Patch: use .pushsection/.popsection

Patch: use .pushsection/.popsection

[Zachary Amsden]

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I think this might fix the X bug...

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diff -r e698e6ee2fa1 arch/i386/kernel/entry.S
--- a/arch/i386/kernel/entry.S	Tue Aug 08 10:18:34 2006 -0700
+++ b/arch/i386/kernel/entry.S	Tue Aug 08 10:36:17 2006 -0700
@@ -162,17 +162,17 @@ 2:	popl %es;	\
 2:	popl %es;	\
 	CFI_ADJUST_CFA_OFFSET -4;\
 	/*CFI_RESTORE es;*/\
-.section .fixup,"ax";	\
+.pushsection .fixup,"ax";	\
 3:	movl $0,(%esp);	\
 	jmp 1b;		\
 4:	movl $0,(%esp);	\
 	jmp 2b;		\
-.previous;		\
-.section __ex_table,"a";\
+.popsection		\
+.pushsection __ex_table,"a";\
 	.align 4;	\
 	.long 1b,3b;	\
 	.long 2b,4b;	\
-.previous
+.popsection
 
 #define RING0_INT_FRAME \
 	CFI_STARTPROC simple;\
@@ -300,10 +300,10 @@ sysenter_past_esp:
 	cmpl $__PAGE_OFFSET-3,%ebp
 	jae syscall_fault
 1:	movl (%ebp),%ebp
-.section __ex_table,"a"
+.pushsection __ex_table,"a"
 	.align 4
 	.long 1b,syscall_fault
-.previous
+.popsection
 
 	pushl %eax
 	CFI_ADJUST_CFA_OFFSET 4
@@ -378,18 +378,18 @@ restore_nocheck_notrace:
 	addl $4, %esp
 	CFI_ADJUST_CFA_OFFSET -4
 1:	INTERRUPT_RETURN
-.section .fixup,"ax"
+.pushsection .fixup,"ax"
 iret_exc:
 	TRACE_IRQS_ON
 	ENABLE_INTERRUPTS
 	pushl $0			# no error code
 	pushl $do_iret_error
 	jmp error_code
-.previous
-.section __ex_table,"a"
+.popsection
+.pushsection __ex_table,"a"
 	.align 4
 	.long 1b,iret_exc
-.previous
+.popsection
 
 	CFI_RESTORE_STATE
 ldt_ss:
@@ -415,11 +415,11 @@ ldt_ss:
 	TRACE_IRQS_IRET
 	RESTORE_REGS
 	lss 20+4(%esp), %esp	# switch to 16bit stack
-1:	INTERRUPT_RETURN
-.section __ex_table,"a"
+1:	iret
+.pushsection __ex_table,"a"
 	.align 4
 	.long 1b,iret_exc
-.previous
+.popsection
 	CFI_ENDPROC
 
 	# perform work that needs to be done immediately before resumption
@@ -525,14 +525,14 @@ syscall_badsys:
 	je 28f; \
 27:	popl %eax; \
 	CFI_ADJUST_CFA_OFFSET -4; \
-.section .fixup,"ax"; \
+.pushsection .fixup,"ax"; \
 28:	movl $__KERNEL_DS, %eax; \
 	movl %eax, %ds; \
 	movl %eax, %es; \
 	/* switch to 32bit stack */ \
 	FIXUP_ESPFIX_STACK; \
 	jmp 27b; \
-.previous
+.popsection
 
 /*
  * Build the entry stubs and pointer table with
@@ -639,7 +639,7 @@ error_code:
 	call *%edi
 	jmp ret_from_exception
 	CFI_ENDPROC
-.previous
+KPROBE_EXIT
 
 ENTRY(coprocessor_error)
 	RING0_INT_FRAME
@@ -715,7 +715,7 @@ debug_stack_correct:
 	call do_debug
 	jmp ret_from_exception
 	CFI_ENDPROC
-.previous
+KPROBE_EXIT
 
