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[multiboot] Place multiboot modules low in memory
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Solaris assumes that there is enough space above the Multiboot modules
to use as a decompression and scratch area.  This assumption is
invalid when using iPXE, which places the Multiboot modules near the
top of (32-bit) memory.

Fix by copying the modules to an area of memory immediately following
the loaded kernel.

Debugged-by: Michael Brown <mcb30@ipxe.org>
Debugged-by: Scott McWhirter <scottm@joyent.com>
Tested-by: Robin Smidsrød <robin@smidsrod.no>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
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@mcb30
mcb30 committed Apr 19, 2012
1 parent 2a0154d commit 62eb229
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Showing 4 changed files with 69 additions and 52 deletions.
3 changes: 2 additions & 1 deletion src/arch/i386/image/elfboot.c
View file
Expand Up @@ -42,10 +42,11 @@ FEATURE ( FEATURE_IMAGE, "ELF", DHCP_EB_FEATURE_ELF, 1 );
*/
static int elfboot_exec ( struct image *image ) {
physaddr_t entry;
physaddr_t max;
int rc;

/* Load the image using core ELF support */
if ( ( rc = elf_load ( image, &entry ) ) != 0 ) {
if ( ( rc = elf_load ( image, &entry, &max ) ) != 0 ) {
DBGC ( image, "ELF %p could not load: %s\n",
image, strerror ( rc ) );
return rc;
Expand Down
98 changes: 51 additions & 47 deletions src/arch/i386/image/multiboot.c
View file
Expand Up @@ -143,7 +143,7 @@ static void multiboot_build_memmap ( struct image *image,
* @v image Image
* @ret physaddr Physical address of command line
*/
physaddr_t multiboot_add_cmdline ( struct image *image ) {
static physaddr_t multiboot_add_cmdline ( struct image *image ) {
char *mb_cmdline = ( mb_cmdlines + mb_cmdline_offset );
size_t remaining = ( sizeof ( mb_cmdlines ) - mb_cmdline_offset );
char *buf = mb_cmdline;
Expand Down Expand Up @@ -174,28 +174,26 @@ physaddr_t multiboot_add_cmdline ( struct image *image ) {
}

/**
* Build multiboot module list
* Add multiboot modules
*
* @v image Multiboot image
* @v modules Module list to fill, or NULL
* @ret count Number of modules
* @v start Start address for modules
* @v mbinfo Multiboot information structure
* @v modules Multiboot module list
* @ret rc Return status code
*/
static unsigned int
multiboot_build_module_list ( struct image *image,
struct multiboot_module *modules,
unsigned int limit ) {
static int multiboot_add_modules ( struct image *image, physaddr_t start,
struct multiboot_info *mbinfo,
struct multiboot_module *modules,
unsigned int limit ) {
struct image *module_image;
struct multiboot_module *module;
unsigned int count = 0;
unsigned int insert;
physaddr_t start;
physaddr_t end;
unsigned int i;
int rc;

/* Add each image as a multiboot module */
for_each_image ( module_image ) {

if ( count >= limit ) {
if ( mbinfo->mods_count >= limit ) {
DBGC ( image, "MULTIBOOT %p limit of %d modules "
"reached\n", image, limit );
break;
Expand All @@ -205,37 +203,36 @@ multiboot_build_module_list ( struct image *image,
if ( module_image == image )
continue;

/* At least some OSes expect the multiboot modules to
* be in ascending order, so we have to support it.
*/
start = user_to_phys ( module_image->data, 0 );
end = user_to_phys ( module_image->data, module_image->len );
for ( insert = 0 ; insert < count ; insert++ ) {
if ( start < modules[insert].mod_start )
break;
/* Page-align the module */
start = ( ( start + 0xfff ) & ~0xfff );

