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[PATCH] ptrace: Fix EFL_OFFSET value according to i386 pda changes 

The PDA patches introduced a bug in ptrace: it reads eflags from the wrong
place on the target's stack, but writes it back to the correct place.  The
result is a corrupted eflags, which is most visible when it turns interrupts
off unexpectedly.

This patch fixes this by making the ptrace code a little less fragile.  It
changes [gs]et_stack_long to take a straightforward byte offset into struct
pt_regs, rather than requiring all callers to do a sizeof(struct pt_regs)
offset adjustment.  This means that the eflag's offset (EFL_OFFSET) on the
target stack can be simply computed with offsetof().

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Frederik Deweerdt <deweerdt@free.fr>
Cc: 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:
Jeremy Fitzhardinge 2006-12-22 01:11:21 -08:00 committed by Linus Torvalds
parent 7c7e9425f1
commit 8701ea957d
1 changed files with 10 additions and 11 deletions
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21
arch/i386/kernel/ptrace.c
View File

@ -45,7 +45,7 @@
/*
* Offset of eflags on child stack..
*/
#define EFL_OFFSET ((EFL-2)*4-sizeof(struct pt_regs))
#define EFL_OFFSET offsetof(struct pt_regs, eflags)
static inline struct pt_regs *get_child_regs(struct task_struct *task)
{
@ -54,24 +54,24 @@ static inline struct pt_regs *get_child_regs(struct task_struct *task)
}
/*
* this routine will get a word off of the processes privileged stack.
* the offset is how far from the base addr as stored in the TSS.
* this routine assumes that all the privileged stacks are in our
* This routine will get a word off of the processes privileged stack.
* the offset is bytes into the pt_regs structure on the stack.
* This routine assumes that all the privileged stacks are in our
* data space.
*/
static inline int get_stack_long(struct task_struct *task, int offset)
{
unsigned char *stack;
stack = (unsigned char *)task->thread.esp0;
stack = (unsigned char *)task->thread.esp0 - sizeof(struct pt_regs);
stack += offset;
return (*((int *)stack));
}
/*
* this routine will put a word on the processes privileged stack.
* the offset is how far from the base addr as stored in the TSS.
* this routine assumes that all the privileged stacks are in our
* This routine will put a word on the processes privileged stack.
* the offset is bytes into the pt_regs structure on the stack.
* This routine assumes that all the privileged stacks are in our
* data space.
*/
static inline int put_stack_long(struct task_struct *task, int offset,
@ -79,7 +79,7 @@ static inline int put_stack_long(struct task_struct *task, int offset,
{
unsigned char * stack;
stack = (unsigned char *) task->thread.esp0;
stack = (unsigned char *)task->thread.esp0 - sizeof(struct pt_regs);
stack += offset;
*(unsigned long *) stack = data;
return 0;
@ -114,7 +114,7 @@ static int putreg(struct task_struct *child,
}
if (regno > ES*4)
regno -= 1*4;
put_stack_long(child, regno - sizeof(struct pt_regs), value);
put_stack_long(child, regno, value);
return 0;
}
@ -137,7 +137,6 @@ static unsigned long getreg(struct task_struct *child,
default:
if (regno > ES*4)
regno -= 1*4;
regno = regno - sizeof(struct pt_regs);
retval &= get_stack_long(child, regno);
}
return retval;