Commit ea8e61b7 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

x86, ptrace: Fix block-step 



Implement ptrace-block-step using TIF_BLOCKSTEP which will set
DEBUGCTLMSR_BTF when set for a task while preserving any other
DEBUGCTLMSR bits.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100325135414.017536066@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent faa4602e

arch/x86/include/asm/thread_info.h

+3 −1
Original line number Diff line number Diff line
@@ -92,6 +92,7 @@ struct thread_info { 
#define TIF_IO_BITMAP		22	/* uses I/O bitmap */

#define TIF_FREEZE		23	/* is freezing for suspend */

#define TIF_FORCED_TF		24	/* true if TF in eflags artificially */

#define TIF_BLOCKSTEP		25	/* set when we want DEBUGCTLMSR_BTF */

#define TIF_LAZY_MMU_UPDATES	27	/* task is updating the mmu lazily */

#define TIF_SYSCALL_TRACEPOINT	28	/* syscall tracepoint instrumentation */
@@ -113,6 +114,7 @@ struct thread_info { 
#define _TIF_IO_BITMAP		(1 << TIF_IO_BITMAP)

#define _TIF_FREEZE		(1 << TIF_FREEZE)

#define _TIF_FORCED_TF		(1 << TIF_FORCED_TF)

#define _TIF_BLOCKSTEP		(1 << TIF_BLOCKSTEP)

#define _TIF_LAZY_MMU_UPDATES	(1 << TIF_LAZY_MMU_UPDATES)

#define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
@@ -143,7 +145,7 @@ struct thread_info { 


/* flags to check in __switch_to() */

#define _TIF_WORK_CTXSW							\

	(_TIF_IO_BITMAP|_TIF_NOTSC)

	(_TIF_IO_BITMAP|_TIF_NOTSC|_TIF_BLOCKSTEP)



#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)

#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW|_TIF_DEBUG)

arch/x86/kernel/kprobes.c

+12 −2
Original line number Diff line number Diff line
@@ -422,12 +422,22 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, 


static void __kprobes clear_btf(void)

{

	/* XXX */

	if (test_thread_flag(TIF_BLOCKSTEP)) {

		unsigned long debugctl = get_debugctlmsr();



		debugctl &= ~DEBUGCTLMSR_BTF;

		update_debugctlmsr(debugctl);

	}

}



static void __kprobes restore_btf(void)

{

	/* XXX */

	if (test_thread_flag(TIF_BLOCKSTEP)) {

		unsigned long debugctl = get_debugctlmsr();



		debugctl |= DEBUGCTLMSR_BTF;

		update_debugctlmsr(debugctl);

	}

}



void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,

arch/x86/kernel/process.c

+11 −0
Original line number Diff line number Diff line
@@ -195,6 +195,17 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, 
	prev = &prev_p->thread;

	next = &next_p->thread;



	if (test_tsk_thread_flag(prev_p, TIF_BLOCKSTEP) ^

	    test_tsk_thread_flag(next_p, TIF_BLOCKSTEP)) {

		unsigned long debugctl = get_debugctlmsr();



		debugctl &= ~DEBUGCTLMSR_BTF;

		if (test_tsk_thread_flag(next_p, TIF_BLOCKSTEP))

			debugctl |= DEBUGCTLMSR_BTF;



		update_debugctlmsr(debugctl);

	}



	if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^

	    test_tsk_thread_flag(next_p, TIF_NOTSC)) {

		/* prev and next are different */

arch/x86/kernel/step.c

+20 −4
Original line number Diff line number Diff line
@@ -169,9 +169,19 @@ static void enable_step(struct task_struct *child, bool block) 
	 * So noone should try to use debugger block stepping in a program

	 * that uses user-mode single stepping itself.

	 */

	if (!enable_single_step(child))

		return;

	/* XXX */

	if (enable_single_step(child) && block) {

		unsigned long debugctl = get_debugctlmsr();



		debugctl |= DEBUGCTLMSR_BTF;

		update_debugctlmsr(debugctl);

		set_tsk_thread_flag(child, TIF_BLOCKSTEP);

	} else if (test_tsk_thread_flag(child, TIF_BLOCKSTEP)) {

		unsigned long debugctl = get_debugctlmsr();



		debugctl &= ~DEBUGCTLMSR_BTF;

		update_debugctlmsr(debugctl);

		clear_tsk_thread_flag(child, TIF_BLOCKSTEP);

	}

}



void user_enable_single_step(struct task_struct *child)
@@ -189,7 +199,13 @@ void user_disable_single_step(struct task_struct *child) 
	/*

	 * Make sure block stepping (BTF) is disabled.

	 */

	/* XXX */

	if (test_tsk_thread_flag(child, TIF_BLOCKSTEP)) {

		unsigned long debugctl = get_debugctlmsr();



		debugctl &= ~DEBUGCTLMSR_BTF;

		update_debugctlmsr(debugctl);

		clear_tsk_thread_flag(child, TIF_BLOCKSTEP);

	}



	/* Always clear TIF_SINGLESTEP... */

	clear_tsk_thread_flag(child, TIF_SINGLESTEP);

arch/x86/kernel/traps.c

+5 −0
Original line number Diff line number Diff line
@@ -544,6 +544,11 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code) 
	/* DR6 may or may not be cleared by the CPU */

	set_debugreg(0, 6);



	/*

	 * The processor cleared BTF, so don't mark that we need it set.

	 */

	clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP);



	/* Store the virtualized DR6 value */

	tsk->thread.debugreg6 = dr6;

arch/x86/include/asm/processor.h

+2 −2

File changed.

Contains only whitespace changes.

CRA Git | Maintained and supported by SUSTech CRA and CCSE