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load_elf.c
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load_elf.c
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#include <libstatic/libstatic.h>
#include <elf.h>
#include <sys/mman.h>
#include <ulexec.h>
#define ROUNDUP(x, y) ((((x)+((y)-1))/(y))*(y))
#define ALIGN(k, v) (((k)+((v)-1))&(~((v)-1)))
#define ALIGNDOWN(k, v) ((unsigned long)(k)&(~((unsigned long)(v)-1)))
void *memcopy(void *dest, const void *src, unsigned long n);
void *
load_elf(char *mapped, int anywhere, Elf64_Ehdr **elf_ehdr, Elf64_Ehdr **ldso_ehdr)
{
Elf64_Ehdr *hdr;
Elf64_Phdr *pdr, *interp = NULL;
int i;
void *text_segment = NULL;
void *entry_point = NULL;
unsigned long initial_vaddr = 0;
unsigned long brk_addr = 0;
char buf[128];
unsigned int mapflags = MAP_PRIVATE|MAP_ANONYMOUS;
if (!anywhere)
mapflags |= MAP_FIXED;
/* Just addresses in mapped-in file. */
hdr = (Elf64_Ehdr *)mapped;
pdr = (Elf64_Phdr *)(mapped + hdr->e_phoff);
entry_point = (void *)hdr->e_entry;
for (i = 0; i < hdr->e_phnum; ++i, ++pdr)
{
unsigned int protflags = 0;
unsigned long map_addr = 0, rounded_len, k;
unsigned long unaligned_map_addr = 0;
void *segment;
if (pdr->p_type == 0x03) /* PT_INTERP */
{
interp = pdr;
continue;
}
if (pdr->p_type != PT_LOAD) /* Segment not "loadable" */
continue;
if (text_segment != 0 && anywhere)
{
unaligned_map_addr
= (unsigned long)text_segment
+ ((unsigned long)pdr->p_vaddr - (unsigned long)initial_vaddr)
;
map_addr = ALIGNDOWN((unsigned long)unaligned_map_addr, 0x1000);
mapflags |= MAP_FIXED;
} else if (!anywhere) {
map_addr = ALIGNDOWN(pdr->p_vaddr, 0x1000);
} else {
map_addr = 0UL;
}
if (!anywhere && initial_vaddr == 0)
initial_vaddr = pdr->p_vaddr;
/* mmap() freaks out if you give it a non-multiple of pagesize */
rounded_len = (unsigned long)pdr->p_memsz + ((unsigned long)pdr->p_vaddr % 0x1000);
rounded_len = ROUNDUP(rounded_len, 0x1000);
segment = linux_mmap(
(void *)map_addr,
rounded_len,
PROT_WRITE, mapflags, -1, 0
);
if (segment == (void *) -1)
{
print_string(1, "Failed to mmap() ");
to_hex(pdr->p_memsz, buf);
print_string(1, buf);
print_string(1, " bytes at 0x");
to_hex(map_addr, buf);
print_string(1, buf);
print_string(1, "\n");
linux_exit(3);
}
memcopy(
!anywhere? (void *)pdr->p_vaddr:
(void *)((unsigned long)segment + ((unsigned long)pdr->p_vaddr % 0x1000)),
mapped + pdr->p_offset,
pdr->p_filesz
);
if (!text_segment)
{
*elf_ehdr = segment;
text_segment = segment;
initial_vaddr = pdr->p_vaddr;
if (anywhere)
entry_point = (void *)((unsigned long)entry_point
- (unsigned long)pdr->p_vaddr
+ (unsigned long)text_segment);
}
if (pdr->p_flags & PF_R)
protflags |= PROT_READ;
if (pdr->p_flags & PF_W)
protflags |= PROT_WRITE;
if (pdr->p_flags & PF_X)
protflags |= PROT_EXEC;
linux_mprotect(segment, rounded_len, protflags);
k = pdr->p_vaddr + pdr->p_memsz;
if (k > brk_addr) brk_addr = k;
}
if (interp)
{
Elf64_Ehdr *junk_ehdr = NULL;
unsigned long sz_dummy;
entry_point = load_elf(map_file(&(((char *)mapped)[interp->p_offset]), &sz_dummy), 1, ldso_ehdr, &junk_ehdr);
}
if (!anywhere)
linux_brk(ROUNDUP(brk_addr, 0x1000));
return (void *)entry_point;
}
void *
memcopy(void *dest, const void *src, unsigned long n)
{
unsigned long i;
unsigned char *d = (unsigned char *)dest;
unsigned char *s = (unsigned char *)src;
/*
char buf[64];
print_string(1, "load_elf() copying 0x");
to_hex(n, buf);
print_string(1, buf);
print_string(1, " bytes from 0x");
to_hex((unsigned long)src, buf);
print_string(1, buf);
print_string(1, " to 0x");
to_hex((unsigned long)dest, buf);
print_string(1, buf);
print_string(1, "\n");
linux_read(0, buf, 1);
*/
for (i = 0; i < n; ++i)
d[i] = s[i];
return dest;
}