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Subject[RFC] syscalls-by-name (aka dynamic syscalls / vsyscalls)
The attached patch implements syscalls-by-name in an initial and 
rather crud method -- the x86isms need tidying up, but the technique
is usable across platforms. Syscalls provided by name are made
available to userland by means of a dynamic shared library that
maps and provides a jumptable into a set of vsyscalls. The vsyscalls
can then enter the kernel through whatever mechanism (the only means
implemented right now is via a new syscall, sys_dynamic_syscall) the
kernel choses. Version mismatch between the kernel and the library
is prevented by means of a unique fingerprint the library checks on
load against what the kernel provides via /dev/vsys.

/dev/vsys is a simple device node that allows user code to map the
vsyscall area into their address space. This is different from the
fixed address that x86-64 uses to allow UML emulation of vsyscalls,
and prevent other problems that could crop up with the intrusion of
unexpected code into user address space.

For a quick example on how a new syscall is declared, I added the following
lines into fs/aio.c in the aio patch:

#include <asm/vsyscall.h>
... rest of file ...
add_dynamic_syscall(sys_io_setup);
add_dynamic_syscall(sys_io_destroy);
add_dynamic_syscall(sys_io_submit);
add_dynamic_syscall(sys_io_cancel);
add_dynamic_syscall(sys_io_wait);
add_dynamic_syscall(sys_io_getevents);

Similarly, vsyscalls can be added by means of adding an attribute to a
function declaration that puts the code into the VSYSCALL segment. This
segment is linked at a virtual address just above the top of the default
user stack, but is kept within the kernel image and mapped via /dev/vsys.

My current todos on the code are to clean it up so that the arch specific
parts are better seperated, add symbol versions, and resurrect the
sysenter / sysexit code as the means of entering the dynamic syscalls.
There's also TSC based gettimeofday() code to finish off and add...

The patch is against 2.4.9-acsomething + aio + stuff, but should be pretty
easy to merge into recent kernels. If anyone has any comments or tweaks,
I'd like to hear about them. Cheers,

-ben

:r ~/syscall-by-name-A4.diff
diff -urN linux.wrk.orig/Makefile linux.wrk.diff/Makefile
--- linux.wrk.orig/Makefile Mon Jan 14 23:22:42 2002
+++ linux.wrk.diff/Makefile Thu Jan 17 16:00:55 2002
@@ -236,7 +236,7 @@
drivers/sound/pndsperm.c \
drivers/sound/pndspini.c \
drivers/atm/fore200e_*_fw.c drivers/atm/.fore200e_*.fw \
- .version .config* config.in config.old \
+ .uniquebytes .version .config* config.in config.old \
scripts/tkparse scripts/kconfig.tk scripts/kconfig.tmp \
scripts/lxdialog/*.o scripts/lxdialog/lxdialog \
.menuconfig.log \
@@ -283,6 +283,7 @@

vmlinux: include/linux/version.h $(CONFIGURATION) init/main.o init/version.o linuxsubdirs
@$(MAKE) CFLAGS="$(CFLAGS) $(CFLAGS_KERNEL)" kallsyms
+ @$(MAKE) -C ulib

.PHONY: kallsyms

@@ -332,14 +333,17 @@

linuxsubdirs: $(patsubst %, _dir_%, $(SUBDIRS))

-$(patsubst %, _dir_%, $(SUBDIRS)) : dummy include/linux/version.h include/config/MARKER
+$(patsubst %, _dir_%, $(SUBDIRS)) : dummy include/linux/compile.h include/config/MARKER
$(MAKE) CFLAGS="$(CFLAGS) $(CFLAGS_KERNEL)" -C $(patsubst _dir_%, %, $@)

