From a343c75d338aa2afaea4a2a8e40de9e67b6fb4a7 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 12 Oct 2009 14:11:09 -0700 Subject: [PATCH] x86: use kernel_stack_pointer() in dumpstack.c The way to obtain a kernel-mode stack pointer from a struct pt_regs in 32-bit mode is "subtle": the stack doesn't actually contain the stack pointer, but rather the location where it would have been marks the actual previous stack frame. For clarity, use kernel_stack_pointer() instead of coding this weirdness explicitly. Furthermore, user_mode() is only valid when the process is known to not run in V86 mode. Use the safer user_mode_vm() instead. Signed-off-by: H. Peter Anvin --- arch/x86/kernel/dumpstack.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 2d8a371..b8ce165 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -268,11 +268,12 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err) show_registers(regs); #ifdef CONFIG_X86_32 - sp = (unsigned long) (®s->sp); - savesegment(ss, ss); - if (user_mode(regs)) { + if (user_mode_vm(regs)) { sp = regs->sp; ss = regs->ss & 0xffff; + } else { + sp = kernel_stack_pointer(regs); + savesegment(ss, ss); } printk(KERN_EMERG "EIP: [<%08lx>] ", regs->ip); print_symbol("%s", regs->ip); -- 2.7.4