/*
* Copyright (c) 2006 Sergey Bondari
* Copyright (c) 2006 Jakub Jermar
* Copyright (c) 2008 Jiri Svoboda
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* - The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/** @addtogroup generic
* @{
*/
/**
* @file
* @brief Userspace ELF loader.
*
* This module allows loading ELF binaries (both executables and
* shared objects) from VFS. The current implementation allocates
* anonymous memory, fills it with segment data and then adjusts
* the memory areas' flags to the final value. In the future,
* the segments will be mapped directly from the file.
*/
#include <stdio.h>
#include <sys/types.h>
#include <align.h>
#include <assert.h>
#include <as.h>
#include <unistd.h>
#include <fcntl.h>
#include "elf.h"
#include "pcb.h"
#include "elf_load.h"
static char *error_codes[] = {
"no error",
"invalid image",
"address space error",
"incompatible image",
"unsupported image type",
"irrecoverable error"
};
static unsigned int elf_load(elf_ld_t *elf, size_t so_bias);
static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry);
static int section_header(elf_ld_t *elf, elf_section_header_t *entry);
static int load_segment(elf_ld_t *elf, elf_segment_header_t *entry);
/** Load ELF binary from a file.
*
* Load an ELF binary from the specified file. If the file is
* an executable program, it is loaded unbiased. If it is a shared
* object, it is loaded with the bias @a so_bias. Some information
* extracted from the binary is stored in a elf_info_t structure
* pointed to by @a info.
*
* @param file_name Path to the ELF file.
* @param so_bias Bias to use if the file is a shared object.
* @param info Pointer to a structure for storing information
* extracted from the binary.
*
* @return EOK on success or negative error code.
*/
int elf_load_file(char *file_name, size_t so_bias, elf_info_t *info)
{
elf_ld_t elf;
int fd;
int rc;
printf("open and read '%s'...\n", file_name
);
fd = open(file_name, O_RDONLY);
if (fd < 0) {
printf("failed opening file\n"); return -1;
}
elf.fd = fd;
elf.info = info;
rc = elf_load(&elf, so_bias);
printf("elf_load() -> %d\n", rc
);
close(fd);
return rc;
}
/** Run an ELF executable.
*
* Transfers control to the entry point of an ELF executable loaded
* earlier with elf_load_file(). This function does not return.
*
* @param info Info structure filled earlier by elf_load_file()
*/
void elf_run(elf_info_t *info)
{
(*info->entry)();
/* not reached */
}
/** Create the program control block (PCB).
*
* Create and install the program control block, initialising it
* with program information from @a info.
*
* @param info Program info structure
* @return EOK on success or negative error code
*/
int elf_create_pcb(elf_info_t *info)
{
pcb_t *pcb;
void *a;
pcb = __pcb_get();
a = as_area_create(pcb, sizeof(pcb_t), AS_AREA_READ | AS_AREA_WRITE);
if (a == (void *)(-1)) {
printf("elf_create_pcb: memory mapping failed\n"); return EE_MEMORY;
}
pcb->entry = info->entry;
pcb->dynamic = info->dynamic;
return 0;
}
/** Load an ELF binary.
*
* The @a elf structure contains the loader state, including
* an open file, from which the binary will be loaded,
* a pointer to the @c info structure etc.
*
* @param elf Pointer to loader state buffer.
* @param so_bias Bias to use if the file is a shared object.
* @return EE_OK on success or EE_xx error code.