$(TOPDIR)/include/linux/version.h: include/linux/version.h
$(TOPDIR)/include/linux/compile.h: include/linux/compile.h

newversion:
- . scripts/mkversion > .version
+ . scripts/mkversion > .tmpversion
+ @mv -f .tmpversion .version
+ rm -f .uniquebytes
+ dd if=/dev/urandom of=.uniquebytes bs=1 count=16

include/linux/compile.h: $(CONFIGURATION) include/linux/version.h newversion
@echo -n \#define UTS_VERSION \"\#`cat .version` > .ver
@@ -357,9 +361,10 @@
echo \#define LINUX_COMPILE_DOMAIN ; \
fi >> .ver
@echo \#define LINUX_COMPILER \"`$(CC) $(CFLAGS) -v 2>&1 | tail -1`\" >> .ver
+ @echo \#define LINUX_UNIQUE_BYTES `hexdump -e '1/1 "0x%02x, "' .uniquebytes | sed -e 's/, \$$//g'` >>.ver
@mv -f .ver $@

-include/linux/version.h: ./Makefile include/linux/autoconf.h
+include/linux/version.h: ./Makefile include/linux/autoconf.h
@echo \#define UTS_RELEASE \"$(KERNELRELEASE)\" > .ver
@echo \#define LINUX_VERSION_CODE `expr $(VERSION) \\* 65536 + $(PATCHLEVEL) \\* 256 + $(SUBLEVEL)` >> .ver
@echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))' >>.ver
@@ -453,6 +458,7 @@
rm -f $(CLEAN_FILES)
rm -rf $(CLEAN_DIRS)
$(MAKE) -C Documentation/DocBook clean
+ $(MAKE) -C ulib clean

mrproper: clean archmrproper
find . \( -size 0 -o -name .depend \) -type f -print | xargs rm -f
diff -urN linux.wrk.orig/arch/i386/Makefile linux.wrk.diff/arch/i386/Makefile
--- linux.wrk.orig/arch/i386/Makefile Mon Jan 14 23:22:41 2002
+++ linux.wrk.diff/arch/i386/Makefile Thu Jan 17 15:13:37 2002
@@ -127,7 +127,7 @@
zlilo: vmlinux
@$(MAKEBOOT) BOOTIMAGE=zImage zlilo

-tmp:
+tmp: ulib
@$(MAKEBOOT) BOOTIMAGE=bzImage zlilo
bzlilo: vmlinux
@$(MAKEBOOT) BOOTIMAGE=bzImage zlilo
diff -urN linux.wrk.orig/arch/i386/kernel/Makefile linux.wrk.diff/arch/i386/kernel/Makefile
--- linux.wrk.orig/arch/i386/kernel/Makefile Mon Jan 14 23:22:40 2002
+++ linux.wrk.diff/arch/i386/kernel/Makefile Thu Jan 17 15:08:43 2002
@@ -23,8 +23,7 @@
obj-y := process.o semaphore.o signal.o entry.o traps.o irq.o vm86.o \
ptrace.o i8259.o ioport.o ldt.o setup.o time.o sys_i386.o \
pci-dma.o i386_ksyms.o i387.o bluesmoke.o dmi_scan.o \
- bootflag.o
-
+ bootflag.o vsysdata.o vunique.o dynamic_syscall.o

