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[PATCH] MIPS: Fix syscall_get_nr for the syscall exit tracing.

To: linux-mips@linux-mips.org, ralf@linux-mips.org
Subject: [PATCH] MIPS: Fix syscall_get_nr for the syscall exit tracing.
From: Lars Persson <lars.persson@axis.com>
Date: Tue, 3 Feb 2015 17:08:17 +0100
Cc: Lars Persson <larper@axis.com>
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Register 2 is alredy overwritten by the return value when
syscall_trace_leave() is called.

Signed-off-by: Lars Persson <larper@axis.com>
---
 arch/mips/include/asm/syscall.h     |    8 +-------
 arch/mips/include/asm/thread_info.h |    1 +
 arch/mips/kernel/ptrace.c           |    2 ++
 3 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/mips/include/asm/syscall.h b/arch/mips/include/asm/syscall.h
index bb79637..6499d93 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 99eea59..e4440f9 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 9d1487d..5104528 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;
 
-- 
1.7.10.4


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