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Commit 54ad726c authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/asm/entry/32: Improve code readability 



Make the 64-bit compat 32-bit syscall entry code a bit more readable:

 - eliminate whitespace noise

 - use consistent vertical spacing

 - use consistent assembly coding style similar to entry_64.S

 - fix various comments

No code changed:

arch/x86/entry/ia32entry.o:

   text	   data	    bss	    dec	    hex	filename
   1391	      0	      0	   1391	    56f	ia32entry.o.before
   1391	      0	      0	   1391	    56f	ia32entry.o.after

md5:
   f28501dcc366e68b557313942c6496d6  ia32entry.o.before.asm
   f28501dcc366e68b557313942c6496d6  ia32entry.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 53e9accf

arch/x86/entry/ia32entry.S

+146 −141
Original line number Diff line number Diff line
@@ -3,7 +3,6 @@ 
 *

 * Copyright 2000-2002 Andi Kleen, SuSE Labs.

 */



#include "calling.h"

#include <asm/asm-offsets.h>

#include <asm/current.h>
@@ -37,7 +36,7 @@ ENDPROC(native_usergs_sysret32) 
#endif



/*

 * 32bit SYSENTER instruction entry.

 * 32-bit SYSENTER instruction entry.

 *

 * SYSENTER loads ss, rsp, cs, and rip from previously programmed MSRs.

 * IF and VM in rflags are cleared (IOW: interrupts are off).
@@ -91,7 +90,7 @@ ENTRY(ia32_sysenter_target) 


	/*

	 * no need to do an access_ok check here because rbp has been

	 * 32bit zero extended

	 * 32-bit zero extended

	 */

	ASM_STAC

1:	movl	(%rbp), %ebp
@@ -112,7 +111,7 @@ sysenter_flags_fixed: 
	jnz	sysenter_tracesys



sysenter_do_call:

	/* 32bit syscall -> 64bit C ABI argument conversion */

	/* 32-bit syscall -> 64-bit C ABI argument conversion */

	movl	%edi, %r8d		/* arg5 */

	movl	%ebp, %r9d		/* arg6 */

	xchg	%ecx, %esi		/* rsi:arg2, rcx:arg4 */
@@ -142,7 +141,7 @@ sysexit_from_sys_call: 
	andl    $~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)

	movl	RIP(%rsp), %ecx		/* User %eip */

	RESTORE_RSI_RDI

	xorl	%edx,%edx		/* avoid info leaks */

	xorl	%edx, %edx		/* Do not leak kernel information */

	xorq	%r8, %r8

	xorq	%r9, %r9

	xorq	%r10, %r10
@@ -212,7 +211,7 @@ sysexit_from_sys_call: 
	TRACE_IRQS_OFF

	testl	%edi, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)

	jz	\exit

	xorl	%eax, %eax	/* do not leak kernel information */

	xorl	%eax, %eax		/* Do not leak kernel information */

	movq	%rax, R11(%rsp)

	movq	%rax, R10(%rsp)

	movq	%rax, R9(%rsp)
@@ -240,7 +239,7 @@ sysenter_tracesys: 
	jz	sysenter_auditsys

#endif

	SAVE_EXTRA_REGS

	xorl	%eax, %eax	/* do not leak kernel information */

	xorl	%eax, %eax		/* Do not leak kernel information */

	movq	%rax, R11(%rsp)

	movq	%rax, R10(%rsp)

	movq	%rax, R9(%rsp)
@@ -260,16 +259,16 @@ sysenter_tracesys: 
ENDPROC(ia32_sysenter_target)



/*

 * 32bit SYSCALL instruction entry.

 * 32-bit SYSCALL instruction entry.

 *

 * 32bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11,

 * 32-bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11,

 * then loads new ss, cs, and rip from previously programmed MSRs.

 * rflags gets masked by a value from another MSR (so CLD and CLAC

 * are not needed). SYSCALL does not save anything on the stack

 * and does not change rsp.

 *

 * Note: rflags saving+masking-with-MSR happens only in Long mode

 * (in legacy 32bit mode, IF, RF and VM bits are cleared and that's it).

 * (in legacy 32-bit mode, IF, RF and VM bits are cleared and that's it).

