From 9218b1714949095bff9d9739d80f431d58e561d6 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Sun, 6 May 2007 14:51:10 -0700 Subject: uml: remove user_util.h user_util.h isn't needed any more, so delete it and remove all includes of it. Signed-off-by: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/os-Linux/file.c | 1 - 1 file changed, 1 deletion(-) (limited to 'arch/um/os-Linux/file.c') diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c index 371b4335f46d..4a9510c67622 100644 --- a/arch/um/os-Linux/file.c +++ b/arch/um/os-Linux/file.c @@ -18,7 +18,6 @@ #include "os.h" #include "user.h" #include "kern_util.h" -#include "user_util.h" static void copy_stat(struct uml_stat *dst, struct stat64 *src) { -- cgit v1.2.1 From 3d564047a5f45cb628ec72514f68076e532988f3 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Sun, 6 May 2007 14:51:32 -0700 Subject: uml: start fixing os_read_file and os_write_file This patch starts the removal of a very old, very broken piece of code. This stems from the problem of passing a userspace buffer into read() or write() on the host. If that buffer had not yet been faulted in, read and write will return -EFAULT. To avoid this problem, the solution was to fault the buffer in before the system call by touching the pages that hold the buffer by doing a copy-user of a byte to each page. This is obviously bogus, but it does usually work, in tt mode, since the kernel and process are in the same address space and userspace addresses can be accessed directly in the kernel. In skas mode, where the kernel and process are in separate address spaces, it is completely bogus because the userspace address, which is invalid in the kernel, is passed into the system call instead of the corresponding physical address, which would be valid. Here, it appears that this code, on every host read() or write(), tries to fault in a random process page. This doesn't seem to cause any correctness problems, but there is a performance impact. This patch, and the ones following, result in a 10-15% performance gain on a kernel build. This code can't be immediately tossed out because when it is, you can't log in. Apparently, there is some code in the console driver which depends on this somehow. However, we can start removing it by switching the code which does I/O using kernel addresses to using plain read() and write(). This patch introduces os_read_file_k and os_write_file_k for use with kernel buffers and converts all call locations which use obvious kernel buffers to use them. These include I/O using buffers which are local variables which are on the stack or kmalloc-ed. Later patches will handle the less obvious cases, followed by a mass conversion back to the original interface. Signed-off-by: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/os-Linux/file.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'arch/um/os-Linux/file.c') diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c index 4a9510c67622..5e9b8dcf34d4 100644 --- a/arch/um/os-Linux/file.c +++ b/arch/um/os-Linux/file.c @@ -334,12 +334,30 @@ int os_read_file(int fd, void *buf, int len) copy_from_user_proc); } +int os_read_file_k(int fd, void *buf, int len) +{ + int n = read(fd, buf, len); + + if(n < 0) + return -errno; + return n; +} + int os_write_file(int fd, const void *buf, int len) { return file_io(fd, (void *) buf, len, (int (*)(int, void *, int)) write, copy_to_user_proc); } +int os_write_file_k(int fd, const void *buf, int len) +{ + int n = write(fd, (void *) buf, len); + + if(n < 0) + return -errno; + return n; +} + int os_file_size(char *file, unsigned long long *size_out) { struct uml_stat buf; -- cgit v1.2.1 From a6ea4cceed18edebe1eb6001cb9e0f88cd741a6c Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Sun, 6 May 2007 14:51:43 -0700 Subject: uml: rename os_{read_write}_file_k back to os_{read_write}_file Rename os_{read_write}_file_k back to os_{read_write}_file, delete the originals and their bogus infrastructure, and fix all the callers. Signed-off-by: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/os-Linux/file.c | 50 ------------------------------------------------- 1 file changed, 50 deletions(-) (limited to 'arch/um/os-Linux/file.c') diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c index 5e9b8dcf34d4..6f92f732d253 100644 --- a/arch/um/os-Linux/file.c +++ b/arch/um/os-Linux/file.c @@ -290,51 +290,7 @@ int os_seek_file(int fd, __u64 offset) return 0; } -static int fault_buffer(void *start, int len, - int (*copy_proc)(void *addr, void *buf, int len)) -{ - int page = getpagesize(), i; - char c; - - for(i = 0; i < len; i += page){ - if((*copy_proc)(start + i, &c, sizeof(c))) - return -EFAULT; - } - if((len % page) != 0){ - if((*copy_proc)(start + len - 1, &c, sizeof(c))) - return -EFAULT; - } - return 0; -} - -static int file_io(int fd, void *buf, int len, - int (*io_proc)(int fd, void *buf, int len), - int (*copy_user_proc)(void *addr, void *buf, int len)) -{ - int n, err; - - do { - n = (*io_proc)(fd, buf, len); - if((n < 0) && (errno == EFAULT)){ - err = fault_buffer(buf, len, copy_user_proc); - if(err) - return err; - n = (*io_proc)(fd, buf, len); - } - } while((n < 0) && (errno == EINTR)); - - if(n < 0) - return -errno; - return n; -} - int os_read_file(int fd, void *buf, int len) -{ - return file_io(fd, buf, len, (int (*)(int, void *, int)) read, - copy_from_user_proc); -} - -int os_read_file_k(int fd, void *buf, int len) { int n = read(fd, buf, len); @@ -344,12 +300,6 @@ int os_read_file_k(int fd, void *buf, int len) } int os_write_file(int fd, const void *buf, int len) -{ - return file_io(fd, (void *) buf, len, - (int (*)(int, void *, int)) write, copy_to_user_proc); -} - -int os_write_file_k(int fd, const void *buf, int len) { int n = write(fd, (void *) buf, len); -- cgit v1.2.1