From 36ad4885c47c2187822f2783fb46fde2d36bf200 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 31 Aug 2007 20:18:51 -0700 Subject: [PATCH] x86: be even more careful about checking the stack frame on dumping lguest didn't initialize the kernel stack the way a real i386 kernel does, and ended up triggering a corner-case in the stack frame checking that doesn't happen on naive i386, and that the stack dumping didn't handle quite right. This makes the frame handling more correct, and tries to clarify the code at the same time so that it's a bit more obvious what is going on. Thanks to Rusty Russell for debugging the lguest failure- Cc: Rusty Russell Signed-off-by: Linus Torvalds --- arch/i386/kernel/traps.c | 33 +++++++++++++++++++++------------ 1 file changed, 21 insertions(+), 12 deletions(-) diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c index cfffe3dd9e..47b0bef335 100644 --- a/arch/i386/kernel/traps.c +++ b/arch/i386/kernel/traps.c @@ -100,36 +100,45 @@ asmlinkage void machine_check(void); int kstack_depth_to_print = 24; static unsigned int code_bytes = 64; -static inline int valid_stack_ptr(struct thread_info *tinfo, void *p) +static inline int valid_stack_ptr(struct thread_info *tinfo, void *p, unsigned size) { return p > (void *)tinfo && - p < (void *)tinfo + THREAD_SIZE - 3; + p <= (void *)tinfo + THREAD_SIZE - size; } +/* The form of the top of the frame on the stack */ +struct stack_frame { + struct stack_frame *next_frame; + unsigned long return_address; +}; + static inline unsigned long print_context_stack(struct thread_info *tinfo, unsigned long *stack, unsigned long ebp, struct stacktrace_ops *ops, void *data) { - unsigned long addr; - #ifdef CONFIG_FRAME_POINTER - while (valid_stack_ptr(tinfo, (void *)ebp)) { - unsigned long new_ebp; - addr = *(unsigned long *)(ebp + 4); + struct stack_frame *frame = (struct stack_frame *)ebp; + while (valid_stack_ptr(tinfo, frame, sizeof(*frame))) { + struct stack_frame *next; + unsigned long addr; + + addr = frame->return_address; ops->address(data, addr); /* * break out of recursive entries (such as * end_of_stack_stop_unwind_function). Also, * we can never allow a frame pointer to * move downwards! - */ - new_ebp = *(unsigned long *)ebp; - if (new_ebp <= ebp) + */ + next = frame->next_frame; + if (next <= frame) break; - ebp = new_ebp; + frame = next; } #else - while (valid_stack_ptr(tinfo, stack)) { + while (valid_stack_ptr(tinfo, stack, sizeof(*stack))) { + unsigned long addr; + addr = *stack++; if (__kernel_text_address(addr)) ops->address(data, addr); -- 2.39.5