linux-kernel - [PATCH] riscv: mm: Fixup compat mode boot failure

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Date: Tue, 19 Dec 2023 06:17:01 -0500
From: guoren@...nel.org
To: linux-kernel@...r.kernel.org,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	alexghiti@...osinc.com,
	charlie@...osinc.com,
	xiao.w.wang@...el.com,
	guoren@...nel.org,
	david@...hat.com,
	panqinglin2020@...as.ac.cn,
	rick.p.edgecombe@...el.com,
	willy@...radead.org
Cc: linux-riscv@...ts.infradead.org,
	Guo Ren <guoren@...ux.alibaba.com>
Subject: [PATCH] riscv: mm: Fixup compat mode boot failure

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

In COMPAT mode, the STACK_TOP is 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
...

Fixes: add2cc6b6515 ("RISC-V: mm: Restrict address space for sv39,sv48,sv57")
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..d2ec5e6fa331 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	(UL(1) << (MMAP_VA_BITS - 1))
 #define TASK_SIZE	(test_thread_flag(TIF_32BIT) ? \
 			 TASK_SIZE_32 : TASK_SIZE_64)
 #else
-- 
2.40.1