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Subject[PATCH v4 2/4] KEYS: Add ELF class-independent certificate insertion support
Date
Use ELF class-independent GElf API for processing the kernel binary. This
patch adds support for compiling the script for 64-bit and the kernel for
32-bit (e.g. make ARCH=i386 on x86-64).

Signed-off-by: Mehmet Kayaalp <mkayaalp@linux.vnet.ibm.com>
---
scripts/Makefile | 1 +
scripts/insert-sys-cert.c | 215 +++++++++++++++++++++++-----------------------
2 files changed, 109 insertions(+), 107 deletions(-)

diff --git a/scripts/Makefile b/scripts/Makefile
index 1d80897..5633f2c 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -25,6 +25,7 @@ HOSTCFLAGS_sortextable.o = -I$(srctree)/tools/include
HOSTCFLAGS_asn1_compiler.o = -I$(srctree)/include
HOSTLOADLIBES_sign-file = -lcrypto
HOSTLOADLIBES_extract-cert = -lcrypto
+HOSTLOADLIBES_insert-sys-cert = -lelf

always := $(hostprogs-y) $(hostprogs-m)

diff --git a/scripts/insert-sys-cert.c b/scripts/insert-sys-cert.c
index 8902836..86a3d41 100644
--- a/scripts/insert-sys-cert.c
+++ b/scripts/insert-sys-cert.c
@@ -24,7 +24,8 @@
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
-#include <elf.h>
+#include <gelf.h>
+#include <linux/types.h>

#define CERT_SYM "system_extra_cert"
#define USED_SYM "system_extra_cert_used"
@@ -34,18 +35,6 @@
#define warn(format, args...) fprintf(stdout, "WARNING: " format, ## args)
#define err(format, args...) fprintf(stderr, "ERROR: " format, ## args)

-#if UINTPTR_MAX == 0xffffffff
-#define CURRENT_ELFCLASS ELFCLASS32
-#define Elf_Ehdr Elf32_Ehdr
-#define Elf_Shdr Elf32_Shdr
-#define Elf_Sym Elf32_Sym
-#else
-#define CURRENT_ELFCLASS ELFCLASS64
-#define Elf_Ehdr Elf64_Ehdr
-#define Elf_Shdr Elf64_Shdr
-#define Elf_Sym Elf64_Sym
-#endif
-
static unsigned char endianness(void)
{
uint16_t two_byte = 0x00FF;
@@ -65,22 +54,17 @@ struct sym {
int size;
};

-static unsigned long get_offset_from_address(Elf_Ehdr *hdr, unsigned long addr)
+static unsigned long get_offset_from_address(Elf *elf, unsigned long addr)
{
- Elf_Shdr *x;
- unsigned int i, num_sections;
-
- x = (void *)hdr + hdr->e_shoff;
- if (hdr->e_shnum == SHN_UNDEF)
- num_sections = x[0].sh_size;
- else
- num_sections = hdr->e_shnum;
-
- for (i = 1; i < num_sections; i++) {
- unsigned long start = x[i].sh_addr;
- unsigned long end = start + x[i].sh_size;
- unsigned long offset = x[i].sh_offset;
-
+ Elf_Scn *scn = NULL;
+ GElf_Shdr shdr;
+ unsigned long start, end, offset;
+
+ while ((scn = elf_nextscn(elf, scn)) != NULL) {
+ gelf_getshdr(scn, &shdr);
+ start = shdr.sh_addr;
+ end = start + shdr.sh_size;
+ offset = shdr.sh_offset;
if (addr >= start && addr <= end)
return addr - start + offset;
}
@@ -90,7 +74,7 @@ static unsigned long get_offset_from_address(Elf_Ehdr *hdr, unsigned long addr)

#define LINE_SIZE 100

-static void get_symbol_from_map(Elf_Ehdr *hdr, FILE *f, char *name,
+static void get_symbol_from_map(Elf *elf, void *base, FILE *f, char *name,
struct sym *s)
{
char l[LINE_SIZE];
@@ -125,76 +109,65 @@ static void get_symbol_from_map(Elf_Ehdr *hdr, FILE *f, char *name,
s->address = strtoul(l, NULL, 16);
if (s->address == 0)
return;
- s->offset = get_offset_from_address(hdr, s->address);
+ s->offset = get_offset_from_address(elf, s->address);
s->name = name;
- s->content = (void *)hdr + s->offset;
-}
-
-static Elf_Sym *find_elf_symbol(Elf_Ehdr *hdr, Elf_Shdr *symtab, char *name)
-{
- Elf_Sym *sym, *symtab_start;
- char *strtab, *symname;
- unsigned int link;
- Elf_Shdr *x;
- int i, n;
-
- x = (void *)hdr + hdr->e_shoff;
- link = symtab->sh_link;
- symtab_start = (void *)hdr + symtab->sh_offset;
- n = symtab->sh_size / symtab->sh_entsize;
- strtab = (void *)hdr + x[link].sh_offset;
-
- for (i = 0; i < n; i++) {
- sym = &symtab_start[i];
- symname = strtab + sym->st_name;
- if (strcmp(symname, name) == 0)
- return sym;
- }
- err("Unable to find symbol: %s\n", name);
- return NULL;
+ s->content = (void *)base + s->offset;
}

