/*
* Copyright (C) 2006 Sergey Bondari
* 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.
*/
/**
* @file elf.c
* @brief Kernel ELF loader.
*/
#include <elf.h>
#include <debug.h>
#include <arch/types.h>
#include <typedefs.h>
#include <mm/as.h>
#include <mm/frame.h>
#include <mm/slab.h>
#include <align.h>
#include <memstr.h>
#include <macros.h>
#include <arch.h>
static char *error_codes[] = {
"no error",
"invalid image",
"address space error",
"incompatible image",
"unsupported image type",
"irrecoverable error"
};
static int segment_header(elf_segment_header_t *entry, elf_header_t *elf, as_t *as);
static int section_header(elf_section_header_t *entry, elf_header_t *elf, as_t *as);
static int load_segment(elf_segment_header_t *entry, elf_header_t *elf, as_t *as);
static int elf_page_fault(as_area_t *area, __address addr, pf_access_t access);
static void elf_frame_free(as_area_t *area, __address page, __address frame);
mem_backend_t elf_backend = {
.backend_page_fault = elf_page_fault,
.backend_frame_free = elf_frame_free
};
/** ELF loader
*
* @param header Pointer to ELF header in memory
* @param as Created and properly mapped address space
* @return EE_OK on success
*/
int elf_load(elf_header_t *header, as_t * as)
{
int i, rc;
/* 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) {
return EE_INCOMPATIBLE;
}
if (header->e_phentsize != sizeof(elf_segment_header_t))
return EE_INCOMPATIBLE;
if (header->e_shentsize != sizeof(elf_section_header_t))
return EE_INCOMPATIBLE;
/* Check if the object type is supported. */
if (header->e_type != ET_EXEC)
return EE_UNSUPPORTED;
/* Walk through all segment headers and process them. */
for (i = 0; i < header->e_phnum; i++) {
rc = segment_header(&((elf_segment_header_t *)(((__u8 *) header) + header->e_phoff))[i], header, as);
if (rc != EE_OK)
return rc;
}
/* Inspect all section headers and proccess them. */
for (i = 0; i < header->e_shnum; i++) {
rc = section_header(&((elf_section_header_t *)(((__u8 *) header) + header->e_shoff))[i], header, as);
if (rc != EE_OK)
return rc;
}
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(int rc)
{
ASSERT(rc < sizeof(error_codes)/sizeof(char *));
return error_codes[rc];
}
/** Process segment header.
*
* @param entry Segment header.
* @param elf ELF header.
* @param as Address space into wich the ELF is being loaded.
*
* @return EE_OK on success, error code otherwise.
*/
static int segment_header(elf_segment_header_t *entry, elf_header_t *elf, as_t *as)
{
switch (entry->p_type) {
case PT_NULL:
case PT_PHDR:
break;
case PT_LOAD:
return load_segment(entry, elf, as);
break;
case PT_DYNAMIC:
case PT_INTERP:
case PT_SHLIB:
case PT_NOTE:
case PT_LOPROC:
case PT_HIPROC:
default:
return EE_UNSUPPORTED;
break;
}
return EE_OK;
}
/** Load segment described by program header entry.
*
* @param entry Program header entry describing segment to be loaded.
* @param elf ELF header.
* @param as Address space into wich the ELF is being loaded.
*
* @return EE_OK on success, error code otherwise.
*/
int load_segment(elf_segment_header_t *entry, elf_header_t *elf, as_t *as)
{
as_area_t *a;
int flags = 0;
void *backend_data[2] = { elf, entry };
if (entry->p_align > 1) {
if ((entry->p_offset % entry->p_align) != (entry->p_vaddr % entry->p_align)) {
return EE_INVALID;
}
}
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;
/*
* Check if the virtual address starts on page boundary.
*/
if (ALIGN_UP(entry->p_vaddr, PAGE_SIZE) != entry->p_vaddr)
return EE_UNSUPPORTED;
a = as_area_create(as, flags, entry->p_memsz, entry->p_vaddr, AS_AREA_ATTR_NONE, &elf_backend, backend_data);
if (!a)
return EE_MEMORY;
/*
* The segment will be mapped on demand by elf_page_fault().
