linux-kernel - [patch] i386: entry.s::error_code is not safe for kprobes

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Date:	Thu, 3 Aug 2006 06:20:19 -0400
From:	Chuck Ebbert <76306.1226@...puserve.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	Prasanna S Panchamukhi <prasanna@...ibm.com>,
	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...l.org>,
	Linus Torvalds <torvalds@...l.org>
Subject: [patch] i386: entry.s::error_code is not safe for kprobes

Because code marked unsafe for kprobes jumps directly to
entry.S::error_code, that must be marked unsafe as well.
The easiest way to do that is to move the page fault entry
point to just before error_code and let it inherit the same
section.

Also moved all the ".previous" asm directives for kprobes
sections to column 1 and removed ".text" from them.

Signed-off-by: Chuck Ebbert <76306.1226@...puserve.com>

---

x86_64 also has this problem but I wasn't sure whether to move
error_entry into .kprobes.text or convert offendors to the
"paranoid" infrastructure.

 arch/i386/kernel/entry.S |   25 +++++++++++++------------
 1 files changed, 13 insertions(+), 12 deletions(-)

--- 2.6.18-rc3-nb.orig/arch/i386/kernel/entry.S
+++ 2.6.18-rc3-nb/arch/i386/kernel/entry.S
@@ -587,11 +587,9 @@ ENTRY(name)				\
 /* The include is where all of the SMP etc. interrupts come from */
 #include "entry_arch.h"
 
-ENTRY(divide_error)
-	RING0_INT_FRAME
-	pushl $0			# no error code
-	CFI_ADJUST_CFA_OFFSET 4
-	pushl $do_divide_error
+KPROBE_ENTRY(page_fault)
+	RING0_EC_FRAME
+	pushl $do_page_fault
 	CFI_ADJUST_CFA_OFFSET 4
 	ALIGN
 error_code:
@@ -641,6 +639,7 @@ error_code:
 	call *%edi
 	jmp ret_from_exception
 	CFI_ENDPROC
+.previous
 
 ENTRY(coprocessor_error)
 	RING0_INT_FRAME
@@ -716,7 +715,8 @@ debug_stack_correct:
 	call do_debug
 	jmp ret_from_exception
 	CFI_ENDPROC
-	.previous .text
+.previous
+
 /*
  * NMI is doubly nasty. It can happen _while_ we're handling
  * a debug fault, and the debug fault hasn't yet been able to
@@ -812,7 +812,7 @@ KPROBE_ENTRY(int3)
 	call do_int3
 	jmp ret_from_exception
 	CFI_ENDPROC
-	.previous .text
+.previous
 
 ENTRY(overflow)
 	RING0_INT_FRAME
@@ -877,7 +877,7 @@ KPROBE_ENTRY(general_protection)
 	CFI_ADJUST_CFA_OFFSET 4
 	jmp error_code
 	CFI_ENDPROC
-	.previous .text
+.previous
 
 ENTRY(alignment_check)
 	RING0_EC_FRAME
@@ -886,13 +886,14 @@ ENTRY(alignment_check)
 	jmp error_code
 	CFI_ENDPROC
 
-KPROBE_ENTRY(page_fault)
-	RING0_EC_FRAME
-	pushl $do_page_fault
+ENTRY(divide_error)
+	RING0_INT_FRAME
+	pushl $0			# no error code
+	CFI_ADJUST_CFA_OFFSET 4
+	pushl $do_divide_error
 	CFI_ADJUST_CFA_OFFSET 4
 	jmp error_code
 	CFI_ENDPROC
-	.previous .text
 
 #ifdef CONFIG_X86_MCE
 ENTRY(machine_check)
-- 
Chuck
-
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