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#include <u.h>
#include <libc.h>
#include "/sys/src/libmach/elf.h"
enum {
Page = 4096,
};
#define ROUND(n) ((n+Page-1)&~(Page-1))
Shdr isect, csect;
static ushort
GETS(void *a)
{
uchar *p = a;
return p[0] | p[1]<<8;
}
static ulong
GETL(void *a)
{
uchar *p = a;
return p[0] | p[1]<<8 | p[2]<<16 | p[3]<<24;
}
static void
PUTS(void *a, ushort v)
{
uchar *p = a;
p[0] = v;
p[1] = v>>8;
}
static void
PUTL(void *a, ulong v)
{
uchar *p = a;
p[0] = v;
p[1] = v>>8;
p[2] = v>>16;
p[3] = v>>24;
}
void
copy(int fin, int fout, ulong src, ulong dst, ulong size)
{
char buf[Page];
int n;
seek(fin, src, 0);
seek(fout, dst, 0);
n = Page;
while (size > 0) {
if (n > size)
n = size;
read(fin, buf, n);
write(fout, buf, n);
size -= n;
}
}
void
main(int argc, char **argv)
{
Ehdr e;
Shdr s;
Phdr p;
int efd, ofd, ns, i, n;
ulong shoff, off, noff, size, msize;
char *sname, *sval;
if (argc != 5)
sysfatal("Usage: xenelf input-elf-file output-elf-file section-name section-contents");
efd = open(argv[1], OREAD);
if (efd < 0)
sysfatal("%s: %r", argv[1]);
ofd = create(argv[2], OWRITE, 0666);
if (ofd < 0)
sysfatal("%s: %r", argv[2]);
sname = argv[3];
sval = argv[4];
read(efd, &e, sizeof e);
//if (e.shstrndx)
// sysfatal("section header string index already present");
/* page-align loadable segments in file */
ns = GETS(&e.phnum);
shoff = GETL(&e.phoff);
noff = shoff+ns*sizeof(Phdr);
noff = ROUND(noff);
for (i = 0; i < ns; i++) {
seek(efd, shoff+i*sizeof(Phdr), 0);
read(efd, &p, sizeof p);
off = GETL(&p.offset);
PUTL(&p.offset, noff);
size = GETL(&p.filesz);
copy(efd, ofd, off, noff, size);
if (GETL(&p.type) == LOAD) {
size = ROUND(size);
PUTL(&p.filesz, size);
if ((msize = GETL(&p.memsz)) != 0 && size > msize)
PUTL(&p.memsz, size);
} else {
/* memory size for symtab segment is actually line number table size */
msize = GETL(&p.memsz);
copy(efd, ofd, off+size, noff+size, msize);
noff += msize;
}
noff += size;
seek(ofd, shoff+i*sizeof(Phdr), 0);
write(ofd, &p, sizeof p);
}
/* append single-entry shstrndx */
PUTL(&isect.offset, seek(ofd, noff, 0));
n = strlen(sname);
PUTL(&isect.size, n+2);
write(ofd, sname+n, 1);
write(ofd, sname, n+1);
/* append comment section contents */
PUTL(&csect.name, 1);
PUTL(&csect.offset, seek(ofd, 0, 2));
n = strlen(sval);
PUTL(&csect.size, n+1);
write(ofd, sval, n+1);
/* copy existing section headers to end */
ns = 0; //GETS(&e.shnum);
shoff = GETL(&e.shoff);
PUTL(&e.shoff, seek(ofd, 0, 2));
for (i = 0; i < ns; i++) {
seek(efd, shoff+i*sizeof(Shdr), 0);
read(efd, &s, sizeof s);
seek(ofd, 0, 2);
write(ofd, &s, sizeof s);
}
/* append section header for comment section */
write(ofd, &csect, sizeof csect);
++ns;
/* append section header for shstrndx */
PUTS(&e.shstrndx, ns);
++ns;
write(ofd, &isect, sizeof isect);
/* rewrite elf header */
PUTS(&e.shentsize, sizeof(Shdr));
PUTS(&e.shnum, ns);
seek(ofd, 0, 0);
write(ofd, &e, sizeof e);
exits(0);
}
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