/* Prepare segment */
if ( ( rc = prep_segment ( phys_to_user ( start ),
module_image->len,
module_image->len ) ) != 0 ) {
DBGC ( image, "MULTIBOOT %p could not prepare module "
"%s: %s\n", image, module_image->name,
strerror ( rc ) );
return rc;
}
module = &modules[insert];
memmove ( ( module + 1 ), module,
( ( count - insert ) * sizeof ( *module ) ) );

/* Copy module */
memcpy_user ( phys_to_user ( start ), 0,
module_image->data, 0, module_image->len );

/* Add module to list */
module = &modules[mbinfo->mods_count++];
module->mod_start = start;
module->mod_end = end;
module->mod_end = ( start + module_image->len );
module->string = multiboot_add_cmdline ( module_image );
module->reserved = 0;

/* We promise to page-align modules */
assert ( ( module->mod_start & 0xfff ) == 0 );

count++;
}

/* Dump module configuration */
for ( i = 0 ; i < count ; i++ ) {
DBGC ( image, "MULTIBOOT %p module %d is [%x,%x)\n",
image, i, modules[i].mod_start,
modules[i].mod_end );
DBGC ( image, "MULTIBOOT %p module %s is [%x,%x)\n",
image, module_image->name, module->mod_start,
module->mod_end );
start += module_image->len;
}

return count;
return 0;
}

/**
Expand Down Expand Up @@ -314,11 +311,12 @@ static int multiboot_find_header ( struct image *image,
* @v image Multiboot file
* @v hdr Multiboot header descriptor
* @ret entry Entry point
* @ret max Maximum used address
* @ret rc Return status code
*/
static int multiboot_load_raw ( struct image *image,
struct multiboot_header_info *hdr,
physaddr_t *entry ) {
physaddr_t *entry, physaddr_t *max ) {
size_t offset;
size_t filesz;
size_t memsz;
Expand Down Expand Up @@ -349,8 +347,9 @@ static int multiboot_load_raw ( struct image *image,
/* Copy image to segment */
memcpy_user ( buffer, 0, image->data, offset, filesz );

/* Record execution entry point */
/* Record execution entry point and maximum used address */
*entry = hdr->mb.entry_addr;
*max = ( hdr->mb.load_addr + memsz );

return 0;
}
Expand All @@ -360,13 +359,15 @@ static int multiboot_load_raw ( struct image *image,
*
* @v image Multiboot file
* @ret entry Entry point
* @ret max Maximum used address
* @ret rc Return status code
*/
static int multiboot_load_elf ( struct image *image, physaddr_t *entry ) {
static int multiboot_load_elf ( struct image *image, physaddr_t *entry,
physaddr_t *max ) {
int rc;

/* Load ELF image*/
if ( ( rc = elf_load ( image, entry ) ) != 0 ) {
if ( ( rc = elf_load ( image, entry, max ) ) != 0 ) {
DBGC ( image, "MULTIBOOT %p ELF image failed to load: %s\n",
image, strerror ( rc ) );
return rc;
Expand All @@ -384,6 +385,7 @@ static int multiboot_load_elf ( struct image *image, physaddr_t *entry ) {
static int multiboot_exec ( struct image *image ) {
struct multiboot_header_info hdr;
physaddr_t entry;
physaddr_t max;
int rc;

/* Locate multiboot header, if present */
Expand All @@ -405,8 +407,8 @@ static int multiboot_exec ( struct image *image ) {
* the ELF header if present, and Solaris relies on this
* behaviour.
*/
if ( ( ( rc = multiboot_load_elf ( image, &entry ) ) != 0 ) &&
( ( rc = multiboot_load_raw ( image, &hdr, &entry ) ) != 0 ) )
if ( ( ( rc = multiboot_load_elf ( image, &entry, &max ) ) != 0 ) &&
( ( rc = multiboot_load_raw ( image, &hdr, &entry, &max ) ) != 0 ))
return rc;

