Re: [PATCH v4 2/3] arm64: split syscall_trace() into separate functions for enter/exit

On Thu, Mar 13, 2014 at 10:11:30AM +0000, AKASHI Takahiro wrote: > 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 <takahiro.akashi(a)linaro.org&gt; > --- > arch/arm64/kernel/entry.S | 10 ++++----- > arch/arm64/kernel/ptrace.c | 48 ++++++++++++++++++++++++++++++++++---------- > 2 files changed, 41 insertions(+), 17 deletions(-) [...] > 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. > 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.

Will