ifdef CONFIG_PCI
obj-y += pci-i386.o
@@ -53,3 +52,4 @@

abi-machdep.o: $(abi-machdep-objs)
$(LD) -r -o $@ $(abi-machdep-objs)
+
diff -urN linux.wrk.orig/arch/i386/kernel/dynamic_syscall.c linux.wrk.diff/arch/i386/kernel/dynamic_syscall.c
--- linux.wrk.orig/arch/i386/kernel/dynamic_syscall.c Wed Dec 31 19:00:00 1969
+++ linux.wrk.diff/arch/i386/kernel/dynamic_syscall.c Thu Jan 17 13:39:07 2002
@@ -0,0 +1,66 @@
+/* arch/i386/kernel/dynamic_syscall.c
+ * Entry code for dynamic syscalls on i386.
+ */
+#include <linux/kernel.h>
+#include <linux/compiler.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <asm/ptrace.h>
+#include <asm/uaccess.h>
+
+struct dummy_args {
+ long data[8];
+};
+
+extern struct vsyscall_entry {
+ long eip;
+ long (*call)(struct dummy_args args);
+} vsyscall_list_begin, vsyscall_list_end;
+
+long sys_dynamic_syscall(struct pt_regs regs) __attribute__((regparm(0)));
+
+long sys_dynamic_syscall(struct pt_regs regs)
+{
+ struct dummy_args dummy_args;
+ struct vsyscall_entry *ent = (void *)regs.edx;
+ void *args = (void *)regs.ecx;
+ long ret;
+
+ pr_debug("ent = %p args = %p\n", ent, args);
+ pr_debug("eip = 0x%08lx\n", regs.eip);
+
+ /* The pointer must be aligned in the table. */
+ if (unlikely((long)ent & (sizeof(*ent) - 1))) {
+ pr_debug("unaligned\n");
+ goto err;
+ }
+
+ /* Bounds checking... */
+ if (unlikely(ent < &vsyscall_list_begin) ||
+ unlikely(ent >= &vsyscall_list_end)) {
+ pr_debug("out of range %p <= %p < %p\n",
+ &vsyscall_list_begin, ent,
+ &vsyscall_list_end);
+ goto err;
+ }
+ /* The entry should be valid now. Verify that the caller's eip
+ * is correct.
+ */
+ if (unlikely(ent->eip != regs.eip)) {
+ pr_debug("eip mismatch (0x%lx vs 0x%lx)\n", ent->eip, regs.eip);
+ goto err;
+ }
+
+ pr_debug("ent->call = %p\n", ent->call);
+
+ if (unlikely(copy_from_user(&dummy_args, args, sizeof(dummy_args))))
+ return -EFAULT;
+
+ ret = ent->call(dummy_args);
+
+ pr_debug("ret = 0x%08lx\n", ret);
+
+ return ret;
+err:
+ return -ENOSYS;
+}
diff -urN linux.wrk.orig/arch/i386/kernel/entry.S linux.wrk.diff/arch/i386/kernel/entry.S
--- linux.wrk.orig/arch/i386/kernel/entry.S Wed Jan 16 00:34:52 2002
+++ linux.wrk.diff/arch/i386/kernel/entry.S Wed Jan 16 17:02:37 2002
@@ -46,6 +46,7 @@
#include <asm/segment.h>
#define ASSEMBLY
#include <asm/smp.h>
+#include <asm/unistd.h>

