Subject: [PATCH V3 07/17] riscv: compat: Re-implement TASK_SIZE for COMPAT_32BIT

From: [email-masked]
Date: Thu, 20 Jan 2022 15:39:00 +0800

From: Guo Ren <[email-masked]>

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 <[email-masked]>
Signed-off-by: Guo Ren <[email-masked]>
Cc: Arnd Bergmann <[email-masked]>
---
 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 67f687aee673..e0add598e66a 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -669,7 +669,16 @@ 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 e87e7f1b1a33..f57f85646a45 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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