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lib: sbi: Only enable TM bit in scounteren

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The S-mode should disable Cycle and instruction counter for user space
to avoid side channel attacks. The Linux kernel already does this so that
any random user space code shouldn't be able to monitor cycle/instruction
without higher privilege mode involvement.

Remove the CY/IR bits in scountern in OpenSBI.

Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20250513-fix_scounteren-v1-1-01018e0c0b0a@rivosinc.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Atish Patra
2025-05-13 17:25:15 -07:00
committed by Anup Patel
parent 663b05a5f7
commit 5b305e30a5
1 changed files with 2 additions and 2 deletions
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4
lib/sbi/sbi_hart.c
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@@ -49,10 +49,10 @@ static void mstatus_init(struct sbi_scratch *scratch)
csr_write(CSR_MSTATUS, mstatus_val); csr_write(CSR_MSTATUS, mstatus_val);
/* Disable user mode usage of all perf counters except default ones (CY, TM, IR) */ /* Disable user mode usage of all perf counters except TM */
if (misa_extension('S') && if (misa_extension('S') &&
sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_10) sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_10)
csr_write(CSR_SCOUNTEREN, 7); csr_write(CSR_SCOUNTEREN, 0x02);
/** /**
* OpenSBI doesn't use any PMU counters in M-mode. * OpenSBI doesn't use any PMU counters in M-mode.