EBX = 0x00
ECX = 0x04
@@ -635,6 +636,11 @@
# endif
#endif

+ .rept __NR_sys_dynamic_syscall-(.-sys_call_table)/4
+ .long SYMBOL_NAME(sys_ni_syscall)
+ .endr
+ .long SYMBOL_NAME(sys_dynamic_syscall)
+
/* More patch resilient means of adding syscalls */
.rept 244-(.-sys_call_table)/4
.long SYMBOL_NAME(sys_ni_syscall)
diff -urN linux.wrk.orig/arch/i386/kernel/vsysdata.c linux.wrk.diff/arch/i386/kernel/vsysdata.c
--- linux.wrk.orig/arch/i386/kernel/vsysdata.c Wed Dec 31 19:00:00 1969
+++ linux.wrk.diff/arch/i386/kernel/vsysdata.c Wed Jan 16 00:35:39 2002
@@ -0,0 +1,11 @@
+/* vsysdata.c - declarations for variables shared with the kernel
+ *
+ * Items placed in .data.vsyscall have a kernel virtual address
+ * and are read/write from kernel space only. The copy placed
+ * in .vsyscall_data are linked at a userspace address and are
+ * read only accessible from userland.
+ */
+#include <linux/vsyscall.h>
+
+union vsys_union user_vsys_cpudata[256] __attribute__((section(".vsyscall_data")));
+//asm(".globl vsys_cpudata ; bobbob = user_vsys_cpudata - vsyscall_text_begin ; vsys_cpudata = bobbob + VSYSCALL_text");
diff -urN linux.wrk.orig/arch/i386/kernel/vunique.S linux.wrk.diff/arch/i386/kernel/vunique.S
--- linux.wrk.orig/arch/i386/kernel/vunique.S Wed Dec 31 19:00:00 1969
+++ linux.wrk.diff/arch/i386/kernel/vunique.S Thu Jan 17 15:09:09 2002
@@ -0,0 +1,7 @@
+#include <linux/compile.h>
+
+ .section .first_vsyscall_text,"xa"
+ .globl signature
+signature:
+ .byte LINUX_UNIQUE_BYTES
+ .size signature,.-signature
diff -urN linux.wrk.orig/arch/i386/vmlinux.lds linux.wrk.diff/arch/i386/vmlinux.lds
--- linux.wrk.orig/arch/i386/vmlinux.lds Mon Jan 14 23:22:37 2002
+++ linux.wrk.diff/arch/i386/vmlinux.lds Thu Jan 17 16:31:17 2002
@@ -13,6 +13,26 @@
*(.fixup)
*(.gnu.warning)
} = 0x9090
+ /* Note: most of these declarations are in kernel/vsysdata.c,vsyscall.S.
+ * We use two segments for the data liked at a kernel virtual address
+ * (.data.vsyscall) and user virtual address (.vsyscall_data).
+ * .vsyscall_text is linked at a kernel virtual address
+ */
+ . = ALIGN(4096);
+ VSYSCALL_text = .;
+ VSYSCALL 0xbfff0000 : AT ( VSYSCALL_text ) {
+ vsyscall_text_begin = .;
+ *(.first_vsyscall_text)
+ *(.vsyscall_text)
+ . = ALIGN(4096);
+ vsyscall_text_end = .;
+ *(.vsyscall_data)
+ . = ALIGN(4096);
+ vsyscall_data_end = .;
+ }
+ vsys_cpudata = user_vsys_cpudata - vsyscall_text_begin + VSYSCALL_text;
+ . = VSYSCALL_text + SIZEOF(VSYSCALL);
+ VSYSCALL_text_end = .;
.text.lock : { *(.text.lock) } /* out-of-line lock text */
.rodata : { *(.rodata) }
.kstrtab : { *(.kstrtab) }
@@ -23,12 +43,21 @@
__start___ksymtab = .; /* Kernel symbol table */
__ksymtab : { *(__ksymtab) }
__stop___ksymtab = .;
- __start___kallsyms = .; /* All kernel symbols */
+ __start___kallsyms = .; /* All kernel symbols */
__kallsyms : { *(__kallsyms) }
__stop___kallsyms = .;
_etext = .; /* End of text section */
.data : { /* Data */
*(.data)
+ . = ALIGN(8);
+ vsyscall_list_begin = .;
+ *(.data.vsyscall_list)
+ vsyscall_list_end = .;
+ . = ALIGN(4096);
+ kernel_vsyscall_data_begin = .;
+ *(.data.vsyscall)
+ . = ALIGN(4096);
+ kernel_vsyscall_data_end = .;
CONSTRUCTORS
}
_edata = .; /* End of data section */
@@ -70,4 +99,15 @@
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
+/*
+# VSYSCALL : {
+# / * vsyscall area *i /
+# __vsyscall_begin = .;
+# *(vsyscall_text)
+# . = ALIGN(4096);
+# *(.data.vsyscall)
+# . = ALIGN(4096);
+# __vsyscall_end = .;
+# } >vsyscall_area
+*/
}
diff -urN linux.wrk.orig/arch/i386/vmlinux.lds.S linux.wrk.diff/arch/i386/vmlinux.lds.S
--- linux.wrk.orig/arch/i386/vmlinux.lds.S Mon Jan 14 23:22:37 2002
+++ linux.wrk.diff/arch/i386/vmlinux.lds.S Thu Jan 17 15:09:34 2002
@@ -13,6 +13,28 @@
*(.fixup)
*(.gnu.warning)
} = 0x9090
+
+ /* Note: most of these declarations are in kernel/vsysdata.c,vsyscall.S.
+ * We use two segments for the data liked at a kernel virtual address
+ * (.data.vsyscall) and user virtual address (.vsyscall_data).
+ * .vsyscall_text is linked at a kernel virtual address
+ */
+ . = ALIGN(4096);
+ VSYSCALL_text = .;
+ VSYSCALL 0xbfff0000 : AT ( VSYSCALL_text ) {
+ vsyscall_text_begin = .;
+ *(.first_vsyscall_text)
+ *(.vsyscall_text)
+ . = ALIGN(4096);
+ vsyscall_text_end = .;
+ *(.vsyscall_data)
+ . = ALIGN(4096);
+ vsyscall_data_end = .;
+ }
+ vsys_cpudata = user_vsys_cpudata - vsyscall_text_begin + VSYSCALL_text;
+ . = VSYSCALL_text + SIZEOF(VSYSCALL);
+ VSYSCALL_text_end = .;
+
.text.lock : { *(.text.lock) } /* out-of-line lock text */
.rodata : { *(.rodata) }
.kstrtab : { *(.kstrtab) }
@@ -34,6 +56,18 @@

