[PATCH] 2.6: mmap complement, fdmap

From: Matt Miller
Date: Sun Mar 21 2004 - 23:47:11 EST

Hi everyone,

This patch (for 2.6.4) exposes a new system call (sys_fdmap) that allows
for mapping a virtual memory range to a file descriptor in the context of
a process. This can be seen as the complement to mmap in that it provides
a mechanism to operate on a range of memory as if it were a file. The
supported file operations are: read, write, llseek, and mmap.

The prototype for the system call is:

int fdmap(void *vma, size_t len, int flags);

or

_syscall3(int,fdmap,void *,vma,size_t,len,int,flags);

``flags'' can be one of O_RDONLY, O_WRONLY, or O_RDWR.

I have verified functionality on ia32 and sparc as these are the only
architectures I currently have some type of access to. To test, start the
kernel configuration process and go under File systems/Pseudo filesystems
and select this option:

[*] Virtual memory file descriptor mapping support

Please let me know about any and all suggestions/bugs/flames. I tried to
be as thorough as possible but do suspect that I've missed some things.
I'm looking forward to hearing feedback.


Matt

-------

Patch details:

Target kernel release : 2.6.4
Target subsystem : fs
Number of new files : 1
Number of modified files: 33
Total file changes : 34

Patched file list:

arch/alpha/kernel/systbls.S | 4
arch/arm/kernel/calls.S | 5
arch/i386/kernel/entry.S | 5
arch/ia64/kernel/entry.S | 4
arch/m68k/kernel/entry.S | 5
arch/mips/kernel/scall32-o32.S | 5
arch/mips/kernel/scall64-64.S | 5
arch/mips/kernel/scall64-n32.S | 5
arch/mips/kernel/scall64-o32.S | 5
arch/parisc/kernel/syscall_table.S | 6
arch/ppc/kernel/misc.S | 5
arch/ppc64/kernel/misc.S | 5
arch/s390/kernel/syscalls.S | 5
arch/sh/kernel/entry.S | 5
arch/sparc/kernel/systbls.S | 8
arch/sparc64/kernel/systbls.S | 16 +
arch/um/kernel/sys_call_table.c | 5
arch/v850/kernel/entry.S | 6
fs/Kconfig | 8
fs/Makefile | 2
fs/fdmap.c | 517
+++++++++++++++++++++++++++++++++++++
include/asm-alpha/unistd.h | 2
include/asm-arm/unistd.h | 1
include/asm-i386/unistd.h | 3
include/asm-ia64/unistd.h | 3
include/asm-m68k/unistd.h | 3
include/asm-mips/unistd.h | 15 -
include/asm-parisc/unistd.h | 3
include/asm-ppc/unistd.h | 3
include/asm-ppc64/unistd.h | 3
include/asm-s390/unistd.h | 5
include/asm-sparc/unistd.h | 2
include/asm-sparc64/unistd.h | 2
include/asm-v850/unistd.h | 1
34 files changed, 657 insertions(+), 20 deletions(-)

Patch contents:

-- CUT HERE --

diff -X dontdiff -uprN linux-2.6.4/arch/alpha/kernel/systbls.S linux-2.6.4-fdmap/arch/alpha/kernel/systbls.S
--- linux-2.6.4/arch/alpha/kernel/systbls.S Wed Mar 10 20:55:35 2004
+++ linux-2.6.4-fdmap/arch/alpha/kernel/systbls.S Sun Mar 21 08:57:18 2004
@@ -292,7 +292,11 @@ sys_call_table:
.quad alpha_ni_syscall
.quad alpha_ni_syscall
.quad alpha_ni_syscall
+#ifdef CONFIG_FDMAP
+ .quad sys_fdmap
+#else
.quad alpha_ni_syscall
+#endif
.quad alpha_ni_syscall /* 275 */
.quad alpha_ni_syscall
.quad alpha_ni_syscall
diff -X dontdiff -uprN linux-2.6.4/arch/arm/kernel/calls.S linux-2.6.4-fdmap/arch/arm/kernel/calls.S
--- linux-2.6.4/arch/arm/kernel/calls.S Wed Mar 10 20:55:55 2004
+++ linux-2.6.4-fdmap/arch/arm/kernel/calls.S Sun Mar 21 08:57:40 2004
@@ -288,6 +288,11 @@ __syscall_start:
.long sys_pciconfig_iobase
.long sys_pciconfig_read
.long sys_pciconfig_write
+#ifdef CONFIG_FDMAP
+ .long sys_fdmap
+#else
+ .long sys_ni_syscall
+#endif
__syscall_end:

.rept NR_syscalls - (__syscall_end - __syscall_start) / 4
diff -X dontdiff -uprN linux-2.6.4/arch/i386/kernel/entry.S linux-2.6.4-fdmap/arch/i386/kernel/entry.S
--- linux-2.6.4/arch/i386/kernel/entry.S Wed Mar 10 20:55:24 2004
+++ linux-2.6.4-fdmap/arch/i386/kernel/entry.S Sun Mar 21 08:58:38 2004
@@ -882,5 +882,10 @@ ENTRY(sys_call_table)
.long sys_utimes
.long sys_fadvise64_64
.long sys_ni_syscall /* sys_vserver */
+#ifdef CONFIG_FDMAP
+ .long sys_fdmap /* 274 */
+#else
+ .long sys_ni_syscall
+#endif

