linux-kernel - Re: [PATCH v3 5/6] arm64: ftrace: Add system call tracepoint

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Message-ID: <20140217192936.GH26590@mudshark.cambridge.arm.com>
Date:	Mon, 17 Feb 2014 19:29:36 +0000
From:	Will Deacon <will.deacon@....com>
To:	AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:	"rostedt@...dmis.org" <rostedt@...dmis.org>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"gkulkarni@...iumnetworks.com" <gkulkarni@...iumnetworks.com>,
	"tim.bird@...ymobile.com" <tim.bird@...ymobile.com>,
	"arndb@...db.de" <arndb@...db.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"patches@...aro.org" <patches@...aro.org>
Subject: Re: [PATCH v3 5/6] arm64: ftrace: Add system call tracepoint

On Fri, Feb 07, 2014 at 10:18:55AM +0000, AKASHI Takahiro wrote:
> 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@...aro.org>
> ---
>  arch/arm64/Kconfig               |    1 +
>  arch/arm64/include/asm/syscall.h |    1 +
>  arch/arm64/include/asm/unistd.h  |    2 ++
>  arch/arm64/kernel/ptrace.c       |    5 +++++
>  4 files changed, 9 insertions(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 43fce76..9bdaf5c 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -42,6 +42,7 @@ config ARM64
>  	select HAVE_HW_BREAKPOINT if PERF_EVENTS
>  	select HAVE_MEMBLOCK
>  	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 64ce39f..f4c3c4e 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.
> @@ -1076,10 +1079,12 @@ asmlinkage int syscall_trace(int dir, struct pt_regs *regs)
>  	}
>  
>  	if (dir) {
> +		trace_sys_exit(regs, regs->syscallno);
>  		tracehook_report_syscall_exit(regs, 0);
>  	} else {
>  		if (tracehook_report_syscall_entry(regs))
>  			regs->syscallno = ~0UL;
> +		trace_sys_enter(regs, regs->syscallno);

Shouldn't these calls be guarded by a TIF_SYSCALL_TRACEPOINT check?

Will
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