.data : { /* Data */
*(.data)
+
+ . = ALIGN(8);
+ vsyscall_list_begin = .;
+ *(.data.vsyscall_list)
+ vsyscall_list_end = .;
+
+ . = ALIGN(4096);
+ kernel_vsyscall_data_begin = .;
+ *(.data.vsyscall)
+ . = ALIGN(4096);
+ kernel_vsyscall_data_end = .;
+
CONSTRUCTORS
}

@@ -83,4 +117,16 @@
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
+
+/*
+# VSYSCALL : {
+# / * vsyscall area *i /
+# __vsyscall_begin = .;
+# *(vsyscall_text)
+# . = ALIGN(4096);
+# *(.data.vsyscall)
+# . = ALIGN(4096);
+# __vsyscall_end = .;
+# } >vsyscall_area
+*/
}
diff -urN linux.wrk.orig/drivers/char/mem.c linux.wrk.diff/drivers/char/mem.c
--- linux.wrk.orig/drivers/char/mem.c Mon Jan 14 23:22:37 2002
+++ linux.wrk.diff/drivers/char/mem.c Thu Jan 17 13:47:22 2002
@@ -25,6 +25,7 @@
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/pgalloc.h>
+#include <asm/a.out.h>

#ifdef CONFIG_SENSORS
extern void sensors_init_all(void);
@@ -539,6 +540,77 @@
write: write_full,
};

