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SubjectRe: [PATCH v2 1/1] arm64: make a single hook to syscall_trace() for all syscall features
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@linaro.org>
> Acked-by: Richard Guy Briggs <rgb@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/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
> index 720e70b..0a8b2a9 100644
> --- a/arch/arm64/include/asm/thread_info.h
> +++ b/arch/arm64/include/asm/thread_info.h
> @@ -91,6 +91,9 @@ static inline struct thread_info *current_thread_info(void)
> /*
> * thread information flags:
> * TIF_SYSCALL_TRACE - syscall trace active
> + * TIF_SYSCALL_TRACEPOINT - syscall tracepoint for ftrace
> + * TIF_SYSCALL_AUDIT - syscall auditing
> + * TIF_SECOMP - syscall secure computing
> * TIF_SIGPENDING - signal pending
> * TIF_NEED_RESCHED - rescheduling necessary
> * TIF_NOTIFY_RESUME - callback before returning to user
> @@ -101,6 +104,9 @@ static inline struct thread_info *current_thread_info(void)
> #define TIF_NEED_RESCHED 1
> #define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
> #define TIF_SYSCALL_TRACE 8
> +#define TIF_SYSCALL_AUDIT 9
> +#define TIF_SYSCALL_TRACEPOINT 10
> +#define TIF_SECCOMP 11
> #define TIF_POLLING_NRFLAG 16
> #define TIF_MEMDIE 18 /* is terminating due to OOM killer */
> #define TIF_FREEZE 19
> @@ -112,10 +118,17 @@ static inline struct thread_info *current_thread_info(void)
> #define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
> #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
> #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
> +#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
> +#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
> +#define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
> +#define _TIF_SECCOMP (1 << TIF_SECCOMP)
> #define _TIF_32BIT (1 << TIF_32BIT)
>
> #define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
> _TIF_NOTIFY_RESUME)
>
> +#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
> + _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP)
> +
> #endif /* __KERNEL__ */
> #endif /* __ASM_THREAD_INFO_H */
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 0d7b789..6d613cd 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -630,8 +630,9 @@ el0_svc_naked: // compat entry point
> enable_irq
>
> get_thread_info tsk
> - ldr x16, [tsk, #TI_FLAGS] // check for syscall tracing
> - tbnz x16, #TIF_SYSCALL_TRACE, __sys_trace // are we tracing syscalls?
> + ldr x16, [tsk, #TI_FLAGS] // check for syscall hooks
> + tst x16, #_TIF_SYSCALL_WORK
> + b.ne __sys_trace
> adr lr, ret_fast_syscall // return address
> cmp scno, sc_nr // check upper syscall limit
> b.hs ni_sys

All looks fine up to here.

> 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?

Will


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