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

diff --git a/modutils/modutils-24.c b/modutils/modutils-24.c
index 169fe54..89bc30f 100644 (file)
--- 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;