Commit bd942ba3 authored by Grant Likely's avatar Grant Likely Committed by Josh Boyer
Browse files

[POWERPC] ppc405 Fix arithmatic rollover bug when memory size under 16M 



mmu_mapin_ram() loops over total_lowmem to setup page tables.  However, if
total_lowmem is less that 16M, the subtraction rolls over and results in
a number just under 4G (because total_lowmem is an unsigned value).

This patch rejigs the loop from countup to countdown to eliminate the
bug.

Special thanks to Magnus Hjorth who wrote the original patch to fix this
bug.  This patch improves on his by making the loop code simpler (which
also eliminates the possibility of another rollover at the high end)
and also applies the change to arch/powerpc.

Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
Signed-off-by: default avatarJosh Boyer <jwboyer@linux.vnet.ibm.com>
parent b98ac05d

arch/powerpc/mm/40x_mmu.c

+8 −9
Original line number Diff line number Diff line
@@ -98,13 +98,12 @@ unsigned long __init mmu_mapin_ram(void) 


	v = KERNELBASE;

	p = PPC_MEMSTART;

	s = 0;

	s = total_lowmem;



	if (__map_without_ltlbs) {

		return s;

	}

	if (__map_without_ltlbs)

		return 0;



	while (s <= (total_lowmem - LARGE_PAGE_SIZE_16M)) {

	while (s >= LARGE_PAGE_SIZE_16M) {

		pmd_t *pmdp;

		unsigned long val = p | _PMD_SIZE_16M | _PAGE_HWEXEC | _PAGE_HWWRITE;
@@ -116,10 +115,10 @@ unsigned long __init mmu_mapin_ram(void) 


		v += LARGE_PAGE_SIZE_16M;

		p += LARGE_PAGE_SIZE_16M;

		s += LARGE_PAGE_SIZE_16M;

		s -= LARGE_PAGE_SIZE_16M;

	}



	while (s <= (total_lowmem - LARGE_PAGE_SIZE_4M)) {

	while (s >= LARGE_PAGE_SIZE_4M) {

		pmd_t *pmdp;

		unsigned long val = p | _PMD_SIZE_4M | _PAGE_HWEXEC | _PAGE_HWWRITE;
@@ -128,8 +127,8 @@ unsigned long __init mmu_mapin_ram(void) 


		v += LARGE_PAGE_SIZE_4M;

		p += LARGE_PAGE_SIZE_4M;

		s += LARGE_PAGE_SIZE_4M;

		s -= LARGE_PAGE_SIZE_4M;

	}



	return s;

	return total_lowmem - s;

}

arch/ppc/mm/4xx_mmu.c

+8 −9
Original line number Diff line number Diff line
@@ -99,13 +99,12 @@ unsigned long __init mmu_mapin_ram(void) 


	v = KERNELBASE;

	p = PPC_MEMSTART;

	s = 0;

	s = total_lowmem;



	if (__map_without_ltlbs) {

		return s;

	}

	if (__map_without_ltlbs)

		return 0;



	while (s <= (total_lowmem - LARGE_PAGE_SIZE_16M)) {

	while (s >= LARGE_PAGE_SIZE_16M) {

		pmd_t *pmdp;

		unsigned long val = p | _PMD_SIZE_16M | _PAGE_HWEXEC | _PAGE_HWWRITE;
@@ -117,10 +116,10 @@ unsigned long __init mmu_mapin_ram(void) 


		v += LARGE_PAGE_SIZE_16M;

		p += LARGE_PAGE_SIZE_16M;

		s += LARGE_PAGE_SIZE_16M;

		s -= LARGE_PAGE_SIZE_16M;

	}



	while (s <= (total_lowmem - LARGE_PAGE_SIZE_4M)) {

	while (s >= LARGE_PAGE_SIZE_4M) {

		pmd_t *pmdp;

		unsigned long val = p | _PMD_SIZE_4M | _PAGE_HWEXEC | _PAGE_HWWRITE;
@@ -129,8 +128,8 @@ unsigned long __init mmu_mapin_ram(void) 


		v += LARGE_PAGE_SIZE_4M;

		p += LARGE_PAGE_SIZE_4M;

		s += LARGE_PAGE_SIZE_4M;

		s -= LARGE_PAGE_SIZE_4M;

	}



	return s;

	return total_lowmem - s;

}

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