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Commit d28c4393 authored by Prasanna S.P's avatar Prasanna S.P Committed by Andi Kleen
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[PATCH] x86: error_code is not safe for kprobes 



This patch moves the entry.S:error_entry to .kprobes.text section,
since code marked unsafe for kprobes jumps directly to entry.S::error_entry,
that must be marked unsafe as well.
This patch also moves all the ".previous.text" asm directives to ".previous"
for kprobes section.

AK: Following a similar i386 patch from Chuck Ebbert
AK: Also merged Jeremy's fix in.

+From: Jeremy Fitzhardinge <jeremy@goop.org>

KPROBE_ENTRY does a .section .kprobes.text, and expects its users to
do a .previous at the end of the function.

Unfortunately, if any code within the function switches sections, for
example .fixup, then the .previous ends up putting all subsequent code
into .fixup.  Worse, any subsequent .fixup code gets intermingled with
the code its supposed to be fixing (which is also in .fixup).  It's
surprising this didn't cause more havok.

The fix is to use .pushsection/.popsection, so this stuff nests
properly.  A further cleanup would be to get rid of all
.section/.previous pairs, since they're inherently fragile.

+From: Chuck Ebbert <76306.1226@compuserve.com>

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: default avatarChuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent 3ca113ea

arch/i386/kernel/entry.S

+13 −12
Original line number Diff line number Diff line
@@ -591,11 +591,9 @@ 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:
@@ -645,6 +643,7 @@ error_code: 
	call *%edi

	jmp ret_from_exception

	CFI_ENDPROC

KPROBE_END(page_fault)



ENTRY(coprocessor_error)

	RING0_INT_FRAME
@@ -720,7 +719,8 @@ debug_stack_correct: 
	call do_debug

	jmp ret_from_exception

	CFI_ENDPROC

	.previous .text

KPROBE_END(debug)



/*

 * NMI is doubly nasty. It can happen _while_ we're handling

 * a debug fault, and the debug fault hasn't yet been able to
@@ -816,7 +816,7 @@ KPROBE_ENTRY(int3) 
	call do_int3

	jmp ret_from_exception

	CFI_ENDPROC

	.previous .text

KPROBE_END(int3)



ENTRY(overflow)

	RING0_INT_FRAME
@@ -881,7 +881,7 @@ KPROBE_ENTRY(general_protection) 
	CFI_ADJUST_CFA_OFFSET 4

	jmp error_code

	CFI_ENDPROC

	.previous .text

KPROBE_END(general_protection)



ENTRY(alignment_check)

	RING0_EC_FRAME
@@ -890,13 +890,14 @@ 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)

arch/x86_64/kernel/entry.S

+7 −12
Original line number Diff line number Diff line
@@ -819,7 +819,7 @@ paranoid_schedule\trace: 
 * Exception entry point. This expects an error code/orig_rax on the stack

 * and the exception handler in %rax.	

 */ 		  				

ENTRY(error_entry)

KPROBE_ENTRY(error_entry)

	_frame RDI

	/* rdi slot contains rax, oldrax contains error code */

	cld
@@ -903,7 +903,7 @@ error_kernelspace: 
	cmpq $gs_change,RIP(%rsp)

        je   error_swapgs

	jmp  error_sti

END(error_entry)

KPROBE_END(error_entry)

	

       /* Reload gs selector with exception handling */

       /* edi:  new selector */
@@ -1025,8 +1025,7 @@ ENDPROC(execve) 


KPROBE_ENTRY(page_fault)

	errorentry do_page_fault

END(page_fault)

	.previous .text

KPROBE_END(page_fault)



ENTRY(coprocessor_error)

	zeroentry do_coprocessor_error
@@ -1047,8 +1046,7 @@ KPROBE_ENTRY(debug) 
	CFI_ADJUST_CFA_OFFSET 8		

	paranoidentry do_debug, DEBUG_STACK

	paranoidexit

END(debug)

	.previous .text

KPROBE_END(debug)



	/* runs on exception stack */	

KPROBE_ENTRY(nmi)
@@ -1062,8 +1060,7 @@ KPROBE_ENTRY(nmi) 
	jmp paranoid_exit1

 	CFI_ENDPROC

#endif

END(nmi)

	.previous .text

KPROBE_END(nmi)



KPROBE_ENTRY(int3)

 	INTR_FRAME
@@ -1072,8 +1069,7 @@ KPROBE_ENTRY(int3) 
 	paranoidentry do_int3, DEBUG_STACK

 	jmp paranoid_exit1

 	CFI_ENDPROC

END(int3)

	.previous .text

KPROBE_END(int3)



ENTRY(overflow)

	zeroentry do_overflow
@@ -1121,8 +1117,7 @@ END(stack_segment) 


KPROBE_ENTRY(general_protection)

	errorentry do_general_protection

END(general_protection)

	.previous .text

KPROBE_END(general_protection)



ENTRY(alignment_check)

	errorentry do_alignment_check

include/linux/linkage.h

+5 −1
Original line number Diff line number Diff line
@@ -35,9 +35,13 @@ 
#endif



#define KPROBE_ENTRY(name) \

  .section .kprobes.text, "ax"; \

  .pushsection .kprobes.text, "ax"; \

  ENTRY(name)



#define KPROBE_END(name) \

  END(name);		 \

  .popsection



#ifndef END

#define END(name) \

  .size name, .-name