+int vsys_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ extern unsigned char vsyscall_text_begin, vsyscall_text_end, VSYSCALL_text[];
+ unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
+ unsigned long len = vma->vm_end - vma->vm_start;
+ unsigned long actual_len = &vsyscall_text_end - &vsyscall_text_begin;
+
+ if ((offset + len) > actual_len)
+ len = actual_len - offset;
+
+ pr_debug("len = 0x%lx, actual_len = 0x%lx\n", len, actual_len);
+
+ vma->vm_start = (unsigned long)&vsyscall_text_begin + offset;
+ vma->vm_end = vma->vm_start + len;
+ vma->vm_flags |= VM_RESERVED;
+
+ pr_debug("vm_start = 0x%lx, vm_end = 0x%lx\n",
+ vma->vm_start, vma->vm_end);
+ pr_debug("va=%p pa=0x%lx\n",
+ VSYSCALL_text + offset,
+ __pa(VSYSCALL_text) + offset);
+
+ if (vma->vm_start < (unsigned long)&vsyscall_text_begin) {
+ pr_debug("vsys_mmap: start < begin\n");
+ return -EINVAL;
+ }
+
+ if (vma->vm_end < (unsigned long)&vsyscall_text_begin) {
+ pr_debug("vsys_mmap: end < begin\n");
+ return -EINVAL;
+ }
+
+ if (vma->vm_end > (unsigned long)&vsyscall_text_end) {
+ pr_debug("vsys_mmap: end(%lx) > text_end(%p)\n",
+ vma->vm_end, &vsyscall_text_end);
+ return -EINVAL;
+ }
+
+ if (vma->vm_start >= vma->vm_end) {
+ pr_debug("vsys_mmap: end\n");
+ return -EINVAL;
+ }
+
+ if (find_vma_intersection(current->mm, vma->vm_start, vma->vm_end)) {
+ pr_debug("vsyscall: mapping collision\n");
+ return -EINVAL;
+ }
+
+ if ((vma->vm_flags & (VM_SHARED | VM_WRITE)) == (VM_SHARED | VM_WRITE)) {
+ pr_debug("vsyscall: attempt to write to mapping\n");
+ return -EPERM;
+ }
+
+ if (remap_page_range(vma->vm_start,
+ __pa(VSYSCALL_text) + offset,
+ vma->vm_end-vma->vm_start,
+ vma->vm_page_prot))
+ return -EAGAIN;
+
+ pr_debug("VSYSCALL_text(%p): %02x %02x %02x %02x\n",
+ VSYSCALL_text,
+ VSYSCALL_text[0], VSYSCALL_text[1],
+ VSYSCALL_text[2], VSYSCALL_text[3]);
+
+ return 0;
+}
+
+static struct file_operations vsys_fops = {
+ mmap: vsys_mmap,
+};
+
static int memory_open(struct inode * inode, struct file * filp)
{
switch (MINOR(inode->i_rdev)) {
@@ -568,6 +640,9 @@
case 9:
filp->f_op = &urandom_fops;
break;
+ case 11:
+ filp->f_op = &vsys_fops;
+ break;
default:
return -ENXIO;
}
@@ -592,7 +667,8 @@
{5, "zero", S_IRUGO | S_IWUGO, &zero_fops},
{7, "full", S_IRUGO | S_IWUGO, &full_fops},
{8, "random", S_IRUGO | S_IWUSR, &random_fops},
- {9, "urandom", S_IRUGO | S_IWUSR, &urandom_fops}
+ {9, "urandom", S_IRUGO | S_IWUSR, &urandom_fops},
+ {11,"vsys", S_IRUGO | S_IWUSR, &vsys_fops},
};
int i;

diff -urN linux.wrk.orig/include/asm-i386/a.out.h linux.wrk.diff/include/asm-i386/a.out.h
--- linux.wrk.orig/include/asm-i386/a.out.h Fri Jun 16 14:33:06 1995
+++ linux.wrk.diff/include/asm-i386/a.out.h Thu Jan 17 16:25:31 2002
@@ -19,7 +19,9 @@

#ifdef __KERNEL__

-#define STACK_TOP TASK_SIZE
+#define VSYSCALL_SIZE 0x10000 /* 64KB for vsyscalls */
+#define STACK_GUARD_SIZE 0x02000 /* 8KB guard area */
+#define STACK_TOP (TASK_SIZE - VSYSCALL_SIZE - STACK_GUARD_SIZE)

#endif

diff -urN linux.wrk.orig/include/asm-i386/unistd.h linux.wrk.diff/include/asm-i386/unistd.h
--- linux.wrk.orig/include/asm-i386/unistd.h Wed Jan 16 00:34:52 2002
+++ linux.wrk.diff/include/asm-i386/unistd.h Wed Jan 16 17:09:10 2002
@@ -228,6 +228,8 @@
#define __NR_getdents64 220
#define __NR_fcntl64 221

