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    Subject[PATCH v5 5/7] arm64: ftrace: Add system call tracepoint
    Date
    This patch allows system call entry or exit to be traced as ftrace events,
    ie. sys_enter_*/sys_exit_*, if CONFIG_FTRACE_SYSCALLS is enabled.
    Those events appear and can be controlled under
    ${sysfs}/tracing/events/syscalls/

    Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
    ---
    arch/arm64/Kconfig | 1 +
    arch/arm64/include/asm/syscall.h | 1 +
    arch/arm64/include/asm/unistd.h | 2 ++
    arch/arm64/kernel/ptrace.c | 52 ++++++++++++++++++++++----------------
    4 files changed, 34 insertions(+), 22 deletions(-)

    diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
    index 6954959..b1dcdb4 100644
    --- a/arch/arm64/Kconfig
    +++ b/arch/arm64/Kconfig
    @@ -43,6 +43,7 @@ config ARM64
    select HAVE_MEMBLOCK
    select HAVE_PATA_PLATFORM
    select HAVE_PERF_EVENTS
    + select HAVE_SYSCALL_TRACEPOINTS
    select IRQ_DOMAIN
    select MODULES_USE_ELF_RELA
    select NO_BOOTMEM
    diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
    index 70ba9d4..383771e 100644
    --- a/arch/arm64/include/asm/syscall.h
    +++ b/arch/arm64/include/asm/syscall.h
    @@ -18,6 +18,7 @@

    #include <linux/err.h>

    +extern const void *sys_call_table[];

    static inline int syscall_get_nr(struct task_struct *task,
    struct pt_regs *regs)
    diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
    index 82ce217..c335479 100644
    --- a/arch/arm64/include/asm/unistd.h
    +++ b/arch/arm64/include/asm/unistd.h
    @@ -28,3 +28,5 @@
    #endif
    #define __ARCH_WANT_SYS_CLONE
    #include <uapi/asm/unistd.h>
    +
    +#define NR_syscalls (__NR_syscalls)
    diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
    index 6a8928b..dc90f9f 100644
    --- a/arch/arm64/kernel/ptrace.c
    +++ b/arch/arm64/kernel/ptrace.c
    @@ -41,6 +41,9 @@
    #include <asm/traps.h>
    #include <asm/system_misc.h>

    +#define CREATE_TRACE_POINTS
    +#include <trace/events/syscalls.h>
    +
    /*
    * TODO: does not yet catch signals sent when the child dies.
    * in exit.c or in signal.c.
    @@ -1062,31 +1065,36 @@ 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 (dir && unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
    + trace_sys_exit(regs, regs_return_value(regs));
    +
    + 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 (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;
    + if (!dir && unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
    + trace_sys_enter(regs, regs->syscallno);

    return regs->syscallno;
    }
    --
    1.7.9.5


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