x86/entry/64: Call all native slow-path syscalls with full pt-regs

This removes all of the remaining asm syscall stubs except for
stub_ptregs_64.  Entries in the main syscall table are now all
callable from C.

The resulting asm is every bit as ridiculous as it looks.  The
next few patches will clean it up.  This patch is here to let
reviewers rest their brains and for bisection.

Signed-off-by: Andy Lutomirski <luto@kernel.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: Frederic Weisbecker <fweisbec@gmail.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>
Link: http://lkml.kernel.org/r/a6b3801be0d505d50aefabda02d3b93efbfc9c73.1454022279.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 1 insertions, 78 deletions

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index f1c8f150728e..f7050a5d9dbc 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -253,7 +253,6 @@ tracesys:
 	 * the value it wants us to use in the table lookup.
 	 */
 	RESTORE_C_REGS_EXCEPT_RAX
-	RESTORE_EXTRA_REGS
 #if __SYSCALL_MASK == ~0
 	cmpq	$__NR_syscall_max, %rax
 #else
@@ -264,6 +263,7 @@ tracesys:
 	movq	%r10, %rcx			/* fixup for C */
 	call	*sys_call_table(, %rax, 8)
 	movq	%rax, RAX(%rsp)
+	RESTORE_EXTRA_REGS
 1:
 	/* Use IRET because user could have changed pt_regs->foo */
 
@@ -384,83 +384,6 @@ END(ptregs_\func)
 #define __SYSCALL_64(nr, sym, qual) __SYSCALL_64_QUAL_##qual(sym)
 #include <asm/syscalls_64.h>
 
-	.macro FORK_LIKE func
-ENTRY(stub_\func)
-	SAVE_EXTRA_REGS 8
-	jmp	sys_\func
-END(stub_\func)
-	.endm
-
-	FORK_LIKE  clone
-	FORK_LIKE  fork
-	FORK_LIKE  vfork
-
-ENTRY(stub_execve)
-	call	sys_execve
-return_from_execve:
-	testl	%eax, %eax
-	jz	1f
-	/* exec failed, can use fast SYSRET code path in this case */
-	ret
-1:
-	/* must use IRET code path (pt_regs->cs may have changed) */
-	addq	$8, %rsp
-	ZERO_EXTRA_REGS
-	movq	%rax, RAX(%rsp)
-	jmp	int_ret_from_sys_call
-END(stub_execve)
-/*
- * Remaining execve stubs are only 7 bytes long.
- * ENTRY() often aligns to 16 bytes, which in this case has no benefits.
- */
-	.align	8
-GLOBAL(stub_execveat)
-	call	sys_execveat
-	jmp	return_from_execve
-END(stub_execveat)
-
-#if defined(CONFIG_X86_X32_ABI)
-	.align	8
-GLOBAL(stub_x32_execve)
-	call	compat_sys_execve
-	jmp	return_from_execve
-END(stub_x32_execve)
-	.align	8
-GLOBAL(stub_x32_execveat)
-	call	compat_sys_execveat
-	jmp	return_from_execve
-END(stub_x32_execveat)
-#endif
-
-/*
- * sigreturn is special because it needs to restore all registers on return.
- * This cannot be done with SYSRET, so use the IRET return path instead.
- */
-ENTRY(stub_rt_sigreturn)
-	/*
-	 * SAVE_EXTRA_REGS result is not normally needed:
-	 * sigreturn overwrites all pt_regs->GPREGS.
-	 * But sigreturn can fail (!), and there is no easy way to detect that.
-	 * To make sure RESTORE_EXTRA_REGS doesn't restore garbage on error,
-	 * we SAVE_EXTRA_REGS here.
-	 */
-	SAVE_EXTRA_REGS 8
-	call	sys_rt_sigreturn
-return_from_stub:
-	addq	$8, %rsp
-	RESTORE_EXTRA_REGS
-	movq	%rax, RAX(%rsp)
-	jmp	int_ret_from_sys_call
-END(stub_rt_sigreturn)
-
-#ifdef CONFIG_X86_X32_ABI
-ENTRY(stub_x32_rt_sigreturn)
-	SAVE_EXTRA_REGS 8
-	call	sys32_x32_rt_sigreturn
-	jmp	return_from_stub
-END(stub_x32_rt_sigreturn)
-#endif
-
 /*
  * A newly forked process directly context switches into this address.
  *