[patch] i386: fix one case of stuck dwarf2 unwinder

From: Chuck Ebbert
Date: Sat Aug 05 2006 - 16:48:47 EST

When the dwarf2 unwinder does its thing, sometimes it ends up in
kernel startup code in head.S. Changing arch_unw_user_mode() to
treat that case as if it were user mode is the easy fix.

Signed-off-by: Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx>


I copied people who posted traces where this happened. Can anyone
test if this fixes the problem?

--- 2.6.18-rc3-d4.orig/include/asm-i386/unwind.h
+++ 2.6.18-rc3-d4/include/asm-i386/unwind.h
@@ -71,13 +71,14 @@ extern asmlinkage int arch_unwind_init_r
void *arg),
void *arg);

+extern void stext(void); /* real start of kernel text */
static inline int arch_unw_user_mode(const struct unwind_frame_info *info)
#if 0 /* This can only work when selector register and EFLAGS saves/restores
are properly annotated (and tracked in UNW_REGISTER_INFO). */
return user_mode_vm(&info->regs);
- return info->regs.eip < PAGE_OFFSET
+ return info->regs.eip < (unsigned long)stext
|| (info->regs.eip >= __fix_to_virt(FIX_VDSO)
&& info->regs.eip < __fix_to_virt(FIX_VDSO) + PAGE_SIZE)
|| info->regs.esp < PAGE_OFFSET;
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