[git commit master] modutils: add FEATURE_INSMOD_TRY_MMAP option
Denys Vlasenko
vda.linux at googlemail.com
Sun Oct 25 03:35:22 UTC 2009
commit: http://git.busybox.net/busybox/commit/?id=77c066ea5cf4b1ee606a81e48388ff0b1d019134
branch: http://git.busybox.net/busybox/commit/?id=refs/heads/master
function old new delta
try_to_mmap_module - 121 +121
bb_init_module_24 4514 4578 +64
bb_init_module 119 173 +54
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/0 up/down: 239/0) Total: 239 bytes
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
modutils/Config.in | 16 ++++++++++++
modutils/modutils-24.c | 25 +++++++++++++-----
modutils/modutils.c | 63 ++++++++++++++++++++++++++++++++++++++++-------
modutils/modutils.h | 6 ++++
4 files changed, 93 insertions(+), 17 deletions(-)
diff --git a/modutils/Config.in b/modutils/Config.in
index d2a2e04..83c12b6 100644
--- a/modutils/Config.in
+++ b/modutils/Config.in
@@ -121,6 +121,22 @@ config FEATURE_2_4_MODULES
This increases size considerably. Say N unless you plan
to run ancient kernels.
+config FEATURE_INSMOD_TRY_MMAP
+ bool "Try to load module from a mmap'ed area"
+ default n
+ depends on INSMOD || MODPROBE_SMALL
+ help
+ This option causes module loading code to try to mmap
+ module first. If it does not work (for example,
+ it does not work for compressed modules), module will be read
+ (and unpacked if needed) into a memory block allocated by malloc.
+
+ The only case when mmap works but malloc does not is when
+ you are trying to load a big module on a very memory-constrained
+ machine. Malloc will momentarily need 2x as much memory as mmap.
+
+ Choosing N saves about 250 bytes of code (on 32-bit x86).
+
config FEATURE_INSMOD_VERSION_CHECKING
bool "Enable module version checking"
default n
diff --git a/modutils/modutils-24.c b/modutils/modutils-24.c
index e5ff54d..a878e74 100644
--- a/modutils/modutils-24.c
+++ b/modutils/modutils-24.c
@@ -3783,12 +3783,20 @@ int FAST_FUNC bb_init_module_24(const char *m_filename, const char *options)
int m_has_modinfo;
#endif
char *image;
- size_t image_size = 64 * 1024 * 1024;
-
- /* Load module into memory and unzip if compressed */
- image = xmalloc_open_zipped_read_close(m_filename, &image_size);
- if (!image)
- return EXIT_FAILURE;
+ size_t image_size;
+ bool mmaped;
+
+ image_size = INT_MAX - 4095;
+ mmaped = 0;
+ image = try_to_mmap_module(m_filename, &image_size);
+ if (image) {
+ mmaped = 1;
+ } else {
+ /* Load module into memory and unzip if compressed */
+ image = xmalloc_open_zipped_read_close(m_filename, &image_size);
+ if (!image)
+ return EXIT_FAILURE;
+ }
m_name = xstrdup(bb_basename(m_filename));
/* "module.o[.gz]" -> "module" */
@@ -3901,7 +3909,10 @@ int FAST_FUNC bb_init_module_24(const char *m_filename, const char *options)
exit_status = EXIT_SUCCESS;
out:
- free(image);
+ if (mmaped)
+ munmap(image, image_size);
+ else
+ free(image);
free(m_name);
return exit_status;
diff --git a/modutils/modutils.c b/modutils/modutils.c
index 969926d..850a868 100644
--- a/modutils/modutils.c
+++ b/modutils/modutils.c
@@ -62,7 +62,7 @@ char* FAST_FUNC filename2modname(const char *filename, char *modname)
return modname;
}
-char * FAST_FUNC parse_cmdline_module_options(char **argv)
+char* FAST_FUNC parse_cmdline_module_options(char **argv)
{
char *options;
int optlen;
@@ -77,6 +77,40 @@ char * FAST_FUNC parse_cmdline_module_options(char **argv)
return options;
}
+#if ENABLE_FEATURE_INSMOD_TRY_MMAP
+void* FAST_FUNC try_to_mmap_module(const char *filename, size_t *image_size_p)
+{
+ /* We have user reports of failure to load 3MB module
+ * on a 16MB RAM machine. Apparently even a transient
+ * memory spike to 6MB during module load
+ * is too big for that system. */
+ void *image;
+ struct stat st;
+ int fd;
+
+ fd = xopen(filename, O_RDONLY);
+ fstat(fd, &st);
+ image = NULL;
+ /* st.st_size is off_t, we can't just pass it to mmap */
+ if (st.st_size <= *image_size_p) {
+ size_t image_size = st.st_size;
+ image = mmap(NULL, image_size, PROT_READ, MAP_PRIVATE, fd, 0);
+ if (image == MAP_FAILED) {
+ image = NULL;
+ } else if (*(uint32_t*)image != SWAP_BE32(0x7f454C46)) {
+ /* No ELF signature. Compressed module? */
+ munmap(image, image_size);
+ image = NULL;
+ } else {
+ /* Success. Report the size */
+ *image_size_p = image_size;
+ }
+ }
+ close(fd);
+ return image;
+}
+#endif
+
/* Return:
* 0 on success,
* -errno on open/read error,
@@ -84,9 +118,10 @@ char * FAST_FUNC parse_cmdline_module_options(char **argv)
*/
int FAST_FUNC bb_init_module(const char *filename, const char *options)
{
- size_t len;
+ size_t image_size;
char *image;
int rc;
+ bool mmaped;
if (!options)
options = "";
@@ -97,17 +132,25 @@ int FAST_FUNC bb_init_module(const char *filename, const char *options)
return bb_init_module_24(filename, options);
#endif
- /* Use the 2.6 way */
- len = INT_MAX - 4095;
- errno = ENOMEM; /* may be changed by e.g. open errors below */
- image = xmalloc_open_zipped_read_close(filename, &len);
- if (!image)
- return -errno;
+ image_size = INT_MAX - 4095;
+ mmaped = 0;
+ image = try_to_mmap_module(filename, &image_size);
+ if (image) {
+ mmaped = 1;
+ } else {
+ errno = ENOMEM; /* may be changed by e.g. open errors below */
+ image = xmalloc_open_zipped_read_close(filename, &image_size);
+ if (!image)
+ return -errno;
+ }
errno = 0;
- init_module(image, len, options);
+ init_module(image, image_size, options);
rc = errno;
- free(image);
+ if (mmaped)
+ munmap(image, image_size);
+ else
+ free(image);
return rc;
}
diff --git a/modutils/modutils.h b/modutils/modutils.h
index 1cf4bba..131a508 100644
--- a/modutils/modutils.h
+++ b/modutils/modutils.h
@@ -51,6 +51,12 @@ enum {
#endif
};
+#if ENABLE_FEATURE_INSMOD_TRY_MMAP
+void* FAST_FUNC try_to_mmap_module(const char *filename, size_t *image_size_p);
+#else
+# define try_to_mmap_module(filename, image_size) NULL
+#endif
+
/* Return:
* 0 on success,
* -errno on open/read error,
--
1.6.3.3
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