syscall_table_size=(.-sys_call_table)
diff -X dontdiff -uprN linux-2.6.4/arch/ia64/kernel/entry.S linux-2.6.4-fdmap/arch/ia64/kernel/entry.S
--- linux-2.6.4/arch/ia64/kernel/entry.S Wed Mar 10 20:55:24 2004
+++ linux-2.6.4-fdmap/arch/ia64/kernel/entry.S Sun Mar 21 08:58:57 2004
@@ -1501,7 +1501,11 @@ sys_call_table:
data8 sys_clock_nanosleep
data8 sys_fstatfs64
data8 sys_statfs64
+#ifdef CONFIG_FDMAP
+ data8 sys_fdmap
+#else
data8 sys_ni_syscall
+#endif
data8 sys_ni_syscall // 1260
data8 sys_ni_syscall
data8 sys_ni_syscall
diff -X dontdiff -uprN linux-2.6.4/arch/m68k/kernel/entry.S linux-2.6.4-fdmap/arch/m68k/kernel/entry.S
--- linux-2.6.4/arch/m68k/kernel/entry.S Wed Mar 10 20:55:21 2004
+++ linux-2.6.4-fdmap/arch/m68k/kernel/entry.S Sun Mar 21 08:59:17 2004
@@ -663,3 +663,8 @@ sys_call_table:
.long sys_lremovexattr
.long sys_fremovexattr
.long sys_futex /* 235 */
+#ifdef CONFIG_FDMAP
+ .long sys_fdmap
+#else
+ .long sys_ni_syscall
+#endif
diff -X dontdiff -uprN linux-2.6.4/arch/mips/kernel/scall32-o32.S linux-2.6.4-fdmap/arch/mips/kernel/scall32-o32.S
--- linux-2.6.4/arch/mips/kernel/scall32-o32.S Wed Mar 10 20:55:22 2004
+++ linux-2.6.4-fdmap/arch/mips/kernel/scall32-o32.S Sun Mar 21 08:59:43 2004
@@ -614,6 +614,11 @@ out: jr ra
sys sys_clock_nanosleep 4 /* 4265 */
sys sys_tgkill 3
sys sys_utimes 2
+#ifdef CONFIG_FDMAP
+ sys sys_fdmap 3
+#else
+ sys sys_ni_syscall 0
+#endif

.endm

diff -X dontdiff -uprN linux-2.6.4/arch/mips/kernel/scall64-64.S linux-2.6.4-fdmap/arch/mips/kernel/scall64-64.S
--- linux-2.6.4/arch/mips/kernel/scall64-64.S Wed Mar 10 20:55:36 2004
+++ linux-2.6.4-fdmap/arch/mips/kernel/scall64-64.S Sun Mar 21 09:07:05 2004
@@ -432,3 +432,8 @@ sys_call_table:
PTR sys_clock_nanosleep
PTR sys_tgkill /* 5225 */
PTR sys_utimes
+#ifdef CONFIG_FDMAP
+ PTR sys_fdmap
+#else
+ PTR sys_ni_syscall
+#endif
diff -X dontdiff -uprN linux-2.6.4/arch/mips/kernel/scall64-n32.S linux-2.6.4-fdmap/arch/mips/kernel/scall64-n32.S
--- linux-2.6.4/arch/mips/kernel/scall64-n32.S Wed Mar 10 20:55:44 2004
+++ linux-2.6.4-fdmap/arch/mips/kernel/scall64-n32.S Sun Mar 21 09:07:17 2004
@@ -341,3 +341,8 @@ EXPORT(sysn32_call_table)
PTR sys_clock_nanosleep
PTR sys_tgkill
PTR compat_sys_utimes /* 6230 */
+#ifdef CONFIG_FDMAP
+ PTR sys_fdmap
+#else
+ PTR sys_ni_syscall
+#endif
diff -X dontdiff -uprN linux-2.6.4/arch/mips/kernel/scall64-o32.S linux-2.6.4-fdmap/arch/mips/kernel/scall64-o32.S
--- linux-2.6.4/arch/mips/kernel/scall64-o32.S Wed Mar 10 20:55:20 2004
+++ linux-2.6.4-fdmap/arch/mips/kernel/scall64-o32.S Sun Mar 21 09:07:29 2004
@@ -523,6 +523,11 @@ out: jr ra
sys sys_clock_nanosleep 4 /* 4265 */
sys sys_tgkill 3
sys compat_sys_utimes 2
+#ifdef CONFIG_FDMAP
+ sys sys_fdmap 3
+#else
+ sys sys_ni_syscall 0
+#endif

.endm

diff -X dontdiff -uprN linux-2.6.4/arch/parisc/kernel/syscall_table.S linux-2.6.4-fdmap/arch/parisc/kernel/syscall_table.S
--- linux-2.6.4/arch/parisc/kernel/syscall_table.S Wed Mar 10 20:55:21 2004
+++ linux-2.6.4-fdmap/arch/parisc/kernel/syscall_table.S Sun Mar 21 09:00:08 2004
@@ -334,3 +334,9 @@
ENTRY_SAME(epoll_ctl) /* 225 */
ENTRY_SAME(epoll_wait)
ENTRY_SAME(remap_file_pages)
+ ENTRY_SMAE(ni_syscall)
+#ifdef CONFIG_FDMAP
+ ENTRY_SAME(fdmap)
+#else
+ ENTRY_SAME(ni_syscall)
+#endif
diff -X dontdiff -uprN linux-2.6.4/arch/ppc/kernel/misc.S linux-2.6.4-fdmap/arch/ppc/kernel/misc.S
--- linux-2.6.4/arch/ppc/kernel/misc.S Wed Mar 10 20:55:44 2004
+++ linux-2.6.4-fdmap/arch/ppc/kernel/misc.S Sun Mar 21 09:00:20 2004
@@ -1380,3 +1380,8 @@ _GLOBAL(sys_call_table)
.long sys_fstatfs64
.long ppc_fadvise64_64
.long sys_ni_syscall /* 255 - rtas (used on ppc64) */
+#ifdef CONFIG_FDMAP
+ .long sys_fdmap
+#else
+ .long sys_ni_syscall
+#endif
diff -X dontdiff -uprN linux-2.6.4/arch/ppc64/kernel/misc.S linux-2.6.4-fdmap/arch/ppc64/kernel/misc.S
--- linux-2.6.4/arch/ppc64/kernel/misc.S Wed Mar 10 20:55:44 2004
+++ linux-2.6.4-fdmap/arch/ppc64/kernel/misc.S Sun Mar 21 09:00:33 2004
@@ -1116,3 +1116,8 @@ _GLOBAL(sys_call_table)
.llong .sys_fstatfs64
.llong .sys_ni_syscall /* 32bit only fadvise64_64 */
.llong .ppc_rtas /* 255 */
+#ifdef CONFIG_FDMAP
+ .llong .sys_fdmap
+#else
+ .llong .sys_ni_syscall
+#endif
diff -X dontdiff -uprN linux-2.6.4/arch/s390/kernel/syscalls.S linux-2.6.4-fdmap/arch/s390/kernel/syscalls.S
--- linux-2.6.4/arch/s390/kernel/syscalls.S Wed Mar 10 20:55:22 2004
+++ linux-2.6.4-fdmap/arch/s390/kernel/syscalls.S Sun Mar 21 09:01:02 2004
@@ -273,3 +273,8 @@ SYSCALL(sys_clock_getres,sys_clock_getre
SYSCALL(sys_clock_nanosleep,sys_clock_nanosleep,sys32_clock_nanosleep_wrapper)
NI_SYSCALL /* reserved for vserver */
SYSCALL(s390_fadvise64_64,sys_ni_syscall,sys32_fadvise64_64_wrapper)
+#ifdef CONFIG_FDMAP
+SYSCALL(sys_fdmap,sys_fdmap,sys_fdmap) /* 265 */
+#else
+NI_SYSCALL
+#endif
diff -X dontdiff -uprN linux-2.6.4/arch/sh/kernel/entry.S linux-2.6.4-fdmap/arch/sh/kernel/entry.S
--- linux-2.6.4/arch/sh/kernel/entry.S Wed Mar 10 20:55:25 2004
+++ linux-2.6.4-fdmap/arch/sh/kernel/entry.S Sun Mar 21 09:01:13 2004
@@ -1129,6 +1129,11 @@ ENTRY(sys_call_table)
.long sys_utimes
.long sys_fadvise64_64_wrapper
.long sys_ni_syscall /* Reserved for vserver */
+#ifdef CONFIG_FDMAP
+ .long sys_fdmap
+#else
+ .long sys_ni_syscall
+#endif

