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[PATCH v2] MIPS: Make TASK_SIZE reflect proper size for both 32 and 64 b

To: linux-mips@linux-mips.org, ralf@linux-mips.org
Subject: [PATCH v2] MIPS: Make TASK_SIZE reflect proper size for both 32 and 64 bit processes.
From: David Daney <ddaney@caviumnetworks.com>
Date: Wed, 13 Oct 2010 10:53:35 -0700
Cc: David Daney <ddaney@caviumnetworks.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
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.

__UA_LIMIT is set to 1 << 63 for 64-bit kernels on the theory that the
TLB handlers cause a fault on all illegal accesses in the bottom half
of the address space.  This allows for more efficient code generation.

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@caviumnetworks.com>
---

This second version reworks the __UA_LIMIT part.

 arch/mips/include/asm/pgtable-64.h |    4 +-
 arch/mips/include/asm/processor.h  |   40 +++++++++++++++++------------------
 arch/mips/include/asm/uaccess.h    |    2 +-
 3 files changed, 22 insertions(+), 24 deletions(-)

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..476348f 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -35,7 +35,7 @@
 
 #ifdef CONFIG_64BIT
 
-#define __UA_LIMIT     (- TASK_SIZE)
+#define __UA_LIMIT     (1ul << 63)
 
 #define __UA_ADDR      ".dword"
 #define __UA_LA                "dla"
-- 
1.7.2.3


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