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

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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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2015-06-08 09:49:11 +02:00
parent b2502b418e
commit a49976d14f
1 changed files with 562 additions and 563 deletions
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91
arch/x86/entry/entry_32.S
View File

@ -1,23 +1,12 @@
/*
*
* 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