arm64: split syscall_trace() into separate functions for enter/exit

As done in arm, this change makes it easy to confirm we invoke syscall
related hooks, including syscall tracepoint, audit and seccomp which would
be implemented later, in correct order. That is, undoing operations in the
opposite order on exit that they were done on entry.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 0c609291e963f19e960b3362eaa76b5f71206939..5b368d51369e36b12308550e4be9efc348f3eade 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -660,9 +660,8 @@ ENDPROC(el0_svc)
         * switches, and waiting for our parent to respond.
         */
 __sys_trace:
-       mov     x1, sp
-       mov     w0, #0                          // trace entry
-       bl      syscall_trace
+       mov     x0, sp
+       bl      syscall_trace_enter
        adr     lr, __sys_trace_return          // return address
        uxtw    scno, w0                        // syscall number (possibly new)
        mov     x1, sp                          // pointer to regs
@@ -677,9 +676,8 @@ __sys_trace:
 
 __sys_trace_return:
        str     x0, [sp]                        // save returned x0
-       mov     x1, sp
-       mov     w0, #1                          // trace exit
-       bl      syscall_trace
+       mov     x0, sp
+       bl      syscall_trace_exit
        b       ret_to_user
 
 /*

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 7190a6544caba71f70de13bee51c278d2b3e0b96..f3b14fd27ab4feaf900b09cd2911e6d680deafaf 100644 (file)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1064,35 +1064,43 @@ long arch_ptrace(struct task_struct *child, long request,
        return ptrace_request(child, request, addr, data);
 }
 
-asmlinkage int syscall_trace(int dir, struct pt_regs *regs)
+enum ptrace_syscall_dir {
+       PTRACE_SYSCALL_ENTER = 0,
+       PTRACE_SYSCALL_EXIT,
+};
+
+static void tracehook_report_syscall(struct pt_regs *regs,
+                                    enum ptrace_syscall_dir dir)
 {
+       int regno;
        unsigned long saved_reg;
 
-       if (!test_thread_flag(TIF_SYSCALL_TRACE))
-               return regs->syscallno;
-
-       if (is_compat_task()) {
-               /* AArch32 uses ip (r12) for scratch */
-               saved_reg = regs->regs[12];
-               regs->regs[12] = dir;
-       } else {
-               /*
-                * Save X7. X7 is used to denote syscall entry/exit:
-                *   X7 = 0 -> entry, = 1 -> exit
-                */
-               saved_reg = regs->regs[7];
-               regs->regs[7] = dir;
-       }
+       /*
+        * A scratch register (ip(r12) on AArch32, x7 on AArch64) is
+        * used to denote syscall entry/exit:
+        */
+       regno = (is_compat_task() ? 12 : 7);
+       saved_reg = regs->regs[regno];
+       regs->regs[regno] = dir;
 
-       if (dir)
+       if (dir == PTRACE_SYSCALL_EXIT)
                tracehook_report_syscall_exit(regs, 0);
        else if (tracehook_report_syscall_entry(regs))
                regs->syscallno = ~0UL;
 
-       if (is_compat_task())
-               regs->regs[12] = saved_reg;
-       else
-               regs->regs[7] = saved_reg;
+       regs->regs[regno] = saved_reg;
+}
+
+asmlinkage int syscall_trace_enter(struct pt_regs *regs)
+{
+       if (test_thread_flag(TIF_SYSCALL_TRACE))
+               tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
 
        return regs->syscallno;
 }
+
+asmlinkage void syscall_trace_exit(struct pt_regs *regs)
+{
+       if (test_thread_flag(TIF_SYSCALL_TRACE))
+               tracehook_report_syscall(regs, PTRACE_SYSCALL_EXIT);
+}