x86/entry: Do not special-case clone(2) in compat entry

With the CPU renaming registers on its own, and all the overhead of the
syscall entry/exit, it is doubtful whether the compiled output of

	mov	%r8, %rax
	mov	%rcx, %r8
	mov	%rax, %rcx
	jmpq	sys_clone

is measurably slower than the hand-crafted version of

	xchg	%r8, %rcx

So get rid of this special case.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: luto@amacapital.net
Cc: viro@zeniv.linux.org.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index e811dd9c5e99e1a1e61d20cce0fb9ba3cf23f535..ff61b7bb750baa52b13f8ff82e72cee91009cc85 100644 (file)
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -406,15 +406,3 @@ ENTRY(entry_INT80_compat)
        TRACE_IRQS_ON
        jmp     swapgs_restore_regs_and_return_to_usermode
 END(entry_INT80_compat)
-
-ENTRY(stub32_clone)
-       /*
-        * 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).
-        *
-        * The native 64-bit kernel's sys_clone() implements the latter,
-        * so we need to swap arguments here before calling it:
-        */
-       xchg    %r8, %rcx
-       jmp     sys_clone
-ENDPROC(stub32_clone)

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index e7fd0a76bf9942a9bc421a962b77a268ecd797ee..2a5e99cff8597278412685867f512858254f2b0c 100644 (file)
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -126,7 +126,7 @@
 117    i386    ipc                     sys_ipc                         compat_sys_ipc
 118    i386    fsync                   sys_fsync
 119    i386    sigreturn               sys_sigreturn                   sys32_sigreturn
-120    i386    clone                   sys_clone                       stub32_clone
+120    i386    clone                   sys_clone                       compat_sys_x86_clone
 121    i386    setdomainname           sys_setdomainname
 122    i386    uname                   sys_newuname
 123    i386    modify_ldt              sys_modify_ldt

diff --git a/arch/x86/ia32/sys_ia32.c b/arch/x86/ia32/sys_ia32.c
index 3bc03446ec441065b42b25128dc644f51fa759b4..6512498bbef69ced1f98c72afb5b11ade91ef4a5 100644 (file)
--- a/arch/x86/ia32/sys_ia32.c
+++ b/arch/x86/ia32/sys_ia32.c
@@ -233,3 +233,14 @@ COMPAT_SYSCALL_DEFINE6(x86_fallocate, int, fd, int, mode,
        return sys_fallocate(fd, mode, ((u64)offset_hi << 32) | offset_lo,
                             ((u64)len_hi << 32) | len_lo);
 }
+
+/*
+ * The 32-bit clone ABI is CONFIG_CLONE_BACKWARDS
+ */
+COMPAT_SYSCALL_DEFINE5(x86_clone, unsigned long, clone_flags,
+                      unsigned long, newsp, int __user *, parent_tidptr,
+                      unsigned long, tls_val, int __user *, child_tidptr)
+{
+       return sys_clone(clone_flags, newsp, parent_tidptr, child_tidptr,
+                       tls_val);
+}

diff --git a/arch/x86/include/asm/sys_ia32.h b/arch/x86/include/asm/sys_ia32.h
index 32831905d97a9c3b04f8fb0718dab7432bbec376..906794aa034e732ec57d32a8be0ef77085a553a6 100644 (file)
--- a/arch/x86/include/asm/sys_ia32.h
+++ b/arch/x86/include/asm/sys_ia32.h
@@ -55,6 +55,8 @@ asmlinkage long compat_sys_x86_fadvise64(int, unsigned int, unsigned int,
                                         size_t, int);
 asmlinkage long compat_sys_x86_fallocate(int, int, unsigned int, unsigned int,
                                         unsigned int, unsigned int);
+asmlinkage long compat_sys_x86_clone(unsigned long, unsigned long, int __user *,
+                                    unsigned long, int __user *);
 
 /* ia32/ia32_signal.c */
 asmlinkage long sys32_sigreturn(void);