 /*
  * NMI is doubly nasty. It can happen _while_ we're handling
@@ -795,12 +795,12 @@ nmi_16bit_stack:
 	call do_nmi
 	RESTORE_REGS
 	lss 12+4(%esp), %esp		# back to 16bit stack
-1:	INTERRUPT_RETURN
-	CFI_ENDPROC
-.section __ex_table,"a"
+1:	iret
+	CFI_ENDPROC
+.pushsection __ex_table,"a"
 	.align 4
 	.long 1b,iret_exc
-.previous
+.popsection
 
 #ifdef CONFIG_PARAVIRT
 ENTRY(nopara_iret)
@@ -821,7 +821,7 @@ KPROBE_ENTRY(int3)
 	call do_int3
 	jmp ret_from_exception
 	CFI_ENDPROC
-.previous
+KPROBE_EXIT
 
 ENTRY(overflow)
 	RING0_INT_FRAME
@@ -886,7 +886,7 @@ KPROBE_ENTRY(general_protection)
 	CFI_ADJUST_CFA_OFFSET 4
 	jmp error_code
 	CFI_ENDPROC
-.previous
+KPROBE_EXIT
 
 ENTRY(alignment_check)
 	RING0_EC_FRAME
diff -r e698e6ee2fa1 include/asm-i386/alternative-asm.i
--- a/include/asm-i386/alternative-asm.i	Tue Aug 08 10:18:34 2006 -0700
+++ b/include/asm-i386/alternative-asm.i	Tue Aug 08 10:33:13 2006 -0700
@@ -3,10 +3,10 @@
 #ifdef CONFIG_SMP
 	.macro LOCK_PREFIX
 1:	lock
-	.section .smp_locks,"a"
+	.pushsection .smp_locks,"a"
 	.align 4
 	.long 1b
-	.previous
+	.popsection
 	.endm
 #else
 	.macro LOCK_PREFIX
diff -r e698e6ee2fa1 include/linux/linkage.h
--- a/include/linux/linkage.h	Tue Aug 08 10:18:34 2006 -0700
+++ b/include/linux/linkage.h	Tue Aug 08 10:35:55 2006 -0700
@@ -35,8 +35,11 @@
 #endif
 
 #define KPROBE_ENTRY(name) \
-  .section .kprobes.text, "ax"; \
+  .pushsection .kprobes.text, "ax"; \
   ENTRY(name)
+
+#define KPROBE_EXIT \
+  .popsection
 
 #ifndef END
 #define END(name) \

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Re: Patch: use .pushsection/.popsection

[Jeremy Fitzhardinge]

Zachary Amsden wrote:
> I think this might fix the X bug...
I just posted an equivalent patch to Andi Kleen/AKPM/LKML.  I haven't 
tested to see if it actually helps yet, but it certainly makes entry.o 
look a lot cleaner.

    J

Re: Patch: use .pushsection/.popsection

[Andi Kleen]

On Wednesday 09 August 2006 08:09, Jeremy Fitzhardinge wrote:
> Zachary Amsden wrote:
> > I think this might fix the X bug...
> I just posted an equivalent patch to Andi Kleen/AKPM/LKML.  I haven't 
> tested to see if it actually helps yet, but it certainly makes entry.o 
> look a lot cleaner.

I have already merged it.

But in theory all code should run fine in .fixup, so it shouldn't
actually unbreak anything.

-Andi

Re: Patch: use .pushsection/.popsection

[Jeremy Fitzhardinge]

Andi Kleen wrote:
> I have already merged it.
>
> But in theory all code should run fine in .fixup, so it shouldn't
> actually unbreak anything.
>   

No, it makes actual broken code without this:

#define RESTORE_REGS	\
	RESTORE_INT_REGS; \
1:	popl %ds;	\
	CFI_ADJUST_CFA_OFFSET -4;\
	/*CFI_RESTORE ds;*/\
2:	popl %es;	\
	CFI_ADJUST_CFA_OFFSET -4;\
	/*CFI_RESTORE es;*/\
.section .fixup,"ax";	\
3:	movl $0,(%esp);	\
	jmp 1b;		\
4:	movl $0,(%esp);	\
	jmp 2b;		\
.previous;		\
...

Those jmp 1b's look a lot like infinite loops if 1: is in the same 
section as 3:.

    J