4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: James Hogan <james.hogan@xxxxxxxxxx>
commit 49955d84cd9ccdca5a16a495e448e1a06fad9e49 upstream.
The MIPS sysmips system call handler may return directly from the
MIPS_ATOMIC_SET case (mips_atomic_set()) to syscall_exit. This path
restores the static (callee saved) registers, however they won't have
been saved on entry to the system call.
Use the save_static_function() macro to create a __sys_sysmips wrapper
function which saves the static registers before calling sys_sysmips, so
that the correct static register state is restored by syscall_exit.
Fixes: f1e39a4a616c ("MIPS: Rewrite sysmips(MIPS_ATOMIC_SET, ...) in C with inline assembler")
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/16149/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/mips/kernel/scall32-o32.S | 2 +-
arch/mips/kernel/scall64-64.S | 2 +-
arch/mips/kernel/scall64-n32.S | 2 +-
arch/mips/kernel/scall64-o32.S | 2 +-
arch/mips/kernel/syscall.c | 6 ++++++
5 files changed, 10 insertions(+), 4 deletions(-)
--- a/arch/mips/kernel/scall32-o32.S
+++ b/arch/mips/kernel/scall32-o32.S
@@ -372,7 +372,7 @@ EXPORT(sys_call_table)
PTR sys_writev
PTR sys_cacheflush
PTR sys_cachectl
- PTR sys_sysmips
+ PTR __sys_sysmips
PTR sys_ni_syscall /* 4150 */
PTR sys_getsid
PTR sys_fdatasync
--- a/arch/mips/kernel/scall64-64.S
+++ b/arch/mips/kernel/scall64-64.S
@@ -312,7 +312,7 @@ EXPORT(sys_call_table)
PTR sys_sched_getaffinity
PTR sys_cacheflush
PTR sys_cachectl
- PTR sys_sysmips
+ PTR __sys_sysmips
PTR sys_io_setup /* 5200 */
PTR sys_io_destroy
PTR sys_io_getevents
--- a/arch/mips/kernel/scall64-n32.S
+++ b/arch/mips/kernel/scall64-n32.S
@@ -298,7 +298,7 @@ EXPORT(sysn32_call_table)
PTR compat_sys_sched_getaffinity
PTR sys_cacheflush
PTR sys_cachectl
- PTR sys_sysmips
+ PTR __sys_sysmips
PTR compat_sys_io_setup /* 6200 */
PTR sys_io_destroy
PTR compat_sys_io_getevents
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -367,7 +367,7 @@ EXPORT(sys32_call_table)
PTR compat_sys_writev
PTR sys_cacheflush
PTR sys_cachectl
- PTR sys_sysmips
+ PTR __sys_sysmips
PTR sys_ni_syscall /* 4150 */
PTR sys_getsid
PTR sys_fdatasync
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -202,6 +202,12 @@ static inline int mips_atomic_set(unsign
unreachable();
}
+/*
+ * mips_atomic_set() normally returns directly via syscall_exit potentially
+ * clobbering static registers, so be sure to preserve them.
+ */
+save_static_function(sys_sysmips);
+
SYSCALL_DEFINE3(sysmips, long, cmd, long, arg1, long, arg2)
{
switch (cmd) {