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SubjectRe: [PATCH v4 2/3] arm64: split syscall_trace() into separate functions for enter/exit
On 03/14/2014 03:41 AM, Will Deacon wrote:
> 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@linaro.org>
>> ---
>> 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.

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

-Takahiro AKASHI


> Will
>


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