the lr
in the ucontext as LNK so the target function will return to our
exit code. */

18
sysdeps/unix/sysv/linux/powerpc/powerpc64/setcontext.S
View File

@ -129,6 +129,10 @@ ENTRY(__novec_setcontext)
lfd fp1,(SIGCONTEXT_FP_REGS+(PT_R1*8))(r31)
lfd fp0,(SIGCONTEXT_FP_REGS+(PT_R0*8))(r31)
/* End FDE now, because the unwind info would be wrong while
we're reloading registers to switch to the new context. */
cfi_endproc
ld r0,(SIGCONTEXT_GP_REGS+(PT_LNK*8))(r31)
ld r1,(SIGCONTEXT_GP_REGS+(PT_R1*8))(r31)
mtlr r0
@ -177,6 +181,11 @@ ENTRY(__novec_setcontext)
ld r31,(SIGCONTEXT_GP_REGS+(PT_R31*8))(r31)
bctr
/* Re-establish FDE for the rest of the actual setcontext routine. */
cfi_startproc
cfi_offset (lr, FRAME_LR_SAVE)
cfi_adjust_cfa_offset (128)
L(nv_error_exit):
ld r0,128+FRAME_LR_SAVE(r1)
addi r1,r1,128
@ -403,6 +412,10 @@ L(has_no_vec):
lfd fp1,(SIGCONTEXT_FP_REGS+(PT_R1*8))(r31)
lfd fp0,(SIGCONTEXT_FP_REGS+(PT_R0*8))(r31)
/* End FDE now, because the unwind info would be wrong while
we're reloading registers to switch to the new context. */
cfi_endproc
ld r0,(SIGCONTEXT_GP_REGS+(PT_LNK*8))(r31)
ld r1,(SIGCONTEXT_GP_REGS+(PT_R1*8))(r31)
mtlr r0
@ -451,6 +464,11 @@ L(has_no_vec):
ld r31,(SIGCONTEXT_GP_REGS+(PT_R31*8))(r31)
bctr
/* Re-establish FDE for the rest of the actual setcontext routine. */
cfi_startproc
cfi_offset (lr, FRAME_LR_SAVE)
cfi_adjust_cfa_offset (128)
L(error_exit):
ld r0,128+FRAME_LR_SAVE(r1)
addi r1,r1,128