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/* rmphdr.c
/* remove program execution header and substantial segments
/* from an elf format object file.
/* May/1994 (c) Toshihiro Matsui, Electrotechnical Laboratory
/*
*/
#include <stdio.h>
#include <sys/types.h>
#include <libelf.h> /* sys/elf.h is read */
#include <fcntl.h>
#define min(x,y) ((x)<(y)?(x):(y))
extern int errno;
void copy_bytes(infd, outfd, offset, nbytes)
int infd, outfd, offset, nbytes;
{ char buf[8192];
int i, s;
lseek(infd, offset, SEEK_SET);
while (nbytes>0) {
s=min(8192, nbytes);
s=read(infd, buf, s);
if (s<=0) {
fprintf(stderr, "cannot read object %d", errno);
return;}
write(outfd, buf, s);
nbytes -= s;}
}
void copy_new_symtab(infd,outfd,symtab)
int infd, outfd;
Elf32_Shdr *symtab;
{ register int i;
int s, ss, k;
Elf32_Sym symbuf[16384]; /* 256KB */
unsigned char info;
s=symtab->sh_size;
if (s>sizeof(symbuf)) { fprintf(stderr, "symtab too big %d\n",s); exit(5);}
lseek(infd, symtab->sh_offset, SEEK_SET);
ss=read(infd, symbuf, s);
if (ss!=s) { fprintf(stderr, "cannt read symtab %d\n", ss); exit(6);}
k=ss/sizeof(Elf32_Sym); /*number of symtab entries*/
for (i=symtab->sh_info; i<k; i++) {
info=symbuf[i].st_info;
if (ELF32_ST_TYPE(info)==STT_OBJECT) {
fprintf(stderr, "symbol[%d] is OBJECT\n", i);
symbuf[i].st_info += 1;}}
write(outfd, symbuf, ss);}
main(argc,argv)
int argc;
char *argv[];
{
char *fname;
int elfd, outfd;
char outfname[128];
Elf *elf;
Elf32_Ehdr *ehdr, newehdr;
Elf_Scn *scn;
Elf32_Shdr *scnhdr, scntab[40], *symtab;
Elf_Data *data;
int scn_symt[40];
int i, j, scn_num, scn_count, scn_total_size, scn_offset;
char *cp;
fname=argv[1];
sprintf(outfname,"%s.r",fname);
elfd=open(fname, 0);
outfd=open(outfname, O_RDWR | O_CREAT, 0777);
if (elfd<=0) {
fprintf(stderr, "%s cannot open %d\n", fname, errno);
exit(2);}
if (outfd<=0) {
fprintf(stderr, "%s cannot open %d\n", outfname, errno);
exit(2);}
fprintf(stderr, "%s opened\n", outfname);
elf_version(EV_CURRENT);
elf=elf_begin(elfd, ELF_C_READ, 0);
if (elf==0) printf("%s\n", elf_errmsg(elf_errno()));
ehdr=elf32_getehdr(elf);
memcpy(&newehdr, ehdr, sizeof(newehdr));
/* printf("elfhdr=%x\n", ehdr); */
/* printf("e_ident="); */
/* for (i=0; i<16; i++) { printf("%2x ", ehdr->e_ident[i]);} */
printf("\ne_type= %d\n", newehdr.e_type);
printf("e_machine= %d\n", newehdr.e_machine);
printf("e_version= %d\n", newehdr.e_version);
printf("e_entry= 0x%x\n", newehdr.e_entry);
printf("e_phoff= 0x%x\n", newehdr.e_phoff);
printf("e_shoff= 0x%x\n", newehdr.e_shoff);
printf("e_flags= 0x%x\n", newehdr.e_flags);
printf("e_ehsize= 0x%x\n", newehdr.e_ehsize);
printf("e_phentsize= %d\n", newehdr.e_phentsize);
printf("e_phnum= %d\n", newehdr.e_phnum);
printf("e_shentsize= %d\n", newehdr.e_shentsize);
printf("e_shnum= %d\n", newehdr.e_shnum);
printf("e_shstrndx= %d\n", newehdr.e_shstrndx);
/* get all section headers and reindex section headers */
scn_num=newehdr.e_shnum;
scn_count=0;
scn_total_size=0;
for (i=0; i<scn_num; i++) {
scn=elf_getscn(elf, i);
scnhdr=elf32_getshdr(scn);
memcpy(&scntab[i], scnhdr, sizeof(Elf32_Shdr));
/* printf("sh_flags[%d]=%d\n", i, scntab[i].sh_flags); */
if (scntab[i].sh_flags==0) {
scn_symt[i]=scn_count++;
if (scntab[i].sh_type == SHT_SYMTAB) symtab=&scntab[i];
scn_total_size +=scntab[i].sh_size; } }
printf("ehdrsize=%d; %d sections are needed.\n",
sizeof(Elf32_Ehdr), scn_count);
/* prepare a new elf header */
newehdr.e_type=ET_REL; /*relocatable*/
newehdr.e_entry=0;
newehdr.e_phoff=0; /* no program execution header*/
newehdr.e_shoff= sizeof(Elf32_Ehdr) + scn_total_size;
newehdr.e_phentsize=0;
newehdr.e_phnum=0;
newehdr.e_shstrndx=scn_symt[newehdr.e_shstrndx];
newehdr.e_shnum=scn_count; /* number of symbol table sections */
fprintf(stderr, "ehdr updated\n");
/* write new elf header */
write(outfd, &newehdr, sizeof(Elf32_Ehdr));
/* no phdr written */
/* copy section contents */
for (i=1; i<scn_num; i++) {
if (scn_symt[i]!=0 && scntab[i].sh_type != SHT_NOBITS) {
fprintf(stderr, "%d size=%d\n", i, scntab[i].sh_size);
if (scntab[i].sh_type==SHT_SYMTAB) {
copy_new_symtab(elfd, outfd, symtab);}
else
copy_bytes(elfd, outfd, scntab[i].sh_offset, scntab[i].sh_size);
}}
/* write updated section headers */
/* write zeroth header */
scn_offset=sizeof(Elf32_Ehdr);
write(outfd, scntab[0], sizeof(Elf32_Shdr));
for (i=1; i<scn_num; i++) {
if (scn_symt[i]!=0) {
j=scntab[i].sh_link;
if (j!=0) scntab[i].sh_link=scn_symt[j]; /*rewrite link*/
scntab[i].sh_offset=scn_offset;
scn_offset += scntab[i].sh_size;
write(outfd, scntab[i], sizeof(Elf32_Shdr));
} }
elf_end(elf);
close(elfd);
close(outfd);
}
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