Commit e1f28773 authored by Roland McGrath's avatar Roland McGrath Committed by Ingo Molnar
Browse files

x86 single_step: TIF_FORCED_TF 



This changes the single-step support to use a new thread_info flag
TIF_FORCED_TF instead of the PT_DTRACE flag in task_struct.ptrace.
This keeps arch implementation uses out of this non-arch field.

This changes the ptrace access to eflags to mask TF and maintain
the TIF_FORCED_TF flag directly if userland sets TF, instead of
relying on ptrace_signal_deliver.  The 64-bit and 32-bit kernels
are harmonized on this same behavior.  The ptrace_signal_deliver
approach works now, but this change makes the low-level register
access code reliable when called from different contexts than a
ptrace stop, which will be possible in the future.

The 64-bit do_debug exception handler is also changed not to clear TF
from user-mode registers.  This matches the 32-bit kernel's behavior.

Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 7122ec81

arch/x86/ia32/ptrace32.c

+18 −2
Original line number Diff line number Diff line
@@ -89,6 +89,15 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 val) 
		__u64 *flags = &stack[offsetof(struct pt_regs, eflags)/8];



		val &= FLAG_MASK;

		/*

		 * If the user value contains TF, mark that

		 * it was not "us" (the debugger) that set it.

		 * If not, make sure it stays set if we had.

		 */

		if (val & X86_EFLAGS_TF)

			clear_tsk_thread_flag(child, TIF_FORCED_TF);

		else if (test_tsk_thread_flag(child, TIF_FORCED_TF))

			val |= X86_EFLAGS_TF;

		*flags = val | (*flags & ~FLAG_MASK);

		break;

	}
@@ -179,9 +188,17 @@ static int getreg32(struct task_struct *child, unsigned regno, u32 *val) 
	R32(eax, rax);

	R32(orig_eax, orig_rax);

	R32(eip, rip);

	R32(eflags, eflags);

	R32(esp, rsp);



	case offsetof(struct user32, regs.eflags):

		/*

		 * If the debugger set TF, hide it from the readout.

		 */

		*val = stack[offsetof(struct pt_regs, eflags)/8];

		if (test_tsk_thread_flag(child, TIF_FORCED_TF))

			*val &= ~X86_EFLAGS_TF;

		break;



	case offsetof(struct user32, u_debugreg[0]):

		*val = child->thread.debugreg0;

		break;
@@ -425,4 +442,3 @@ asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data) 
	put_task_struct(child);

	return ret;

}

arch/x86/kernel/process_32.c

+0 −3
Original line number Diff line number Diff line
@@ -817,9 +817,6 @@ asmlinkage int sys_execve(struct pt_regs regs) 
			(char __user * __user *) regs.edx,

			&regs);

	if (error == 0) {

		task_lock(current);

		current->ptrace &= ~PT_DTRACE;

		task_unlock(current);

		/* Make sure we don't return using sysenter.. */

		set_thread_flag(TIF_IRET);

	}

arch/x86/kernel/process_64.c

+0 −5
Original line number Diff line number Diff line
@@ -709,11 +709,6 @@ long sys_execve(char __user *name, char __user * __user *argv, 
	if (IS_ERR(filename)) 

		return error;

	error = do_execve(filename, argv, envp, &regs); 

	if (error == 0) {

		task_lock(current);

		current->ptrace &= ~PT_DTRACE;

		task_unlock(current);

	}

	putname(filename);

	return error;

}

arch/x86/kernel/ptrace_32.c

+17 −0
Original line number Diff line number Diff line
@@ -104,6 +104,15 @@ static int putreg(struct task_struct *child, 
			break;

		case EFL:

			value &= FLAG_MASK;

			/*

			 * If the user value contains TF, mark that

			 * it was not "us" (the debugger) that set it.

			 * If not, make sure it stays set if we had.

			 */

			if (value & X86_EFLAGS_TF)

				clear_tsk_thread_flag(child, TIF_FORCED_TF);

			else if (test_tsk_thread_flag(child, TIF_FORCED_TF))

				value |= X86_EFLAGS_TF;

			value |= get_stack_long(child, EFL_OFFSET) & ~FLAG_MASK;

			break;

	}
@@ -119,6 +128,14 @@ static unsigned long getreg(struct task_struct *child, 
	unsigned long retval = ~0UL;



	switch (regno >> 2) {

		case EFL:

			/*

			 * If the debugger set TF, hide it from the readout.

			 */

			retval = get_stack_long(child, EFL_OFFSET);

			if (test_tsk_thread_flag(child, TIF_FORCED_TF))

				retval &= ~X86_EFLAGS_TF;

			break;

		case GS:

			retval = child->thread.gs;

			break;

arch/x86/kernel/ptrace_64.c

+20 −0
Original line number Diff line number Diff line
@@ -143,6 +143,15 @@ static int putreg(struct task_struct *child, 
			return 0;

		case offsetof(struct user_regs_struct, eflags):

			value &= FLAG_MASK;

			/*

			 * If the user value contains TF, mark that

			 * it was not "us" (the debugger) that set it.

			 * If not, make sure it stays set if we had.

			 */

			if (value & X86_EFLAGS_TF)

				clear_tsk_thread_flag(child, TIF_FORCED_TF);

			else if (test_tsk_thread_flag(child, TIF_FORCED_TF))

				value |= X86_EFLAGS_TF;

			tmp = get_stack_long(child, EFL_OFFSET); 

			tmp &= ~FLAG_MASK; 

			value |= tmp;
@@ -189,6 +198,17 @@ static unsigned long getreg(struct task_struct *child, unsigned long regno) 
			if (child->thread.gsindex != GS_TLS_SEL)

				return 0;

			return get_desc_base(&child->thread.tls_array[GS_TLS]);

		case offsetof(struct user_regs_struct, eflags):

			/*

			 * If the debugger set TF, hide it from the readout.

			 */

			regno = regno - sizeof(struct pt_regs);

			val = get_stack_long(child, regno);

			if (test_tsk_thread_flag(child, TIF_IA32))

				val &= 0xffffffff;

			if (test_tsk_thread_flag(child, TIF_FORCED_TF))

				val &= ~X86_EFLAGS_TF;

			return val;

		default:

			regno = regno - sizeof(struct pt_regs);

			val = get_stack_long(child, regno);

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