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authorJeremy Fitzhardinge <jeremy@goop.org>2006-12-22 01:11:21 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-22 08:55:51 -0800
commit8701ea957dd2a7c309e17c8dcde3a64b92d8aec0 (patch)
tree37019047caf24df91f617677f72b378d1e23d82e
parent7c7e9425f114a109b07be2c2c1c6c169e34e9bb3 (diff)
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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>
-rw-r--r--arch/i386/kernel/ptrace.c21
1 files changed, 10 insertions, 11 deletions
diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c
index f3f94ac5736..af8aabe8580 100644
--- a/arch/i386/kernel/ptrace.c
+++ b/arch/i386/kernel/ptrace.c
@@ -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;