.rept NR_syscalls-(.-sys_call_table)/4
.long sys_ni_syscall
diff -X dontdiff -uprN linux-2.6.4/arch/sparc/kernel/systbls.S linux-2.6.4-fdmap/arch/sparc/kernel/systbls.S
--- linux-2.6.4/arch/sparc/kernel/systbls.S Wed Mar 10 20:55:27 2004
+++ linux-2.6.4-fdmap/arch/sparc/kernel/systbls.S Sun Mar 21 09:01:34 2004
@@ -61,7 +61,13 @@ sys_call_table:
/*200*/ .long sys_ssetmask, sys_sigsuspend, sys_newlstat, sys_uselib, old_readdir
/*205*/ .long sys_readahead, sys_socketcall, sys_syslog, sys_lookup_dcookie, sys_fadvise64
/*210*/ .long sys_fadvise64_64, sys_tgkill, sys_waitpid, sys_swapoff, sys_sysinfo
-/*215*/ .long sys_ipc, sys_sigreturn, sys_clone, sys_nis_syscall, sys_adjtimex
+/*215*/ .long sys_ipc, sys_sigreturn, sys_clone,
+#ifdef CONFIG_MAP
+/*218*/ .long sys_fdmap
+#else
+/*218*/ .long sys_ni_syscall
+#endif
+/*219*/ .long sys_adjtimex
/*220*/ .long sys_sigprocmask, sys_ni_syscall, sys_delete_module, sys_ni_syscall, sys_getpgid
/*225*/ .long sys_bdflush, sys_sysfs, sys_nis_syscall, sys_setfsuid16, sys_setfsgid16
/*230*/ .long sys_select, sys_time, sys_nis_syscall, sys_stime, sys_statfs64
diff -X dontdiff -uprN linux-2.6.4/arch/sparc64/kernel/systbls.S linux-2.6.4-fdmap/arch/sparc64/kernel/systbls.S
--- linux-2.6.4/arch/sparc64/kernel/systbls.S Wed Mar 10 20:55:26 2004
+++ linux-2.6.4-fdmap/arch/sparc64/kernel/systbls.S Sun Mar 21 09:01:59 2004
@@ -62,7 +62,13 @@ sys_call_table32:
/*200*/ .word sys_ssetmask, sys_sigsuspend, compat_sys_newlstat, sys_uselib, old32_readdir
.word sys32_readahead, sys32_socketcall, sys_syslog, sys32_lookup_dcookie, sys32_fadvise64
/*210*/ .word sys32_fadvise64_64, sys_tgkill, sys_waitpid, sys_swapoff, sys32_sysinfo
- .word sys32_ipc, sys32_sigreturn, sys_clone, sys_nis_syscall, sys32_adjtimex
+/*215*/ .word sys32_ipc, sys32_sigreturn, sys_clone
+#ifdef CONFIG_FDMAP
+/*218*/ .word sys_fdmap,
+#else
+/*218*/ .word sys_ni_syscall
+#endif
+/*219*/ .word sys32_adjtimex
/*220*/ .word compat_sys_sigprocmask, sys_ni_syscall, sys32_delete_module, sys_ni_syscall, sys_getpgid
.word sys32_bdflush, sys32_sysfs, sys_nis_syscall, sys32_setfsuid16, sys32_setfsgid16
/*230*/ .word sys32_select, sys_time, sys_nis_syscall, sys_stime, compat_statfs64
@@ -124,7 +130,13 @@ sys_call_table:
/*200*/ .word sys_ssetmask, sys_nis_syscall, sys_newlstat, sys_uselib, sys_nis_syscall
.word sys_readahead, sys_socketcall, sys_syslog, sys_lookup_dcookie, sys_fadvise64
/*210*/ .word sys_fadvise64_64, sys_tgkill, sys_waitpid, sys_swapoff, sys_sysinfo
- .word sys_ipc, sys_nis_syscall, sys_clone, sys_nis_syscall, sys_adjtimex
+ .word sys_ipc, sys_nis_syscall, sys_clone
+#ifdef CONFIG_FDMAP
+/*218*/ .word sys_fdmap
+#else
+/*218*/ .word sys_ni_syscall
+#endif
+/*219*/ .word sys_adjtimex
/*220*/ .word sys_nis_syscall, sys_ni_syscall, sys_delete_module, sys_ni_syscall, sys_getpgid
.word sys_bdflush, sys_sysfs, sys_nis_syscall, sys_setfsuid, sys_setfsgid
/*230*/ .word sys_select, sys_nis_syscall, sys_nis_syscall, sys_stime, sys_statfs64
diff -X dontdiff -uprN linux-2.6.4/arch/um/kernel/sys_call_table.c linux-2.6.4-fdmap/arch/um/kernel/sys_call_table.c
--- linux-2.6.4/arch/um/kernel/sys_call_table.c Wed Mar 10 20:55:43 2004
+++ linux-2.6.4-fdmap/arch/um/kernel/sys_call_table.c Sun Mar 21 08:56:45 2004
@@ -489,6 +489,11 @@ syscall_handler_t *sys_call_table[] = {
[ __NR_epoll_wait ] = sys_epoll_wait,
[ __NR_remap_file_pages ] = sys_remap_file_pages,
[ __NR_set_tid_address ] = sys_set_tid_address,
+#ifdef __NR_fdmap
+ [ __NR_fdmap ] = sys_fdmap,
+#else
+ [ __NR_fdmap ] = sys_ni_syscall,
+#endif

