MIPS: Fix syscall_get_nr for the syscall exit tracing.

Register 2 is alredy overwritten by the return value when
syscall_trace_leave() is called.

Signed-off-by: Lars Persson <larper@axis.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9187/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 4 insertions, 7 deletions

diff --git a/arch/mips/include/asm/syscall.h b/arch/mips/include/asm/syscall.h
index bb7963753730..6499d93ae68d 100644
--- a/arch/mips/include/asm/syscall.h
+++ b/arch/mips/include/asm/syscall.h
@@ -29,13 +29,7 @@
 static inline long syscall_get_nr(struct task_struct *task,
                                   struct pt_regs *regs)
 {
-        /* O32 ABI syscall() - Either 64-bit with O32 or 32-bit */
-        if ((config_enabled(CONFIG_32BIT) ||
-            test_tsk_thread_flag(task, TIF_32BIT_REGS)) &&
-            (regs->regs[2] == __NR_syscall))
-                return regs->regs[4];
-        else
-                return regs->regs[2];
+        return current_thread_info()->syscall;
 }
 
 static inline unsigned long mips_get_syscall_arg(unsigned long *arg,
diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h
index 99eea59604e9..e4440f92b366 100644
--- a/arch/mips/include/asm/thread_info.h
+++ b/arch/mips/include/asm/thread_info.h
@@ -36,6 +36,7 @@ struct thread_info {
                                                  */
         struct restart_block    restart_block;
         struct pt_regs          *regs;
+        long                    syscall;        /* syscall number */
 };
 
 /*
diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index 9d1487d83293..510452812594 100644
--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -770,6 +770,8 @@ asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall)
         long ret = 0;
         user_exit();
 
+        current_thread_info()->syscall = syscall;
+
         if (secure_computing() == -1)
                 return -1;