*/
static unsigned int elf_load(elf_ld_t *elf, size_t so_bias)
{
elf_header_t header_buf;
elf_header_t *header = &header_buf;
int i, rc;
rc = read(elf->fd, header, sizeof(elf_header_t));
if (rc < 0) {
return EE_INVALID;
}
elf->header = header;
/* Identify ELF */
if (header->e_ident[EI_MAG0] != ELFMAG0 ||
header->e_ident[EI_MAG1] != ELFMAG1 ||
header->e_ident[EI_MAG2] != ELFMAG2 ||
header->e_ident[EI_MAG3] != ELFMAG3) {
return EE_INVALID;
}
/* Identify ELF compatibility */
if (header->e_ident[EI_DATA] != ELF_DATA_ENCODING ||
header->e_machine != ELF_MACHINE ||
header->e_ident[EI_VERSION] != EV_CURRENT ||
header->e_version != EV_CURRENT ||
header->e_ident[EI_CLASS] != ELF_CLASS) {
printf("incompatible data/version/class\n"); return EE_INCOMPATIBLE;
}
if (header->e_phentsize != sizeof(elf_segment_header_t)) {
printf("e_phentsize:%d != %d\n", header
->e_phentsize
, sizeof(elf_segment_header_t));
return EE_INCOMPATIBLE;
}
if (header->e_shentsize != sizeof(elf_section_header_t)) {
printf("e_shentsize:%d != %d\n", header
->e_shentsize
, sizeof(elf_section_header_t));
return EE_INCOMPATIBLE;
}
/* Check if the object type is supported. */
if (header->e_type != ET_EXEC && header->e_type != ET_DYN) {
printf("Object type %d is not supported\n", header
->e_type
); return EE_UNSUPPORTED;
}
/* Shared objects can be loaded with a bias */
printf("Object type: %d\n", header
->e_type
); if (header->e_type == ET_DYN)
elf->bias = so_bias;
else
elf->bias = 0;
printf("Bias set to 0x%x\n", elf
->bias
); elf->info->interp = NULL;
elf->info->dynamic = NULL;
/* Walk through all segment headers and process them. */
for (i = 0; i < header->e_phnum; i++) {
elf_segment_header_t segment_hdr;
/* Seek to start of segment header */
lseek(elf->fd, header->e_phoff
+ i * sizeof(elf_segment_header_t), SEEK_SET);
rc = read(elf->fd, &segment_hdr, sizeof(elf_segment_header_t));
if (rc
< 0) { printf("read error\n"); return EE_INVALID
; }
rc = segment_header(elf, &segment_hdr);
if (rc != EE_OK)
return rc;
}
/* Inspect all section headers and proccess them. */
for (i = 0; i < header->e_shnum; i++) {
elf_section_header_t section_hdr;
/* Seek to start of section header */
lseek(elf->fd, header->e_shoff
+ i * sizeof(elf_section_header_t), SEEK_SET);
rc = read(elf->fd, §ion_hdr, sizeof(elf_section_header_t));
if (rc
< 0) { printf("read error\n"); return EE_INVALID
; }
rc = section_header(elf, §ion_hdr);
if (rc != EE_OK)
return rc;
}
elf->info->entry =
(entry_point_t)((uint8_t *)header->e_entry + elf->bias);
return EE_OK;
}
/** Print error message according to error code.
*
* @param rc Return code returned by elf_load().
*
* @return NULL terminated description of error.
*/
char *elf_error(unsigned int rc)
{
assert(rc
< sizeof(error_codes
) / sizeof(char *));
return error_codes[rc];
}
/** Process segment header.
*
* @param entry Segment header.
*
* @return EE_OK on success, error code otherwise.
*/
static int segment_header(elf_ld_t *elf, elf_segment_header_t *entry)
{
switch (entry->p_type) {
case PT_NULL:
case PT_PHDR:
break;
case PT_LOAD:
return load_segment(elf, entry);
break;
case PT_INTERP:
/* Assume silently interp == "/rtld.so" */
elf->info->interp = "/rtld.so";
break;
case PT_DYNAMIC:
case PT_SHLIB:
case PT_NOTE:
case PT_LOPROC:
case PT_HIPROC:
default:
printf("segment p_type %d unknown\n", entry
->p_type
); return EE_UNSUPPORTED;
break;
}
return EE_OK;
}
/** Load segment described by program header entry.
*
* @param elf Loader state.