ARCH_SYSCALLS
[ LAST_SYSCALL + 1 ... NR_syscalls ] =
diff -X dontdiff -uprN linux-2.6.4/arch/v850/kernel/entry.S linux-2.6.4-fdmap/arch/v850/kernel/entry.S
--- linux-2.6.4/arch/v850/kernel/entry.S Wed Mar 10 20:55:44 2004
+++ linux-2.6.4-fdmap/arch/v850/kernel/entry.S Sun Mar 21 09:02:25 2004
@@ -1117,5 +1117,11 @@ C_DATA(sys_call_table):
.long CSYM(sys_pivot_root) // 200
.long CSYM(sys_gettid)
.long CSYM(sys_tkill)
+#ifdef CONFIG_FDMAP
+ .long CSYM(sys_fdmap)
+#else
+ .long CSYM(sys_ni_syscall)
+#endif
+
sys_call_table_end:
C_END(sys_call_table)
diff -X dontdiff -uprN linux-2.6.4/fs/Kconfig linux-2.6.4-fdmap/fs/Kconfig
--- linux-2.6.4/fs/Kconfig Wed Mar 10 20:55:29 2004
+++ linux-2.6.4-fdmap/fs/Kconfig Sat Mar 20 15:21:41 2004
@@ -864,6 +864,14 @@ config TMPFS

See <file:Documentation/filesystems/tmpfs.txt> for details.

+config FDMAP
+ bool "Virtual memory file descriptor mapping support"
+ help
+ Fdmap allows for accessing a range of memory inside a given process
+ as if it were a file on disk. This can be seen as the counterpart
+ to mmap, simply, fdmap allows for opening a range of memory that
+ can be operated on by way of read, write, lseek, et al.
+
config HUGETLBFS
bool "HugeTLB file system support"
depends X86 || IA64 || PPC64 || SPARC64 || X86_64 || BROKEN
diff -X dontdiff -uprN linux-2.6.4/fs/Makefile linux-2.6.4-fdmap/fs/Makefile
--- linux-2.6.4/fs/Makefile Wed Mar 10 20:55:29 2004
+++ linux-2.6.4-fdmap/fs/Makefile Sat Mar 20 15:22:17 2004
@@ -44,6 +44,8 @@ obj-y += devpts/

