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authorGrant Likely <grant.likely@secretlab.ca>2007-10-31 17:41:20 +1100
committerJosh Boyer <jwboyer@linux.vnet.ibm.com>2007-11-01 07:15:59 -0500
commitbd942ba3db60d3bd4e21febbe7c5e339d973d5a8 (patch)
treeff306770ca15454fb73c040a7fd47a027c7f89f2 /arch/powerpc/mm/40x_mmu.c
parent[POWERPC] 4xx: Deal with 44x virtually tagged icache (diff)
downloadlinux-dev-bd942ba3db60d3bd4e21febbe7c5e339d973d5a8.tar.xz
linux-dev-bd942ba3db60d3bd4e21febbe7c5e339d973d5a8.zip
[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: Grant Likely <grant.likely@secretlab.ca> Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Diffstat (limited to 'arch/powerpc/mm/40x_mmu.c')
-rw-r--r--arch/powerpc/mm/40x_mmu.c17
1 files changed, 8 insertions, 9 deletions
diff --git a/arch/powerpc/mm/40x_mmu.c b/arch/powerpc/mm/40x_mmu.c
index e067df836be2..3899ea97fbdf 100644
--- a/arch/powerpc/mm/40x_mmu.c
+++ b/arch/powerpc/mm/40x_mmu.c
@@ -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;
}