+#define __NR_sys_dynamic_syscall 230
+
/* gap here for now */
#define __NR_io_setup 244
#define __NR_io_destroy 245
diff -urN linux.wrk.orig/include/asm-i386/vsyscall.h linux.wrk.diff/include/asm-i386/vsyscall.h
--- linux.wrk.orig/include/asm-i386/vsyscall.h Wed Dec 31 19:00:00 1969
+++ linux.wrk.diff/include/asm-i386/vsyscall.h Thu Jan 17 01:53:32 2002
@@ -0,0 +1,41 @@
+#ifndef __ASM__VSYSCALL_H
+#define __ASM__VSYSCALL_H
+/* include/asm-i386/vsyscall.h
+ * Copyright 2002 Red Hat, Inc.
+ */
+#include <linux/linkage.h>
+#include <asm/unistd.h>
+
+/* We call sys_dynamic_syscall(long nr, void *args) using regparm(2)
+ * convention. The .text.vsyscall section is mapped into userspace,
+ * whereas .data.vsyscall_list is a kernel-only array of the vsyscalls
+ * and the valid userspace address to call them from. All vsyscalls
+ * are called with C calling convention (ie args on the stack for x86).
+ *
+ * Note: the layout of .data.vsyscall_list must match the entries in
+ * dynamic_syscall.c.
+ */
+#define STRINGIFYa(x) #x
+#define STRINGIFY(x) STRINGIFYa(x)
+#define NR_dyn_sys STRINGIFY(__NR_sys_dynamic_syscall)
+#define add_dynamic_syscall(name) \
+ __asm__(" \n\
+ .section .vsyscall_text, \"xa\" \n\
+ .globl v" #name " \n\
+ v" #name ": \n\
+ push %ecx \n\
+ push %edx \n\
+ movl $" NR_dyn_sys ",%eax \n\
+ movl $2f,%edx \n\
+ leal 12(%esp),%ecx \n\
+ int $0x80 \n\
+ 1: \n\
+ popl %edx \n\
+ popl %ecx \n\
+ ret \n\
+ .size v" #name ",.-v" #name " \n\
+ .section .data.vsyscall_list,\"a\" \n\
+ 2: .long 1b," #name " \n\
+ .previous")
+
+#endif
diff -urN linux.wrk.orig/include/linux/vsyscall.h linux.wrk.diff/include/linux/vsyscall.h
--- linux.wrk.orig/include/linux/vsyscall.h Wed Dec 31 19:00:00 1969
+++ linux.wrk.diff/include/linux/vsyscall.h Wed Jan 16 00:35:39 2002
@@ -0,0 +1,20 @@
+#ifndef _LINUX__VSYSCALL_H
+#define _LINUX__VSYSCALL_H
+
+struct vsys_cpudata {
+ unsigned long context_switches;
+ unsigned long tv_sec;
+ unsigned long tsc_low, tsc_high;
+ unsigned long cycles_per_sec;
+};
+
+union vsys_union {
+ struct vsys_cpudata data;
+ char pad[128];
+};
+
+extern union vsys_union vsys_cpudata[256] __attribute__((section(".data.vsyscall")));
+
+#define vsys_data(cpu) (&vsys_cpudata[cpu].data)
+
+#endif /*ndef _LINUX__VSYSCALL_H*/
diff -urN linux.wrk.orig/ulib/Makefile linux.wrk.diff/ulib/Makefile
--- linux.wrk.orig/ulib/Makefile Wed Dec 31 19:00:00 1969
+++ linux.wrk.diff/ulib/Makefile Thu Jan 17 13:56:25 2002
@@ -0,0 +1,26 @@
+all: libkernel.so
+
+ASFLAGS=-D__KERNEL__ -D__ASSEMBLY__ -I../include -nostdlib -nostartfiles
+CFLAGS=-D__KERNEL__ -I../include -nostdlib -nostartfiles
+
+vsysaddr.S: ../System.map stub.S Makefile
+ rm -f vsysaddr.S
+ echo '#include "stub.S"' >vsysaddr.S
+ awk -- "/^bfff.* vsys_/ { print \"dynamic_syscall(\"\$$3 \",0x\" \$$1 \")\"; }" <../System.map >>vsysaddr.S
+
+vsysaddr.o: vsysaddr.S
+