obj-$(CONFIG_PROFILING) += dcookies.o

+obj-$(CONFIG_FDMAP) += fdmap.o
+
# Do not add any filesystems before this line
obj-$(CONFIG_REISERFS_FS) += reiserfs/
obj-$(CONFIG_EXT3_FS) += ext3/ # Before ext2 so root fs can be ext3
diff -X dontdiff -uprN linux-2.6.4/fs/fdmap.c linux-2.6.4-fdmap/fs/fdmap.c
--- linux-2.6.4/fs/fdmap.c Wed Dec 31 18:00:00 1969
+++ linux-2.6.4-fdmap/fs/fdmap.c Sun Mar 21 04:08:22 2004
@@ -0,0 +1,517 @@
+/*
+ * purpose
+ *
+ * Map process memory ranges to virtual file descriptors. This can be
+ * thought of as being the opposite of mmap, simply, instead of mapping
+ * a file's contents to a memory range, fdmap maps a memory range to
+ * a virtual file. This allows one to read, write, seek, and even
+ * mmap the virtual file's contents as if it were a real file on disk.
+ *
+ * interface
+ *
+ * fdmap exposes a new system call identifier. The system call takes
+ * arguments as the following prototype conveys:
+ *
+ * int fdmap(void *addr, size_t len, int flags);
+ *
+ * ``flags'' can be one of O_RDONLY, O_WRONLY, or O_RDWR.
+ *
+ * syscall number
+ *
+ * alpha, arm, ia32, sh: 274
+ * sparc, sparc64: 218
+ * ia64: 1259
+ * m68k: 236
+ * mips: 32b=4268 64b=5227 64be32=6231
+ * parisc: 229
+ * ppc, ppc64: 256
+ * s390: 265
+ * v850: 203
+ *
+ * based on
+ *
+ * The underlying virtual filesystem code was adapted from sockfs.
+ *
+ * Matt Miller
+ * mmiller@xxxxxxxx
+ * 3/20/04
+ */
+#include <linux/string.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/utime.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mount.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/cache.h>
+#include <asm/uaccess.h>
+
+typedef struct {
+ unsigned long vma;
+ size_t vma_len;
+} fdmap_context;
+
+typedef struct {
+ fdmap_context fdmap;
+ struct inode vfs_inode;
+} fdmap_alloc;
+
+static struct super_block *fdmap_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev, void *data);
+
+static void fdmap_init_once(void *ctx, kmem_cache_t *cachep,
+ unsigned long flags);
+static struct inode *fdmap_alloc_inode(struct super_block *sb);
+static void fdmap_destroy_inode(struct inode *inode);
+
+static int fdmap_delete_dentry(struct dentry *dentry);
+
+static struct page* fdmap_nopage(struct vm_area_struct *area,
+ unsigned long address, int *type);
+
+static int fdmap_open_mem(unsigned long addr, size_t len, int flags);
+
+static loff_t fdmap_llseek(struct file *f, loff_t off, int whence);
+static ssize_t fdmap_read(struct file *f, char *buf, size_t size, loff_t *off);
+static ssize_t fdmap_write(struct file *f, const char *buf, size_t size,
+ loff_t *off);
+static int fdmap_mmap(struct file *f, struct vm_area_struct *vma);
+
+static unsigned int fdmap_copy_from_user_to_user(unsigned long base_dst,
+ unsigned long base_src,
+ unsigned int total);
+static fdmap_context *fdmap_get_context(struct inode *inode);
+
+static struct super_operations fdmap_super_ops =
+{
+ .alloc_inode = fdmap_alloc_inode,
+ .destroy_inode = fdmap_destroy_inode,
+};
+
+static struct file_system_type fdmap_fs_type =
+{
+ .name = "fdmapfs",
+ .get_sb = fdmap_get_sb,
+ .kill_sb = kill_anon_super,
+};
+
+static struct dentry_operations fdmap_dentry_ops =
+{
+ .d_delete = fdmap_delete_dentry,
+};
+
+static struct vm_operations_struct fdmap_vm_ops =
+{
+ .nopage = fdmap_nopage,
+};
+
+static struct file_operations fdmap_file_ops =
+{
+ .llseek = fdmap_llseek,
+ .read = fdmap_read,
+ .write = fdmap_write,
+ .mmap = fdmap_mmap,
+};
+
+#define FDMAP_MAGIC 0x46444d41 // FDMA
+
+static kmem_cache_t *fdmap_inode_cachep;
+static struct vfsmount *fdmap_mnt;
+static atomic_t fdmap_initialized = { 1 };
+
+/*
+ * register and mount the fdmapfs
+ */
+static void fdmap_initialize(void)
+{
+ fdmap_inode_cachep = kmem_cache_create("fdmap_inode_cache",
+ sizeof(fdmap_alloc), 0,
+ SLAB_HWCACHE_ALIGN | SLAB_RECLAIM_ACCOUNT,
+ fdmap_init_once, NULL);
+
+ if (!fdmap_inode_cachep) {
+ printk("fdmap: failed to allocate cache.\n");
+ goto out;
+ }
+
+ register_filesystem(&fdmap_fs_type);
+
+ if (!(fdmap_mnt = kern_mount(&fdmap_fs_type))) {
+ printk("fdmap: failed to mount fdmapfs.\n");
+ }
+
+out:
+}
+
+static struct super_block *fdmap_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev, void *data)
+{
+ return get_sb_pseudo(fs_type, "fdmap:", &fdmap_super_ops, FDMAP_MAGIC);
+}
+
+static void fdmap_init_once(void *ctx, kmem_cache_t *cachep,
+ unsigned long flags)
+{
+ fdmap_alloc *fma = (fdmap_alloc *)ctx;
+
+ if ((flags & SLAB_CTOR_CONSTRUCTOR))
+ inode_init_once(&fma->vfs_inode);
+}
+
+static struct inode *fdmap_alloc_inode(struct super_block *sb)
+{
+ fdmap_alloc *fma = (fdmap_alloc *)kmem_cache_alloc(fdmap_inode_cachep,
+ SLAB_KERNEL);
+
+ if (!fma)
+ return NULL;
+
+ return &fma->vfs_inode;
+}
+
+static void fdmap_destroy_inode(struct inode *inode)
+{
+ kmem_cache_free(fdmap_inode_cachep,
+ container_of(inode, fdmap_alloc, vfs_inode));
+}
+
+static int fdmap_delete_dentry(struct dentry *dentry)
+{
+ return 1;
+}
+
+/*
+ * used in conjunction with mmap of the virtual file, fdmap_nopage will
+ * copy the contents of the mapped memory range at the offset
+ * relative to the address being requested
+ */
+static struct page* fdmap_nopage(struct vm_area_struct *area,
+ unsigned long addr, int *type)
+{
+ struct page *page = alloc_page(GFP_USER);
+ struct file *f = area->vm_file;
+ fdmap_context *fmc = (fdmap_context *)f->private_data;
+ unsigned long offset;
+ struct page *fpage;
+ void *saddr, *daddr;
+ int len = PAGE_SIZE;
+
+ addr &= PAGE_MASK;
+ offset = addr - area->vm_start + (area->vm_pgoff << PAGE_SHIFT);
+
+ if (addr + PAGE_SIZE > area->vm_end)
+ len = area->vm_end - addr;
+
+ if (get_user_pages(current, current->mm, fmc->vma + offset, 1, 0, 0,
+ &fpage, NULL) < 0)
+ return NULL;
+
+ daddr = kmap(page);
+ saddr = kmap(fpage);
+
+ memcpy(daddr, saddr, len);
+
+ kunmap(fpage);
+ kunmap(page);
+
+ if (type)
+ *type = VM_FAULT_MINOR;
+
+ set_page_dirty(page);
+
+ return page;
+}
+
+/*
+ * entry point for the fdmap syscall
+ */
+asmlinkage int sys_fdmap(void *vma, size_t len, int flags)
+{
