[RFC 15/30] x86/entry/64/compat: Set up full pt_regs for all compat syscalls

[Andy Lutomirski]

This is conceptually simpler.  More importantly, it eliminates the
PTREGSCALL stubs, which were not compatible with the C ABI.  This
means that C code can call through the compat syscall table.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
 arch/x86/entry/entry_64_compat.S       | 42 +++++++++++-----------------------
 arch/x86/entry/syscalls/syscall_32.tbl |  8 +++----
 2 files changed, 17 insertions(+), 33 deletions(-)

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 3216e6072312..8c6521d1c450 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -219,12 +219,18 @@ ENTRY(entry_INT80_compat)
 	pushq	%rdx			/* pt_regs->dx */
 	pushq	%rcx			/* pt_regs->cx */
 	pushq	$-ENOSYS		/* pt_regs->ax */
-	pushq	$0			/* pt_regs->r8 */
-	pushq	$0			/* pt_regs->r9 */
-	pushq	$0			/* pt_regs->r10 */
-	pushq	$0			/* pt_regs->r11 */
+	xorq    %r8,%r8
+	pushq   %r8                     /* pt_regs->r8  = 0 */
+	pushq   %r8                     /* pt_regs->r9  = 0 */
+	pushq   %r8                     /* pt_regs->r10 = 0 */
+	pushq   %r8                     /* pt_regs->r11 = 0 */
+	pushq   %rbx                    /* pt_regs->rbx */
+	pushq   %rbp                    /* pt_regs->rbp */
+	pushq   %r8                     /* pt_regs->r12 = 0 */
+	pushq   %r8                     /* pt_regs->r13 = 0 */
+	pushq   %r8                     /* pt_regs->r14 = 0 */
+	pushq   %r8                     /* pt_regs->r15 = 0 */
 	cld
-	sub	$(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */
 
 	orl	$TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
 	testl	$_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -243,10 +249,10 @@ ia32_do_call:
 	call	*ia32_sys_call_table(, %rax, 8)
 	movq	%rax, RAX(%rsp)
 1:
+	RESTORE_EXTRA_REGS
 	jmp	int_ret_from_sys_call
 
 ia32_tracesys:
-	SAVE_EXTRA_REGS
 	movq	%rsp, %rdi			/* &pt_regs -> arg1 */
 	call	syscall_trace_enter
 	/*
@@ -261,25 +267,11 @@ ia32_tracesys:
 	movl	RSI(%rsp), %esi
 	movl	RDI(%rsp), %edi
 	movl	%eax, %eax		/* zero extension */
-	RESTORE_EXTRA_REGS
 	jmp	ia32_do_call
 END(entry_INT80_compat)
 
-	.macro PTREGSCALL label, func
-	ALIGN
-GLOBAL(\label)
-	leaq	\func(%rip), %rax
-	jmp	ia32_ptregs_common
-	.endm
-
-	PTREGSCALL stub32_rt_sigreturn,	sys32_rt_sigreturn
-	PTREGSCALL stub32_sigreturn,	sys32_sigreturn
-	PTREGSCALL stub32_fork,		sys_fork
-	PTREGSCALL stub32_vfork,	sys_vfork
-
 	ALIGN
 GLOBAL(stub32_clone)
-	leaq	sys_clone(%rip), %rax
 	/*
 	 * The 32-bit clone ABI is: clone(..., int tls_val, int *child_tidptr).
 	 * The 64-bit clone ABI is: clone(..., int *child_tidptr, int tls_val).
@@ -288,12 +280,4 @@ GLOBAL(stub32_clone)
 	 * so we need to swap arguments here before calling it:
 	 */
 	xchg	%r8, %rcx
-	jmp	ia32_ptregs_common
-
-	ALIGN
-ia32_ptregs_common:
-	SAVE_EXTRA_REGS 8
-	call	*%rax
-	RESTORE_EXTRA_REGS 8
-	ret
-END(ia32_ptregs_common)
+	jmp	sys_clone
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 25e3cf1cd8fd..3a2a6cd471fb 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -8,7 +8,7 @@
 #
 0	i386	restart_syscall		sys_restart_syscall
 1	i386	exit			sys_exit
-2	i386	fork			sys_fork			stub32_fork
+2	i386	fork			sys_fork			sys_fork
 3	i386	read			sys_read
 4	i386	write			sys_write
 5	i386	open			sys_open			compat_sys_open
@@ -125,7 +125,7 @@
 116	i386	sysinfo			sys_sysinfo			compat_sys_sysinfo
 117	i386	ipc			sys_ipc				compat_sys_ipc
 118	i386	fsync			sys_fsync
-119	i386	sigreturn		sys_sigreturn			stub32_sigreturn
+119	i386	sigreturn		sys_sigreturn			sys32_sigreturn
 120	i386	clone			sys_clone			stub32_clone
 121	i386	setdomainname		sys_setdomainname
 122	i386	uname			sys_newuname
@@ -179,7 +179,7 @@
 170	i386	setresgid		sys_setresgid16
 171	i386	getresgid		sys_getresgid16
 172	i386	prctl			sys_prctl
-173	i386	rt_sigreturn		sys_rt_sigreturn		stub32_rt_sigreturn
+173	i386	rt_sigreturn		sys_rt_sigreturn		sys32_rt_sigreturn
 174	i386	rt_sigaction		sys_rt_sigaction		compat_sys_rt_sigaction
 175	i386	rt_sigprocmask		sys_rt_sigprocmask
 176	i386	rt_sigpending		sys_rt_sigpending		compat_sys_rt_sigpending
@@ -196,7 +196,7 @@
 187	i386	sendfile		sys_sendfile			compat_sys_sendfile
 188	i386	getpmsg
 189	i386	putpmsg
-190	i386	vfork			sys_vfork			stub32_vfork
+190	i386	vfork			sys_vfork			sys_vfork
 191	i386	ugetrlimit		sys_getrlimit			compat_sys_getrlimit
 192	i386	mmap2			sys_mmap_pgoff
 193	i386	truncate64		sys_truncate64			sys32_truncate64
-- 
2.4.3

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