Hi all,
I think I hit a nasty kernel bug testing rt_sigreturn syscall while trying
to understand why it was failing on powerpc64. If anyone is curious I
changed the way swapcontext is done for powerpc64 to pass the new context
as r9:
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/swapcontext.S
b/sysdeps/unix/sysv/linux/powerpc/powerpc64/swapcontext.S
index af5b108..dcd97ca 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/swapcontext.S
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/swapcontext.S
@@ -787,7 +787,7 @@ L(error_exit):
R1 pointing at the dummy frame) state. We do have the ucontext
address in R3, so simply copy R3 to R1 before the syscall. */
L(do_sigret):
- mr r1,r3,
+ mr r9,r3,
li r0,SYS_ify(rt_sigreturn)
sc
/* No return. */
And issue a program that calls swapcontext in a signal handler using the
third argument (configured with SA_SIGINFO). This seems to be an issue with
certain specific kernel version since newer kernels handle the context
information without resorting in syscall argument handling.
Anyway just a heads up that this is probably a nasty issue affecting
CentOS7.
--
"Tradition is not the worship of ashes, but the preservation of fire."
- Gustav Mahler
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