-static void get_symbol_from_table(Elf_Ehdr *hdr, Elf_Shdr *symtab,
+static void get_symbol_from_table(Elf *elf, Elf_Scn *symtab, void *base,
char *name, struct sym *s)
{
- Elf_Shdr *sec;
- int secndx;
- Elf_Sym *elf_sym;
- Elf_Shdr *x;
+ GElf_Shdr shdr;
+ Elf_Data *data;
+ int count;
+ int i;
+ GElf_Sym sym;
+ char *symname;
+ int found = 0;
+ size_t secndx;
+ Elf_Scn *sec;
+
+ gelf_getshdr(symtab, &shdr);
+ data = elf_getdata(symtab, NULL);
+ count = shdr.sh_size / shdr.sh_entsize;
+
+ for (i = 0; i < count; i++) {
+ gelf_getsym(data, i, &sym);
+ symname = elf_strptr(elf, shdr.sh_link, sym.st_name);
+ if (strcmp(symname, name) == 0) {
+ found = 1;
+ break;
+ }
+ }

- x = (void *)hdr + hdr->e_shoff;
s->size = 0;
s->address = 0;
s->offset = 0;
- elf_sym = find_elf_symbol(hdr, symtab, name);
- if (!elf_sym)
+ if (!found)
return;
- secndx = elf_sym->st_shndx;
+ secndx = sym.st_shndx;
if (!secndx)
return;
- sec = &x[secndx];
- s->size = elf_sym->st_size;
- s->address = elf_sym->st_value;
- s->offset = s->address - sec->sh_addr
- + sec->sh_offset;
+ sec = elf_getscn(elf, secndx);
+ gelf_getshdr(sec, &shdr);
+ s->size = sym.st_size;
+ s->address = sym.st_value;
+ s->offset = s->address - shdr.sh_addr
+ + shdr.sh_offset;
s->name = name;
- s->content = (void *)hdr + s->offset;
+ s->content = base + s->offset;
}

-static Elf_Shdr *get_symbol_table(Elf_Ehdr *hdr)
+static Elf_Scn *get_symbol_table(Elf *elf)
{
- Elf_Shdr *x;
- unsigned int i, num_sections;
-
- x = (void *)hdr + hdr->e_shoff;
- if (hdr->e_shnum == SHN_UNDEF)
- num_sections = x[0].sh_size;
- else
- num_sections = hdr->e_shnum;
+ Elf_Scn *scn = NULL;
+ GElf_Shdr shdr;

- for (i = 1; i < num_sections; i++)
- if (x[i].sh_type == SHT_SYMTAB)
- return &x[i];
+ while ((scn = elf_nextscn(elf, scn)) != NULL) {
+ gelf_getshdr(scn, &shdr);
+ if (shdr.sh_type == SHT_SYMTAB)
+ return scn;
+ }
return NULL;
}

@@ -257,7 +230,7 @@ static char *read_file(char *file_name, int *size)
return buf;
}

-static void print_sym(Elf_Ehdr *hdr, struct sym *s)
+static void print_sym(struct sym *s)
{
info("sym: %s\n", s->name);
info("addr: 0x%lx\n", s->address);
@@ -277,14 +250,15 @@ int main(int argc, char **argv)
char *cert_file = NULL;
int vmlinux_size;
int cert_size;
- Elf_Ehdr *hdr;
+ char *vmlinux;
char *cert;
FILE *system_map;
- unsigned long *lsize;
int *used;
int opt;
- Elf_Shdr *symtab = NULL;
struct sym cert_sym, lsize_sym, used_sym;
+ Elf *elf;
+ GElf_Ehdr hdr_s, *hdr;
+ Elf_Scn *symtab = NULL;

while ((opt = getopt(argc, argv, "b:c:s:")) != -1) {
switch (opt) {
@@ -311,12 +285,24 @@ int main(int argc, char **argv)
if (!cert)
exit(EXIT_FAILURE);

