[PATCH 1/3] xtensa: expose syscall through user_pt_regs

[Max Filippov]

Use one of the reserved slots in struct user_pt_regs to return syscall
number in the GPR regset. Update syscall number from the GPR regset only
when it's non-zero.

Signed-off-by: Max Filippov <jcmvb...@gmail.com>
---
 arch/xtensa/include/uapi/asm/ptrace.h | 3 ++-
 arch/xtensa/kernel/ptrace.c           | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/xtensa/include/uapi/asm/ptrace.h 
b/arch/xtensa/include/uapi/asm/ptrace.h
index 2ec0f9100a06..50db3e0a6341 100644
--- a/arch/xtensa/include/uapi/asm/ptrace.h
+++ b/arch/xtensa/include/uapi/asm/ptrace.h
@@ -50,7 +50,8 @@ struct user_pt_regs {
        __u32 windowstart;
        __u32 windowbase;
        __u32 threadptr;
-       __u32 reserved[7 + 48];
+       __u32 syscall;
+       __u32 reserved[6 + 48];
        __u32 a[64];
 };
 
diff --git a/arch/xtensa/kernel/ptrace.c b/arch/xtensa/kernel/ptrace.c
index 0278d7dfb4d6..437b4297948d 100644
--- a/arch/xtensa/kernel/ptrace.c
+++ b/arch/xtensa/kernel/ptrace.c
@@ -52,6 +52,7 @@ static int gpr_get(struct task_struct *target,
                .threadptr = regs->threadptr,
                .windowbase = regs->windowbase,
                .windowstart = regs->windowstart,
+               .syscall = regs->syscall,
        };
 
        memcpy(newregs.a,
@@ -91,6 +92,9 @@ static int gpr_set(struct task_struct *target,
        regs->sar = newregs.sar;
        regs->threadptr = newregs.threadptr;
 
+       if (newregs.syscall)
+               regs->syscall = newregs.syscall;
+
        if (newregs.windowbase != regs->windowbase ||
            newregs.windowstart != regs->windowstart) {
                u32 rotws, wmask;
-- 
2.20.1