Re: [git Patch] UML: a build error fix

From: Jeff Dike
Date: Fri Feb 01 2008 - 12:38:47 EST

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On Thu, Jan 31, 2008 at 11:17:41PM +0800, WANG Cong wrote:
> This patch fixed this error:
>
> arch/um/kernel/skas/syscall.c: In function 'handle_syscall':
> arch/um/kernel/skas/syscall.c:33: error: 'NR_syscalls' undeclared (first use in this function)

That works, but I think doing things the way that i386 does them is cleaner.

Andrew, can you stick the patch below into -mm and push it to Linus?

Jeff

--
Work email - jdike at linux dot intel dot com

Redo the calculation of NR_syscalls since that disappeared from i386
and use a similar mechanism on x86_64.

We now figure out the size of the system call table in arch code and
stick that in syscall_table_size. arch/um/kernel/skas/syscall.c
defines NR_syscalls in terms of that since its the only thing that
needs to know how many system calls there are.

The old mechananism that was used on x86_64 is gone.

arch/um/include/sysdep-i386/syscalls.h got some formatting since I was
looking at it.

Signed-off-by: Jeff Dike <jdike@xxxxxxxxxxxxxxx>
Cc: WANG Cong <xiyou.wangcong@xxxxxxxxx>
---
arch/um/include/sysdep-i386/syscalls.h | 5 +++--
arch/um/include/sysdep-x86_64/kernel-offsets.h | 9 ---------
arch/um/include/sysdep-x86_64/syscalls.h | 2 --
arch/um/kernel/skas/syscall.c | 3 +++
arch/um/sys-i386/sys_call_table.S | 5 +++++
arch/um/sys-x86_64/syscall_table.c | 17 ++++++++++++++---
6 files changed, 25 insertions(+), 16 deletions(-)

Index: linux-2.6-git/arch/um/include/sysdep-x86_64/syscalls.h
===================================================================
--- linux-2.6-git.orig/arch/um/include/sysdep-x86_64/syscalls.h 2008-02-01 11:24:32.000000000 -0500
+++ linux-2.6-git/arch/um/include/sysdep-x86_64/syscalls.h 2008-02-01 11:47:51.000000000 -0500
@@ -30,6 +30,4 @@ extern long old_mmap(unsigned long addr,
extern syscall_handler_t sys_modify_ldt;
extern syscall_handler_t sys_arch_prctl;

-#define NR_syscalls (UM_NR_syscall_max + 1)
-
#endif
Index: linux-2.6-git/arch/um/kernel/skas/syscall.c
===================================================================
--- linux-2.6-git.orig/arch/um/kernel/skas/syscall.c 2008-02-01 11:24:32.000000000 -0500
+++ linux-2.6-git/arch/um/kernel/skas/syscall.c 2008-02-01 11:48:02.000000000 -0500
@@ -9,6 +9,9 @@
#include "sysdep/ptrace.h"
#include "sysdep/syscalls.h"

+extern int syscall_table_size;
+#define NR_syscalls (syscall_table_size / sizeof(void *))
+
void handle_syscall(struct uml_pt_regs *r)
{
struct pt_regs *regs = container_of(r, struct pt_regs, regs);
Index: linux-2.6-git/arch/um/sys-i386/sys_call_table.S
===================================================================
--- linux-2.6-git.orig/arch/um/sys-i386/sys_call_table.S 2008-02-01 11:24:32.000000000 -0500
+++ linux-2.6-git/arch/um/sys-i386/sys_call_table.S 2008-02-01 12:08:17.000000000 -0500
@@ -9,4 +9,9 @@

#define old_mmap old_mmap_i386

+.section .rodata,"a"
+
#include "../../x86/kernel/syscall_table_32.S"
+
+ENTRY(syscall_table_size)
+.long .-sys_call_table
Index: linux-2.6-git/arch/um/include/sysdep-i386/syscalls.h
===================================================================
--- linux-2.6-git.orig/arch/um/include/sysdep-i386/syscalls.h 2007-11-28 13:01:17.000000000 -0500
+++ linux-2.6-git/arch/um/include/sysdep-i386/syscalls.h 2008-02-01 11:48:02.000000000 -0500
@@ -1,5 +1,5 @@
/*
- * Copyright (C) 2000 Jeff Dike (jdike@xxxxxxxxxx)
+ * Copyright (C) 2000 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/

@@ -18,7 +18,8 @@ extern syscall_handler_t old_mmap_i386;
extern syscall_handler_t *sys_call_table[];

