[PATCH for review] [137/145] i386: KPROBE_ENTRY ends up putting code into .fixup

Andi Kleen
2006-08-10T19:38:49Z

r

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.

Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andi Kleen <ak@suse.de>

---
arch/i386/kernel/entry.S | 8 ++++----
arch/x86_64/kernel/entry.S | 12 ++++++------
include/linux/linkage.h | 2 +-
3 files changed, 11 insertions(+), 11 deletions(-)

Index: linux/arch/i386/kernel/entry.S
===================================================================
--- linux.orig/arch/i386/kernel/entry.S
+++ linux/arch/i386/kernel/entry.S
@@ -639,7 +639,7 @@ error_code:
call *%edi
jmp ret_from_exception
CFI_ENDPROC
-.previous
+.popsection

ENTRY(coprocessor_error)
RING0_INT_FRAME
@@ -715,7 +715,7 @@ debug_stack_correct:
call do_debug
jmp ret_from_exception
CFI_ENDPROC
-.previous
+.popsection

/*
* NMI is doubly nasty. It can happen _while_ we're handling
@@ -812,7 +812,7 @@ KPROBE_ENTRY(int3)
call do_int3
jmp ret_from_exception
CFI_ENDPROC
-.previous
+.popsection

ENTRY(overflow)
RING0_INT_FRAME
@@ -877,7 +877,7 @@ KPROBE_ENTRY(general_protection)
CFI_ADJUST_CFA_OFFSET 4
jmp error_code
CFI_ENDPROC
-.previous
+.popsection

ENTRY(alignment_check)
RING0_EC_FRAME
Index: linux/arch/x86_64/kernel/entry.S
===================================================================
--- linux.orig/arch/x86_64/kernel/entry.S
+++ linux/arch/x86_64/kernel/entry.S
@@ -904,7 +904,7 @@ error_kernelspace:
je error_swapgs
jmp error_sti
END(error_entry)
- .previous
+ .popsection

/* Reload gs selector with exception handling */
/* edi: new selector */
@@ -1024,7 +1024,7 @@ ENDPROC(execve)
KPROBE_ENTRY(page_fault)
errorentry do_page_fault
END(page_fault)
- .previous
+ .popsection

ENTRY(coprocessor_error)
zeroentry do_coprocessor_error
@@ -1046,7 +1046,7 @@ KPROBE_ENTRY(debug)
paranoidentry do_debug, DEBUG_STACK
paranoidexit
END(debug)
- .previous
+ .popsection

/* runs on exception stack */
KPROBE_ENTRY(nmi)
@@ -1061,7 +1061,7 @@ KPROBE_ENTRY(nmi)
CFI_ENDPROC
#endif
END(nmi)
- .previous
+ .popsection

KPROBE_ENTRY(int3)
INTR_FRAME
@@ -1071,7 +1071,7 @@ KPROBE_ENTRY(int3)
jmp paranoid_exit1
CFI_ENDPROC
END(int3)
- .previous
+ .popsection

ENTRY(overflow)
zeroentry do_overflow
@@ -1120,7 +1120,7 @@ END(stack_segment)
KPROBE_ENTRY(general_protection)
errorentry do_general_protection
END(general_protection)
- .previous
+ .popsection

ENTRY(alignment_check)
errorentry do_alignment_check
Index: linux/include/linux/linkage.h
===================================================================
--- linux.orig/include/linux/linkage.h
+++ linux/include/linux/linkage.h
@@ -35,7 +35,7 @@
#endif

#define KPROBE_ENTRY(name) \
- .section .kprobes.text, "ax"; \
+ .pushsection .kprobes.text, "ax"; \
ENTRY(name)

#ifndef END