diff mbox

[v5,2/4] arm64: split syscall_trace() into separate functions for enter/exit

Message ID 1394861948-28712-3-git-send-email-takahiro.akashi@linaro.org
State New
Headers show

Commit Message

AKASHI Takahiro March 15, 2014, 5:39 a.m. UTC 
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 | 50 +++++++++++++++++++++++++++-------------------
 2 files changed, 33 insertions(+), 27 deletions(-)

Comments

Richard Guy Briggs March 16, 2014, 7:46 p.m. UTC | #1 
On 14/03/15, 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>

Minor variable mis-spelling of "scratch" noted below, but other than
that:

Acked-by: Richard Guy Briggs <rgb@redhat.com>

> ---
>  arch/arm64/kernel/entry.S  | 10 ++++------
>  arch/arm64/kernel/ptrace.c | 50 +++++++++++++++++++++++++++-------------------
>  2 files changed, 33 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index f9f2cae..00d6eb9 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -649,9 +649,8 @@ ENDPROC(el0_svc)
>  	 * switches, and waiting for our parent to respond.
>  	 */
>  __sys_trace:
> -	mov	x1, sp
> -	mov	w0, #0				// trace entry
> -	bl	syscall_trace
> +	mov	x0, sp
> +	bl	syscall_trace_enter
>  	adr	lr, __sys_trace_return		// return address
>  	uxtw	scno, w0			// syscall number (possibly new)
>  	mov	x1, sp				// pointer to regs
> @@ -666,9 +665,8 @@ __sys_trace:
>  
>  __sys_trace_return:
>  	str	x0, [sp]			// save returned x0
> -	mov	x1, sp
> -	mov	w0, #1				// trace exit
> -	bl	syscall_trace
> +	mov	x0, sp
> +	bl	syscall_trace_exit
>  	b	ret_to_user
>  
>  /*
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 6a8928b..f606276 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -1058,35 +1058,43 @@ 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)
> +enum ptrace_syscall_dir {
> +	PTRACE_SYSCALL_ENTER = 0,
> +	PTRACE_SYSCALL_EXIT,
> +};
> +
> +static void tracehook_report_syscall(struct pt_regs *regs,
> +				     enum ptrace_syscall_dir dir)
>  {
> +	int scrach;

"scratch"

>  	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;
> -	}
> +	/*
> +	 * A scrach register (ip(r12) on AArch32, x7 on AArch64) is
> +	 * used to denote syscall entry/exit:
> +	 */
> +	scrach = (is_compat_task() ? 12 : 7);
> +	saved_reg = regs->regs[scrach];
> +	regs->regs[scrach] = dir;
>  
> -	if (dir)
> +	if (dir == PTRACE_SYSCALL_EXIT)
>  		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;
> +	regs->regs[scrach] = saved_reg;
> +}
> +
> +asmlinkage int syscall_trace_enter(struct pt_regs *regs)
> +{
> +	if (test_thread_flag(TIF_SYSCALL_TRACE))
> +		tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
>  
>  	return regs->syscallno;
>  }
> +
> +asmlinkage void syscall_trace_exit(struct pt_regs *regs)
> +{
> +	if (test_thread_flag(TIF_SYSCALL_TRACE))
> +		tracehook_report_syscall(regs, PTRACE_SYSCALL_EXIT);
> +}
> -- 
> 1.8.3.2

- RGB

--
Richard Guy Briggs <rbriggs@redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
diff mbox

Patch

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f9f2cae..00d6eb9 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -649,9 +649,8 @@  ENDPROC(el0_svc)
 	 * switches, and waiting for our parent to respond.
 	 */
 __sys_trace:
-	mov	x1, sp
-	mov	w0, #0				// trace entry
-	bl	syscall_trace
+	mov	x0, sp
+	bl	syscall_trace_enter
 	adr	lr, __sys_trace_return		// return address
 	uxtw	scno, w0			// syscall number (possibly new)
 	mov	x1, sp				// pointer to regs
@@ -666,9 +665,8 @@  __sys_trace:
 
 __sys_trace_return:
 	str	x0, [sp]			// save returned x0
-	mov	x1, sp
-	mov	w0, #1				// trace exit
-	bl	syscall_trace
+	mov	x0, sp
+	bl	syscall_trace_exit
 	b	ret_to_user
 
 /*
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 6a8928b..f606276 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1058,35 +1058,43 @@  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)
+enum ptrace_syscall_dir {
+	PTRACE_SYSCALL_ENTER = 0,
+	PTRACE_SYSCALL_EXIT,
+};
+
+static void tracehook_report_syscall(struct pt_regs *regs,
+				     enum ptrace_syscall_dir dir)
 {
+	int scrach;
 	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;
-	}
+	/*
+	 * A scrach register (ip(r12) on AArch32, x7 on AArch64) is
+	 * used to denote syscall entry/exit:
+	 */
+	scrach = (is_compat_task() ? 12 : 7);
+	saved_reg = regs->regs[scrach];
+	regs->regs[scrach] = dir;
 
-	if (dir)
+	if (dir == PTRACE_SYSCALL_EXIT)
 		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;
+	regs->regs[scrach] = saved_reg;
+}
+
+asmlinkage int syscall_trace_enter(struct pt_regs *regs)
+{
+	if (test_thread_flag(TIF_SYSCALL_TRACE))
+		tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
 
 	return regs->syscallno;
 }
+
+asmlinkage void syscall_trace_exit(struct pt_regs *regs)
+{
+	if (test_thread_flag(TIF_SYSCALL_TRACE))
+		tracehook_report_syscall(regs, PTRACE_SYSCALL_EXIT);
+}