[syslinux] [PATCH 4/4] efi: PE file size differ from in-memory size
Celelibi
celelibi at gmail.com
Wed Nov 27 05:38:31 PST 2013
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: Celelibi <celelibi at gmail.com>
---
Again, I'm not 100% positive about the semantics of NOLOAD in a linker script.
However I found this make things work better.
Actually the file core/fs/fs.o have a .bss16 section that is not empty. If I
understood correctly, only .bss can be empty in a .o. Thus ld generates the
zeros that belong to that section in the .o. Then, when merging the section
.bss16 into the .bss of syslinux.so, ld is forced to generate ALL the zeros
that belong to the .bss section. Marking this section as NOLOAD make ld to
ignore its content but still produce a PT_LOAD program header with the right
memory size, as needed for the bss.
efi/i386/syslinux.ld | 4 +-
efi/wrapper.c | 138 +++++++++++++++----------------------------------
efi/x86_64/syslinux.ld | 4 +-
3 files changed, 45 insertions(+), 101 deletions(-)
diff --git a/efi/i386/syslinux.ld b/efi/i386/syslinux.ld
index 523a9b9..bab3fc7 100644
--- a/efi/i386/syslinux.ld
+++ b/efi/i386/syslinux.ld
@@ -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 = .;
@@ -153,7 +153,7 @@ SECTIONS
__bss_dwords = (__bss_len + 3) >> 2;
. = ALIGN(128);
-
+
/* Very large objects which don't need to be zeroed */
.hugebss : {
diff --git a/efi/wrapper.c b/efi/wrapper.c
index 9652368..a5247ae 100644
--- a/efi/wrapper.c
+++ b/efi/wrapper.c
@@ -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
@@ -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;
@@ -96,7 +96,7 @@ 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);
@@ -119,7 +119,7 @@ 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);
@@ -157,17 +157,16 @@ 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]);
@@ -180,11 +179,6 @@ 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");
@@ -194,15 +188,14 @@ 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
@@ -213,10 +206,9 @@ 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);
@@ -230,98 +222,47 @@ 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);
@@ -330,7 +271,7 @@ 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);
@@ -341,5 +282,8 @@ int main(int argc, char **argv)
}
fwrite(buf, datasz, rv, f_out);
+ free(buf);
+ fclose(f_out);
+ fclose(f_in);
return 0;
}
diff --git a/efi/x86_64/syslinux.ld b/efi/x86_64/syslinux.ld
index 95160bd..450641c 100644
--- a/efi/x86_64/syslinux.ld
+++ b/efi/x86_64/syslinux.ld
@@ -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 = .;
@@ -153,7 +153,7 @@ SECTIONS
__bss_dwords = (__bss_len + 3) >> 2;
. = ALIGN(128);
-
+
/* Very large objects which don't need to be zeroed */
.hugebss : {
--
1.8.4.3
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