Robert Millan wrote:
On Sat, Mar 21, 2009 at 07:05:23PM +0100, phcoder wrote:
Robert Millan wrote:
On Sat, Mar 21, 2009 at 06:58:58PM +0100, phcoder wrote:
Robert Millan wrote:
On Wed, Mar 18, 2009 at 02:26:40PM +0100, phcoder wrote:
Robert Millan wrote:
On Fri, Mar 13, 2009 at 09:52:39PM +0100, phcoder wrote:
- grub_multiboot_payload_entry_offset = ehdr->e_entry -
phdr(lowest_segment)->p_vaddr;
+ for (i = 0; i < ehdr->e_phnum; i++)
+ if (phdr(i)->p_vaddr <= ehdr->e_entry + &&
phdr(i)->p_vaddr + phdr(i)->p_memsz > ehdr->e_entry)
+ grub_multiboot_payload_entry_offset = (ehdr->e_entry - phdr(i)->p_vaddr)
+ + (phdr(i)->p_paddr - phdr(lowest_segment)->p_paddr);
You need to handle the case in which grub_multiboot_payload_entry_offset is left
uninitialized (it needs to be initialized each time the multiboot command is
run, not just when the module is loaded).
module? actually it's when loading image. Perhaps you mean that
additional error check is necessary
I meant GRUB's multiboot.mod, not the payload's module. Sorry I wasn't clear.
With this error check if grub_multiboot_payload_entry_offset it can
happen only if no image is loaded. And actually
grub_multiboot_payload_entry_offset is set to 0 at multiboot.mod load
So I don't really understand the problem
You can't rely on grub_multiboot_payload_entry_offset being set to 0, because
any subsequent call of "multiboot /something" has the potential to override
this. You must not assume the multiboot command is only going to be run once.
No but it always corresponds to the current image. It's set either in
multiboot.c or in grub_multiboot_load_elf
It is now, but your code makes this conditional.
--
Regards
Vladimir 'phcoder' Serbinenko
diff --git a/loader/i386/multiboot_elfxx.c b/loader/i386/multiboot_elfxx.c
index 801800c..ce9e4fe 100644
--- a/loader/i386/multiboot_elfxx.c
+++ b/loader/i386/multiboot_elfxx.c
@@ -49,7 +49,7 @@ CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, void *buffer)
{
Elf_Ehdr *ehdr = (Elf_Ehdr *) buffer;
char *phdr_base;
- int lowest_segment = 0, highest_segment = 0;
+ int lowest_segment = -1, highest_segment = -1;
int i;
if (ehdr->e_ident[EI_CLASS] != ELFCLASSXX)
@@ -83,11 +83,18 @@ CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, void *buffer)
for (i = 0; i < ehdr->e_phnum; i++)
if (phdr(i)->p_type == PT_LOAD && phdr(i)->p_filesz != 0)
{
- if (phdr(i)->p_paddr < phdr(lowest_segment)->p_paddr)
+ /* Beware that segment 0 isn't necessarily loadable */
+ if (lowest_segment == -1
+ || phdr(i)->p_paddr < phdr(lowest_segment)->p_paddr)
lowest_segment = i;
- if (phdr(i)->p_paddr > phdr(highest_segment)->p_paddr)
+ if (highest_segment == -1
+ || phdr(i)->p_paddr > phdr(highest_segment)->p_paddr)
highest_segment = i;
}
+
+ if (lowest_segment == -1)
+ return grub_error (GRUB_ERR_BAD_OS, "ELF contains no loadable segments");
+
code_size = (phdr(highest_segment)->p_paddr + phdr(highest_segment)->p_memsz) - phdr(lowest_segment)->p_paddr;
grub_multiboot_payload_dest = phdr(lowest_segment)->p_paddr;
@@ -105,8 +112,8 @@ CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, void *buffer)
{
char *load_this_module_at = (char *) (grub_multiboot_payload_orig + (long) (phdr(i)->p_paddr - phdr(lowest_segment)->p_paddr));
- grub_dprintf ("multiboot_loader", "segment %d: paddr=0x%lx, memsz=0x%lx\n",
- i, (long) phdr(i)->p_paddr, (long) phdr(i)->p_memsz);
+ grub_dprintf ("multiboot_loader", "segment %d: paddr=0x%lx, memsz=0x%lx, vaddr=0x%lx\n",
+ i, (long) phdr(i)->p_paddr, (long) phdr(i)->p_memsz, (long) phdr(i)->p_vaddr);
if (grub_file_seek (file, (grub_off_t) phdr(i)->p_offset)
== (grub_off_t) -1)
@@ -124,7 +131,17 @@ CONCAT(grub_multiboot_load_elf, XX) (grub_file_t file, void *buffer)
}
}
- grub_multiboot_payload_entry_offset = ehdr->e_entry - phdr(lowest_segment)->p_vaddr;
+ for (i = 0; i < ehdr->e_phnum; i++)
+ if (phdr(i)->p_vaddr <= ehdr->e_entry
+ && phdr(i)->p_vaddr + phdr(i)->p_memsz > ehdr->e_entry)
+ {
+ grub_multiboot_payload_entry_offset = (ehdr->e_entry - phdr(i)->p_vaddr)
+ + (phdr(i)->p_paddr - phdr(lowest_segment)->p_paddr);
+ break;
+ }
+
+ if (i == ehdr->e_phnum)
+ return grub_error (GRUB_ERR_BAD_OS, "entry point isn't in a segment");
#undef phdr
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