The TASK_SIZE macro should reflect the size of a user process virtual
address space. Previously for 64-bit kernels, this was not the case.
The immediate cause of pain was in
hugetlbfs/inode.c:hugetlb_get_unmapped_area() where 32-bit processes
trying to mmap a huge page would be served a page with an address
outside of the 32-bit address range. But there are other uses of
TASK_SIZE in the kernel as well that would like an accurate value.
The new definition is nice because it now makes TASK_SIZE and
TASK_SIZE_OF() yield the same value for any given process.
For 32-bit kernels there should be no change, although I did factor
out some code in asm/processor.h that became identical for the 32-bit and
64-bit cases.
Another, perhaps non-obvious, change is that in 64-bit kernels, the
get_fs() value (A.K.A current_thread_info()->addr_limit) will now vary
depending on the address space size of the process. This is a change,
as previously even 32-bit processes would have an addr_limit
appropriate for a 64-bit process. This will change the behavior of
access_ok(), but I think the new behavior is desirable.
Before the patch it may have been possible for a user space process to
pass a pointer to the kernel that would pass the access_ok() check,
but be outside of the 32-bit address space.
With the patch applied, I can still run o32, n32 and n64 processes,
and have an o32 shell fork/exec both n32 and n64 processes.
Signed-off-by: David Daney <ddaney@xxxxxxxxxxxxxxxxxx>
---
arch/mips/include/asm/elf.h | 1 +
arch/mips/include/asm/pgtable-64.h | 4 +-
arch/mips/include/asm/processor.h | 40 +++++++++++++++++------------------
arch/mips/include/asm/uaccess.h | 3 +-
4 files changed, 24 insertions(+), 24 deletions(-)
diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index fd1d39e..ca8cb9f 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -306,6 +306,7 @@ do { \
\
if (current->personality != PER_LINUX32) \
set_personality(PER_LINUX); \
+ set_fs(USER_DS); /* Update addr_limit for TIF_32BIT_ADDR. */ \
} while (0)
#endif /* CONFIG_64BIT */
diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-64.h
index 1be4b0f..82d881a 100644
--- a/arch/mips/include/asm/pgtable-64.h
+++ b/arch/mips/include/asm/pgtable-64.h
@@ -113,10 +113,10 @@
#endif
#define PTRS_PER_PTE ((PAGE_SIZE << PTE_ORDER) / sizeof(pte_t))
-#if PGDIR_SIZE >= TASK_SIZE
+#if PGDIR_SIZE >= TASK_SIZE64
#define USER_PTRS_PER_PGD (1)
#else
-#define USER_PTRS_PER_PGD (TASK_SIZE / PGDIR_SIZE)
+#define USER_PTRS_PER_PGD (TASK_SIZE64 / PGDIR_SIZE)
#endif
#define FIRST_USER_ADDRESS 0UL
diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index 0d629bb..ead6928 100644
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -50,13 +50,10 @@ extern unsigned int vced_count, vcei_count;
* so don't change it unless you know what you are doing.
*/
#define TASK_SIZE 0x7fff8000UL
-#define STACK_TOP ((TASK_SIZE & PAGE_MASK) - SPECIAL_PAGES_SIZE)
-/*
- * This decides where the kernel will search for a free chunk of vm
- * space during mmap's.
- */
-#define TASK_UNMAPPED_BASE ((TASK_SIZE / 3) & ~(PAGE_SIZE))
+#ifdef __KERNEL__
+#define STACK_TOP_MAX TASK_SIZE
+#endif
#define TASK_IS_32BIT_ADDR 1
@@ -71,28 +68,29 @@ extern unsigned int vced_count, vcei_count;
* 8192EB ...
*/
#define TASK_SIZE32 0x7fff8000UL
-#define TASK_SIZE 0x10000000000UL
-#define STACK_TOP \
- (((test_thread_flag(TIF_32BIT_ADDR) ? \
- TASK_SIZE32 : TASK_SIZE) & PAGE_MASK) - SPECIAL_PAGES_SIZE)
+#define TASK_SIZE64 0x10000000000UL
+#define TASK_SIZE (test_thread_flag(TIF_32BIT_ADDR) ? TASK_SIZE32 : TASK_SIZE64)
+
+#ifdef __KERNEL__
+#define STACK_TOP_MAX TASK_SIZE64
+#endif
+
-/*
- * This decides where the kernel will search for a free chunk of vm
- * space during mmap's.
- */
-#define TASK_UNMAPPED_BASE \
- (test_thread_flag(TIF_32BIT_ADDR) ? \
- PAGE_ALIGN(TASK_SIZE32 / 3) : PAGE_ALIGN(TASK_SIZE / 3))
#define TASK_SIZE_OF(tsk) \
- (test_tsk_thread_flag(tsk, TIF_32BIT_ADDR) ? TASK_SIZE32 : TASK_SIZE)
+ (test_tsk_thread_flag(tsk, TIF_32BIT_ADDR) ? TASK_SIZE32 : TASK_SIZE64)
#define TASK_IS_32BIT_ADDR test_thread_flag(TIF_32BIT_ADDR)
#endif
-#ifdef __KERNEL__
-#define STACK_TOP_MAX TASK_SIZE
-#endif
+#define STACK_TOP ((TASK_SIZE & PAGE_MASK) - SPECIAL_PAGES_SIZE)
+
+/*
+ * This decides where the kernel will search for a free chunk of vm
+ * space during mmap's.
+ */
+#define TASK_UNMAPPED_BASE PAGE_ALIGN(TASK_SIZE / 3)
+
#define NUM_FPU_REGS 32
diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index c2d53c1..8f7b5fd 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -35,7 +35,8 @@
#ifdef CONFIG_64BIT
-#define __UA_LIMIT (- TASK_SIZE)
+#define __UA_LIMIT \
+ (test_thread_flag(TIF_32BIT_ADDR) ? 0xffffffff80000000ul : -TASK_SIZE64)
#define __UA_ADDR ".dword"
#define __UA_LA "dla"
--
1.7.2.3
