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Commit 3f471126 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Russell King
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[ARM] 3262/4: allow ptraced syscalls to be overriden 



Patch from Nicolas Pitre

This is needed by strace to properly handle the tracing of some system
calls. It could be useful for other applications as well.

Based on an earlier patch from Daniel Jacobowitz.

Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarDaniel Jacobowitz <dan@debian.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 6c90c872

arch/arm/kernel/entry-common.S

+3 −0
Original line number Diff line number Diff line
@@ -214,11 +214,13 @@ ENTRY(vector_swi) 
	 * context switches, and waiting for our parent to respond.

	 */

__sys_trace:

	mov	r2, scno

	add	r1, sp, #S_OFF

	mov	r0, #0				@ trace entry [IP = 0]

	bl	syscall_trace



	adr	lr, __sys_trace_return		@ return address

	mov	scno, r0			@ syscall number (possibly new)

	add	r1, sp, #S_R0 + S_OFF		@ pointer to regs

	cmp	scno, #NR_syscalls		@ check upper syscall limit

	ldmccia	r1, {r0 - r3}			@ have to reload r0 - r3
@@ -227,6 +229,7 @@ __sys_trace: 


__sys_trace_return:

	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0

	mov	r2, scno

	mov	r1, sp

	mov	r0, #1				@ trace exit [IP = 1]

	bl	syscall_trace

arch/arm/kernel/ptrace.c

+12 −3
Original line number Diff line number Diff line
@@ -766,6 +766,11 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data) 
				       (unsigned long __user *) data);

			break;



		case PTRACE_SET_SYSCALL:

			ret = 0;

			child->ptrace_message = data;

			break;



		default:

			ret = ptrace_request(child, request, addr, data);

			break;
@@ -774,14 +779,14 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data) 
	return ret;

}



asmlinkage void syscall_trace(int why, struct pt_regs *regs)

asmlinkage int syscall_trace(int why, struct pt_regs *regs, int scno)

{

	unsigned long ip;



	if (!test_thread_flag(TIF_SYSCALL_TRACE))

		return;

		return scno;

	if (!(current->ptrace & PT_PTRACED))

		return;

		return scno;



	/*

	 * Save IP.  IP is used to denote syscall entry/exit:
@@ -790,6 +795,8 @@ asmlinkage void syscall_trace(int why, struct pt_regs *regs) 
	ip = regs->ARM_ip;

	regs->ARM_ip = why;



	current->ptrace_message = scno;



	/* the 0x80 provides a way for the tracing parent to distinguish

	   between a syscall stop and SIGTRAP delivery */

	ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
@@ -804,4 +811,6 @@ asmlinkage void syscall_trace(int why, struct pt_regs *regs) 
		current->exit_code = 0;

	}

	regs->ARM_ip = ip;



	return current->ptrace_message;

}

include/asm-arm/ptrace.h

+3 −0
Original line number Diff line number Diff line
@@ -23,6 +23,9 @@ 
#define PTRACE_OLDSETOPTIONS	21



#define PTRACE_GET_THREAD_AREA	22



#define PTRACE_SET_SYSCALL	23



/*

 * PSR bits

 */