+kso_init.o: ../include/linux/compile.h
+
+libkernel.so.1: vsysaddr.o kso_init.o
+ ld -E -symbolic -shared -soname=libkernel.so -o $@ vsysaddr.o kso_init.o
+
+libkernel.so: libkernel.so.1
+ ln -sf $< $@
+
+clean:
+ rm -f *.o libkernel.so myln libkernel.so.1 vsysaddr.S
+
+# test app
+myln: myln.c libkernel.so Makefile
+ cc -g -o myln myln.c -L. -lkernel
diff -urN linux.wrk.orig/ulib/kso_init.c linux.wrk.diff/ulib/kso_init.c
--- linux.wrk.orig/ulib/kso_init.c Wed Dec 31 19:00:00 1969
+++ linux.wrk.diff/ulib/kso_init.c Thu Jan 17 16:16:15 2002
@@ -0,0 +1,48 @@
+#include <linux/compile.h>
+#include <linux/types.h>
+#include <asm/unistd.h>
+#include <asm/fcntl.h>
+#include <asm/mman.h>
+#include <asm/a.out.h>
+
+char libkernel_enosys = 1; /* the asm in stub.S depends on this */
+
+long _init(void)
+{
+ static char unique[] = { LINUX_UNIQUE_BYTES };
+ int errno;
+ long addr;
+ int fd;
+ int i;
+
+ _syscall6(int, mmap2, unsigned long, addr, unsigned long, len,
+ unsigned long, prot, unsigned long, flags,
+ unsigned long, fd, unsigned long, pgoff)
+ _syscall2(long, munmap, unsigned long, addr, size_t, len)
+ _syscall2(int, open, const char *, name, int, flags)
+ _syscall1(int, close, int, fd)
+
+ if (sizeof(unique) != 16)
+ return -1;
+
+ fd = open("/dev/vsys", O_RDONLY);
+ if (-1 == fd)
+ return -1;
+
+ addr = mmap2(0, VSYSCALL_SIZE, PROT_READ | PROT_EXEC, MAP_SHARED, fd, 0);
+ if (-1 == addr)
+ return -1;
+
+ close(fd);
+
+ for (i=0; i<sizeof(unique); i++)
+ if (unique[i] != ((char *)addr)[i]) {
+ munmap(addr, VSYSCALL_SIZE);
+ return -1;
+ }
+
+ /* okay, all the syscalls we provide are now good */
+ libkernel_enosys = 0;
+ return 0;
+}
+
diff -urN linux.wrk.orig/ulib/myln.c linux.wrk.diff/ulib/myln.c
--- linux.wrk.orig/ulib/myln.c Wed Dec 31 19:00:00 1969
+++ linux.wrk.diff/ulib/myln.c Thu Jan 17 09:18:59 2002
@@ -0,0 +1,25 @@
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+int main ()
+{
+ long ctx = 0;
+ extern long vsys_io_setup(long, long *);
+ unsigned char *bob = (void*)&vsys_io_setup;
+ long ret;
+ int i;
+ printf("%p\n", bob);
+ //printf("%p\n", mmap(0, 65536, PROT_READ | PROT_EXEC, MAP_SHARED,
+ // open("/dev/vsys", O_RDONLY), 0));
+ //for (i=0; i<16; i++)
+ // printf(" %02x\n", bob[i]);
+ //printf("\n");
+
+ ret = vsys_io_setup(100, &ctx);
+
+ printf("ret=%ld, ctx=0x%lx\n", ret, ctx);
+ return 0;
+}
diff -urN linux.wrk.orig/ulib/stub.S linux.wrk.diff/ulib/stub.S
--- linux.wrk.orig/ulib/stub.S Wed Dec 31 19:00:00 1969
+++ linux.wrk.diff/ulib/stub.S Thu Jan 17 16:25:38 2002
@@ -0,0 +1,18 @@
+/* stub.S */
+#include <asm/segment.h>
+#include <asm/errno.h>
+
+ .text
+
+#define dynamic_syscall(x,a) \
+ .globl x ;\
+ .align 16 ;\
+ x: ;\
+ cmpb $0,libkernel_enosys ;\
+ jne 1f ;\
+ ljmp $__USER_CS, $a ;\
+ 1: ;\
+ movl $-ENOSYS,%eax ;\
+ ret ;\
+ .size x,.-x
+
-
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