linux-kernel - [RFC 24/30] x86/entry/32: Switch INT80 to the new C syscall path

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Message-Id: <7d490a264327832aba54379b5f63e4780e080339.1441146105.git.luto@kernel.org>
Date:	Tue,  1 Sep 2015 15:41:24 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>
Subject: [RFC 24/30] x86/entry/32: Switch INT80 to the new C syscall path

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/entry/entry_32.S | 34 +++++++++++++---------------------
 1 file changed, 13 insertions(+), 21 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 36b6beb181f6..02881e528945 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -153,13 +153,13 @@
 
 #endif /* CONFIG_X86_32_LAZY_GS */
 
-.macro SAVE_ALL
+.macro SAVE_ALL pt_regs_ax=%eax
 	cld
 	PUSH_GS
 	pushl	%fs
 	pushl	%es
 	pushl	%ds
-	pushl	%eax
+	pushl	\pt_regs_ax
 	pushl	%ebp
 	pushl	%edi
 	pushl	%esi
@@ -370,20 +370,17 @@ ENDPROC(entry_SYSENTER_32)
 	# system call handler stub
 ENTRY(entry_INT80_32)
 	ASM_CLAC
-	pushl	%eax				# save orig_eax
-	SAVE_ALL
-	GET_THREAD_INFO(%ebp)
-						# system call tracing in operation / emulation
-	testl	$_TIF_WORK_SYSCALL_ENTRY, TI_flags(%ebp)
-	jnz	syscall_trace_entry
-	cmpl	$(NR_syscalls), %eax
-	jae	syscall_badsys
-syscall_call:
-	call	*sys_call_table(, %eax, 4)
-syscall_after_call:
-	movl	%eax, PT_EAX(%esp)		# store the return value
-syscall_exit:
-	jmp	syscall_exit_work
+	pushl	%eax			/* pt_regs->orig_ax */
+	SAVE_ALL pt_regs_ax=$-ENOSYS	/* save rest, load -ENOSYS into ax */
+
+	/*
+	 * User mode is traced as though IRQs are on, and the interrupt gate
+	 * turned them off.
+	 */
+	TRACE_IRQS_OFF
+
+	movl	%esp, %eax
+	call	do_int80_syscall_32
 
 restore_all:
 	TRACE_IRQS_IRET
@@ -491,11 +488,6 @@ syscall_fault:
 	jmp	resume_userspace
 END(syscall_fault)
 
-syscall_badsys:
-	movl	$-ENOSYS, %eax
-	jmp	syscall_after_call
-END(syscall_badsys)
-
 sysenter_badsys:
 	movl	$-ENOSYS, %eax
 	jmp	sysenter_after_call
-- 
2.4.3

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