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authorStefan Liebler <stli@linux.ibm.com>2022-08-25 12:17:48 +0200
committerStefan Liebler <stli@linux.ibm.com>2022-08-30 10:54:46 +0200
commite57d8fc97b90127de4ed3e3a9cdf663667580935 (patch)
treef6b33a78454ea861ddef36b3ed8eb28289094f28 /sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S
parent1d495912a746e2a1ffb780c9a81fd234ec2464e8 (diff)
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S390: Always use svc 0
On s390x syscalls are triggered by svc instruction. One can
pass the syscall number encoded in the instruction "svc 123"
or by storing it in r1:
lghi r1,123
svc 0

If the syscall number is encoded in the instruction, this can
cause broken syscall restarts.  Therefore this patch is now just
passing the syscall number in r1.

See also kernel-commit:
"s390/signal: switch to using vdso for sigreturn and syscall restart"
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/s390/[%e2%80%a6]call.c?h=v6.0-rc1&id=df29a7440c4b5c65765c8f60396b3b13063e24e9

As information, the "svc 0" feature was introduced in kernel 2.5.62:
commit b5aad611393ef2e132e3648fa4c6e56a9cfa8708
Diffstat (limited to 'sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S')
-rw-r--r--sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S8
1 files changed, 5 insertions, 3 deletions
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S b/sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S
index 83fc2b436f..14251bc39c 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/setcontext.S
@@ -30,16 +30,18 @@
   other than the PRESERVED state.  */
 
 ENTRY(__setcontext)
-	lr	%r1,%r2
+	lr	%r0,%r2
 
 	/* rt_sigprocmask (SIG_SETMASK, &sc->sc_mask, NULL, sigsetsize).  */
+	la	%r3,SC_MASK(%r2)
 	la      %r2,SIG_SETMASK
-	la	%r3,SC_MASK(%r1)
 	slr	%r4,%r4
 	lhi	%r5,_NSIG8
-	svc	SYS_ify(rt_sigprocmask)
+	lhi	%r1,SYS_ify(rt_sigprocmask)
+	svc	0
 
 	/* Load fpu context.  */
+	lr	%r1,%r0
 	lfpc	SC_FPC(%r1)
 	ld	%f0,SC_FPRS(%r1)
 	ld      %f1,SC_FPRS+8(%r1)