Commit 058ddee5 authored Aug 07, 2008 by Russell King Committed by Russell King Aug 07, 2008

[ARM] Fix SMP booting with non-zero PHYS_OFFSET



The existing code tries to get the pmd for the temporary page table
by doing:

        pgd = pgd_alloc(&init_mm);
        pmd = pmd_offset(pgd, PHYS_OFFSET);

Since we have a two level page table, pmd_offset() is a no-op, so
this just has a casting effect from a pgd to a pmd - the address
argument is unused.  So this can't work.

Normally, we'd do:

	pgd = pgd_offset(&init_mm, PHYS_OFFSET);
	...
	pmd = pmd_offset(pgd, PHYS_OFFSET);

to get the pmd you want.  However, pgd_offset() takes the mm_struct,
not the (unattached) pgd we just allocated.  So, instead use:

        pgd = pgd_alloc(&init_mm);
        pmd = pmd_offset(pgd + pgd_index(PHYS_OFFSET), PHYS_OFFSET);

Reported-by: Antti P Miettinen <ananaza@iki.fi>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

parent afd2fc02

arch/arm/kernel/smp.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -100,7 +100,7 @@ int __cpuinit __cpu_up(unsigned int cpu)
		* a 1:1 mapping for the physical address of the kernel.
		*/
		pgd = pgd_alloc(&init_mm);
		pmd = pmd_offset(pgd, PHYS_OFFSET);
		pmd = pmd_offset(pgd + pgd_index(PHYS_OFFSET), PHYS_OFFSET);
		*pmd = __pmd((PHYS_OFFSET & PGDIR_MASK) \|
		PMD_TYPE_SECT \| PMD_SECT_AP_WRITE);

		@@ -139,7 +139,7 @@ int __cpuinit __cpu_up(unsigned int cpu)
		secondary_data.stack = NULL;
		secondary_data.pgdir = 0;

		*pmd_offset(pgd, PHYS_OFFSET) = __pmd(0);
		*pmd = __pmd(0);
		pgd_free(&init_mm, pgd);

		if (ret) {

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