* @param entry Program header entry describing segment to be loaded.
*
* @return EE_OK on success, error code otherwise.
*/
int load_segment(elf_ld_t *elf, elf_segment_header_t *entry)
{
void *a;
int flags = 0;
uintptr_t bias;
uintptr_t base;
size_t mem_sz;
int rc;
printf("load segment at addr 0x%x, size 0x%x\n", entry
->p_vaddr
, entry->p_memsz);
bias = elf->bias;
if (entry->p_align > 1) {
if ((entry->p_offset % entry->p_align) !=
(entry->p_vaddr % entry->p_align)) {
printf("align check 1 failed offset%%align=%d, vaddr%%align=%d\n", entry->p_offset % entry->p_align,
entry->p_vaddr % entry->p_align
);
return EE_INVALID;
}
}
/* Final flags that will be set for the memory area */
if (entry->p_flags & PF_X)
flags |= AS_AREA_EXEC;
if (entry->p_flags & PF_W)
flags |= AS_AREA_WRITE;
if (entry->p_flags & PF_R)
flags |= AS_AREA_READ;
flags |= AS_AREA_CACHEABLE;
base = ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE);
mem_sz = entry->p_memsz + (entry->p_vaddr - base);
printf("map to p_vaddr=0x%x-0x%x...\n", entry
->p_vaddr
+ bias
, entry->p_vaddr + bias + ALIGN_UP(entry->p_memsz, PAGE_SIZE));
/*
* For the course of loading, the area needs to be readable
* and writeable.
*/
a = as_area_create((uint8_t *)base + bias,
mem_sz, AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE);
if (a == (void *)(-1)) {
printf("memory mapping failed\n"); return EE_MEMORY;
}
printf("as_area_create(0x%lx, 0x%x, %d) -> 0x%lx\n", entry->p_vaddr+bias, entry->p_memsz, flags, (uintptr_t)a);
/*
* Load segment data
*/
printf("seek to %d\n", entry
->p_offset
); rc = lseek(elf->fd, entry->p_offset, SEEK_SET);
if (rc
< 0) { printf("seek error\n"); return EE_INVALID
; }
printf("read 0x%x bytes to address 0x%x\n", entry
->p_filesz
, entry
->p_vaddr
+bias
); /* rc = read(fd, (void *)(entry->p_vaddr + bias), entry->p_filesz);
if (rc < 0) { printf("read error\n"); return EE_INVALID; }*/
/* Long reads are not possible yet. Load segment picewise */
unsigned left, now;
uint8_t *dp;
left = entry->p_filesz;
dp = (uint8_t *)(entry->p_vaddr + bias);
while (left > 0) {
now = 16384;
if (now > left) now = left;
rc = read(elf->fd, dp, now);
if (rc
< 0) { printf("read error\n"); return EE_INVALID
; }
left -= now;
dp += now;
}
printf("set area flags to %d\n", flags
); rc = as_area_change_flags((uint8_t *)entry->p_vaddr + bias, flags);
if (rc != 0) {
printf("failed to set memory area flags\n"); return EE_MEMORY;
}
return EE_OK;
}
/** Process section header.
*
* @param elf Loader state.
* @param entry Segment header.
*
* @return EE_OK on success, error code otherwise.
*/
static int section_header(elf_ld_t *elf, elf_section_header_t *entry)
{
switch (entry->sh_type) {
case SHT_PROGBITS:
if (entry->sh_flags & SHF_TLS) {
/* .tdata */
}
break;
case SHT_NOBITS:
if (entry->sh_flags & SHF_TLS) {
/* .tbss */
}
break;
case SHT_DYNAMIC:
/* Record pointer to dynamic section into info structure */
elf->info->dynamic =
(void *)((uint8_t *)entry->sh_addr + elf->bias);
printf("dynamic section found at 0x%x\n", (uintptr_t)elf->info->dynamic);
break;
default:
break;
}
return EE_OK;
}
/** @}
*/