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Commit c0c3322e authored by Denys Vlasenko's avatar Denys Vlasenko Committed by Thomas Gleixner
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x86/asm/entry/32: Revert 'Do not use R9 in SYSCALL32' commit 

This change reverts most of commit 53e9accf 'Do not use R9 in
SYSCALL32'. I don't yet understand how, but code in that commit
sometimes fails to preserve EBP.

See https://bugzilla.kernel.org/show_bug.cgi?id=101061


"Problems while executing 32-bit code on AMD64"

Reported-and-tested-by: default avatarKrzysztof A. Sobiecki <sobkas@gmail.com>
Signed-off-by: default avatarDenys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Will Drewry <wad@chromium.org>
Cc: Kees Cook <keescook@chromium.org>
CC: x86@kernel.org
Link: http://lkml.kernel.org/r/1437740203-11552-1-git-send-email-dvlasenk@redhat.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 8a0a5da6

arch/x86/entry/entry_64_compat.S

+9 −5
Original line number Diff line number Diff line
@@ -205,7 +205,6 @@ sysexit_from_sys_call: 
	movl	RDX(%rsp), %edx		/* arg3 */

	movl	RSI(%rsp), %ecx		/* arg4 */

	movl	RDI(%rsp), %r8d		/* arg5 */

	movl	%ebp, %r9d		/* arg6 */

	.endm



	.macro auditsys_exit exit
@@ -236,6 +235,7 @@ sysexit_from_sys_call: 


sysenter_auditsys:

	auditsys_entry_common

	movl	%ebp, %r9d		/* reload 6th syscall arg */

	jmp	sysenter_dispatch



sysexit_audit:
@@ -336,7 +336,7 @@ ENTRY(entry_SYSCALL_compat) 
	 * 32-bit zero extended:

	 */

	ASM_STAC

1:	movl	(%r8), %ebp

1:	movl	(%r8), %r9d

	_ASM_EXTABLE(1b, ia32_badarg)

	ASM_CLAC

	orl	$TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
@@ -346,7 +346,7 @@ ENTRY(entry_SYSCALL_compat) 
cstar_do_call:

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

	movl	%edi, %r8d		/* arg5 */

	movl	%ebp, %r9d		/* arg6 */

	/* r9 already loaded */		/* arg6 */

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

	movl	%ebx, %edi		/* arg1 */

	movl	%edx, %edx		/* arg3 (zero extension) */
@@ -358,7 +358,6 @@ cstar_dispatch: 
	call	*ia32_sys_call_table(, %rax, 8)

	movq	%rax, RAX(%rsp)

1:

	movl	RCX(%rsp), %ebp

	DISABLE_INTERRUPTS(CLBR_NONE)

	TRACE_IRQS_OFF

	testl	$_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -392,7 +391,9 @@ sysretl_from_sys_call: 


#ifdef CONFIG_AUDITSYSCALL

cstar_auditsys:

	movl	%r9d, R9(%rsp)		/* register to be clobbered by call */

	auditsys_entry_common

	movl	R9(%rsp), %r9d		/* reload 6th syscall arg */

	jmp	cstar_dispatch



sysretl_audit:
@@ -404,14 +405,16 @@ cstar_tracesys: 
	testl	$(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)

	jz	cstar_auditsys

#endif

	xchgl	%r9d, %ebp

	SAVE_EXTRA_REGS

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

	movq	%rax, R11(%rsp)

	movq	%rax, R10(%rsp)

	movq	%rax, R9(%rsp)

	movq	%r9, R9(%rsp)

	movq	%rax, R8(%rsp)

	movq	%rsp, %rdi		/* &pt_regs -> arg1 */

	call	syscall_trace_enter

	movl	R9(%rsp), %r9d



	/* Reload arg registers from stack. (see sysenter_tracesys) */

	movl	RCX(%rsp), %ecx
@@ -421,6 +424,7 @@ cstar_tracesys: 
	movl	%eax, %eax		/* zero extension */



	RESTORE_EXTRA_REGS

	xchgl	%ebp, %r9d

	jmp	cstar_do_call

END(entry_SYSCALL_compat)