On 03/14/2014 03:41 AM, Will Deacon wrote:

On Thu, Mar 13, 2014 at 10:11:30AM +0000, AKASHI Takahiro wrote:

quoted

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.

Signed-off-by: AKASHI Takahiro <redacted>
---
  arch/arm64/kernel/entry.S  |   10 ++++-----
  arch/arm64/kernel/ptrace.c |   48 ++++++++++++++++++++++++++++++++++----------
  2 files changed, 41 insertions(+), 17 deletions(-)

[...]

quoted

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 6a8928b..9993a8f 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c

@@ -1058,29 +1058,27 @@ 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)
+asmlinkage int syscall_trace_enter(struct pt_regs *regs)
  {
  	unsigned long saved_reg;

  	if (!test_thread_flag(TIF_SYSCALL_TRACE))
  		return regs->syscallno;

+	/*
+	 * A scrach register (ip(r12) on AArch32, x7 on AArch64) is
+	 * used to denote syscall entry/exit:
+	 *   0 -> entry
+	 */

You could add an enum, like we have on ARM (ptrace_syscall_dir) for the two
directions.

quoted

  	if (is_compat_task()) {
-		/* AArch32 uses ip (r12) for scratch */
  		saved_reg = regs->regs[12];
-		regs->regs[12] = dir;
+		regs->regs[12] = 0;
  	} 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;
+		regs->regs[7] = 0;

This code could also be refactored so we calculated the register number
once, then avoid the if (is_compact_task()) check all over the place.

Similarly on the exit path.

OK, I will implement tracehook_report_syscall() as in arm.

-Takahiro AKASHI

Will