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riscv: avoid Imbalance in RAS

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Inspired by[1], modify the code to remove the code of modifying ra to
avoid imbalance RAS (return address stack) which may lead to incorret
predictions on return.

Link: https://lore.kernel.org/linux-riscv/20240607061335.2197383-1-cyrilbur@tenstorrent.com/ [1]
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Cyril Bur <cyrilbur@tenstorrent.com>
Link: https://lore.kernel.org/r/20240720170659.1522-1-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Jisheng Zhang 2024-07-21 01:06:59 +08:00 committed by Palmer Dabbelt
parent 7e340f4fad
commit 8f1534e744
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1 changed files with 2 additions and 2 deletions
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arch/riscv/kernel/entry.S
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@ -326,8 +326,8 @@ SYM_CODE_START(ret_from_fork)
jalr s0
1:
move a0, sp /* pt_regs */
la ra, ret_from_exception
tail syscall_exit_to_user_mode
call syscall_exit_to_user_mode
j ret_from_exception
SYM_CODE_END(ret_from_fork)
#ifdef CONFIG_IRQ_STACKS