MIPS: Save static registers before sysmips

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@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16149/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S
index 80ed68b..27c2f90 100644 (file)
--- a/arch/mips/kernel/scall32-o32.S
+++ b/arch/mips/kernel/scall32-o32.S
@@ -371,7 +371,7 @@ 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

diff --git a/arch/mips/kernel/scall64-64.S b/arch/mips/kernel/scall64-64.S
index 49765b4..65d5aee 100644 (file)
--- a/arch/mips/kernel/scall64-64.S
+++ b/arch/mips/kernel/scall64-64.S
@@ -311,7 +311,7 @@ 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

diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
index 90bad2d..cbf190e 100644 (file)
--- a/arch/mips/kernel/scall64-n32.S
+++ b/arch/mips/kernel/scall64-n32.S
@@ -302,7 +302,7 @@ 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

diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
index 2dd70bd..c30bc52 100644 (file)
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -371,7 +371,7 @@ 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

diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index 95e1b30..3e5d82e 100644 (file)
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -192,6 +192,12 @@ static inline int mips_atomic_set(unsigned long addr, unsigned long new)
        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) {