[PATCH V11 10/20] riscv: compat: Support TASK_SIZE for compat mode

guoren
2022-04-02T13:54:47Z

Make TASK_SIZE from const to dynamic detect TIF_32BIT flag
function. Refer to arm64 to implement DEFAULT_MAP_WINDOW_64 for
efi-stub.

Limit 32-bit compatible process in 0-2GB virtual address range
(which is enough for real scenarios), because it could avoid
address sign extend problem when 32-bit enter 64-bit and ease
software design.

The standard 32-bit TASK_SIZE is 0x9dc00000:FIXADDR_START, and
compared to a compatible 32-bit, it increases 476MB for the
application's virtual address.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
---
arch/riscv/include/asm/pgtable.h | 13 +++++++++++--
arch/riscv/include/asm/processor.h | 6 +++++-
2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index e3549e50de95..afdc9ece2ba4 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -705,8 +705,17 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
* 63–48 all equal to bit 47, or else a page-fault exception will occur."
*/
#ifdef CONFIG_64BIT
-#define TASK_SIZE (PGDIR_SIZE * PTRS_PER_PGD / 2)
-#define TASK_SIZE_MIN (PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
+#define TASK_SIZE_64 (PGDIR_SIZE * PTRS_PER_PGD / 2)
+#define TASK_SIZE_MIN (PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
+
+#ifdef CONFIG_COMPAT
+#define TASK_SIZE_32 (_AC(0x80000000, UL) - PAGE_SIZE)
+#define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \
+ TASK_SIZE_32 : TASK_SIZE_64)
+#else
+#define TASK_SIZE TASK_SIZE_64
+#endif
+
#else
#define TASK_SIZE FIXADDR_START
#define TASK_SIZE_MIN TASK_SIZE
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 0749924d9e55..21c8072dce17 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -19,7 +19,11 @@
#define TASK_UNMAPPED_BASE PAGE_ALIGN(TASK_SIZE / 3)

#define STACK_TOP TASK_SIZE
-#define STACK_TOP_MAX STACK_TOP
+#ifdef CONFIG_64BIT
+#define STACK_TOP_MAX TASK_SIZE_64
+#else
+#define STACK_TOP_MAX TASK_SIZE
+#endif
#define STACK_ALIGN 16

#ifndef __ASSEMBLY__
--
2.25.1