Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=bd942ba3db60d3bd4e21febbe7c5e339d973d5a8
Commit: bd942ba3db60d3bd4e21febbe7c5e339d973d5a8
Parent: b98ac05d5e460301fbea24cceed0f2a601c82e22
Author: Grant Likely <[EMAIL PROTECTED]>
AuthorDate: Wed Oct 31 17:41:20 2007 +1100
Committer: Josh Boyer <[EMAIL PROTECTED]>
CommitDate: Thu Nov 1 07:15:59 2007 -0500
[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 <[EMAIL PROTECTED]>
Signed-off-by: Josh Boyer <[EMAIL PROTECTED]>
---
arch/powerpc/mm/40x_mmu.c | 17 ++++++++---------
arch/ppc/mm/4xx_mmu.c | 17 ++++++++---------
2 files changed, 16 insertions(+), 18 deletions(-)
diff --git a/arch/powerpc/mm/40x_mmu.c b/arch/powerpc/mm/40x_mmu.c
index e067df8..3899ea9 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;
}
diff --git a/arch/ppc/mm/4xx_mmu.c b/arch/ppc/mm/4xx_mmu.c
index 838e09d..ea785db 100644
--- a/arch/ppc/mm/4xx_mmu.c
+++ b/arch/ppc/mm/4xx_mmu.c
@@ -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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