libc/i386: Do not export .cerror.

For some reason, libc exports the symbol .cerror (HIDENAME(cerror)), albeit
in the FBSDprivate_1.0 version. It looks like there is no reason for this
since it is not used from other libraries. Given that it cannot be accessed
from C and its strange calling convention, it is rather unlikely that other
things rely on it. Perhaps it is from a time when symbols could not be
hidden.

Not exporting .cerror causes it to be jumped to directly instead of via the
PLT.

This change also takes advantage of .cerror's new status by not saving and
loading %ebx before jumping to it. (Therefore, .cerror now saves and loads
%ebx itself.) Where there was a conditional jump to a jump to .cerror, the
conditional jump has been changed to jump to .cerror directly (many modern
CPUs don't do static prediction and in any case it is not much of a benefit
anyway).

This change makes libc.so.7 a few kilobytes smaller.

Reviewed by:	kib

lib/libc/i386/SYS.h

@@ -36,21 +36,21 @@
 #include <sys/syscall.h>
 #include <machine/asm.h>
 
-#define	SYSCALL(x)	2: PIC_PROLOGUE; jmp PIC_PLT(HIDENAME(cerror));	\
-			ENTRY(__CONCAT(__sys_,x));			\
+#define	SYSCALL(x)	ENTRY(__CONCAT(__sys_,x));			\
 			.weak CNAME(x);					\
 			.set CNAME(x),CNAME(__CONCAT(__sys_,x));	\
 			.weak CNAME(__CONCAT(_,x));			\
 			.set CNAME(__CONCAT(_,x)),CNAME(__CONCAT(__sys_,x)); \
-			mov __CONCAT($SYS_,x),%eax; KERNCALL; jb 2b
+			mov __CONCAT($SYS_,x),%eax; KERNCALL;		\
+ 			jb HIDENAME(cerror)
 
 #define	RSYSCALL(x)	SYSCALL(x); ret; END(__CONCAT(__sys_,x))
 
-#define	PSEUDO(x)	2: PIC_PROLOGUE; jmp PIC_PLT(HIDENAME(cerror)); \
-			ENTRY(__CONCAT(__sys_,x));			\
+#define	PSEUDO(x)	ENTRY(__CONCAT(__sys_,x));			\
 			.weak CNAME(__CONCAT(_,x));			\
 			.set CNAME(__CONCAT(_,x)),CNAME(__CONCAT(__sys_,x)); \
-			mov __CONCAT($SYS_,x),%eax; KERNCALL; jb 2b; ret; \
+			mov __CONCAT($SYS_,x),%eax; KERNCALL;		\
+ 			jb HIDENAME(cerror); ret; \
 			END(__CONCAT(__sys_,x))
 
 /* gas messes up offset -- although we don't currently need it, do for BCS */

lib/libc/i386/Symbol.map

@@ -63,7 +63,6 @@ FBSDprivate_1.0 {
 	__sys_vfork;
 	_vfork;
 	_end;
-	.cerror;
 	_brk;
 	.curbrk;
 	.minbrk;

lib/libc/i386/gen/rfork_thread.S

@@ -113,8 +113,7 @@ ENTRY(rfork_thread)
 	popl	%esi
 	movl	%ebp, %esp
 	popl	%ebp
-	PIC_PROLOGUE
-	jmp	PIC_PLT(HIDENAME(cerror))
+	jmp	HIDENAME(cerror)
 END(rfork_thread)
 
 	.section .note.GNU-stack,"",%progbits

lib/libc/i386/sys/Ovfork.S

@@ -50,8 +50,7 @@ ENTRY(__sys_vfork)
 	jmp	*%ecx
 1:
 	pushl	%ecx
-	PIC_PROLOGUE
-	jmp     PIC_PLT(HIDENAME(cerror))
+	jmp     HIDENAME(cerror)
 END(__sys_vfork)
 
 	.section .note.GNU-stack,"",%progbits

lib/libc/i386/sys/brk.S

@@ -58,14 +58,11 @@ ENTRY(brk)
 ok:
 	mov	$SYS_break,%eax
 	KERNCALL
-	jb	err
+	jb	HIDENAME(cerror)
 	movl	4(%esp),%eax
 	movl	%eax,(%edx)
 	movl	$0,%eax
 	ret
-err:
-	PIC_PROLOGUE
-	jmp	PIC_PLT(HIDENAME(cerror))
 
