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

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Message-ID: <200608051640_MC3-1-C736-44E2@compuserve.com>
Date:	Sat, 5 Aug 2006 16:36:46 -0400
From:	Chuck Ebbert <76306.1226@...puserve.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	Jan Beulich <jbeulich@...ell.com>, Andi Kleen <ak@...e.de>,
	Dave Jones <davej@...hat.com>,
	Jesper Juhl <jesper.juhl@...il.com>,
	Andrew Morton <akpm@...l.org>
Subject: [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@...puserve.com>

---

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);
 #else
-	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;
-- 
Chuck
-
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