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authorMax Filippov <jcmvbkbc@gmail.com>2012-12-22 06:35:04 +0400
committerChris Zankel <chris@zankel.net>2013-02-23 19:12:53 -0800
commitde73b6b1bd7480301c8e8fbe58184448b1757945 (patch)
tree9aca0e26cfa96e18e1d353777349ee30cc25718d /arch/xtensa
parent475c32d0a1b836fc3798ea96cc334a4bfffec2cf (diff)
xtensa: avoid mmap cache aliasing
Provide arch_get_unmapped_area function aligning shared memory mapping addresses to the biggest of the page size or the cache way size. That guarantees that corresponding virtual addresses of shared mappings are cached by the same cache sets. Signed-off-by: Max Filippov <jcmvbkbc@gmail.com> Signed-off-by: Chris Zankel <chris@zankel.net>
Diffstat (limited to 'arch/xtensa')
-rw-r--r--arch/xtensa/include/asm/pgtable.h4
-rw-r--r--arch/xtensa/kernel/syscall.c41
2 files changed, 45 insertions, 0 deletions
diff --git a/arch/xtensa/include/asm/pgtable.h b/arch/xtensa/include/asm/pgtable.h
index c90ea5bfa1b..d7546c94da5 100644
--- a/arch/xtensa/include/asm/pgtable.h
+++ b/arch/xtensa/include/asm/pgtable.h
@@ -410,6 +410,10 @@ typedef pte_t *pte_addr_t;
#define __HAVE_ARCH_PTEP_SET_WRPROTECT
#define __HAVE_ARCH_PTEP_MKDIRTY
#define __HAVE_ARCH_PTE_SAME
+/* We provide our own get_unmapped_area to cope with
+ * SHM area cache aliasing for userland.
+ */
+#define HAVE_ARCH_UNMAPPED_AREA
#include <asm-generic/pgtable.h>
diff --git a/arch/xtensa/kernel/syscall.c b/arch/xtensa/kernel/syscall.c
index 54fa8425cee..5d3f7a119ed 100644
--- a/arch/xtensa/kernel/syscall.c
+++ b/arch/xtensa/kernel/syscall.c
@@ -36,6 +36,10 @@ syscall_t sys_call_table[__NR_syscall_count] /* FIXME __cacheline_aligned */= {
#include <uapi/asm/unistd.h>
};
+#define COLOUR_ALIGN(addr, pgoff) \
+ ((((addr) + SHMLBA - 1) & ~(SHMLBA - 1)) + \
+ (((pgoff) << PAGE_SHIFT) & (SHMLBA - 1)))
+
asmlinkage long xtensa_shmat(int shmid, char __user *shmaddr, int shmflg)
{
unsigned long ret;
@@ -52,3 +56,40 @@ asmlinkage long xtensa_fadvise64_64(int fd, int advice,
{
return sys_fadvise64_64(fd, offset, len, advice);
}
+
+unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+ struct vm_area_struct *vmm;
+
+ if (flags & MAP_FIXED) {
+ /* We do not accept a shared mapping if it would violate
+ * cache aliasing constraints.
+ */
+ if ((flags & MAP_SHARED) &&
+ ((addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1)))
+ return -EINVAL;
+ return addr;
+ }
+
+ if (len > TASK_SIZE)
+ return -ENOMEM;
+ if (!addr)
+ addr = TASK_UNMAPPED_BASE;
+
+ if (flags & MAP_SHARED)
+ addr = COLOUR_ALIGN(addr, pgoff);
+ else
+ addr = PAGE_ALIGN(addr);
+
+ for (vmm = find_vma(current->mm, addr); ; vmm = vmm->vm_next) {
+ /* At this point: (!vmm || addr < vmm->vm_end). */
+ if (TASK_SIZE - len < addr)
+ return -ENOMEM;
+ if (!vmm || addr + len <= vmm->vm_start)
+ return addr;
+ addr = vmm->vm_end;
+ if (flags & MAP_SHARED)
+ addr = COLOUR_ALIGN(addr, pgoff);
+ }
+}