/* Populate multiboot information structure */
Expand All @@ -415,11 +417,13 @@ static int multiboot_exec ( struct image *image ) {
MBI_FLAG_CMDLINE | MBI_FLAG_MODS );
mb_cmdline_offset = 0;
mbinfo.cmdline = multiboot_add_cmdline ( image );
mbinfo.mods_count = multiboot_build_module_list ( image, mbmodules,
( sizeof(mbmodules) / sizeof(mbmodules[0]) ) );
mbinfo.mods_addr = virt_to_phys ( mbmodules );
mbinfo.mmap_addr = virt_to_phys ( mbmemmap );
mbinfo.boot_loader_name = virt_to_phys ( mb_bootloader_name );
if ( ( rc = multiboot_add_modules ( image, max, &mbinfo, mbmodules,
( sizeof ( mbmodules ) /
sizeof ( mbmodules[0] ) ) ) ) !=0)
return rc;

/* Multiboot images may not return and have no callback
* interface, so shut everything down prior to booting the OS.
Expand Down
18 changes: 15 additions & 3 deletions src/image/elf.c
View file
Expand Up @@ -47,11 +47,14 @@ typedef Elf32_Off Elf_Off;
* @v phdr ELF program header
* @v ehdr ELF executable header
* @ret entry Entry point, if found
* @ret max Maximum used address
* @ret rc Return status code
*/
static int elf_load_segment ( struct image *image, Elf_Phdr *phdr,
Elf_Ehdr *ehdr, physaddr_t *entry ) {
Elf_Ehdr *ehdr, physaddr_t *entry,
physaddr_t *max ) {
physaddr_t dest;
physaddr_t end;
userptr_t buffer;
unsigned long e_offset;
int rc;
Expand Down Expand Up @@ -79,6 +82,7 @@ static int elf_load_segment ( struct image *image, Elf_Phdr *phdr,
return -ENOEXEC;
}
buffer = phys_to_user ( dest );
end = ( dest + phdr->p_memsz );

DBGC ( image, "ELF %p loading segment [%x,%x) to [%x,%x,%x)\n", image,
phdr->p_offset, ( phdr->p_offset + phdr->p_filesz ),
Expand All @@ -93,6 +97,10 @@ static int elf_load_segment ( struct image *image, Elf_Phdr *phdr,
return rc;
}

/* Update maximum used address, if applicable */
if ( end > *max )
*max = end;

/* Copy image to segment */
memcpy_user ( buffer, 0, image->data, phdr->p_offset, phdr->p_filesz );

Expand All @@ -119,9 +127,10 @@ static int elf_load_segment ( struct image *image, Elf_Phdr *phdr,
*
* @v image ELF file
* @ret entry Entry point
* @ret max Maximum used address
* @ret rc Return status code
*/
int elf_load ( struct image *image, physaddr_t *entry ) {
int elf_load ( struct image *image, physaddr_t *entry, physaddr_t *max ) {
static const uint8_t e_ident[] = {
[EI_MAG0] = ELFMAG0,
[EI_MAG1] = ELFMAG1,
Expand All @@ -143,6 +152,9 @@ int elf_load ( struct image *image, physaddr_t *entry ) {
return -ENOEXEC;
}

/* Initialise maximum used address */
*max = 0;

/* Invalidate entry point */
*entry = 0;

Expand All @@ -156,7 +168,7 @@ int elf_load ( struct image *image, physaddr_t *entry ) {
}
copy_from_user ( &phdr, image->data, phoff, sizeof ( phdr ) );
if ( ( rc = elf_load_segment ( image, &phdr, &ehdr,
entry ) ) != 0 ) {
entry, max ) ) != 0 ) {
return rc;
}
}
Expand Down
2 changes: 1 addition & 1 deletion src/include/ipxe/elf.h
View file
Expand Up @@ -12,6 +12,6 @@ FILE_LICENCE ( GPL2_OR_LATER );

#include <elf.h>

extern int elf_load ( struct image *image, physaddr_t *entry );
extern int elf_load ( struct image *image, physaddr_t *entry, physaddr_t *max );

#endif /* _IPXE_ELF_H */

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