From 8701ea957dd2a7c309e17c8dcde3a64b92d8aec0 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Fri, 22 Dec 2006 01:11:21 -0800 Subject: [PATCH] [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 Cc: Frederik Deweerdt Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/ptrace.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c index f3f94ac5736a..af8aabe85800 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; -- 2.39.2