#define EXECUTE_SYSCALL(syscall, regs) \
- ((long (*)(struct syscall_args)) (*sys_call_table[syscall]))(SYSCALL_ARGS(&regs->regs))
+ ((long (*)(struct syscall_args)) \
+ (*sys_call_table[syscall]))(SYSCALL_ARGS(&regs->regs))

extern long sys_mmap2(unsigned long addr, unsigned long len,
unsigned long prot, unsigned long flags,
Index: linux-2.6-git/arch/um/include/sysdep-x86_64/kernel-offsets.h
===================================================================
--- linux-2.6-git.orig/arch/um/include/sysdep-x86_64/kernel-offsets.h 2007-12-03 23:56:34.000000000 -0500
+++ linux-2.6-git/arch/um/include/sysdep-x86_64/kernel-offsets.h 2008-02-01 11:48:01.000000000 -0500
@@ -17,16 +17,7 @@
#define OFFSET(sym, str, mem) \
DEFINE(sym, offsetof(struct str, mem));

-#define __NO_STUBS 1
-#undef __SYSCALL
-#undef _ASM_X86_64_UNISTD_H_
-#define __SYSCALL(nr, sym) [nr] = 1,
-static char syscalls[] = {
-#include <asm/arch/unistd.h>
-};
-
void foo(void)
{
#include <common-offsets.h>
-DEFINE(UM_NR_syscall_max, sizeof(syscalls) - 1);
}
Index: linux-2.6-git/arch/um/sys-x86_64/syscall_table.c
===================================================================
--- linux-2.6-git.orig/arch/um/sys-x86_64/syscall_table.c 2008-01-25 11:14:05.000000000 -0500
+++ linux-2.6-git/arch/um/sys-x86_64/syscall_table.c 2008-02-01 11:48:01.000000000 -0500
@@ -46,8 +46,19 @@ typedef void (*sys_call_ptr_t)(void);

extern void sys_ni_syscall(void);

-sys_call_ptr_t sys_call_table[UM_NR_syscall_max+1] __cacheline_aligned = {
- /* Smells like a like a compiler bug -- it doesn't work when the & below is removed. */
- [0 ... UM_NR_syscall_max] = &sys_ni_syscall,
+/*
+ * We used to have a trick here which made sure that holes in the
+ * x86_64 table were filled in with sys_ni_syscall, but a comment in
+ * unistd_64.h says that holes aren't allowed, so the trick was
+ * removed.
+ * The trick looked like this
+ * [0 ... UM_NR_syscall_max] = &sys_ni_syscall
+ * before including unistd_64.h - the later initializations overwrote
+ * the sys_ni_syscall filler.
+ */
+
+sys_call_ptr_t sys_call_table[] __cacheline_aligned = {
#include <asm-x86/unistd_64.h>
};
+
+int syscall_table_size = sizeof(sys_call_table);
Redo the calculation of NR_syscalls since that disappeared from i386
and use a similar mechanism on x86_64.

We now figure out the size of the system call table in arch code and
stick that in syscall_table_size. arch/um/kernel/skas/syscall.c
defines NR_syscalls in terms of that since its the only thing that
needs to know how many system calls there are.

The old mechananism that was used on x86_64 is gone.

arch/um/include/sysdep-i386/syscalls.h got some formatting since I was
looking at it.

Signed-off-by: Jeff Dike <jdike@xxxxxxxxxxxxxxx>
---
arch/um/include/sysdep-i386/syscalls.h | 5 +++--
arch/um/include/sysdep-x86_64/kernel-offsets.h | 9 ---------
arch/um/include/sysdep-x86_64/syscalls.h | 2 --
arch/um/kernel/skas/syscall.c | 3 +++
arch/um/sys-i386/sys_call_table.S | 5 +++++
arch/um/sys-x86_64/syscall_table.c | 17 ++++++++++++++---
6 files changed, 25 insertions(+), 16 deletions(-)

Index: linux-2.6-git/arch/um/include/sysdep-x86_64/syscalls.h
===================================================================
--- linux-2.6-git.orig/arch/um/include/sysdep-x86_64/syscalls.h 2008-02-01 11:24:32.000000000 -0500
+++ linux-2.6-git/arch/um/include/sysdep-x86_64/syscalls.h 2008-02-01 11:47:51.000000000 -0500
@@ -30,6 +30,4 @@ extern long old_mmap(unsigned long addr,
extern syscall_handler_t sys_modify_ldt;
extern syscall_handler_t sys_arch_prctl;

-#define NR_syscalls (UM_NR_syscall_max + 1)
-
#endif
Index: linux-2.6-git/arch/um/kernel/skas/syscall.c
===================================================================
--- linux-2.6-git.orig/arch/um/kernel/skas/syscall.c 2008-02-01 11:24:32.000000000 -0500
+++ linux-2.6-git/arch/um/kernel/skas/syscall.c 2008-02-01 11:48:02.000000000 -0500
@@ -9,6 +9,9 @@
#include "sysdep/ptrace.h"
#include "sysdep/syscalls.h"

