Re: [PATCH v2 1/1] arm64: make a single hook to syscall_trace() for all syscall features
On 02/26/2014 08:25 PM, Will Deacon wrote:
On Wed, Feb 26, 2014 at 02:00:19AM +0000, AKASHI Takahiro wrote:
> On 02/26/2014 12:00 AM, Will Deacon wrote:
>> On Tue, Feb 25, 2014 at 09:14:43AM +0000, AKASHI Takahiro wrote:
>>> Currently syscall_trace() is called only for ptrace.
>>> With additional TIF_xx flags defined, it is now called in all the cases
>>> of audit, ftrace and seccomp in addition to ptrace.
>>>
>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi(a)linaro.org>
>>> Acked-by: Richard Guy Briggs <rgb(a)redhat.com>
>>> ---
>>> arch/arm64/include/asm/thread_info.h | 13 ++++++++++
>>> arch/arm64/kernel/entry.S | 5 ++--
>>> arch/arm64/kernel/ptrace.c | 45
+++++++++++++++++-----------------
>>> 3 files changed, 38 insertions(+), 25 deletions(-)
>
> [...]
>
>>> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
>>> index 6a8928b..c70133e 100644
>>> --- a/arch/arm64/kernel/ptrace.c
>>> +++ b/arch/arm64/kernel/ptrace.c
>>> @@ -1062,31 +1062,30 @@ asmlinkage int syscall_trace(int dir, struct pt_regs
*regs)
>>> {
>>> 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;
>>> - }
>>> + if (test_thread_flag(TIF_SYSCALL_TRACE)) {
>>> + 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;
>>> + }
>>>
>>> - if (dir)
>>> - tracehook_report_syscall_exit(regs, 0);
>>> - else if (tracehook_report_syscall_entry(regs))
>>> - regs->syscallno = ~0UL;
>>> + if (dir)
>>> + 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;
>>> + if (is_compat_task())
>>> + regs->regs[12] = saved_reg;
>>> + else
>>> + regs->regs[7] = saved_reg;
>>> + }
>>
>> Aren't these changes (to ptrace.c) just a giant NOP?
>
> Umm, the purpose of this big "if" is to run the code only if
TIF_SYSCALL_TRACE is set,
> and to make it easy to add additional hooks, audit and ftrace, around
tracehook_report_*()
> later on.
The existing code already checks TIF_SYSCALL_TRACE. I'd rather you added
this new code when it's actually nedded (e.g. when adding audit on top).
* This patch is required only if you really merge my audit and/or ftrace patch.
* Putting these changes in audit patch would impose an extra (unnecessary) dependency on
ftrace patch.
* Putting them both in audit and ftrace patch would cause a conflict when applying both
patches.
Even so, since I don't bother you on this minor issue, I will follow your comment and
make changes on:
* arm64: make a single hook to syscall_trace() for all syscall features
* arm64: Add audit support
* arm64: Add ftrace support
-Takahiro AKASHI
Will