+ unsigned long addr = (unsigned long)vma;
+ int fd = -EINVAL;
+
+ if ((atomic_read(&fdmap_initialized) == 1) &&
+ (atomic_dec_and_test(&fdmap_initialized)))
+ fdmap_initialize();
+
+ if ((!len) ||
+ ((addr + len) > TASK_SIZE) ||
+ ((addr + len) < addr)) {
+ fd = -EINVAL;
+ goto out;
+ }
+
+ fd = fdmap_open_mem(addr, len, flags);
+
+out:
+ return fd;
+}
+
+/*
+ * open a virtual file and corresponding file descriptor that is tied
+ * to the passed in memory range.
+ */
+static int fdmap_open_mem(unsigned long addr, size_t len, int flags)
+{
+ struct inode *inode = NULL;
+ fdmap_context *fmc = NULL;
+ struct file *file = NULL;
+ struct qstr this;
+ int fd = 0,
+ res = -ENFILE;
+ char name[32];
+
+ flags &= (O_RDONLY | O_WRONLY | O_RDWR);
+
+ if (flags & O_RDONLY)
+ flags &= ~O_WRONLY;
+ if (flags & O_WRONLY)
+ flags &= ~O_RDONLY;
+
+ if (!(inode = new_inode(fdmap_mnt->mnt_sb)))
+ goto out;
+
+ inode->i_mode = S_IRWXUGO;
+ inode->i_uid = current->fsuid;
+ inode->i_gid = current->fsgid;
+ inode->i_size = (loff_t)len;
+
+ fmc = fdmap_get_context(inode);
+
+ if ((fd = get_unused_fd()) < 0)
+ goto cleanup;
+
+ if (!(file = get_empty_filp()))
+ goto cleanup;
+
+ sprintf(name, "[%lu]", inode->i_ino);
+
+ this.name = name;
+ this.len = strlen(name);
+ this.hash = inode->i_ino;
+
+ file->f_dentry = d_alloc(fdmap_mnt->mnt_sb->s_root, &this);
+
+ if (!file->f_dentry) {
+ res = -ENOMEM;
+ goto cleanup;
+ }
+
+ file->f_dentry->d_op = &fdmap_dentry_ops;
+
+ d_add(file->f_dentry, inode);
+
+ file->f_vfsmnt = mntget(fdmap_mnt);
+ file->f_mapping = file->f_dentry->d_inode->i_mapping;
+ file->f_op = inode->i_fop = &fdmap_file_ops;
+ file->f_mode = 3;
+ file->f_flags = flags;
+ file->f_pos = 0;
+ file->private_data = fmc;
+
+ fd_install(fd, file);
+
+ fmc->vma = addr;
+ fmc->vma_len = len;
+
+ res = fd;
+
+ goto out;
+
+cleanup:
+ if (file)
+ put_filp(file);
+
+ if (fd >= 0)
+ put_unused_fd(fd);
+out:
+ return res;
+}
+
+static loff_t fdmap_llseek(struct file *f, loff_t off, int whence)
+{
+ fdmap_context *fmc = (fdmap_context *)f->private_data;
+ int res = -EINVAL;
+
+ if (!fmc)
+ goto out;
+
+ switch (whence) {
+
+ case 0:
+ if (off < 0 || off > fmc->vma_len)
+ break;
+
+ f->f_pos = off;
+ res = 0;
+ break;
+ case 1:
+ if ((off < 0) && (f->f_pos + off < fmc->vma_len))
+ break;
+ if ((off >= 0) && (f->f_pos + off >= fmc->vma_len))
+ break;
+
+ f->f_pos += off;
+ res = 0;
+ break;
+ case 2:
+ if (off > 0)
+ break;
+ if (fmc->vma_len + off < 0)
+ break;
+
+ f->f_pos = fmc->vma_len + off;
+ res = 0;
+ break;
+ default:
+ break;
+ }
+
+out:
+ return (res < 0) ? res : f->f_pos;
+}
+
+static ssize_t fdmap_read(struct file *f, char *buf, size_t size, loff_t *off)
+{
+ fdmap_context *fmc = (fdmap_context *)f->private_data;
+ ssize_t total = -EINVAL;
+
+ if ((!fmc) ||
+ (!buf) ||
+ ((unsigned long)(buf + size) > TASK_SIZE) ||
+ ((unsigned long)(buf + size) < (unsigned long)buf))
+ goto out;
+
+
+ if (f->f_flags == O_WRONLY) {
+ total = -EACCES;
+ goto out;
+ }
+
+ total = (size > fmc->vma_len - f->f_pos) ? fmc->vma_len - f->f_pos
+ : size;
+
+ if (total)
+ total = fdmap_copy_from_user_to_user((unsigned long)buf,
+ fmc->vma + f->f_pos, (unsigned int)total);
+
+
+ f->f_pos += total;
+
+ if (off)
+ *off = f->f_pos;
+
+out:
+ return total;
+}
+
+static ssize_t fdmap_write(struct file *f, const char *buf, size_t size,
+ loff_t *off)
+{
+ fdmap_context *fmc = (fdmap_context *)f->private_data;
+ ssize_t total = -EINVAL;
+
+ if ((!fmc) ||
+ (!buf) ||
+ ((unsigned long)(buf + size) > TASK_SIZE) ||
+ ((unsigned long)(buf + size) < (unsigned long)buf))
+ goto out;
+
+ if (f->f_flags == O_RDONLY) {
+ total = -EACCES;
+ goto out;
+ }
+
+ total = (size > fmc->vma_len - f->f_pos) ? fmc->vma_len - f->f_pos
+ : size;
+
+ if (total)
+ total = fdmap_copy_from_user_to_user(fmc->vma + f->f_pos,
+ (unsigned long)buf, (unsigned int)total);
+
+ f->f_pos += total;
+
+ if (off)
+ *off = f->f_pos;
+
+out:
+ return total;
+}
+
+static int fdmap_mmap(struct file *f, struct vm_area_struct *vma)
+{
+ fdmap_context *fmc = (fdmap_context *)f->private_data;
+
+ if (vma->vm_end - (vma->vm_start + vma->vm_pgoff) > fmc->vma_len)
+ return -EFBIG;
+
+ vma->vm_ops = &fdmap_vm_ops;
+
+ return 0;
+}
+
+/*
+ * copy memory from one user address to another user address for a given
+ * number of bytes
+ */
+static unsigned int fdmap_copy_from_user_to_user(unsigned long base_dst,
+ unsigned long base_src, unsigned int total)
+{
+ unsigned int curr = 0;
+
+ while (curr < total) {
+
+ unsigned long src = (unsigned long)(base_src + curr);
+ unsigned long src_offset = src % PAGE_SIZE;
+ unsigned long dst = (unsigned long)(base_dst + curr);
+ unsigned long dst_offset = dst % PAGE_SIZE;
+ unsigned long len = total - curr;
+ struct page *spage, *dpage;
+ void *skaddr, *dkaddr;
+
+ if (len > PAGE_SIZE)
+ len = PAGE_SIZE;
+
+ down_read(&current->mm->mmap_sem);
+
+ spage = dpage = NULL;
+
+ if ((get_user_pages(current, current->mm, src, 1, 0, 0, &spage,
+ NULL) < 0) ||
+ (get_user_pages(current, current->mm, dst, 1, 1, 0, &dpage,
+ NULL) < 0)) {
+
+ if (spage)
+ put_page(spage);
+
+ up_read(&current->mm->mmap_sem);
+ break;
+ }
+
+ skaddr = kmap_atomic(spage, KM_USER0);
+ dkaddr = kmap_atomic(dpage, KM_USER0);
+
+ memcpy(dkaddr + dst_offset, skaddr + src_offset, len);
+
+ kunmap_atomic(dkaddr, KM_USER0);
+ kunmap_atomic(skaddr, KM_USER0);
+
+ set_page_dirty_lock(dpage);
+
+ put_page(dpage);
+ put_page(spage);
+
+ up_read(&current->mm->mmap_sem);
+
+ curr += len;
+ }
+
+ return curr;
+}
+
+static fdmap_context *fdmap_get_context(struct inode *inode)
+{
+ return &container_of(inode, fdmap_alloc, vfs_inode)->fdmap;
+}
diff -X dontdiff -uprN linux-2.6.4/include/asm-alpha/unistd.h linux-2.6.4-fdmap/include/asm-alpha/unistd.h
--- linux-2.6.4/include/asm-alpha/unistd.h Wed Mar 10 20:55:26 2004
+++ linux-2.6.4-fdmap/include/asm-alpha/unistd.h Sun Mar 21 03:53:01 2004
@@ -232,7 +232,7 @@
#define __NR_osf_swapctl 259 /* not implemented */
#define __NR_osf_memcntl 260 /* not implemented */
#define __NR_osf_fdatasync 261 /* not implemented */
-
+#define __NR_fdmap 274

