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Commit a49976d1 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/asm/entry/32: Clean up entry_32.S 



Make the 32-bit syscall entry code a bit more readable:

 - use consistent assembly coding style similar to entry_64.S

 - remove old comments that are not true anymore

 - eliminate whitespace noise

 - use consistent vertical spacing

 - fix various comments

No code changed:

  # arch/x86/entry/entry_32.o:

   text    data     bss     dec     hex filename
   6025       0       0    6025    1789 entry_32.o.before
   6025       0       0    6025    1789 entry_32.o.after

md5:
   f3fa16b2b0dca804f052deb6b30ba6cb  entry_32.o.before.asm
   f3fa16b2b0dca804f052deb6b30ba6cb  entry_32.o.after.asm

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b2502b41

arch/x86/entry/entry_32.S

+570 −571
Original line number Diff line number Diff line 
/*

 *

 *  Copyright (C) 1991,1992  Linus Torvalds

 */



/*

 * entry.S contains the system-call and fault low-level handling routines.

 * This also contains the timer-interrupt handler, as well as all interrupts

 * and faults that can result in a task-switch.

 *

 * NOTE: This code handles signal-recognition, which happens every time

 * after a timer-interrupt and after each system call.

 *

 * I changed all the .align's to 4 (16 byte alignment), as that's faster

 * on a 486.

 * entry_32.S contains the system-call and low-level fault and trap handling routines.

 *

 * Stack layout in 'syscall_exit':

 * 	ptrace needs to have all regs on the stack.

 *	if the order here is changed, it needs to be

 *	updated in fork.c:copy_process, signal.c:do_signal,

 *	ptrace needs to have all registers on the stack.

 *	If the order here is changed, it needs to be

 *	updated in fork.c:copy_process(), signal.c:do_signal(),

 *	ptrace.c and ptrace.h

 *

 *	 0(%esp) - %ebx
@@ -37,8 +26,6 @@ 
 *	38(%esp) - %eflags

 *	3C(%esp) - %oldesp

 *	40(%esp) - %oldss

 *

 * "current" is in register %ebx during any slow entries.

 */



#include <linux/linkage.h>
@@ -303,10 +290,13 @@ need_resched: 
END(resume_kernel)

#endif



/* SYSENTER_RETURN points to after the "sysenter" instruction in

   the vsyscall page.  See vsyscall-sysentry.S, which defines the symbol.  */

/*

 * SYSENTER_RETURN points to after the SYSENTER instruction

 * in the vsyscall page.  See vsyscall-sysentry.S, which defines

 * the symbol.

 */



	# sysenter call handler stub

	# SYSENTER  call handler stub

ENTRY(entry_SYSENTER_32)

	movl	TSS_sysenter_sp0(%esp), %esp

sysenter_past_esp:
@@ -444,9 +434,11 @@ restore_all: 
restore_all_notrace:

#ifdef CONFIG_X86_ESPFIX32

	movl	PT_EFLAGS(%esp), %eax		# mix EFLAGS, SS and CS

	# Warning: PT_OLDSS(%esp) contains the wrong/random values if we

	# are returning to the kernel.

	# See comments in process.c:copy_thread() for details.

	/*

	 * Warning: PT_OLDSS(%esp) contains the wrong/random values if we

	 * are returning to the kernel.

	 * See comments in process.c:copy_thread() for details.

	 */

	movb	PT_OLDSS(%esp), %ah

	movb	PT_CS(%esp), %al

	andl	$(X86_EFLAGS_VM | (SEGMENT_TI_MASK << 8) | SEGMENT_RPL_MASK), %eax
@@ -501,9 +493,11 @@ ldt_ss: 
	mov	%dh, GDT_ESPFIX_SS + 7		/* bits 24..31 */

	pushl	$__ESPFIX_SS

	pushl	%eax				/* new kernel esp */

	/* Disable interrupts, but do not irqtrace this section: we

	/*

	 * Disable interrupts, but do not irqtrace this section: we

	 * will soon execute iret and the tracer was already set to

	 * the irqstate after the iret */

	 * the irqstate after the IRET:

	 */

	DISABLE_INTERRUPTS(CLBR_EAX)

	lss	(%esp), %esp			/* switch to espfix segment */

	jmp	restore_nocheck
@@ -680,8 +674,7 @@ ENDPROC(name) 




#ifdef CONFIG_TRACING

#define TRACE_BUILD_INTERRUPT(name, nr)		\

	BUILD_INTERRUPT3(trace_##name, nr, smp_trace_##name)

# define TRACE_BUILD_INTERRUPT(name, nr)	BUILD_INTERRUPT3(trace_##name, nr, smp_trace_##name)

#else

# define TRACE_BUILD_INTERRUPT(name, nr)

#endif
@@ -809,8 +802,10 @@ ENTRY(spurious_interrupt_bug) 
END(spurious_interrupt_bug)



#ifdef CONFIG_XEN

/* Xen doesn't set %esp to be precisely what the normal sysenter

   entrypoint expects, so fix it up before using the normal path. */

/*

 * Xen doesn't set %esp to be precisely what the normal SYSENTER

 * entry point expects, so fix it up before using the normal path.

 */

ENTRY(xen_sysenter_target)

	addl	$5*4, %esp			/* remove xen-provided frame */

	jmp	sysenter_past_esp
@@ -820,11 +815,13 @@ ENTRY(xen_hypervisor_callback) 
	SAVE_ALL

	TRACE_IRQS_OFF



	/* Check to see if we got the event in the critical

	   region in xen_iret_direct, after we've reenabled

	   events and checked for pending events.  This simulates

	   iret instruction's behaviour where it delivers a

	   pending interrupt when enabling interrupts. */

	/*

	 * Check to see if we got the event in the critical

	 * region in xen_iret_direct, after we've reenabled

	 * events and checked for pending events.  This simulates

	 * iret instruction's behaviour where it delivers a

	 * pending interrupt when enabling interrupts:

	 */

	movl	PT_EIP(%esp), %eax

	cmpl	$xen_iret_start_crit, %eax

	jb	1f
@@ -842,16 +839,18 @@ ENTRY(xen_do_upcall) 
	jmp	ret_from_intr

ENDPROC(xen_hypervisor_callback)



# Hypervisor uses this for application faults while it executes.

# We get here for two reasons:

#  1. Fault while reloading DS, ES, FS or GS

#  2. Fault while executing IRET

# Category 1 we fix up by reattempting the load, and zeroing the segment

# register if the load fails.

# Category 2 we fix up by jumping to do_iret_error. We cannot use the

# normal Linux return path in this case because if we use the IRET hypercall

# to pop the stack frame we end up in an infinite loop of failsafe callbacks.

# We distinguish between categories by maintaining a status value in EAX.

/*

 * Hypervisor uses this for application faults while it executes.

 * We get here for two reasons:

 *  1. Fault while reloading DS, ES, FS or GS

 *  2. Fault while executing IRET

 * Category 1 we fix up by reattempting the load, and zeroing the segment

 * register if the load fails.

 * Category 2 we fix up by jumping to do_iret_error. We cannot use the

 * normal Linux return path in this case because if we use the IRET hypercall

 * to pop the stack frame we end up in an infinite loop of failsafe callbacks.

 * We distinguish between categories by maintaining a status value in EAX.

 */

ENTRY(xen_failsafe_callback)

	pushl	%eax

	movl	$1, %eax
@@ -1169,7 +1168,8 @@ ENTRY(nmi) 
	je	nmi_stack_fixup

	pushl	%eax

	movl	%esp, %eax

	/* Do not access memory above the end of our stack page,

	/*

	 * Do not access memory above the end of our stack page,

	 * it might not exist.

	 */

	andl	$(THREAD_SIZE-1), %eax
@@ -1246,4 +1246,3 @@ ENTRY(async_page_fault) 
	jmp	error_code

END(async_page_fault)

#endif