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Re: [PATCH roland/nptl-mips] MIPS: Consolidate NPTL/non versions of vfork

From: Roland McGrath <roland at hack dot frob dot com>
To: "Joseph S. Myers" <joseph at codesourcery dot com>
Cc: "GNU C. Library" <libc-alpha at sourceware dot org>
Date: Wed, 25 Jun 2014 16:24:05 -0700 (PDT)
Subject: Re: [PATCH roland/nptl-mips] MIPS: Consolidate NPTL/non versions of vfork
Authentication-results: sourceware.org; auth=none
References: <20140625220124 dot 0BD4F2C39D4 at topped-with-meat dot com> <Pine dot LNX dot 4 dot 64 dot 1406252211490 dot 13162 at digraph dot polyomino dot org dot uk>

> This appears to be a copy of the clone patch, not a vfork patch....

Oops.  The branch had the right thing.

> The generic pt-vfork.c gives a #error for the non-IFUNC case.  The AArch64 
> version (which I now notice is returning void not pid_t, which looks 
> suspicious to me) won't work for MIPS n32/n64 - for the 64-bit ABIs, gp 
> ($28) is callee-saved, and so the attempt at a tail call involves saving 
> the caller's value and computing a new value, then restoring the old value 
> of gp after the non-tail call before returning.  It might work for o32, 
> but it seems simpler just to #include the alpha version for all three 
> ABIs.

OK.  I've updated the branch to do that.  The new patch is below.


Thanks,
Roland



	* sysdeps/unix/sysv/linux/mips/vfork.S: Incorporate
	SAVE_PID and RESTORE_PID blocks from nptl/pt-vfork.S.
	* sysdeps/unix/sysv/linux/mips/nptl/vfork.S: File removed.
	* sysdeps/unix/sysv/linux/mips/nptl/pt-vfork.S: File removed.
	* sysdeps/unix/sysv/linux/mips/pt-vfork.S: New file.

diff --git a/sysdeps/unix/sysv/linux/mips/nptl/pt-vfork.S b/sysdeps/unix/sysv/linux/mips/nptl/pt-vfork.S
deleted file mode 100644
index 85c55c9..0000000
--- a/sysdeps/unix/sysv/linux/mips/nptl/pt-vfork.S
+++ /dev/null
@@ -1,36 +0,0 @@
-/* Copyright (C) 2005-2014 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#include <tls.h>
-
-/* Save the PID value.  */
-#define SAVE_PID \
-	READ_THREAD_POINTER(v1);	/* Get the thread pointer.  */	\
-	lw	a2, PID_OFFSET(v1);	/* Load the saved PID.  */	\
-	subu	a2, $0, a2;		/* Negate it.  */		\
-	sw	a2, PID_OFFSET(v1);	/* Store the temporary PID.  */
-
-/* Restore the old PID value in the parent.  */
-#define RESTORE_PID \
-	beqz	v0, 1f;			/* If we are the parent... */	\
-	READ_THREAD_POINTER(v1);	/* Get the thread pointer.  */	\
-	lw	a2, PID_OFFSET(v1);	/* Load the saved PID.  */	\
-	subu	a2, $0, a2;		/* Re-negate it.  */		\
-	sw	a2, PID_OFFSET(v1);	/* Restore the PID.  */		\
-1:
-
-#include <sysdeps/unix/sysv/linux/mips/vfork.S>
diff --git a/sysdeps/unix/sysv/linux/mips/nptl/vfork.S b/sysdeps/unix/sysv/linux/mips/nptl/vfork.S
deleted file mode 100644
index 7f1068c..0000000
--- a/sysdeps/unix/sysv/linux/mips/nptl/vfork.S
+++ /dev/null
@@ -1,41 +0,0 @@
-/* Copyright (C) 2005-2014 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#include <tls.h>
-
-/* Save the PID value.  */
-#define SAVE_PID \
-	READ_THREAD_POINTER(v1);	/* Get the thread pointer.  */	\
-	lw	a2, PID_OFFSET(v1);	/* Load the saved PID.  */	\
-	subu	a2, $0, a2;		/* Negate it.  */		\
-	bnez	a2, 1f;			/* If it was zero... */		\
-	lui	a2, 0x8000;		/* use 0x80000000 instead.  */	\
-1:	sw	a2, PID_OFFSET(v1);	/* Store the temporary PID.  */
-
-/* Restore the old PID value in the parent.  */
-#define RESTORE_PID \
-	beqz	v0, 1f;			/* If we are the parent... */	\
-	READ_THREAD_POINTER(v1);	/* Get the thread pointer.  */	\
-	lw	a2, PID_OFFSET(v1);	/* Load the saved PID.  */	\
-	subu	a2, $0, a2;		/* Re-negate it.  */		\
-	lui	a0, 0x8000;		/* Load 0x80000000... */	\
-	bne	a2, a0, 2f;		/* ... compare against it... */	\
-	li	a2, 0;			/* ... use 0 instead.  */	\
-2:	sw	a2, PID_OFFSET(v1);	/* Restore the PID.  */		\
-1:
-
-#include <sysdeps/unix/sysv/linux/mips/vfork.S>
diff --git a/sysdeps/unix/sysv/linux/mips/pt-vfork.S b/sysdeps/unix/sysv/linux/mips/pt-vfork.S
new file mode 100644
index 0000000..65cc382
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/mips/pt-vfork.S
@@ -0,0 +1 @@
+#include <sysdeps/unix/sysv/linux/alpha/pt-vfork.S>
diff --git a/sysdeps/unix/sysv/linux/mips/vfork.S b/sysdeps/unix/sysv/linux/mips/vfork.S
index 0913d6b..80c362d 100644
--- a/sysdeps/unix/sysv/linux/mips/vfork.S
+++ b/sysdeps/unix/sysv/linux/mips/vfork.S
@@ -21,14 +21,7 @@
 #include <sysdep.h>
 #include <asm/unistd.h>
 #include <sgidefs.h>
-
-#ifndef SAVE_PID
-#define SAVE_PID
-#endif
-
-#ifndef RESTORE_PID
-#define RESTORE_PID
-#endif
+#include <tls.h>
 
 
 /* int vfork() */
@@ -67,7 +60,13 @@ NESTED(__vfork,FRAMESZ,sp)
 	PTR_ADDU	sp, FRAMESZ
 	cfi_adjust_cfa_offset (-FRAMESZ)
 
-	SAVE_PID
+	/* Save the PID value.  */
+	READ_THREAD_POINTER(v1)	   /* Get the thread pointer.  */
+	lw	a2, PID_OFFSET(v1) /* Load the saved PID.  */
+	subu	a2, $0, a2	   /* Negate it.  */
+	bnez	a2, 1f		   /* If it was zero... */
+	lui	a2, 0x8000	   /* use 0x80000000 instead.  */
+1:	sw	a2, PID_OFFSET(v1) /* Store the temporary PID.  */
 
 	li		a0, 0x4112	/* CLONE_VM | CLONE_VFORK | SIGCHLD */
 	move		a1, sp
@@ -76,7 +75,16 @@ NESTED(__vfork,FRAMESZ,sp)
 	li		v0,__NR_clone
 	syscall
 
-	RESTORE_PID
+	/* Restore the old PID value in the parent.  */
+	beqz	v0, 1f		/* If we are the parent... */
+	READ_THREAD_POINTER(v1)	/* Get the thread pointer.  */
+	lw	a2, PID_OFFSET(v1) /* Load the saved PID.  */
+	subu	a2, $0, a2	   /* Re-negate it.  */
+	lui	a0, 0x8000	   /* Load 0x80000000... */
+	bne	a2, a0, 2f	   /* ... compare against it... */
+	li	a2, 0		   /* ... use 0 instead.  */
+2:	sw	a2, PID_OFFSET(v1) /* Restore the PID.  */
+1:
 
 	cfi_remember_state
 	bnez		a3,L(error)

Follow-Ups:
- Re: [PATCH roland/nptl-mips] MIPS: Consolidate NPTL/non versions of vfork
  - From: Joseph S. Myers

References:
- [PATCH roland/nptl-mips] MIPS: Consolidate NPTL/non versions of vfork
  - From: Roland McGrath
- Re: [PATCH roland/nptl-mips] MIPS: Consolidate NPTL/non versions of vfork
  - From: Joseph S. Myers

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