[PATCH] x86_64: Handle programs that set TF in user space using popf while single stepping (e502cdd6) · Commits · 戴 / test

arch/x86_64/kernel/ptrace.c

+88 −0

Original line number	Diff line number	Diff line
		@@ -86,6 +86,84 @@ static inline long put_stack_long(struct task_struct *task, int offset,
		return 0;
		}

		#define LDT_SEGMENT 4

		unsigned long convert_rip_to_linear(struct task_struct child, struct pt_regs regs)
		{
		unsigned long addr, seg;

		addr = regs->rip;
		seg = regs->cs & 0xffff;

		/*
		* We'll assume that the code segments in the GDT
		* are all zero-based. That is largely true: the
		* TLS segments are used for data, and the PNPBIOS
		* and APM bios ones we just ignore here.
		*/
		if (seg & LDT_SEGMENT) {
		u32 *desc;
		unsigned long base;

		down(&child->mm->context.sem);
		desc = child->mm->context.ldt + (seg & ~7);
		base = (desc[0] >> 16) \| ((desc[1] & 0xff) << 16) \| (desc[1] & 0xff000000);

		/* 16-bit code segment? */
		if (!((desc[1] >> 22) & 1))
		addr &= 0xffff;
		addr += base;
		up(&child->mm->context.sem);
		}
		return addr;
		}

		static int is_at_popf(struct task_struct child, struct pt_regs regs)
		{
		int i, copied;
		unsigned char opcode[16];
		unsigned long addr = convert_rip_to_linear(child, regs);

		copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
		for (i = 0; i < copied; i++) {
		switch (opcode[i]) {
		/* popf */
		case 0x9d:
		return 1;

		/* CHECKME: 64 65 */

		/* opcode and address size prefixes */
		case 0x66: case 0x67:
		continue;
		/* irrelevant prefixes (segment overrides and repeats) */
		case 0x26: case 0x2e:
		case 0x36: case 0x3e:
		case 0x64: case 0x65:
		case 0xf0: case 0xf2: case 0xf3:
		continue;

		/* REX prefixes */
		case 0x40 ... 0x4f:
		continue;

		/* CHECKME: f0, f2, f3 */

		/*
		* pushf: NOTE! We should probably not let
		* the user see the TF bit being set. But
		* it's more pain than it's worth to avoid
		* it, and a debugger could emulate this
		* all in user space if it _really_ cares.
		*/
		case 0x9c:
		default:
		return 0;
		}
		}
		return 0;
		}

		static void set_singlestep(struct task_struct *child)
		{
		struct pt_regs *regs = get_child_regs(child);
		@@ -106,6 +184,16 @@ static void set_singlestep(struct task_struct *child)
		/* Set TF on the kernel stack.. */
		regs->eflags \|= TRAP_FLAG;

		/*
		* ..but if TF is changed by the instruction we will trace,
		* don't mark it as being "us" that set it, so that we
		* won't clear it by hand later.
		*
		* AK: this is not enough, LAHF and IRET can change TF in user space too.
		*/
		if (is_at_popf(child, regs))
		return;

		child->ptrace \|= PT_DTRACE;
		}

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