Skip to content

Commit

Permalink
efi: PE file size differ from in-memory size
Browse files Browse the repository at this point in the history 
PE headers code_sz and image_sz indicate more or less, the size of the
file and the size of the in-memory image. They are now given the right
value.

In the ELF format, only the program headers are reliable to determine
the actually needed part of the file and the in-memory size.

The .bss section should always be marked as NOLOAD for ld since its
content shouldn't be included into the binary file.

Signed-off-by: Sylvain Gault <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>
  • Loading branch information
Sylvain Gault authored and H. Peter Anvin committed Feb 15, 2014
1 parent 0468e14 commit 9e49e29
Show file tree
Hide file tree
Showing 3 changed files with 45 additions and 101 deletions.
4 changes: 2 additions & 2 deletions efi/i386/syslinux.ld
View file
Original file line number Diff line number Diff line change
Expand Up @@ -136,7 +136,7 @@ SECTIONS
*(.strtab)
}

.bss : {
.bss (NOLOAD) : {
/* the EFI loader doesn't seem to like a .bss section,
so we stick it all into .data: */
__bss_start = .;
Expand All @@ -153,7 +153,7 @@ SECTIONS
__bss_dwords = (__bss_len + 3) >> 2;

. = ALIGN(128);

/* Very large objects which don't need to be zeroed */

.hugebss : {
Expand Down
138 changes: 41 additions & 97 deletions efi/wrapper.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ typedef Elf64_Addr Elf_Addr;
#endif

/*
* 'so_size' is the file size of the ELF shared object.
* 'so_memsz' is the size of the ELF shared object once loaded.
* 'data_size' is the size of initialised data in the shared object.
* 'class' dictates how the header is written
* For 32bit machines (class == ELFCLASS32), the optional
Expand All @@ -44,7 +44,7 @@ typedef Elf64_Addr Elf_Addr;
* header includes PE32+header fields
*/
static void write_header(FILE *f, __uint32_t entry, size_t data_size,
__uint32_t so_size, __uint8_t class)
__uint32_t so_memsz, __uint8_t class)
{
struct optional_hdr o_hdr;
struct optional_hdr_pe32p o_hdr_pe32p;
Expand Down Expand Up @@ -100,7 +100,7 @@ static void write_header(FILE *f, __uint32_t entry, size_t data_size,
memset(&e_hdr, 0, sizeof(e_hdr));
e_hdr.section_align = 4096;
e_hdr.file_align = 512;
e_hdr.image_sz = hdr_sz + so_size;
e_hdr.image_sz = hdr_sz + so_memsz;
e_hdr.headers_sz = hdr_sz;
e_hdr.subsystem = IMAGE_SUBSYSTEM_EFI_APPLICATION;
e_hdr.rva_and_sizes_nr = sizeof(e_hdr.data_directory) / sizeof(__uint64_t);
Expand All @@ -123,7 +123,7 @@ static void write_header(FILE *f, __uint32_t entry, size_t data_size,
memset(&e_hdr_pe32p, 0, sizeof(e_hdr_pe32p));
e_hdr_pe32p.section_align = 4096;
e_hdr_pe32p.file_align = 512;
e_hdr_pe32p.image_sz = hdr_sz + so_size;
e_hdr_pe32p.image_sz = hdr_sz + so_memsz;
e_hdr_pe32p.headers_sz = hdr_sz;
e_hdr_pe32p.subsystem = IMAGE_SUBSYSTEM_EFI_APPLICATION;
e_hdr_pe32p.rva_and_sizes_nr = sizeof(e_hdr_pe32p.data_directory) / sizeof(__uint64_t);
Expand Down Expand Up @@ -177,17 +177,16 @@ static void usage(char *progname)

int main(int argc, char **argv)
{
struct stat st;
Elf32_Ehdr e32_hdr;
Elf64_Ehdr e64_hdr;
__uint32_t entry;
__uint8_t class;
__uint64_t shoff;
__uint16_t shnum, shentsize, shstrndx;
__uint64_t phoff = 0;
__uint16_t phnum = 0, phentsize = 0;
unsigned char *id;
FILE *f_in, *f_out;
void *buf;
size_t datasz, rv;
size_t datasz, memsz, rv;

if (argc < 3) {
usage(argv[0]);
Expand All @@ -200,11 +199,6 @@ int main(int argc, char **argv)
exit(EXIT_FAILURE);
}

if (stat(argv[1], &st) != 0) {
perror("stat");
exit(EXIT_FAILURE);
}

f_out = fopen(argv[2], "w");
if (!f_out) {
perror("fopen");
Expand All @@ -214,15 +208,14 @@ int main(int argc, char **argv)
/*
* Parse the ELF header and find the entry point.
*/
fread((void *)&e32_hdr, sizeof(e32_hdr), 1, f_in);
fread((void *)&e32_hdr, sizeof(e32_hdr), 1, f_in);
if (e32_hdr.e_ident[EI_CLASS] == ELFCLASS32) {
id = e32_hdr.e_ident;
class = ELFCLASS32;
entry = e32_hdr.e_entry;
shoff = e32_hdr.e_shoff;
shnum = e32_hdr.e_shnum;
shstrndx = e32_hdr.e_shstrndx;
shentsize = e32_hdr.e_shentsize;
phoff = e32_hdr.e_phoff;
phnum = e32_hdr.e_phnum;
phentsize = e32_hdr.e_phentsize;
}
else if (e32_hdr.e_ident[EI_CLASS] == ELFCLASS64) {
/* read the header again for x86_64
Expand All @@ -233,10 +226,9 @@ int main(int argc, char **argv)
fread((void *)&e64_hdr, sizeof(e64_hdr), 1, f_in);
id = e64_hdr.e_ident;
entry = e64_hdr.e_entry;
shoff = e64_hdr.e_shoff;
shnum = e64_hdr.e_shnum;
shstrndx = e64_hdr.e_shstrndx;
shentsize = e64_hdr.e_shentsize;
phoff = e64_hdr.e_phoff;
phnum = e64_hdr.e_phnum;
phentsize = e64_hdr.e_phentsize;
} else {
fprintf(stderr, "Unsupported architecture\n");
exit(EXIT_FAILURE);
Expand All @@ -250,98 +242,47 @@ int main(int argc, char **argv)
exit(EXIT_FAILURE);
}