*/
return EE_OK;
}
/** Process section header.
*
* @param entry Segment header.
* @param elf ELF header.
* @param as Address space into wich the ELF is being loaded.
*
* @return EE_OK on success, error code otherwise.
*/
static int section_header(elf_section_header_t *entry, elf_header_t *elf, as_t *as)
{
switch (entry->sh_type) {
default:
break;
}
return EE_OK;
}
/** Service a page fault in the ELF backend address space area.
*
* The address space area and page tables must be already locked.
*
* @param area Pointer to the address space area.
* @param addr Faulting virtual address.
* @param access Access mode that caused the fault (i.e. read/write/exec).
*
* @return AS_PF_FAULT on failure (i.e. page fault) or AS_PF_OK on success (i.e. serviced).
*/
int elf_page_fault(as_area_t *area, __address addr, pf_access_t access)
{
elf_header_t *elf = (elf_header_t *) area->backend_data[0];
elf_segment_header_t *entry = (elf_segment_header_t *) area->backend_data[1];
__address base, frame;
index_t i;
if (!as_area_check_access(area, access))
return AS_PF_FAULT;
ASSERT((addr >= entry->p_vaddr) && (addr < entry->p_vaddr + entry->p_memsz));
i = (addr - entry->p_vaddr) >> PAGE_WIDTH;
base = (__address) (((void *) elf) + entry->p_offset);
ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
if (ALIGN_DOWN(addr, PAGE_SIZE) + PAGE_SIZE < entry->p_vaddr + entry->p_filesz) {
/*
* Initialized portion of the segment. The memory is backed
* directly by the content of the ELF image. Pages are
* only copied if the segment is writable so that there
* can be more instantions of the same memory ELF image
* used at a time. Note that this could be later done
* as COW.
*/
if (entry->p_flags & PF_W) {
frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
memcpy((void *) PA2KA
(frame
), (void *) (base
+ i
*FRAME_SIZE
), FRAME_SIZE
); } else {
frame = KA2PA(base + i*FRAME_SIZE);
}
} else if (ALIGN_DOWN(addr, PAGE_SIZE) >= ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
/*
* This is the uninitialized portion of the segment.
* It is not physically present in the ELF image.
* To resolve the situation, a frame must be allocated
* and cleared.
*/
frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
memsetb(PA2KA(frame), FRAME_SIZE, 0);
} else {
size_t size;
/*
* The mixed case.
* The lower part is backed by the ELF image and
* the upper part is anonymous memory.
*/
size = entry->p_filesz - (i<<PAGE_WIDTH);
frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
memsetb(PA2KA(frame) + size, FRAME_SIZE - size, 0);
memcpy((void *) PA2KA
(frame
), (void *) (base
+ i
*FRAME_SIZE
), size
); }
page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
panic("Could not insert used space.\n");
return AS_PF_OK;
}
/** Free a frame that is backed by the ELF backend.
*
* The address space area and page tables must be already locked.
*
* @param area Pointer to the address space area.
* @param page Page that is mapped to frame. Must be aligned to PAGE_SIZE.
* @param frame Frame to be released.
*
*/
void elf_frame_free(as_area_t *area, __address page, __address frame)
{
elf_header_t *elf = (elf_header_t *) area->backend_data[0];
elf_segment_header_t *entry = (elf_segment_header_t *) area->backend_data[1];
__address base;
index_t i;
ASSERT((page >= entry->p_vaddr) && (page < entry->p_vaddr + entry->p_memsz));
i = (page - entry->p_vaddr) >> PAGE_WIDTH;
base = (__address) (((void *) elf) + entry->p_offset);
ASSERT(ALIGN_UP(base, FRAME_SIZE) == base);
if (page + PAGE_SIZE < ALIGN_UP(entry->p_vaddr + entry->p_filesz, PAGE_SIZE)) {
if (entry->p_flags & PF_W) {
/*
* Free the frame with the copy of writable segment data.
*/
frame_free(ADDR2PFN(frame));
}
} else {
/*
* The frame is either anonymous memory or the mixed case (i.e. lower
* part is backed by the ELF image and the upper is anonymous).
* In any case, a frame needs to be freed.
*/
frame_free(ADDR2PFN(frame));
}
}