libkmod: store common section off/size and use them

Currently, we repeatedly loop over the elf headers looking for five well
known sections. Just do it once in kmod_elf_new() and reuse the data as
needed.

Note that not all sections are guaranteed to be available, so check and
ELFDBG print the ones which are missing.

v2: quit looping when found, ELFDBG print missing sections
v3: match the first section name, use a loop

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Link: https://github.com/kmod-project/kmod/pull/210
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>

diff --git a/libkmod/libkmod-elf.c b/libkmod/libkmod-elf.c
index d2b91438c03287de7446bbb2c2268978c906a602..8ff04f8f2c00b572ae24ac2eeb9d6b27739831bd 100644 (file)
--- a/libkmod/libkmod-elf.c
+++ b/libkmod/libkmod-elf.c
@@ -27,6 +27,23 @@ struct kmod_modversion64 {
        char name[64 - sizeof(uint64_t)];
 };
 
+enum kmod_elf_section {
+       KMOD_ELF_SECTION_KSYMTAB,
+       KMOD_ELF_SECTION_MODINFO,
+       KMOD_ELF_SECTION_STRTAB,
+       KMOD_ELF_SECTION_SYMTAB,
+       KMOD_ELF_SECTION_VERSIONS,
+       KMOD_ELF_SECTION_MAX,
+};
+
+static const char *const section_name_map[] = {
+       [KMOD_ELF_SECTION_KSYMTAB] = "__ksymtab_strings",
+       [KMOD_ELF_SECTION_MODINFO] = ".modinfo",
+       [KMOD_ELF_SECTION_STRTAB] = ".strtab",
+       [KMOD_ELF_SECTION_SYMTAB] = ".symtab",
+       [KMOD_ELF_SECTION_VERSIONS] = "__versions",
+};
+
 struct kmod_elf {
        const uint8_t *memory;
        uint64_t size;
@@ -45,6 +62,10 @@ struct kmod_elf {
                } strings;
                uint16_t machine;
        } header;
+       struct {
+               uint64_t offset;
+               uint64_t size;
+       } sections[KMOD_ELF_SECTION_MAX];
 };
 
 //#undef ENABLE_ELFDBG
@@ -248,6 +269,42 @@ fail:
        return -EINVAL;
 }
 
+static void kmod_elf_save_sections(struct kmod_elf *elf)
+{
+       const uint16_t all_sec = (1 << KMOD_ELF_SECTION_MAX) - 1;
+       uint16_t found_sec = 0;
+       enum kmod_elf_section sec;
+
+       for (uint16_t i = 1; i < elf->header.section.count && found_sec != all_sec; i++) {
+               uint64_t off, size;
+               const char *n;
+               int err = elf_get_section_info(elf, i, &off, &size, &n);
+               if (err < 0)
+                       continue;
+
+               for (sec = KMOD_ELF_SECTION_KSYMTAB; sec < KMOD_ELF_SECTION_MAX; sec++) {
+                       if (found_sec & (1 << sec))
+                               continue;
+
+                       if (streq(section_name_map[sec], n)) {
+                               elf->sections[sec].offset = off;
+                               elf->sections[sec].size = size;
+                               found_sec |= 1 << sec;
+                               break;
+                       }
+               }
+       }
+
+       for (sec = KMOD_ELF_SECTION_KSYMTAB; sec < KMOD_ELF_SECTION_MAX; sec++) {
+               if (found_sec & (1 << sec))
+                       continue;
+
+               ELFDBG(elf, "section %s not found\n", section_name_map[sec]);
+               elf->sections[sec].offset = 0;
+               elf->sections[sec].size = 0;
+       }
+}
+
 struct kmod_elf *kmod_elf_new(const void *memory, off_t size)
 {
        struct kmod_elf *elf;
@@ -335,6 +392,7 @@ struct kmod_elf *kmod_elf_new(const void *memory, off_t size)
                }
        }
 
+       kmod_elf_save_sections(elf);
        return elf;
 
 invalid:
@@ -390,13 +448,13 @@ int kmod_elf_get_modinfo_strings(const struct kmod_elf *elf, char ***array)
        uint64_t off, size;
        const char *strings;
        char *s, **a;
-       int err;
 
        *array = NULL;
 
-       err = kmod_elf_get_section(elf, ".modinfo", &off, &size);
-       if (err < 0)
-               return err;
+       off = elf->sections[KMOD_ELF_SECTION_MODINFO].offset;
+       size = elf->sections[KMOD_ELF_SECTION_MODINFO].size;
+       if (off == 0)
+               return -ENODATA;
 
        strings = elf_get_mem(elf, off);
 
@@ -486,15 +544,16 @@ int kmod_elf_get_modversions(const struct kmod_elf *elf, struct kmod_modversion
        size_t off, crclen, namlen, verlen;
        uint64_t sec_off, size;
        struct kmod_modversion *a;
-       int i, count, err;
+       int i, count;
 
        elf_get_modversion_lengths(elf, &verlen, &crclen, &namlen);
 