if (!shoff || !shnum || (shstrndx == SHN_UNDEF)) {
fprintf(stderr, "Cannot find section table\n");
if (!phoff || !phnum) {
fprintf(stderr, "Cannot find segment table\n");
exit(EXIT_FAILURE);
}

/*
* Find the beginning of the .bss section. Everything preceding
* it is copied verbatim to the output file.
* Find the LOAD program header. Everything in this segment
* is copied verbatim to the output file.
* Although there may be several LOAD program headers, only
* one is currently copied.
*/
if (e32_hdr.e_ident[EI_CLASS] == ELFCLASS32) {
const char *shstrtab, *name;
Elf32_Shdr shdr;
Elf32_Phdr phdr;
int i;
void *strtab;

fseek(f_in, shoff, SEEK_SET);

/* First find the strtab section */
fseek(f_in, shstrndx * shentsize, SEEK_CUR);
fread(&shdr, sizeof(shdr), 1, f_in);

strtab = malloc(shdr.sh_size);
if (!strtab) {
fprintf(stderr, "Failed to malloc strtab\n");
exit(EXIT_FAILURE);
}

fseek(f_in, shdr.sh_offset, SEEK_SET);
fread(strtab, shdr.sh_size, 1, f_in);

/* Now search for the .bss section */
fseek(f_in, shoff, SEEK_SET);
for (i = 0; i < shnum; i++) {
rv = fread(&shdr, sizeof(shdr), 1, f_in);
if (!rv) {
fprintf(stderr, "Failed to read section table\n");
exit(EXIT_FAILURE);
}
/* Find the first LOAD program header */
for (i = 0; i < phnum; i++) {
fseek(f_in, phoff + i * phentsize, SEEK_SET);
fread(&phdr, sizeof(phdr), 1, f_in);

name = strtab + shdr.sh_name;
if (!strcmp(name, ".bss"))
if (phdr.p_type == PT_LOAD)
break;
}

if (i == shnum) {
fprintf(stderr, "Failed to find .bss section\n");
exit(EXIT_FAILURE);
}

datasz = shdr.sh_offset;
}
else if (e32_hdr.e_ident[EI_CLASS] == ELFCLASS64) {
const char *shstrtab, *name;
Elf64_Shdr shdr;
datasz = phdr.p_filesz;
memsz = phdr.p_memsz;
} else if (e32_hdr.e_ident[EI_CLASS] == ELFCLASS64) {
Elf64_Phdr phdr;
int i;
void *strtab;

fseek(f_in, shoff, SEEK_SET);

/* First find the strtab section */
fseek(f_in, shstrndx * shentsize, SEEK_CUR);
fread(&shdr, sizeof(shdr), 1, f_in);

strtab = malloc(shdr.sh_size);
if (!strtab) {
fprintf(stderr, "Failed to malloc strtab\n");
exit(EXIT_FAILURE);
}
/* Find the first LOAD program header */
for (i = 0; i < phnum; i++) {
fseek(f_in, phoff + i * phentsize, SEEK_SET);
fread(&phdr, sizeof(phdr), 1, f_in);

fseek(f_in, shdr.sh_offset, SEEK_SET);
fread(strtab, shdr.sh_size, 1, f_in);

/* Now search for the .bss section */
fseek(f_in, shoff, SEEK_SET);
for (i = 0; i < shnum; i++) {
rv = fread(&shdr, sizeof(shdr), 1, f_in);
if (!rv) {
fprintf(stderr, "Failed to read section table\n");
exit(EXIT_FAILURE);
}

name = strtab + shdr.sh_name;
if (!strcmp(name, ".bss"))
if (phdr.p_type == PT_LOAD)
break;
}

if (i == shnum) {
fprintf(stderr, "Failed to find .bss section\n");
exit(EXIT_FAILURE);
}

datasz = shdr.sh_offset;
datasz = phdr.p_filesz;
memsz = phdr.p_memsz;
}

buf = malloc(datasz);
Expand All @@ -350,7 +291,7 @@ int main(int argc, char **argv)
exit(EXIT_FAILURE);
}

write_header(f_out, entry, datasz, st.st_size, class);
write_header(f_out, entry, datasz, memsz, class);

/* Write out the entire ELF shared object */
rewind(f_in);
Expand All @@ -361,5 +302,8 @@ int main(int argc, char **argv)
}

fwrite(buf, datasz, rv, f_out);
free(buf);
fclose(f_out);
fclose(f_in);
return 0;
}
4 changes: 2 additions & 2 deletions efi/x86_64/syslinux.ld
View file
Original file line number Diff line number Diff line change
Expand Up @@ -136,7 +136,7 @@ SECTIONS
*(.strtab)
}

.bss : {
.bss (NOLOAD) : {
/* the EFI loader doesn't seem to like a .bss section,
so we stick it all into .data: */
__bss_start = .;
Expand All @@ -153,7 +153,7 @@ SECTIONS
__bss_dwords = (__bss_len + 3) >> 2;

. = ALIGN(128);

/* Very large objects which don't need to be zeroed */

.hugebss : {
Expand Down

0 comments on commit 9e49e29

Please sign in to comment.