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Simplify map_object() by breaking out the ELF header validation bits

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into a separate function.
This commit is contained in:
Matthew N. Dodd 2003-05-31 14:48:59 +00:00
parent 1aac1ed634
commit 341b3de62b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=115446
1 changed files with 67 additions and 58 deletions
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125
libexec/rtld-elf/map_object.c
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@ -38,6 +38,7 @@
#include "debug.h"
#include "rtld.h"
static Elf_Ehdr *get_elf_header (int, const char *);
static int convert_prot(int); /* Elf flags -> mmap protection */
static int convert_flags(int); /* Elf flags -> mmap flags */
@ -53,12 +54,8 @@ Obj_Entry *
map_object(int fd, const char *path, const struct stat *sb)
{
Obj_Entry *obj;
union {
Elf_Ehdr hdr;
char buf[PAGE_SIZE];
} u;
Elf_Ehdr *hdr;
int i;
ssize_t nbytes;
Elf_Phdr *phdr;
Elf_Phdr *phlimit;
Elf_Phdr **segs;
@ -86,53 +83,9 @@ map_object(int fd, const char *path, const struct stat *sb)
Elf_Addr bss_vlimit;
caddr_t bss_addr;
if ((nbytes = read(fd, u.buf, PAGE_SIZE)) == -1) {
_rtld_error("%s: read error: %s", path, strerror(errno));
return NULL;
}
/* Make sure the file is valid */
if (nbytes < (ssize_t)sizeof(Elf_Ehdr)
|| u.hdr.e_ident[EI_MAG0] != ELFMAG0
|| u.hdr.e_ident[EI_MAG1] != ELFMAG1
|| u.hdr.e_ident[EI_MAG2] != ELFMAG2
|| u.hdr.e_ident[EI_MAG3] != ELFMAG3) {
_rtld_error("%s: invalid file format", path);
return NULL;
}
if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS
|| u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) {
_rtld_error("%s: unsupported file layout", path);
return NULL;
}
if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT
|| u.hdr.e_version != EV_CURRENT) {
_rtld_error("%s: unsupported file version", path);
return NULL;
}
if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) {
_rtld_error("%s: unsupported file type", path);
return NULL;
}
if (u.hdr.e_machine != ELF_TARG_MACH) {
_rtld_error("%s: unsupported machine", path);
return NULL;
}
/*
* We rely on the program header being in the first page. This is
* not strictly required by the ABI specification, but it seems to
* always true in practice. And, it simplifies things considerably.
*/
if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) {
_rtld_error(
"%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
return NULL;
}
if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) {
_rtld_error("%s: program header too large", path);
return NULL;
}
hdr = get_elf_header(fd, path);
if (hdr == NULL)
return (NULL);
/*
* Scan the program header entries, and save key information.
@ -140,11 +93,11 @@ map_object(int fd, const char *path, const struct stat *sb)
* We rely on there being exactly two load segments, text and data,
* in that order.
*/
phdr = (Elf_Phdr *) (u.buf + u.hdr.e_phoff);
phlimit = phdr + u.hdr.e_phnum;
phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff);
phlimit = phdr + hdr->e_phnum;
nsegs = -1;
phdyn = phphdr = phinterp = NULL;
segs = alloca(sizeof(segs[0]) * u.hdr.e_phnum);
segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
while (phdr < phlimit) {
switch (phdr->p_type) {
@ -190,7 +143,7 @@ map_object(int fd, const char *path, const struct stat *sb)
base_vaddr = trunc_page(segs[0]->p_vaddr);
base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
mapsize = base_vlimit - base_vaddr;
base_addr = u.hdr.e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL;
base_addr = hdr->e_type == ET_EXEC ? (caddr_t) base_vaddr : NULL;
mapbase = mmap(base_addr, mapsize, convert_prot(segs[0]->p_flags),
convert_flags(segs[0]->p_flags), fd, base_offset);
@ -267,8 +220,8 @@ map_object(int fd, const char *path, const struct stat *sb)
obj->vaddrbase = base_vaddr;
obj->relocbase = mapbase - base_vaddr;
obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
if (u.hdr.e_entry != 0)
obj->entry = (caddr_t) (obj->relocbase + u.hdr.e_entry);
if (hdr->e_entry != 0)
obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry);
if (phphdr != NULL) {
obj->phdr = (const Elf_Phdr *) (obj->relocbase + phphdr->p_vaddr);
obj->phsize = phphdr->p_memsz;
@ -279,6 +232,62 @@ map_object(int fd, const char *path, const struct stat *sb)
return obj;
}
static Elf_Ehdr *
get_elf_header (int fd, const char *path)
{
static union {
Elf_Ehdr hdr;
char buf[PAGE_SIZE];
} u;
ssize_t nbytes;
if ((nbytes = read(fd, u.buf, PAGE_SIZE)) == -1) {
_rtld_error("%s: read error: %s", path, strerror(errno));
return NULL;
}
/* Make sure the file is valid */
if (nbytes < (ssize_t)sizeof(Elf_Ehdr) || !IS_ELF(u.hdr)) {
_rtld_error("%s: invalid file format", path);
return NULL;
}
if (u.hdr.e_ident[EI_CLASS] != ELF_TARG_CLASS
|| u.hdr.e_ident[EI_DATA] != ELF_TARG_DATA) {
_rtld_error("%s: unsupported file layout", path);
return NULL;
}
if (u.hdr.e_ident[EI_VERSION] != EV_CURRENT
|| u.hdr.e_version != EV_CURRENT) {
_rtld_error("%s: unsupported file version", path);
return NULL;
}
if (u.hdr.e_type != ET_EXEC && u.hdr.e_type != ET_DYN) {
_rtld_error("%s: unsupported file type", path);
return NULL;
}
if (u.hdr.e_machine != ELF_TARG_MACH) {
_rtld_error("%s: unsupported machine", path);
return NULL;
}
/*
* We rely on the program header being in the first page. This is
* not strictly required by the ABI specification, but it seems to
* always true in practice. And, it simplifies things considerably.
*/
if (u.hdr.e_phentsize != sizeof(Elf_Phdr)) {
_rtld_error(
"%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
return NULL;
}
if (u.hdr.e_phoff + u.hdr.e_phnum * sizeof(Elf_Phdr) > (size_t)nbytes) {
_rtld_error("%s: program header too large", path);
return NULL;
}
return (&u.hdr);
}
void
obj_free(Obj_Entry *obj)
{