+extern int syscall_table_size;
+#define NR_syscalls (syscall_table_size / sizeof(void *))
+
void handle_syscall(struct uml_pt_regs *r)
{
struct pt_regs *regs = container_of(r, struct pt_regs, regs);
Index: linux-2.6-git/arch/um/sys-i386/sys_call_table.S
===================================================================
--- linux-2.6-git.orig/arch/um/sys-i386/sys_call_table.S 2008-02-01 11:24:32.000000000 -0500
+++ linux-2.6-git/arch/um/sys-i386/sys_call_table.S 2008-02-01 12:08:17.000000000 -0500
@@ -9,4 +9,9 @@

#define old_mmap old_mmap_i386

+.section .rodata,"a"
+
#include "../../x86/kernel/syscall_table_32.S"
+
+ENTRY(syscall_table_size)
+.long .-sys_call_table
Index: linux-2.6-git/arch/um/include/sysdep-i386/syscalls.h
===================================================================
--- linux-2.6-git.orig/arch/um/include/sysdep-i386/syscalls.h 2007-11-28 13:01:17.000000000 -0500
+++ linux-2.6-git/arch/um/include/sysdep-i386/syscalls.h 2008-02-01 11:48:02.000000000 -0500
@@ -1,5 +1,5 @@
/*
- * Copyright (C) 2000 Jeff Dike (jdike@xxxxxxxxxx)
+ * Copyright (C) 2000 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/

@@ -18,7 +18,8 @@ extern syscall_handler_t old_mmap_i386;
extern syscall_handler_t *sys_call_table[];

#define EXECUTE_SYSCALL(syscall, regs) \
- ((long (*)(struct syscall_args)) (*sys_call_table[syscall]))(SYSCALL_ARGS(&regs->regs))
+ ((long (*)(struct syscall_args)) \
+ (*sys_call_table[syscall]))(SYSCALL_ARGS(&regs->regs))

extern long sys_mmap2(unsigned long addr, unsigned long len,
unsigned long prot, unsigned long flags,
Index: linux-2.6-git/arch/um/include/sysdep-x86_64/kernel-offsets.h
===================================================================
--- linux-2.6-git.orig/arch/um/include/sysdep-x86_64/kernel-offsets.h 2007-12-03 23:56:34.000000000 -0500
+++ linux-2.6-git/arch/um/include/sysdep-x86_64/kernel-offsets.h 2008-02-01 11:48:01.000000000 -0500
@@ -17,16 +17,7 @@
#define OFFSET(sym, str, mem) \
DEFINE(sym, offsetof(struct str, mem));

-#define __NO_STUBS 1
-#undef __SYSCALL
-#undef _ASM_X86_64_UNISTD_H_
-#define __SYSCALL(nr, sym) [nr] = 1,
-static char syscalls[] = {
-#include <asm/arch/unistd.h>
-};
-
void foo(void)
{
#include <common-offsets.h>
-DEFINE(UM_NR_syscall_max, sizeof(syscalls) - 1);
}
Index: linux-2.6-git/arch/um/sys-x86_64/syscall_table.c
===================================================================
--- linux-2.6-git.orig/arch/um/sys-x86_64/syscall_table.c 2008-01-25 11:14:05.000000000 -0500
+++ linux-2.6-git/arch/um/sys-x86_64/syscall_table.c 2008-02-01 11:48:01.000000000 -0500
@@ -46,8 +46,19 @@ typedef void (*sys_call_ptr_t)(void);

extern void sys_ni_syscall(void);

-sys_call_ptr_t sys_call_table[UM_NR_syscall_max+1] __cacheline_aligned = {
- /* Smells like a like a compiler bug -- it doesn't work when the & below is removed. */
- [0 ... UM_NR_syscall_max] = &sys_ni_syscall,
+/*
+ * We used to have a trick here which made sure that holes in the
+ * x86_64 table were filled in with sys_ni_syscall, but a comment in
+ * unistd_64.h says that holes aren't allowed, so the trick was
+ * removed.
+ * The trick looked like this
+ * [0 ... UM_NR_syscall_max] = &sys_ni_syscall
+ * before including unistd_64.h - the later initializations overwrote
+ * the sys_ni_syscall filler.
+ */
+
+sys_call_ptr_t sys_call_table[] __cacheline_aligned = {
#include <asm-x86/unistd_64.h>
};
+
+int syscall_table_size = sizeof(sys_call_table);
--
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Next message: Oleg Nesterov: "Re: [PATCH 5/5] hrtimer_nanosleep_restart: don't play with restart_block->fn"
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