- hdr = map_file(vmlinux_file, &vmlinux_size);
- if (!hdr)
+ vmlinux = map_file(vmlinux_file, &vmlinux_size);
+ if (!vmlinux)
exit(EXIT_FAILURE);

- if (vmlinux_size < sizeof(*hdr)) {
- err("Invalid ELF file.\n");
+ if (elf_version(EV_CURRENT) == EV_NONE) {
+ err("Init libelf failed.\n");
+ exit(EXIT_FAILURE);
+ }
+
+ elf = elf_memory(vmlinux, vmlinux_size);
+ if (!elf) {
+ err("Unable to read Elf: %s\n", elf_errmsg(elf_errno()));
+ exit(EXIT_FAILURE);
+ }
+
+ hdr = gelf_getehdr(elf, &hdr_s);
+ if (!hdr) {
+ err("Unable to read Elf_hdr: %s\n", elf_errmsg(elf_errno()));
exit(EXIT_FAILURE);
}

@@ -328,11 +314,6 @@ int main(int argc, char **argv)
exit(EXIT_FAILURE);
}

- if (hdr->e_ident[EI_CLASS] != CURRENT_ELFCLASS) {
- err("ELF class mismatch.\n");
- exit(EXIT_FAILURE);
- }
-
if (hdr->e_ident[EI_DATA] != endianness()) {
err("ELF endian mismatch.\n");
exit(EXIT_FAILURE);
@@ -343,7 +324,7 @@ int main(int argc, char **argv)
exit(EXIT_FAILURE);
}

- symtab = get_symbol_table(hdr);
+ symtab = get_symbol_table(elf);
if (!symtab) {
warn("Could not find the symbol table.\n");
if (!system_map_file) {
@@ -357,27 +338,32 @@ int main(int argc, char **argv)
perror(system_map_file);
exit(EXIT_FAILURE);
}
- get_symbol_from_map(hdr, system_map, CERT_SYM, &cert_sym);
- get_symbol_from_map(hdr, system_map, USED_SYM, &used_sym);
- get_symbol_from_map(hdr, system_map, LSIZE_SYM, &lsize_sym);
+ get_symbol_from_map(elf, vmlinux, system_map,
+ CERT_SYM, &cert_sym);
+ get_symbol_from_map(elf, vmlinux, system_map,
+ USED_SYM, &used_sym);
+ get_symbol_from_map(elf, vmlinux, system_map,
+ LSIZE_SYM, &lsize_sym);
cert_sym.size = used_sym.address - cert_sym.address;
} else {
info("Symbol table found.\n");
if (system_map_file)
warn("System.map is ignored.\n");
- get_symbol_from_table(hdr, symtab, CERT_SYM, &cert_sym);
- get_symbol_from_table(hdr, symtab, USED_SYM, &used_sym);
- get_symbol_from_table(hdr, symtab, LSIZE_SYM, &lsize_sym);
+ get_symbol_from_table(elf, symtab, vmlinux,
+ CERT_SYM, &cert_sym);
+ get_symbol_from_table(elf, symtab, vmlinux,
+ USED_SYM, &used_sym);
+ get_symbol_from_table(elf, symtab, vmlinux,
+ LSIZE_SYM, &lsize_sym);
}

if (!cert_sym.offset || !lsize_sym.offset || !used_sym.offset)
exit(EXIT_FAILURE);

- print_sym(hdr, &cert_sym);
- print_sym(hdr, &used_sym);
- print_sym(hdr, &lsize_sym);
+ print_sym(&cert_sym);
+ print_sym(&used_sym);
+ print_sym(&lsize_sym);

- lsize = (unsigned long *)lsize_sym.content;
used = (int *)used_sym.content;

if (cert_sym.size < cert_size) {
@@ -400,11 +386,26 @@ int main(int argc, char **argv)
memset(cert_sym.content + cert_size,
0, cert_sym.size - cert_size);

- *lsize = *lsize + cert_size - *used;
+ if (hdr->e_ident[EI_CLASS] == ELFCLASS64) {
+ u64 *lsize;
+
+ lsize = (u64 *)lsize_sym.content;
+ *lsize = *lsize + cert_size - *used;
+ } else {
+ u32 *lsize;
+
+ lsize = (u32 *)lsize_sym.content;
+ *lsize = *lsize + cert_size - *used;
+ }
*used = cert_size;
info("Inserted the contents of %s into %lx.\n", cert_file,
cert_sym.address);
info("Used %d bytes out of %d bytes reserved.\n", *used,
cert_sym.size);
+ if (munmap(vmlinux, vmlinux_size) == -1) {
+ perror(vmlinux_file);
+ exit(EXIT_FAILURE);
+ }
+
exit(EXIT_SUCCESS);
}
--
2.7.4
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