On 8/28/23 23:25, Huacai Chen wrote:
Both shm_align_mask and SHMLBA want to avoid cache alias. But they are
inconsistent: shm_align_mask is (PAGE_SIZE - 1) while SHMLBA is SZ_64K,
but PAGE_SIZE is not always equal to SZ_64K.
This may cause problems when shmat() twice. Fix this problem by removing
shm_align_mask and using SHMLBA (SHMLBA - 1, strctly) instead.
"strictly SHMLBA - 1"?
Reported-by: Jiantao Shan <shanjiantao@xxxxxxxxxxx>
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
---
arch/loongarch/mm/cache.c | 1 -
arch/loongarch/mm/mmap.c | 12 ++++--------
3 files changed, 8 insertions(+), 9 deletions(-)
diff --git a/arch/loongarch/mm/cache.c b/arch/loongarch/mm/cache.c
index 72685a48eaf0..6be04d36ca07 100644
--- a/arch/loongarch/mm/cache.c
+++ b/arch/loongarch/mm/cache.c
@@ -156,7 +156,6 @@ void cpu_cache_init(void)
current_cpu_data.cache_leaves_present = leaf;
current_cpu_data.options |= LOONGARCH_CPU_PREFETCH;
- shm_align_mask = PAGE_SIZE - 1;
}
static const pgprot_t protection_map[16] = {
diff --git a/arch/loongarch/mm/mmap.c b/arch/loongarch/mm/mmap.c
index fbe1a4856fc4..c99c8015651a 100644
--- a/arch/loongarch/mm/mmap.c
+++ b/arch/loongarch/mm/mmap.c
@@ -8,12 +8,8 @@
#include <linux/mm.h>
#include <linux/mman.h>
-unsigned long shm_align_mask = PAGE_SIZE - 1; /* Sane caches */
-EXPORT_SYMBOL(shm_align_mask);
By removing this altogether, a lot of code duplication is introduced it
seems. Better make this a private #define so use sites remain nicely
symbolic:
"#define SHM_ALIGN_MASK (SHMLBA - 1)"
-
-#define COLOUR_ALIGN(addr, pgoff) \
- ((((addr) + shm_align_mask) & ~shm_align_mask) + \
- (((pgoff) << PAGE_SHIFT) & shm_align_mask))
+#define COLOUR_ALIGN(addr, pgoff) \
+ ((((addr) + (SHMLBA - 1)) & ~(SHMLBA - 1)) + (((pgoff) << PAGE_SHIFT) & (SHMLBA - 1)))
enum mmap_allocation_direction {UP, DOWN};
@@ -40,7 +36,7 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
* cache aliasing constraints.
*/
if ((flags & MAP_SHARED) &&
- ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
+ ((addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1)))
return -EINVAL;
return addr;
}
@@ -63,7 +59,7 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
}
info.length = len;
- info.align_mask = do_color_align ? (PAGE_MASK & shm_align_mask) : 0;
+ info.align_mask = do_color_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
info.align_offset = pgoff << PAGE_SHIFT;
if (dir == DOWN) {
--
WANG "xen0n" Xuerui
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