linux-kernel - [PATCH V4 1/4] riscv: mm: Fixup compat mode boot failure

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Message-Id: <20240107063025.1628475-2-guoren@kernel.org>
Date: Sun,  7 Jan 2024 01:30:22 -0500
From: guoren@...nel.org
To: paul.walmsley@...ive.com,
	palmer@...belt.com,
	alexghiti@...osinc.com,
	charlie@...osinc.com,
	guoren@...nel.org,
	panqinglin2020@...as.ac.cn,
	bjorn@...osinc.com,
	conor.dooley@...rochip.com,
	leobras@...hat.com,
	cleger@...osinc.com,
	willy@...radead.org
Cc: linux-kernel@...r.kernel.org,
	Guo Ren <guoren@...ux.alibaba.com>,
	stable@...r.kernel.org
Subject: [PATCH V4 1/4] riscv: mm: Fixup compat mode boot failure

From: Guo Ren <guoren@...ux.alibaba.com>

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.

Cc: stable@...r.kernel.org
Fixes: add2cc6b6515 ("RISC-V: mm: Restrict address space for sv39,sv48,sv57")
Reviewed-by: Leonardo Bras <leobras@...hat.com>
Reviewed-by: Charlie Jenkins <charlie@...osinc.com>
Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Signed-off-by: Guo Ren <guoren@...nel.org>
---
 arch/riscv/include/asm/pgtable.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index ab00235b018f..74ffb2178f54 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -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