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

From: Chuck Ebbert
Date: Sun Aug 06 2006 - 01:04:12 EST

In-Reply-To: <200608060430.06935.ak@xxxxxxx>

On Sun, 6 Aug 2006 04:30:06 +0200, Andi Kleen wrote:
> > +extern void stext(void); /* real start of kernel text */
> Can't you use _stext[] from asm/sections.h?


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

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>

--- 2.6.18-rc3-32.orig/include/asm-i386/unwind.h
+++ 2.6.18-rc3-32/include/asm-i386/unwind.h
@@ -13,6 +13,7 @@
#include <asm/fixmap.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>
+#include <asm/sections.h>

struct unwind_frame_info
@@ -71,13 +72,14 @@ extern asmlinkage int arch_unwind_init_r
void *arg),
void *arg);

+/* check if unwind has reached either user mode or kernel startup code */
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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