/*
* Linux-specific system calls begin at 300
diff -X dontdiff -uprN linux-2.6.4/include/asm-arm/unistd.h linux-2.6.4-fdmap/include/asm-arm/unistd.h
--- linux-2.6.4/include/asm-arm/unistd.h Wed Mar 10 20:55:44 2004
+++ linux-2.6.4-fdmap/include/asm-arm/unistd.h Sun Mar 21 03:55:24 2004
@@ -299,6 +299,7 @@
#define __NR_pciconfig_iobase (__NR_SYSCALL_BASE+271)
#define __NR_pciconfig_read (__NR_SYSCALL_BASE+272)
#define __NR_pciconfig_write (__NR_SYSCALL_BASE+273)
+#define __NR_fdmap (__NR_SYSCALL_BASE+274)

/*
* The following SWIs are ARM private.
diff -X dontdiff -uprN linux-2.6.4/include/asm-i386/unistd.h linux-2.6.4-fdmap/include/asm-i386/unistd.h
--- linux-2.6.4/include/asm-i386/unistd.h Wed Mar 10 20:55:35 2004
+++ linux-2.6.4-fdmap/include/asm-i386/unistd.h Sun Mar 21 03:55:54 2004
@@ -279,8 +279,9 @@
#define __NR_utimes 271
#define __NR_fadvise64_64 272
#define __NR_vserver 273
+#define __NR_fdmap 274

-#define NR_syscalls 274
+#define NR_syscalls 275

/* user-visible error numbers are in the range -1 - -124: see <asm-i386/errno.h> */

diff -X dontdiff -uprN linux-2.6.4/include/asm-ia64/unistd.h linux-2.6.4-fdmap/include/asm-ia64/unistd.h
--- linux-2.6.4/include/asm-ia64/unistd.h Wed Mar 10 20:55:22 2004
+++ linux-2.6.4-fdmap/include/asm-ia64/unistd.h Sun Mar 21 04:01:10 2004
@@ -248,10 +248,11 @@
#define __NR_clock_nanosleep 1256
#define __NR_fstatfs64 1257
#define __NR_statfs64 1258
+#define __NR_fdmap 1259

#ifdef __KERNEL__

-#define NR_syscalls 256 /* length of syscall table */
+#define NR_syscalls 257 /* length of syscall table */

#if !defined(__ASSEMBLY__) && !defined(ASSEMBLER)

diff -X dontdiff -uprN linux-2.6.4/include/asm-m68k/unistd.h linux-2.6.4-fdmap/include/asm-m68k/unistd.h
--- linux-2.6.4/include/asm-m68k/unistd.h Wed Mar 10 20:55:27 2004
+++ linux-2.6.4-fdmap/include/asm-m68k/unistd.h Sun Mar 21 04:01:35 2004
@@ -238,8 +238,9 @@
#define __NR_lremovexattr 233
#define __NR_fremovexattr 234
#define __NR_futex 235
+#define __NR_fdmap 236

-#define NR_syscalls 236
+#define NR_syscalls 237

/* user-visible error numbers are in the range -1 - -124: see
<asm-m68k/errno.h> */
diff -X dontdiff -uprN linux-2.6.4/include/asm-mips/unistd.h linux-2.6.4-fdmap/include/asm-mips/unistd.h
--- linux-2.6.4/include/asm-mips/unistd.h Wed Mar 10 20:55:21 2004
+++ linux-2.6.4-fdmap/include/asm-mips/unistd.h Sun Mar 21 04:06:08 2004
@@ -288,16 +288,17 @@
#define __NR_clock_nanosleep (__NR_Linux + 265)
#define __NR_tgkill (__NR_Linux + 266)
#define __NR_utimes (__NR_Linux + 267)
+#define __NR_fdmap (__NR_Linux + 268)

/*
* Offset of the last Linux o32 flavoured syscall
*/
-#define __NR_Linux_syscalls 267
+#define __NR_Linux_syscalls 268

#endif /* _MIPS_SIM == _MIPS_SIM_ABI32 */

#define __NR_O32_Linux 4000
-#define __NR_O32_Linux_syscalls 267
+#define __NR_O32_Linux_syscalls 268

#if _MIPS_SIM == _MIPS_SIM_ABI64

@@ -532,16 +533,17 @@
#define __NR_clock_nanosleep (__NR_Linux + 224)
#define __NR_tgkill (__NR_Linux + 225)
#define __NR_utimes (__NR_Linux + 226)
+#define __NR_fdmap (__NR_Linux + 227)

/*
* Offset of the last Linux flavoured syscall
*/
-#define __NR_Linux_syscalls 226
+#define __NR_Linux_syscalls 227

#endif /* _MIPS_SIM == _MIPS_SIM_ABI64 */

#define __NR_64_Linux 5000
-#define __NR_64_Linux_syscalls 226
+#define __NR_64_Linux_syscalls 227

