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77c066ea5

Denys Vlasenko

2009-10-25

FAILED Duration: 32s

Subject

modutils: add FEATURE_INSMOD_TRY_MMAP option

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No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

Build Log

(log yok)

Commit Diff GitHub →

modutils/Config.in +16 -0 modutils/modutils-24.c +18 -7 modutils/modutils.c +53 -10 modutils/modutils.h +6 -0

modutils/Config.in+16 -0

@@ -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

modutils/modutils-24.c+18 -7

@@ -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;

modutils/modutils.c+53 -10

@@ -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;
	}

modutils/modutils.h+6 -0

@@ -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,