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mboot.c32: add ELF64 support for Multiboot1
mboot.c32 lacks support for loading ELF64 binaries (supported by GRUB2,
for example). This is a trivial patch to add such feature.

[reflow some changes to fit ~80 columns; remove trailing whitespace
- gene.cumm@gmail.com]
Signed-off-by: Gene Cumm <gene.cumm@gmail.com>
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Barracuda72 authored and geneC committed Oct 10, 2015
1 parent d04e8b2 commit 9146346
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123 changes: 123 additions & 0 deletions com32/mboot/map.c
Expand Up @@ -106,6 +106,11 @@ struct multiboot_header *map_image(void *ptr, size_t len)
Elf32_Ehdr *eh = ptr;
Elf32_Phdr *ph;
Elf32_Shdr *sh;

Elf64_Ehdr *eh64 = ptr;
Elf64_Phdr *ph64;
Elf64_Shdr *sh64;

unsigned int i, mbh_offset;
uint32_t bad_flags;

Expand Down Expand Up @@ -150,6 +155,18 @@ struct multiboot_header *map_image(void *ptr, size_t len)
!eh->e_phnum || eh->e_phoff + eh->e_phentsize * eh->e_phnum > len)
eh = NULL; /* No valid ELF header found */

/* Determine 64-bit images */
if ((eh != NULL) ||
len < sizeof(Elf64_Ehdr) ||
memcmp(eh64->e_ident, "\x7f" "ELF\2\1\1", 6) ||
(eh64->e_machine != EM_X86_64) ||
eh64->e_version != EV_CURRENT ||
eh64->e_ehsize < sizeof(Elf64_Ehdr) || eh64->e_ehsize >= len ||
eh64->e_phentsize < sizeof(Elf64_Phdr) ||
!eh64->e_phnum ||
eh64->e_phoff + eh64->e_phentsize * eh64->e_phnum > len)
eh64 = NULL; /* No valid ELF64 header found */

/* Is this a Solaris kernel? */
if (!set.solaris && eh && kernel_is_solaris(eh))
opt.solaris = true;
Expand Down Expand Up @@ -265,6 +282,112 @@ struct multiboot_header *map_image(void *ptr, size_t len)
sh[i].sh_addr = addr;
}
}
} else if (eh64 && !(opt.aout && mbh_len &&
(mbh->flags & MULTIBOOT_AOUT_KLUDGE))) {
/* Load 64-bit ELF */
regs.eip = eh64->e_entry; /* Can be overridden further down... */

ph64 = (Elf64_Phdr *) (cptr + eh64->e_phoff);

for (i = 0; i < eh64->e_phnum; i++) {
if (ph64->p_type == PT_LOAD || ph64->p_type == PT_PHDR) {
/*
* This loads at p_paddr, which matches Grub. However, if
* e_entry falls within the p_vaddr range of this PHDR, then
* adjust it to match the p_paddr range... this is how Grub
* behaves, so it's by definition correct (it doesn't have to
* make sense...)
*/
addr_t addr = ph64->p_paddr;
addr_t msize = ph64->p_memsz;
addr_t dsize = min(msize, ph64->p_filesz);

if (eh64->e_entry >= ph64->p_vaddr
&& eh64->e_entry < ph64->p_vaddr + msize)
regs.eip = eh64->e_entry + (ph64->p_paddr - ph64->p_vaddr);

dprintf("Segment at 0x%08x data 0x%08x len 0x%08x\n",
addr, dsize, msize);

if (syslinux_memmap_type(amap, addr, msize) != SMT_FREE) {
printf
("Memory segment at 0x%08x (len 0x%08x) is unavailable\n",
addr, msize);
return NULL; /* Memory region unavailable */
}

/* Mark this region as allocated in the available map */
if (syslinux_add_memmap(&amap, addr, msize, SMT_ALLOC)) {
error("Overlapping segments found in ELF header\n");
return NULL;
}

if (ph64->p_filesz) {
/* Data present region. Create a move entry for it. */
if (syslinux_add_movelist
(&ml, addr, (addr_t) cptr + ph64->p_offset, dsize)) {
error("Failed to map PHDR data\n");
return NULL;
}
}
if (msize > dsize) {
/* Zero-filled region. Mark as a zero region in the memory map. */
if (syslinux_add_memmap
(&mmap, addr + dsize, msize - dsize, SMT_ZERO)) {
error("Failed to map PHDR zero region\n");
return NULL;
}
}
if (addr + msize > mboot_high_water_mark)
mboot_high_water_mark = addr + msize;
} else {
/* Ignore this program header */
}

ph64 = (Elf64_Phdr *) ((char *)ph64 + eh64->e_phentsize);
}

/* Load the ELF symbol table */
if (eh64->e_shoff) {
addr_t addr, len;

sh64 = (Elf64_Shdr *) ((char *)eh64 + eh64->e_shoff);

len = eh64->e_shentsize * eh64->e_shnum;
/*
* Align this, but don't pad -- in general this means a bunch of
* smaller sections gets packed into a single page.
*/
addr = map_data(sh64, len, 4096, MAP_HIGH | MAP_NOPAD);
if (!addr) {
error("Failed to map symbol table\n");
return NULL;
}

mbinfo.flags |= MB_INFO_ELF_SHDR;
mbinfo.syms.e.addr = addr;
mbinfo.syms.e.num = eh64->e_shnum;
mbinfo.syms.e.size = eh64->e_shentsize;
mbinfo.syms.e.shndx = eh64->e_shstrndx;

for (i = 0; i < eh64->e_shnum; i++) {
addr_t align;

if (!sh64[i].sh_size)
continue; /* Empty section */
if (sh64[i].sh_flags & SHF_ALLOC)
continue; /* SHF_ALLOC sections should have PHDRs */

align = sh64[i].sh_addralign ? sh64[i].sh_addralign : 0;
addr = map_data((char *)ptr + sh64[i].sh_offset,
sh64[i].sh_size, align, MAP_HIGH);
if (!addr) {
error("Failed to map symbol section\n");
return NULL;
}
sh64[i].sh_addr = addr;
}
}
} else if (mbh_len && (mbh->flags & MULTIBOOT_AOUT_KLUDGE)) {
/*
* a.out kludge thing...
Expand Down
1 change: 1 addition & 0 deletions com32/mboot/mboot.h
Expand Up @@ -46,6 +46,7 @@
#include <minmax.h>
#include <sys/stat.h>
#include <elf.h>
#include <sys/elf64.h>
#include <console.h>

#include <syslinux/loadfile.h>
Expand Down

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