module loading for 2.4: use fd-based io instead of FILE based;

 use xlseek and xread; simpler check for ELF signature.

   text    data     bss     dec     hex filename
 824460     476    7616  832552   cb428 busybox_old
 824333     476    7616  832425   cb3a9 busybox_unstripped

1 files changed, 27 insertions, 35 deletions

diff --git a/modutils/modutils-24.c b/modutils/modutils-24.c
index 169fe54..89bc30f 100644
--- a/modutils/modutils-24.c
+++ b/modutils/modutils-24.c
@@ -625,7 +625,7 @@ static unsigned long obj_load_size(struct obj_file *f);
 
 static int obj_relocate(struct obj_file *f, ElfW(Addr) base);
 
-static struct obj_file *obj_load(FILE *f, int loadprogbits);
+static struct obj_file *obj_load(int fd, int loadprogbits);
 
 static int obj_create_image(struct obj_file *f, char *image);
 
@@ -3191,8 +3191,13 @@ static int obj_create_image(struct obj_file *f, char *image)
 
 /*======================================================================*/
 
-static struct obj_file *obj_load(FILE *fp, int loadprogbits UNUSED_PARAM)
+static struct obj_file *obj_load(int fd, int loadprogbits UNUSED_PARAM)
 {
+#if BB_LITTLE_ENDIAN
+# define ELFMAG_U32 ((uint32_t)(ELFMAG0 + 0x100 * (ELFMAG1 + (0x100 * (ELFMAG2 + 0x100 * ELFMAG3)))))
+#else
+# define ELFMAG_U32 ((uint32_t)((((ELFMAG0 * 0x100) + ELFMAG1) * 0x100 + ELFMAG2) * 0x100 + ELFMAG3))
+#endif
 	struct obj_file *f;
 	ElfW(Shdr) * section_headers;
 	size_t shnum, i;
@@ -3205,16 +3210,10 @@ static struct obj_file *obj_load(FILE *fp, int loadprogbits UNUSED_PARAM)
 	f->symbol_hash = obj_elf_hash;
 	f->load_order_search_start = &f->load_order;
 
-	fseek(fp, 0, SEEK_SET);
-	if (fread(&f->header, sizeof(f->header), 1, fp) != 1) {
-		bb_perror_msg_and_die("error reading ELF header");
-	}
+	xlseek(fd, 0, SEEK_SET);
+	xread(fd, &f->header, sizeof(f->header));
 
-	if (f->header.e_ident[EI_MAG0] != ELFMAG0
-	 || f->header.e_ident[EI_MAG1] != ELFMAG1
-	 || f->header.e_ident[EI_MAG2] != ELFMAG2
-	 || f->header.e_ident[EI_MAG3] != ELFMAG3
-	) {
+	if (*(uint32_t*)(&f->header.e_ident) != ELFMAG_U32) {
 		bb_error_msg_and_die("not an ELF file");
 	}
 	if (f->header.e_ident[EI_CLASS] != ELFCLASSM
@@ -3243,10 +3242,8 @@ static struct obj_file *obj_load(FILE *fp, int loadprogbits UNUSED_PARAM)
 	f->sections = xzalloc(sizeof(f->sections[0]) * (shnum + 4));
 
 	section_headers = alloca(sizeof(ElfW(Shdr)) * shnum);
-	fseek(fp, f->header.e_shoff, SEEK_SET);
-	if (fread(section_headers, sizeof(ElfW(Shdr)), shnum, fp) != shnum) {
-		bb_perror_msg_and_die("error reading ELF section headers");
-	}
+	xlseek(fd, f->header.e_shoff, SEEK_SET);
+	xread(fd, section_headers, sizeof(ElfW(Shdr)) * shnum);
 
 	/* Read the section data.  */
 
@@ -3278,10 +3275,8 @@ static struct obj_file *obj_load(FILE *fp, int loadprogbits UNUSED_PARAM)
 				sec->contents = NULL;
 				if (sec->header.sh_size > 0) {
 					sec->contents = xmalloc(sec->header.sh_size);
-					fseek(fp, sec->header.sh_offset, SEEK_SET);
-					if (fread(sec->contents, sec->header.sh_size, 1, fp) != 1) {
-						bb_perror_msg_and_die("error reading ELF section data");
-					}
+					xlseek(fd, sec->header.sh_offset, SEEK_SET);
+					xread(fd, sec->contents, sec->header.sh_size);
 				}
 				break;
 #if SHT_RELM == SHT_REL
@@ -3397,27 +3392,24 @@ static struct obj_file *obj_load(FILE *fp, int loadprogbits UNUSED_PARAM)
  * kernel for the module
  */
 
-static int obj_load_progbits(FILE *fp, struct obj_file *f, char *imagebase)
+static int obj_load_progbits(int fd, struct obj_file *f, char *imagebase)
 {
 	ElfW(Addr) base = f->baseaddr;
 	struct obj_section* sec;
 
 	for (sec = f->load_order; sec; sec = sec->load_next) {
-
 		/* section already loaded? */
 		if (sec->contents != NULL)
 			continue;
-
 		if (sec->header.sh_size == 0)
 			continue;
-
 		sec->contents = imagebase + (sec->header.sh_addr - base);
-		fseek(fp, sec->header.sh_offset, SEEK_SET);
-		if (fread(sec->contents, sec->header.sh_size, 1, fp) != 1) {
+		xlseek(fd, sec->header.sh_offset, SEEK_SET);
+		errno = 0; /* read may be short without errno being set */
+		if (full_read(fd, sec->contents, sec->header.sh_size) != sec->header.sh_size) {
 			bb_perror_msg("error reading ELF section data");
 			return 0;
 		}
-
 	}
 	return 1;
 }
@@ -3779,22 +3771,23 @@ int FAST_FUNC bb_init_module_24(const char *m_filename, const char *options)
 	struct utsname uts;
 	int exit_status = EXIT_FAILURE;
 	int m_has_modinfo;
-	char *m_name;
+	char *m_name, *p;
 #if ENABLE_FEATURE_INSMOD_VERSION_CHECKING
 	char m_strversion[STRVERSIONLEN];
 	int m_version, m_crcs;
 #endif
-	FILE *fp;
+	int fd;
 
 	uname(&uts);
-	fp = fopen_for_read(m_filename);
-	if (fp == NULL)
+	fd = open_or_warn(m_filename, O_RDONLY);
+	if (fd < 0)
 		return EXIT_FAILURE;
 
 	m_name = xstrdup(bb_basename(m_filename));
-	*strrchr(m_name, '.') = 0;
+	p = strrchr(m_name, '.');
+	if (p) *p = '\0';
 
-	f = obj_load(fp, LOADBITS);
+	f = obj_load(fd, LOADBITS);
 
 	m_has_modinfo = (get_modinfo_value(f, "kernel_version") != NULL);
 
@@ -3876,7 +3869,7 @@ int FAST_FUNC bb_init_module_24(const char *m_filename, const char *options)
 	 * the PROGBITS section was not loaded by the obj_load
 	 * now we can load them directly into the kernel memory
 	 */
-	if (!obj_load_progbits(fp, f, (char*)m_addr)) {
+	if (!obj_load_progbits(fd, f, (char*)m_addr)) {
 		delete_module(m_name, 0);
 		goto out;
 	}
@@ -3898,8 +3891,7 @@ int FAST_FUNC bb_init_module_24(const char *m_filename, const char *options)
 	exit_status = EXIT_SUCCESS;
 
  out:
-	if (fp)
-		fclose(fp);
+	close(fd);
 	free(m_name);
 
 	return exit_status;