xtensa: rearrange syscall tracing

system_call saves and restores syscall number across system call to make
clone and execv entry and exit tracing match. This complicates things
when syscall code may be changed by ptrace.
Preserve syscall code in copy_thread and start_thread directly instead of
doing tricks in system_call.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

diff --git a/arch/xtensa/include/asm/processor.h b/arch/xtensa/include/asm/processor.h
index 7495520..6fa903d 100644 (file)
--- a/arch/xtensa/include/asm/processor.h
+++ b/arch/xtensa/include/asm/processor.h
@@ -195,6 +195,7 @@ struct thread_struct {
 /* Clearing a0 terminates the backtrace. */
 #define start_thread(regs, new_pc, new_sp) \
        do { \
+               unsigned long syscall = (regs)->syscall; \
                memset((regs), 0, sizeof(*(regs))); \
                (regs)->pc = (new_pc); \
                (regs)->ps = USER_PS_VALUE; \
@@ -204,7 +205,7 @@ struct thread_struct {
                (regs)->depc = 0; \
                (regs)->windowbase = 0; \
                (regs)->windowstart = 1; \
-               (regs)->syscall = NO_SYSCALL; \
+               (regs)->syscall = syscall; \
        } while (0)
 
 /* Forward declaration */

diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 2ca209e..59af494 100644 (file)
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -1895,8 +1895,6 @@ ENTRY(system_call)
        l32i    a7, a2, PT_SYSCALL
 
 1:
-       s32i    a7, a1, 4
-
        /* syscall = sys_call_table[syscall_nr] */
 
        movi    a4, sys_call_table
@@ -1930,12 +1928,8 @@ ENTRY(system_call)
        abi_ret(4)
 
 1:
-       l32i    a4, a1, 4
-       l32i    a3, a2, PT_SYSCALL
-       s32i    a4, a2, PT_SYSCALL
        mov     a6, a2
        call4   do_syscall_trace_leave
-       s32i    a3, a2, PT_SYSCALL
        abi_ret(4)
 
 ENDPROC(system_call)

diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c
index db278a9..9e1c491 100644 (file)
--- a/arch/xtensa/kernel/process.c
+++ b/arch/xtensa/kernel/process.c
@@ -264,6 +264,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
                               &regs->areg[XCHAL_NUM_AREGS - len/4], len);
                }
 
+               childregs->syscall = regs->syscall;
+
                /* The thread pointer is passed in the '4th argument' (= a5) */
                if (clone_flags & CLONE_SETTLS)
                        childregs->threadptr = childregs->areg[5];