Commit 3157858f authored by AKASHI Takahiro's avatar AKASHI Takahiro Committed by Catalin Marinas
Browse files

arm64: split syscall_trace() into separate functions for enter/exit 



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.

Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 449f81a4

arch/arm64/kernel/entry.S

+4 −6
Original line number Diff line number Diff line
@@ -628,9 +628,8 @@ 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
@@ -645,9 +644,8 @@ __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



/*

arch/arm64/kernel/ptrace.c

+29 −21
Original line number Diff line number Diff line
@@ -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 regno;

	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

	 * A scratch register (ip(r12) on AArch32, x7 on AArch64) is

	 * used to denote syscall entry/exit:

	 */

		saved_reg = regs->regs[7];

		regs->regs[7] = dir;

	}

	regno = (is_compat_task() ? 12 : 7);

	saved_reg = regs->regs[regno];

	regs->regs[regno] = 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[regno] = 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);

}

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