        *array = NULL;
 
-       err = kmod_elf_get_section(elf, "__versions", &sec_off, &size);
-       if (err < 0)
-               return err;
+       sec_off = elf->sections[KMOD_ELF_SECTION_VERSIONS].offset;
+       size = elf->sections[KMOD_ELF_SECTION_VERSIONS].size;
+       if (sec_off == 0)
+               return -ENODATA;
 
        if (size == 0)
                return 0;
@@ -560,11 +619,11 @@ static int elf_strip_vermagic(const struct kmod_elf *elf, uint8_t *changed)
 {
        uint64_t i, sec_off, size;
        const char *strings;
-       int err;
 
-       err = kmod_elf_get_section(elf, ".modinfo", &sec_off, &size);
-       if (err < 0)
-               return err == -ENODATA ? 0 : err;
+       sec_off = elf->sections[KMOD_ELF_SECTION_MODINFO].offset;
+       size = elf->sections[KMOD_ELF_SECTION_MODINFO].size;
+       if (sec_off == 0)
+               return 0;
        strings = elf_get_mem(elf, sec_off);
 
        /* skip zero padding */
@@ -645,14 +704,15 @@ static int kmod_elf_get_symbols_symtab(const struct kmod_elf *elf,
        uint64_t i, last, off, size;
        const char *strings;
        struct kmod_modversion *a;
-       int count, err;
+       int count;
        size_t total_size;
 
        *array = NULL;
 
-       err = kmod_elf_get_section(elf, "__ksymtab_strings", &off, &size);
-       if (err < 0)
-               return err;
+       off = elf->sections[KMOD_ELF_SECTION_KSYMTAB].offset;
+       size = elf->sections[KMOD_ELF_SECTION_KSYMTAB].size;
+       if (off == 0)
+               return -ENODATA;
        strings = elf_get_mem(elf, off);
 
        /* skip zero padding */
@@ -757,16 +817,17 @@ int kmod_elf_get_symbols(const struct kmod_elf *elf, struct kmod_modversion **ar
        uint64_t strtablen, symtablen, str_sec_off, sym_sec_off, str_off, sym_off;
        struct kmod_modversion *a;
        size_t i, count, symcount, symlen;
-       int err;
 
-       err = kmod_elf_get_section(elf, ".strtab", &str_sec_off, &strtablen);
-       if (err < 0) {
+       str_sec_off = elf->sections[KMOD_ELF_SECTION_STRTAB].offset;
+       strtablen = elf->sections[KMOD_ELF_SECTION_STRTAB].size;
+       if (str_sec_off == 0) {
                ELFDBG(elf, "no .strtab found.\n");
                goto fallback;
        }
 
-       err = kmod_elf_get_section(elf, ".symtab", &sym_sec_off, &symtablen);
-       if (err < 0) {
+       sym_sec_off = elf->sections[KMOD_ELF_SECTION_SYMTAB].offset;
+       symtablen = elf->sections[KMOD_ELF_SECTION_SYMTAB].size;
+       if (sym_sec_off == 0) {
                ELFDBG(elf, "no .symtab found.\n");
                goto fallback;
        }
@@ -913,13 +974,14 @@ int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,
        uint64_t str_sec_off, sym_sec_off;
        struct kmod_modversion *a;
        size_t namlen, verlen, symlen, crclen;
-       int i, count, symcount, vercount, err;
+       int i, count, symcount, vercount;
        bool handle_register_symbols;
        uint8_t *visited_versions;
        uint64_t *symcrcs;
 
-       err = kmod_elf_get_section(elf, "__versions", &ver_off, &versionslen);
-       if (err < 0) {
+       ver_off = elf->sections[KMOD_ELF_SECTION_VERSIONS].offset;
+       versionslen = elf->sections[KMOD_ELF_SECTION_VERSIONS].size;
+       if (ver_off == 0) {
                versionslen = 0;
                verlen = 0;
                crclen = 0;
@@ -936,14 +998,16 @@ int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,
                }
        }
 
-       err = kmod_elf_get_section(elf, ".strtab", &str_sec_off, &strtablen);
-       if (err < 0) {
+       str_sec_off = elf->sections[KMOD_ELF_SECTION_STRTAB].offset;
+       strtablen = elf->sections[KMOD_ELF_SECTION_STRTAB].size;
+       if (str_sec_off == 0) {
                ELFDBG(elf, "no .strtab found.\n");
                return -EINVAL;
        }
 
-       err = kmod_elf_get_section(elf, ".symtab", &sym_sec_off, &symtablen);
-       if (err < 0) {
+       sym_sec_off = elf->sections[KMOD_ELF_SECTION_SYMTAB].offset;
+       symtablen = elf->sections[KMOD_ELF_SECTION_SYMTAB].size;
+       if (sym_sec_off == 0) {
                ELFDBG(elf, "no .symtab found.\n");
                return -EINVAL;
        }