linux-kernel - [PATCH 2/5] x86/asm/entry/32: Expand auditsys

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Date:	Mon, 27 Jul 2015 22:33:45 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Krzysztof A. Sobiecki" <sobkas@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/5] x86/asm/entry/32: Expand auditsys_FOO macros in SYSCALL32 code path

This is a preparatory change which allows to drop most of SYSENTER machinery
and make SYSENTER reuse SYSCALL code: we will be deleting entire
SYSENTER code block, including auditsys_entry_common and
auditsys_exit macros.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
CC: Ingo Molnar <mingo@...nel.org>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Krzysztof A. Sobiecki <sobkas@...il.com>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: Borislav Petkov <bp@...en8.de>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Oleg Nesterov <oleg@...hat.com>
CC: Frederic Weisbecker <fweisbec@...il.com>
CC: Alexei Starovoitov <ast@...mgrid.com>
CC: Will Drewry <wad@...omium.org>
CC: Kees Cook <keescook@...omium.org>
CC: x86@...nel.org
CC: linux-kernel@...r.kernel.org
---
 arch/x86/entry/entry_64_compat.S | 57 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 53 insertions(+), 4 deletions(-)

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 9f9dfa5..df102e8 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -396,13 +396,62 @@ 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 */
+	movl	%r9d, R9(%rsp)		/* R9 is callee-clobbered, save it */
+	/*
+	 * At this point, registers hold syscall args in the 32-bit syscall ABI:
+	 * EAX is syscall number, the 6 args are in EBX,ECX,EDX,ESI,EDI,
+	 * 6th arg is in R9.
+	 *
+	 * We want to pass them to __audit_syscall_entry(), which is a 64-bit
+	 * C function with 5 parameters, so shuffle them to match what
+	 * the function expects: RDI,RSI,RDX,RCX,R8.
+	 */
+	movl	%esi, %r8d		/* arg5 (R8 ) <= 4th syscall arg (ESI) */
+	xchg	%ecx, %edx		/* arg4 (RCX) <= 3rd syscall arg (EDX) */
+					/* arg3 (RDX) <= 2nd syscall arg (ECX) */
+	movl	%ebx, %esi		/* arg2 (RSI) <= 1st syscall arg (EBX) */
+	movl	%eax, %edi		/* arg1 (RDI) <= syscall number  (EAX) */
+	call	__audit_syscall_entry
+
+	/*
+	 * We are going to jump back to the syscall dispatch code.
+	 * Prepare syscall args as required by the 64-bit C ABI.
+	 * Registers clobbered by __audit_syscall_entry() are
+	 * loaded from pt_regs on stack:
+	 */
+	movl	ORIG_RAX(%rsp), %eax	/* syscall number */
+	movl	%ebx, %edi		/* arg1 */
+	movl	RCX(%rsp), %esi		/* arg2 */
+	movl	RDX(%rsp), %edx		/* arg3 */
+	movl	RSI(%rsp), %ecx		/* arg4 */
+	movl	RDI(%rsp), %r8d		/* arg5 */
+	movl	R9(%rsp), %r9d		/* arg6 */
 	jmp	cstar_dispatch
 
 sysretl_audit:
-	auditsys_exit sysretl_from_sys_call
+	TRACE_IRQS_ON
+	ENABLE_INTERRUPTS(CLBR_NONE)
+	testl	$(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jnz	ia32_ret_from_sys_call
+	movl	%eax, %esi		/* second arg, syscall return value */
+	cmpl	$-MAX_ERRNO, %eax	/* is it an error ? */
+	jbe	1f
+	movslq	%eax, %rsi		/* if error sign extend to 64 bits */
+1:	setbe	%al			/* 1 if error, 0 if not */
+	movzbl	%al, %edi		/* zero-extend that into %edi */
+	call	__audit_syscall_exit
+	movq	RAX(%rsp), %rax		/* reload syscall return value */
+	movl	$(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %edi
+	DISABLE_INTERRUPTS(CLBR_NONE)
+	TRACE_IRQS_OFF
+	testl	%edi, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
+	jz	sysretl_from_sys_call
+	xorl	%eax, %eax		/* Do not leak kernel information */
+	movq	%rax, R11(%rsp)
+	movq	%rax, R10(%rsp)
+	movq	%rax, R9(%rsp)
+	movq	%rax, R8(%rsp)
+	jmp	int_ret_from_sys_call_irqs_off
 #endif
 
 cstar_tracesys:
-- 
1.8.1.4

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