riscv: mm: Fixup & Optimize COMPAT mode

From: Guo Ren <[email protected]>

When the task is in COMPAT mode, the TASK_SIZE should be 2GB, so STACK_TOP_MAX and arch_get_mmap_end must be limited to 2 GB. This series fixes the problem made by commit: add2cc6b6515 ("RISC-V: mm: Restrict address space for sv39,sv48,sv57") and optimizes the related coding convention of TASK_SIZE.

Changelog:
v4:
- Add "Reviewed-by" tags

v3:
https://lore.kernel.org/linux-riscv/[email protected]/
- Remove wrong modification of arch_get_mmap_end
- Remove is_compat_task optimization
- Update comment log

v2:
https://lore.kernel.org/linux-riscv/[email protected]/
- Separate rename from fixup
- Add STACK_TOP_MAX fixup for compat
- Add Cleanup & rename patches

v1:
https://lore.kernel.org/linux-riscv/[email protected]/

Guo Ren (4):
riscv: mm: Fixup compat mode boot failure
riscv: mm: Fixup compat arch_get_mmap_end
riscv: mm: Remove unused TASK_SIZE_MIN
riscv: mm: Optimize TASK_SIZE definition

 arch/riscv/include/asm/pgtable.h   | 7 +++----
 arch/riscv/include/asm/processor.h | 2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

2.40.1

From: Guo Ren <[email protected]>

In COMPAT mode, the STACK_TOP is DEFAULT_MAP_WINDOW (0x80000000), but the TASK_SIZE is 0x7fff000. When the user stack is upon 0x7fff000, it will cause a user segment fault. Sometimes, it would cause boot failure when the whole rootfs is rv32.

Freeing unused kernel image (initmem) memory: 2236K
Run /sbin/init as init process
Starting init: /sbin/init exists but couldn't execute it (error -14) Run /etc/init as init process
...

Increase the TASK_SIZE to cover STACK_TOP.

---
 arch/riscv/include/asm/pgtable.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index ab00235b018f..74ffb2178f54 100644
@@ -881,7 +881,7 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
 #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_32	(_AC(0x80000000, UL))
 #define TASK_SIZE	(test_thread_flag(TIF_32BIT) ? \
 			 TASK_SIZE_32 : TASK_SIZE_64)
 #else

2.40.1

From: Guo Ren <[email protected]>

When the task is in COMPAT mode, the arch_get_mmap_end should be 2GB, not TASK_SIZE_64. The TASK_SIZE has contained is_compat_mode() detection, so change the definition of STACK_TOP_MAX to TASK_SIZE directly.

---
 arch/riscv/include/asm/processor.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index f19f861cda54..e1944ff0757a 100644
@@ -16,7 +16,7 @@
 
 #ifdef CONFIG_64BIT
 #define DEFAULT_MAP_WINDOW	(UL(1) << (MMAP_VA_BITS - 1))
-#define STACK_TOP_MAX		TASK_SIZE_64
+#define STACK_TOP_MAX		TASK_SIZE
 
 #define arch_get_mmap_end(addr, len, flags)			\
 ({								\

2.40.1

From: Guo Ren <[email protected]>

Remove TASK_SIZE_MIN because it's not used anymore.

---
 arch/riscv/include/asm/pgtable.h | 2 --
 1 file changed, 2 deletions(-)

index 74ffb2178f54..e415582276ec 100644
@@ -878,7 +878,6 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
  */
 #ifdef CONFIG_64BIT
 #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))

@@ -890,7 +889,6 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
 
 #else
 #define TASK_SIZE	FIXADDR_START
-#define TASK_SIZE_MIN	TASK_SIZE
 #endif
 
 #else /* CONFIG_MMU */

2.40.1

From: Guo Ren <[email protected]>

Unify the TASK_SIZE definition with VA_BITS for better readability. Add COMPAT mode user address space info in the comment.

---
 arch/riscv/include/asm/pgtable.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

index e415582276ec..271565e1956f 100644
@@ -866,6 +866,7 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
  * Note that PGDIR_SIZE must evenly divide TASK_SIZE.
  * Task size is:
  * -        0x9fc00000	(~2.5GB) for RV32.
+ * -        0x80000000	(   2GB) for RV64 compat mode
  * -      0x4000000000	( 256GB) for RV64 using SV39 mmu
  * -    0x800000000000	( 128TB) for RV64 using SV48 mmu
  * - 0x100000000000000	(  64PB) for RV64 using SV57 mmu

@@ -877,10 +878,10 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
  * Similarly for SV57, bits 63–57 must be equal to bit 56.
  */
 #ifdef CONFIG_64BIT
-#define TASK_SIZE_64	(PGDIR_SIZE * PTRS_PER_PGD / 2)
+#define TASK_SIZE_64	(UL(1) << (VA_BITS - 1))
 
 #ifdef CONFIG_COMPAT
-#define TASK_SIZE_32	(_AC(0x80000000, UL))
+#define TASK_SIZE_32	(UL(1) << (VA_BITS_SV32 - 1))
 #define TASK_SIZE	(test_thread_flag(TIF_32BIT) ? \
 			 TASK_SIZE_32 : TASK_SIZE_64)
 #else

2.40.1