linux-kernel - [PATCH 1/2] RISC-V: Align the shadow stack

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Message-Id: <20221130023515.20217-1-palmer@rivosinc.com>
Date:   Tue, 29 Nov 2022 18:35:14 -0800
From:   Palmer Dabbelt <palmer@...osinc.com>
To:     jszhang@...nel.org, guoren@...nel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Palmer Dabbelt <palmer@...osinc.com>
Subject: [PATCH 1/2] RISC-V: Align the shadow stack

The standard RISC-V ABIs all require 16-byte stack alignment.  We're
only calling that one function on the shadow stack so I doubt it'd
result in a real issue, but might as well keep this lined up.

Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection")
Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
---
 arch/riscv/kernel/traps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index be54ccea8c47..acdfcacd7e57 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -206,7 +206,7 @@ static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)],
  * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used
  * to get per-cpu overflow stack(get_overflow_stack).
  */
-long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)];
+long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16);
 asmlinkage unsigned long get_overflow_stack(void)
 {
 	return (unsigned long)this_cpu_ptr(overflow_stack) +
-- 
2.38.1