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[PATCH] x86_64: Handle programs that set TF in user space using popf while single stepping 

Ported from i386/Linus

Still won't handle other TF changing instructions like IRET or LAHF.

Prefix handling must be double checked...

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andi Kleen 2005-04-16 15:24:58 -07:00 committed by Linus Torvalds
parent be61bff789
commit e502cdd63d
1 changed files with 88 additions and 0 deletions
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88
arch/x86_64/kernel/ptrace.c
View File

@ -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;
}