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 169fe54ae..89bc30fe5 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;