 * Don't get confused: rflags saving+masking depends on Long Mode Active bit

 * (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes

 * or target CS descriptor's L bit (SYSCALL does not read segment descriptors).
@@ -319,8 +318,8 @@ ENTRY(ia32_cstar_target) 
	sub	$(10*8), %rsp		/* pt_regs->r8-11, bp, bx, r12-15 not saved */



	/*

	 * no need to do an access_ok check here because r8 has been

	 * 32bit zero extended

	 * No need to do an access_ok check here because r8 has been

	 * 32-bit zero extended:

	 */

	ASM_STAC

1:	movl	(%r8), %ebp
@@ -331,15 +330,17 @@ ENTRY(ia32_cstar_target) 
	jnz   cstar_tracesys



cstar_do_call:

	/* 32bit syscall -> 64bit C ABI argument conversion */

	/* 32-bit syscall -> 64-bit C ABI argument conversion */

	movl	%edi, %r8d		/* arg5 */

	movl	%ebp, %r9d		/* arg6 */

	xchg	%ecx, %esi		/* rsi:arg2, rcx:arg4 */

	movl	%ebx, %edi		/* arg1 */

	movl	%edx, %edx		/* arg3 (zero extension) */



cstar_dispatch:

	cmpq	$(IA32_NR_syscalls-1), %rax

	ja	1f



	call	*ia32_sys_call_table(, %rax, 8)

	movq	%rax, RAX(%rsp)

1:
@@ -347,6 +348,7 @@ cstar_dispatch: 
	TRACE_IRQS_OFF

	testl	$_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)

	jnz	sysretl_audit



sysretl_from_sys_call:

	andl	$~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)

	movl	RCX(%rsp), %ebp
@@ -359,10 +361,10 @@ sysretl_from_sys_call: 
	TRACE_IRQS_ON

	movl	RSP(%rsp), %esp

	/*

	 * 64bit->32bit SYSRET restores eip from ecx,

	 * 64-bit->32-bit SYSRET restores eip from ecx,

	 * eflags from r11 (but RF and VM bits are forced to 0),

	 * cs and ss are loaded from MSRs.

	 * (Note: 32bit->32bit SYSRET is different: since r11

	 * (Note: 32-bit->32-bit SYSRET is different: since r11

	 * does not exist, it merely sets eflags.IF=1).

	 *

	 * NB: On AMD CPUs with the X86_BUG_SYSRET_SS_ATTRS bug, the ss
@@ -390,7 +392,7 @@ cstar_tracesys: 
	jz	cstar_auditsys

#endif

	SAVE_EXTRA_REGS

	xorl	%eax, %eax	/* do not leak kernel information */

	xorl	%eax, %eax		/* Do not leak kernel information */

	movq	%rax, R11(%rsp)

	movq	%rax, R10(%rsp)

	movq	%rax, R9(%rsp)
@@ -415,7 +417,7 @@ ia32_badarg: 
	jmp	ia32_sysret



ia32_ret_from_sys_call:

	xorl	%eax, %eax	/* do not leak kernel information */

	xorl	%eax, %eax		/* Do not leak kernel information */

	movq	%rax, R11(%rsp)

	movq	%rax, R10(%rsp)

	movq	%rax, R9(%rsp)
@@ -473,8 +475,9 @@ ENTRY(ia32_syscall) 
	orl	$TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)

	testl	$_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)

	jnz	ia32_tracesys



ia32_do_call:

	/* 32bit syscall -> 64bit C ABI argument conversion */

	/* 32-bit syscall -> 64-bit C ABI argument conversion */

	movl	%edi, %r8d		/* arg5 */

	movl	%ebp, %r9d		/* arg6 */

	xchg	%ecx, %esi		/* rsi:arg2, rcx:arg4 */
@@ -482,7 +485,9 @@ ia32_do_call: 
	movl	%edx, %edx		/* arg3 (zero extension) */

	cmpq	$(IA32_NR_syscalls-1), %rax

	ja	1f

	call *ia32_sys_call_table(,%rax,8) # xxx: rip relative



	call	*ia32_sys_call_table(, %rax, 8) /* RIP relative */



ia32_sysret:

	movq	%rax, RAX(%rsp)

1: