[PATCH 5/6] UML - Stop saving process FP state

From: Jeff Dike
Date: Thu Aug 02 2007 - 17:07:35 EST


Throw out a lot of code dealing with saving and restoring
floating-point state. In skas mode, where processes run in a
different host process (and have a different register set), saving and
restoring floating-point state on kernel entry and exit is pointless.

This eliminates most of arch/um/os-Linux/sys-{i386,x86_64}/registers.c.
Most of what remained is now arch-indpendent, and can be moved up to
arch/um/os-Linux/registers.c. Both arches need the jmp_buf accessor
get_thread_reg, and i386 needs {save,restore}_fp_regs because it
cheats during sigreturn by getting the fp state using ptrace rather
than copying it out of the process sigcontext.

After this, it turns out that arch/um/include/skas/mode-skas.h is
almost completely unneeded. The declarations in it are variables
which either don't exist or which don't have global scope. The one
exception is kill_off_processes_skas. If that's removed, this header
can be deleted.

This uncovered a bug in user.h, which wasn't correctly making sure
that a size_t definition was available to both userspace and
kernelspace files.

Signed-off-by: Jeff Dike <jdike@xxxxxxxxxxxxxxx>
--
arch/um/include/os.h | 2
arch/um/include/registers.h | 2
arch/um/include/skas/mode-skas.h | 9 --
arch/um/include/sysdep-i386/ptrace.h | 11 ---
arch/um/include/user.h | 8 +-
arch/um/os-Linux/Makefile | 8 +-
arch/um/os-Linux/registers.c | 54 ++++++++++++++++
arch/um/os-Linux/skas/mem.c | 2
arch/um/os-Linux/skas/process.c | 8 --
arch/um/os-Linux/sys-i386/registers.c | 108 --------------------------------
arch/um/os-Linux/sys-x86_64/Makefile | 2
arch/um/os-Linux/sys-x86_64/registers.c | 76 ----------------------
12 files changed, 74 insertions(+), 216 deletions(-)

Index: linux-2.6.21-mm/arch/um/os-Linux/sys-i386/registers.c
===================================================================
--- linux-2.6.21-mm.orig/arch/um/os-Linux/sys-i386/registers.c 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/os-Linux/sys-i386/registers.c 2007-08-02 16:43:26.000000000 -0400
@@ -4,30 +4,10 @@
*/

#include <errno.h>
-#include <string.h>
-#include "sysdep/ptrace_user.h"
-#include "sysdep/ptrace.h"
-#include "uml-config.h"
-#include "skas_ptregs.h"
-#include "registers.h"
+#include <sysdep/ptrace_user.h>
#include "longjmp.h"
#include "user.h"

-/* These are set once at boot time and not changed thereafter */
-
-static unsigned long exec_regs[MAX_REG_NR];
-static unsigned long exec_fp_regs[HOST_FP_SIZE];
-static unsigned long exec_fpx_regs[HOST_XFP_SIZE];
-static int have_fpx_regs = 1;
-
-void init_thread_registers(union uml_pt_regs *to)
-{
- memcpy(to->skas.regs, exec_regs, sizeof(to->skas.regs));
- memcpy(to->skas.fp, exec_fp_regs, sizeof(to->skas.fp));
- if(have_fpx_regs)
- memcpy(to->skas.xfp, exec_fpx_regs, sizeof(to->skas.xfp));
-}
-
/* XXX These need to use [GS]ETFPXREGS and copy_sc_{to,from}_user_skas needs
* to pass in a sufficiently large buffer
*/
@@ -45,92 +25,6 @@ int restore_fp_registers(int pid, unsign
return 0;
}

-static int move_registers(int pid, int int_op, union uml_pt_regs *regs,
- int fp_op, unsigned long *fp_regs)
-{
- if(ptrace(int_op, pid, 0, regs->skas.regs) < 0)
- return -errno;
-
- if(ptrace(fp_op, pid, 0, fp_regs) < 0)
- return -errno;
-
- return 0;
-}
-
-void save_registers(int pid, union uml_pt_regs *regs)
-{
- unsigned long *fp_regs;
- int err, fp_op;
-
- if(have_fpx_regs){
- fp_op = PTRACE_GETFPXREGS;
- fp_regs = regs->skas.xfp;
- }
- else {
- fp_op = PTRACE_GETFPREGS;
- fp_regs = regs->skas.fp;
- }
-
- err = move_registers(pid, PTRACE_GETREGS, regs, fp_op, fp_regs);
- if(err)
- panic("save_registers - saving registers failed, errno = %d\n",
- -err);
-}
-
-void restore_registers(int pid, union uml_pt_regs *regs)
-{
- unsigned long *fp_regs;
- int err, fp_op;
-
- if(have_fpx_regs){
- fp_op = PTRACE_SETFPXREGS;
- fp_regs = regs->skas.xfp;
- }
- else {
- fp_op = PTRACE_SETFPREGS;
- fp_regs = regs->skas.fp;
- }
-
- err = move_registers(pid, PTRACE_SETREGS, regs, fp_op, fp_regs);
- if(err)
- panic("restore_registers - saving registers failed, "
- "errno = %d\n", -err);
-}
-
-void init_registers(int pid)
-{
- int err;
-
- memset(exec_regs, 0, sizeof(exec_regs));
- err = ptrace(PTRACE_GETREGS, pid, 0, exec_regs);
- if(err)
- panic("check_ptrace : PTRACE_GETREGS failed, errno = %d",
- errno);
-
- errno = 0;
- err = ptrace(PTRACE_GETFPXREGS, pid, 0, exec_fpx_regs);
- if(!err)
- return;
- if(errno != EIO)
- panic("check_ptrace : PTRACE_GETFPXREGS failed, errno = %d",
- errno);
-
- have_fpx_regs = 0;
-
- err = ptrace(PTRACE_GETFPREGS, pid, 0, exec_fp_regs);
- if(err)
- panic("check_ptrace : PTRACE_GETFPREGS failed, errno = %d",
- errno);
-}
-
-void get_safe_registers(unsigned long *regs, unsigned long *fp_regs)
-{
- memcpy(regs, exec_regs, sizeof(exec_regs));
- if(fp_regs != NULL)
- memcpy(fp_regs, exec_fp_regs,
- HOST_FP_SIZE * sizeof(unsigned long));
-}
-
unsigned long get_thread_reg(int reg, jmp_buf *buf)
{
switch(reg){
Index: linux-2.6.21-mm/arch/um/include/os.h
===================================================================
--- linux-2.6.21-mm.orig/arch/um/include/os.h 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/include/os.h 2007-08-02 16:43:26.000000000 -0400
@@ -307,6 +307,8 @@ extern int protect(struct mm_id * mm_idp
extern int is_skas_winch(int pid, int fd, void *data);
extern int start_userspace(unsigned long stub_stack);
extern int copy_context_skas0(unsigned long stack, int pid);
+extern void save_registers(int pid, union uml_pt_regs *regs);
+extern void restore_registers(int pid, union uml_pt_regs *regs);
extern void userspace(union uml_pt_regs *regs);
extern void map_stub_pages(int fd, unsigned long code,
unsigned long data, unsigned long stack);
Index: linux-2.6.21-mm/arch/um/include/registers.h
===================================================================
--- linux-2.6.21-mm.orig/arch/um/include/registers.h 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/include/registers.h 2007-08-02 16:43:26.000000000 -0400
@@ -15,7 +15,7 @@ extern int restore_fp_registers(int pid,
extern void save_registers(int pid, union uml_pt_regs *regs);
extern void restore_registers(int pid, union uml_pt_regs *regs);
extern void init_registers(int pid);
-extern void get_safe_registers(unsigned long * regs, unsigned long * fp_regs);
+extern void get_safe_registers(unsigned long *regs);
extern unsigned long get_thread_reg(int reg, jmp_buf *buf);

#endif
Index: linux-2.6.21-mm/arch/um/os-Linux/skas/mem.c
===================================================================
--- linux-2.6.21-mm.orig/arch/um/os-Linux/skas/mem.c 2007-08-02 16:43:20.000000000 -0400
+++ linux-2.6.21-mm/arch/um/os-Linux/skas/mem.c 2007-08-02 16:43:26.000000000 -0400
@@ -44,7 +44,7 @@ static unsigned long syscall_regs[MAX_RE

static int __init init_syscall_regs(void)
{
- get_safe_registers(syscall_regs, NULL);
+ get_safe_registers(syscall_regs);
syscall_regs[REGS_IP_INDEX] = UML_CONFIG_STUB_CODE +
((unsigned long) &batch_syscall_stub -
(unsigned long) &__syscall_stub_start);
Index: linux-2.6.21-mm/arch/um/os-Linux/skas/process.c
===================================================================
--- linux-2.6.21-mm.orig/arch/um/os-Linux/skas/process.c 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/os-Linux/skas/process.c 2007-08-02 16:43:26.000000000 -0400
@@ -357,11 +357,10 @@ void userspace(union uml_pt_regs *regs)
}

static unsigned long thread_regs[MAX_REG_NR];
-static unsigned long thread_fp_regs[HOST_FP_SIZE];

static int __init init_thread_regs(void)
{
- get_safe_registers(thread_regs, thread_fp_regs);
+ get_safe_registers(thread_regs);
/* Set parent's instruction pointer to start of clone-stub */
thread_regs[REGS_IP_INDEX] = UML_CONFIG_STUB_CODE +
(unsigned long) stub_clone_handler -
@@ -398,11 +397,6 @@ int copy_context_skas0(unsigned long new
panic("copy_context_skas0 : PTRACE_SETREGS failed, "
"pid = %d, errno = %d\n", pid, -err);

- err = ptrace_setfpregs(pid, thread_fp_regs);
- if(err < 0)
- panic("copy_context_skas0 : PTRACE_SETFPREGS failed, "
- "pid = %d, errno = %d\n", pid, -err);
-
/* set a well known return code for detection of child write failure */
child_data->err = 12345678;

Index: linux-2.6.21-mm/arch/um/os-Linux/sys-x86_64/registers.c
===================================================================
--- linux-2.6.21-mm.orig/arch/um/os-Linux/sys-x86_64/registers.c 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/os-Linux/sys-x86_64/registers.c 2007-08-02 16:43:26.000000000 -0400
@@ -1,83 +1,13 @@
/*
- * Copyright (C) 2004 PathScale, Inc
+ * Copyright (C) 2006-2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/

-#include <errno.h>
-#include <string.h>
-#include "ptrace_user.h"
-#include "uml-config.h"
-#include "skas_ptregs.h"
-#include "registers.h"
+#define __FRAME_OFFSETS
+#include <asm/ptrace.h>
#include "longjmp.h"
#include "user.h"

-/* These are set once at boot time and not changed thereafter */
-
-static unsigned long exec_regs[MAX_REG_NR];
-static unsigned long exec_fp_regs[HOST_FP_SIZE];
-
-void init_thread_registers(union uml_pt_regs *to)
-{
- memcpy(to->skas.regs, exec_regs, sizeof(to->skas.regs));
- memcpy(to->skas.fp, exec_fp_regs, sizeof(to->skas.fp));
-}
-
-static int move_registers(int pid, int int_op, int fp_op,
- union uml_pt_regs *regs)
-{
- if(ptrace(int_op, pid, 0, regs->skas.regs) < 0)
- return -errno;
-
- if(ptrace(fp_op, pid, 0, regs->skas.fp) < 0)
- return -errno;
-
- return 0;
-}
-
-void save_registers(int pid, union uml_pt_regs *regs)
-{
- int err;
-
- err = move_registers(pid, PTRACE_GETREGS, PTRACE_GETFPREGS, regs);
- if(err)
- panic("save_registers - saving registers failed, errno = %d\n",
- -err);
-}
-
-void restore_registers(int pid, union uml_pt_regs *regs)
-{
- int err;
-
- err = move_registers(pid, PTRACE_SETREGS, PTRACE_SETFPREGS, regs);
- if(err)
- panic("restore_registers - saving registers failed, "
- "errno = %d\n", -err);
-}
-
-void init_registers(int pid)
-{
- int err;
-
- err = ptrace(PTRACE_GETREGS, pid, 0, exec_regs);
- if(err)
- panic("check_ptrace : PTRACE_GETREGS failed, errno = %d",
- errno);
-
- err = ptrace(PTRACE_GETFPREGS, pid, 0, exec_fp_regs);
- if(err)
- panic("check_ptrace : PTRACE_GETFPREGS failed, errno = %d",
- errno);
-}
-
-void get_safe_registers(unsigned long *regs, unsigned long *fp_regs)
-{
- memcpy(regs, exec_regs, sizeof(exec_regs));
- if(fp_regs != NULL)
- memcpy(fp_regs, exec_fp_regs,
- HOST_FP_SIZE * sizeof(unsigned long));
-}
-
unsigned long get_thread_reg(int reg, jmp_buf *buf)
{
switch(reg){
Index: linux-2.6.21-mm/arch/um/os-Linux/Makefile
===================================================================
--- linux-2.6.21-mm.orig/arch/um/os-Linux/Makefile 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/os-Linux/Makefile 2007-08-02 16:43:26.000000000 -0400
@@ -4,8 +4,8 @@
#

obj-y = aio.o elf_aux.o execvp.o file.o helper.o irq.o main.o mem.o process.o \
- sigio.o signal.o start_up.o time.o trap.o tty.o uaccess.o umid.o tls.o \
- user_syms.o util.o drivers/ sys-$(SUBARCH)/
+ registers.o sigio.o signal.o start_up.o time.o trap.o tty.o uaccess.o \
+ umid.o tls.o user_syms.o util.o drivers/ sys-$(SUBARCH)/

obj-$(CONFIG_MODE_SKAS) += skas/

@@ -16,8 +16,8 @@ obj-$(CONFIG_TTY_LOG) += tty_log.o
user-objs-$(CONFIG_TTY_LOG) += tty_log.o

USER_OBJS := $(user-objs-y) aio.o elf_aux.o execvp.o file.o helper.o irq.o \
- main.o mem.o process.o sigio.o signal.o start_up.o time.o trap.o tty.o \
- tls.o uaccess.o umid.o util.o
+ main.o mem.o process.o registers.o sigio.o signal.o start_up.o time.o \
+ trap.o tty.o tls.o uaccess.o umid.o util.o

