* Matt Fleming <m...@codeblueprint.co.uk> wrote:
> > > + npages = (_end - _text) >> PAGE_SHIFT;
> >
> > You really need to PFN_ALIGN _end and _text. Has been wrong in the
> > existing code as well.
>
> Hmm... very good point.
So I think we should instead guarantee that _end and _text are page aligned.
_text is already page aligned:
SECTIONS
{
#ifdef CONFIG_X86_32
. = LOAD_OFFSET + LOAD_PHYSICAL_ADDR;
phys_startup_32 = startup_32 - LOAD_OFFSET;
#else
. = __START_KERNEL;
phys_startup_64 = startup_64 - LOAD_OFFSET;
#endif
/* Text and read-only data */
.text : AT(ADDR(.text) - LOAD_OFFSET) {
_text = .;
The reason for aligning _end as well is that we already page-align the BSS and
BRK
sections of the kernel and its various section boundary symbols:
/* BSS */
. = ALIGN(PAGE_SIZE);
.bss : AT(ADDR(.bss) - LOAD_OFFSET) {
__bss_start = .;
*(.bss..page_aligned)
*(.bss)
. = ALIGN(PAGE_SIZE);
__bss_stop = .;
}
. = ALIGN(PAGE_SIZE);
.brk : AT(ADDR(.brk) - LOAD_OFFSET) {
__brk_base = .;
. += 64 * 1024; /* 64k alignment slop space */
*(.brk_reservation) /* areas brk users have reserved */
__brk_limit = .;
}
_end = .;
STABS_DEBUG
DWARF_DEBUG
_end is the only odd one out, so we should align it as well - because it's easy
to
make such pfn conversion bugs.
This will also make it easier to mark STABS_DEBUG and DWARF_DEBUG as read-only,
which they should fundamentally be I think. Alternatively they could be moved
to
the read-only section - at which point _end becomes page aligned 'for free'.
Thanks,
Ingo
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