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Subject[PATCH V2 08/17] riscv: compat: Re-implement TASK_SIZE for COMPAT_32BIT
Date
From: Guo Ren <guoren@linux.alibaba.com>

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>
Cc: Arnd Bergmann <arnd@arndb.de>
---
arch/riscv/include/asm/pgtable.h | 11 ++++++++++-
arch/riscv/include/asm/processor.h | 6 ++++++
drivers/firmware/efi/libstub/efi-stub.c | 2 +-
3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index bf204e7c1f74..2dd5b8674380 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -663,7 +663,16 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
* Note that PGDIR_SIZE must evenly divide TASK_SIZE.
*/
#ifdef CONFIG_64BIT
-#define TASK_SIZE (PGDIR_SIZE * PTRS_PER_PGD / 2)
+#define TASK_SIZE_64 (PGDIR_SIZE * 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
#endif
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 0749924d9e55..8649436b8fcf 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -61,6 +61,12 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset,
extern void start_thread(struct pt_regs *regs,
unsigned long pc, unsigned long sp);

+#ifdef CONFIG_COMPAT
+#define DEFAULT_MAP_WINDOW_64 TASK_SIZE_64
+#else
+#define DEFAULT_MAP_WINDOW_64 TASK_SIZE
+#endif
+
/* Free all resources held by a thread. */
static inline void release_thread(struct task_struct *dead_task)
{
diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index 26e69788f27a..4075fd19d219 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -38,7 +38,7 @@
#define EFI_RT_VIRTUAL_BASE SZ_512M
#define EFI_RT_VIRTUAL_SIZE SZ_512M

-#ifdef CONFIG_ARM64
+#if defined(CONFIG_ARM64) || defined(CONFIG_RISCV)
# define EFI_RT_VIRTUAL_LIMIT DEFAULT_MAP_WINDOW_64
#else
# define EFI_RT_VIRTUAL_LIMIT TASK_SIZE
--
2.25.1
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