CFLAGS_user_syms.o += -DSUBARCH_$(SUBARCH)

Index: linux-2.6.21-mm/arch/um/os-Linux/registers.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.21-mm/arch/um/os-Linux/registers.c 2007-08-02 16:43:26.000000000 -0400
@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2004 PathScale, Inc
+ * Licensed under the GPL
+ */
+
+#include <errno.h>
+#include <string.h>
+#include <sys/ptrace.h>
+#include "user.h"
+#include "sysdep/ptrace.h"
+
+/* This is set once at boot time and not changed thereafter */
+
+static unsigned long exec_regs[MAX_REG_NR];
+
+void init_thread_registers(union uml_pt_regs *to)
+{
+ memcpy(to->skas.regs, exec_regs, sizeof(to->skas.regs));
+}
+
+void save_registers(int pid, union uml_pt_regs *regs)
+{
+ int err;
+
+ err = ptrace(PTRACE_GETREGS, pid, 0, regs->skas.regs);
+ if(err < 0)
+ panic("save_registers - saving registers failed, errno = %d\n",
+ errno);
+}
+
+void restore_registers(int pid, union uml_pt_regs *regs)
+{
+ int err;
+
+ err = ptrace(PTRACE_SETREGS, pid, 0, regs->skas.regs);
+ if(err < 0)
+ panic("restore_registers - saving registers failed, "
+ "errno = %d\n", errno);
+}
+
+void init_registers(int pid)
+{
+ int err;
+
+ err = ptrace(PTRACE_GETREGS, pid, 0, exec_regs);
+ if(err)
+ panic("check_ptrace : PTRACE_GETREGS failed, errno = %d",
+ errno);
+}
+
+void get_safe_registers(unsigned long *regs)
+{
+ memcpy(regs, exec_regs, sizeof(exec_regs));
+}
Index: linux-2.6.21-mm/arch/um/os-Linux/sys-x86_64/Makefile
===================================================================
--- linux-2.6.21-mm.orig/arch/um/os-Linux/sys-x86_64/Makefile 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/os-Linux/sys-x86_64/Makefile 2007-08-02 16:43:26.000000000 -0400
@@ -1,5 +1,5 @@
#
-# Copyright (C) 2000 Jeff Dike (jdike@xxxxxxxxxx)
+# Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
# Licensed under the GPL
#

Index: linux-2.6.21-mm/arch/um/include/sysdep-i386/ptrace.h
===================================================================
--- linux-2.6.21-mm.orig/arch/um/include/sysdep-i386/ptrace.h 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/include/sysdep-i386/ptrace.h 2007-08-02 16:43:26.000000000 -0400
@@ -219,14 +219,3 @@ struct syscall_args {
CHOOSE_MODE((&(r)->tt.faultinfo), (&(r)->skas.faultinfo))

#endif
-
-/*
- * Overrides for Emacs so that we follow Linus's tabbing style.
- * Emacs will notice this stuff at the end of the file and automatically
- * adjust the settings for this buffer only. This must remain at the end
- * of the file.
- * ---------------------------------------------------------------------------
- * Local variables:
- * c-file-style: "linux"
- * End:
- */
Index: linux-2.6.21-mm/arch/um/include/skas/mode-skas.h
===================================================================
--- linux-2.6.21-mm.orig/arch/um/include/skas/mode-skas.h 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/include/skas/mode-skas.h 2007-08-02 16:43:26.000000000 -0400
@@ -1,18 +1,11 @@
/*
- * Copyright (C) 2002 Jeff Dike (jdike@xxxxxxxxxx)
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
* Licensed under the GPL
*/

#ifndef __MODE_SKAS_H__
#define __MODE_SKAS_H__

-#include <sysdep/ptrace.h>
-
-extern unsigned long exec_regs[];
-extern unsigned long exec_fp_regs[];
-extern unsigned long exec_fpx_regs[];
-extern int have_fpx_regs;
-
extern void kill_off_processes_skas(void);

#endif
Index: linux-2.6.21-mm/arch/um/include/user.h
===================================================================
--- linux-2.6.21-mm.orig/arch/um/include/user.h 2007-08-02 16:43:16.000000000 -0400
+++ linux-2.6.21-mm/arch/um/include/user.h 2007-08-02 16:43:26.000000000 -0400
@@ -14,10 +14,12 @@
*/
#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))

-/*
- * This will provide the size_t definition in both kernel and userspace builds
- */
+/* This is to get size_t */
+#ifdef __KERNEL__
#include <linux/types.h>
+#else
+#include <stddef.h>
+#endif

extern void panic(const char *fmt, ...)
__attribute__ ((format (printf, 1, 2)));
-
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