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authorHelge Deller <deller@gmx.de>2016-01-19 16:08:49 +0100
committerHelge Deller <deller@gmx.de>2016-03-01 23:06:07 +0100
commit98e8b6c9ac9d1b1e9d1122dfa6783d5d566bb8f7 (patch)
tree336ac5725ed95cac56829aaa3a0f3cea76cc176b /arch/parisc/kernel/syscall.S
parentparisc: Use parentheses around expression in floppy.h (diff)
downloadlinux-98e8b6c9ac9d1b1e9d1122dfa6783d5d566bb8f7.tar.xz
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parisc: Fix ptrace syscall number and return value modification
Mike Frysinger reported that his ptrace testcase showed strange behaviour on parisc: It was not possible to avoid a syscall and the return value of a syscall couldn't be changed. To modify a syscall number, we were missing to save the new syscall number to gr20 which is then picked up later in assembly again. The effect that the return value couldn't be changed is a side-effect of another bug in the assembly code. When a process is ptraced, userspace expects each syscall to report entrance and exit of a syscall. If a syscall number was given which doesn't exist, we jumped to the normal syscall exit code instead of informing userspace that the (non-existant) syscall exits. This unexpected behaviour confuses userspace and thus the bug was misinterpreted as if we can't change the return value. This patch fixes both problems and was tested on 64bit kernel with 32bit userspace. Signed-off-by: Helge Deller <deller@gmx.de> Cc: Mike Frysinger <vapier@gentoo.org> Cc: stable@vger.kernel.org # v4.0+ Tested-by: Mike Frysinger <vapier@gentoo.org>
Diffstat (limited to 'arch/parisc/kernel/syscall.S')
-rw-r--r--arch/parisc/kernel/syscall.S5
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S
index 3fbd7252a4b2..fbafa0d0e2bf 100644
--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -343,7 +343,7 @@ tracesys_next:
#endif
comiclr,>>= __NR_Linux_syscalls, %r20, %r0
- b,n .Lsyscall_nosys
+ b,n .Ltracesys_nosys
LDREGX %r20(%r19), %r19
@@ -359,6 +359,9 @@ tracesys_next:
be 0(%sr7,%r19)
ldo R%tracesys_exit(%r2),%r2
+.Ltracesys_nosys:
+ ldo -ENOSYS(%r0),%r28 /* set errno */
+
/* Do *not* call this function on the gateway page, because it
makes a direct call to syscall_trace. */