 #else
 
@@ -77,13 +74,11 @@ err:
 ok:
 	mov	$SYS_break,%eax
 	KERNCALL
-	jb	err
+	jb	HIDENAME(cerror)
 	movl	4(%esp),%eax
 	movl	%eax,HIDENAME(curbrk)
 	movl	$0,%eax
 	ret
-err:
-	jmp	HIDENAME(cerror)
 #endif
 END(brk)
 

lib/libc/i386/sys/cerror.S

@@ -48,13 +48,14 @@ __FBSDID("$FreeBSD$");
 	.globl	CNAME(__error)
 	.type	CNAME(__error),@function
 HIDENAME(cerror):
-	pushl	%eax
 #ifdef PIC
-	/* The caller must execute the PIC prologue before jumping to cerror. */
+	PIC_PROLOGUE
+	pushl	%eax
 	call	PIC_PLT(CNAME(__error))
 	popl	%ecx
 	PIC_EPILOGUE
 #else
+	pushl	%eax
 	call	CNAME(__error)
 	popl	%ecx
 #endif

lib/libc/i386/sys/exect.S

@@ -47,8 +47,7 @@ ENTRY(exect)
 	pushl	%edx
 	popf
 	KERNCALL
-	PIC_PROLOGUE
-	jmp	PIC_PLT(HIDENAME(cerror))	/* exect(file, argv, env); */
+	jmp	HIDENAME(cerror)	/* exect(file, argv, env); */
 END(exect)
 
 	.section .note.GNU-stack,"",%progbits

lib/libc/i386/sys/getcontext.S

@@ -42,12 +42,9 @@ ENTRY(__sys_getcontext)
 	movl	(%esp),%ecx	/* save getcontext return address */
 	mov	$SYS_getcontext,%eax
 	KERNCALL
-	jb	1f
+	jb	HIDENAME(cerror)
 	addl	$4,%esp		/* remove stale (setcontext) return address */
 	jmp	*%ecx		/* restore return address */
-1:
-	PIC_PROLOGUE
-	jmp	PIC_PLT(HIDENAME(cerror))
 END(__sys_getcontext)
 
 	.section .note.GNU-stack,"",%progbits

lib/libc/i386/sys/ptrace.S

@@ -50,11 +50,8 @@ ENTRY(ptrace)
 #endif
 	mov	$SYS_ptrace,%eax
 	KERNCALL
-	jb	err
+	jb	HIDENAME(cerror)
 	ret
-err:
-	PIC_PROLOGUE
-	jmp	PIC_PLT(HIDENAME(cerror))
 END(ptrace)
 
 	.section .note.GNU-stack,"",%progbits

lib/libc/i386/sys/sbrk.S

@@ -59,7 +59,7 @@ ENTRY(sbrk)
 	addl	%eax,4(%esp)
 	mov	$SYS_break,%eax
 	KERNCALL
-	jb	err
+	jb	HIDENAME(cerror)
 	PIC_PROLOGUE
 	movl	PIC_GOT(HIDENAME(curbrk)),%edx
 	movl	(%edx),%eax
@@ -67,9 +67,6 @@ ENTRY(sbrk)
 	PIC_EPILOGUE
 back:
 	ret
-err:
-	PIC_PROLOGUE
-	jmp	PIC_PLT(HIDENAME(cerror))
 
 #else /* !PIC */
 
@@ -80,13 +77,11 @@ err:
 	addl	%eax,4(%esp)
 	mov	$SYS_break,%eax
 	KERNCALL
-	jb	err
+	jb	HIDENAME(cerror)
 	movl	HIDENAME(curbrk),%eax
 	addl	%ecx,HIDENAME(curbrk)
 back:
 	ret
-err:
-	jmp	HIDENAME(cerror)
 #endif /* PIC */
 END(sbrk)
 

lib/libc/i386/sys/syscall.S

@@ -45,11 +45,8 @@ ENTRY(syscall)
 	KERNCALL
 	push	%ecx	/* need to push a word to keep stack frame intact
 			   upon return; the word must be the return address. */
-	jb	1f
+	jb	HIDENAME(cerror)
 	ret
-1:
-	PIC_PROLOGUE
-	jmp	PIC_PLT(HIDENAME(cerror))
 END(syscall)
 
 	.section .note.GNU-stack,"",%progbits