#if _MIPS_SIM == _MIPS_SIM_NABI32

@@ -780,16 +782,17 @@
#define __NR_clock_nanosleep (__NR_Linux + 228)
#define __NR_tgkill (__NR_Linux + 229)
#define __NR_utimes (__NR_Linux + 230)
+#define __NR_fdmap (__NR_Linux + 231)

/*
* Offset of the last N32 flavoured syscall
*/
-#define __NR_Linux_syscalls 230
+#define __NR_Linux_syscalls 231

#endif /* _MIPS_SIM == _MIPS_SIM_NABI32 */

#define __NR_N32_Linux 6000
-#define __NR_N32_Linux_syscalls 230
+#define __NR_N32_Linux_syscalls 231

#ifndef __ASSEMBLY__

diff -X dontdiff -uprN linux-2.6.4/include/asm-parisc/unistd.h linux-2.6.4-fdmap/include/asm-parisc/unistd.h
--- linux-2.6.4/include/asm-parisc/unistd.h Wed Mar 10 20:55:20 2004
+++ linux-2.6.4-fdmap/include/asm-parisc/unistd.h Sun Mar 21 04:06:54 2004
@@ -721,9 +721,10 @@
#define __NR_epoll_wait (__NR_Linux + 226)
#define __NR_remap_file_pages (__NR_Linux + 227)
#define __NR_semtimedop (__NR_Linux + 228)
+#define __NR_fdmap (__NR_Linux + 229)


-#define __NR_Linux_syscalls 228
+#define __NR_Linux_syscalls 229

#define HPUX_GATEWAY_ADDR 0xC0000004
#define LINUX_GATEWAY_ADDR 0x100
diff -X dontdiff -uprN linux-2.6.4/include/asm-ppc/unistd.h linux-2.6.4-fdmap/include/asm-ppc/unistd.h
--- linux-2.6.4/include/asm-ppc/unistd.h Wed Mar 10 20:55:23 2004
+++ linux-2.6.4-fdmap/include/asm-ppc/unistd.h Sun Mar 21 04:08:40 2004
@@ -260,8 +260,9 @@
#define __NR_fstatfs64 253
#define __NR_fadvise64_64 254
#define __NR_rtas 255
+#define __NR_fdmap 256

-#define __NR_syscalls 256
+#define __NR_syscalls 257

#define __NR(n) #n

diff -X dontdiff -uprN linux-2.6.4/include/asm-ppc64/unistd.h linux-2.6.4-fdmap/include/asm-ppc64/unistd.h
--- linux-2.6.4/include/asm-ppc64/unistd.h Wed Mar 10 20:55:21 2004
+++ linux-2.6.4-fdmap/include/asm-ppc64/unistd.h Sun Mar 21 04:09:16 2004
@@ -266,8 +266,9 @@
#define __NR_fstatfs64 253
#define __NR_fadvise64_64 254
#define __NR_rtas 255
+#define __NR_fdmap 256

-#define __NR_syscalls 256
+#define __NR_syscalls 257
#ifdef __KERNEL__
#define NR_syscalls __NR_syscalls
#endif
diff -X dontdiff -uprN linux-2.6.4/include/asm-s390/unistd.h linux-2.6.4-fdmap/include/asm-s390/unistd.h
--- linux-2.6.4/include/asm-s390/unistd.h Wed Mar 10 20:55:55 2004
+++ linux-2.6.4-fdmap/include/asm-s390/unistd.h Sun Mar 21 04:09:53 2004
@@ -256,12 +256,13 @@
#define __NR_clock_gettime (__NR_timer_create+6)
#define __NR_clock_getres (__NR_timer_create+7)
#define __NR_clock_nanosleep (__NR_timer_create+8)
+#define __NR_fdmap 265
/*
* Number 263 is reserved for vserver
*/
-#define __NR_fadvise64_64 264
+#define __NR_fadvise64_64 265

-#define NR_syscalls 265
+#define NR_syscalls 266

/*
* There are some system calls that are not present on 64 bit, some
diff -X dontdiff -uprN linux-2.6.4/include/asm-sparc/unistd.h linux-2.6.4-fdmap/include/asm-sparc/unistd.h
--- linux-2.6.4/include/asm-sparc/unistd.h Wed Mar 10 20:55:22 2004
+++ linux-2.6.4-fdmap/include/asm-sparc/unistd.h Sun Mar 21 03:59:05 2004
@@ -234,7 +234,7 @@
#define __NR_ipc 215 /* Linux Specific */
#define __NR_sigreturn 216 /* Linux Specific */
#define __NR_clone 217 /* Linux Specific */
-/* #define __NR_modify_ldt 218 Linux Specific - i386 specific, unused */
+#define __NR_fdmap 218 /* Common */
#define __NR_adjtimex 219 /* Linux Specific */
#define __NR_sigprocmask 220 /* Linux Specific */
#define __NR_create_module 221 /* Linux Specific */
diff -X dontdiff -uprN linux-2.6.4/include/asm-sparc64/unistd.h linux-2.6.4-fdmap/include/asm-sparc64/unistd.h
--- linux-2.6.4/include/asm-sparc64/unistd.h Wed Mar 10 20:55:23 2004
+++ linux-2.6.4-fdmap/include/asm-sparc64/unistd.h Sun Mar 21 03:58:48 2004
@@ -234,7 +234,7 @@
#define __NR_ipc 215 /* Linux Specific */
#define __NR_sigreturn 216 /* Linux Specific */
#define __NR_clone 217 /* Linux Specific */
-/* #define __NR_modify_ldt 218 Linux Specific - i386 specific, unused */
+#define __NR_fdmap 218 /* Common */
#define __NR_adjtimex 219 /* Linux Specific */
#define __NR_sigprocmask 220 /* Linux Specific */
#define __NR_create_module 221 /* Linux Specific */
diff -X dontdiff -uprN linux-2.6.4/include/asm-v850/unistd.h linux-2.6.4-fdmap/include/asm-v850/unistd.h
--- linux-2.6.4/include/asm-v850/unistd.h Wed Mar 10 20:55:50 2004
+++ linux-2.6.4-fdmap/include/asm-v850/unistd.h Sun Mar 21 04:10:21 2004
@@ -205,6 +205,7 @@
#define __NR_pivot_root 200
#define __NR_gettid 201
#define __NR_tkill 202
+#define __NR_fdmap 203


/* Syscall protocol:

-
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