From beef2f693785499153b00f330d0205f91c3add4e Mon Sep 17 00:00:00 2001 From: Samuel Holland Date: Thu, 29 Aug 2024 13:22:36 -0700 Subject: [PATCH] lib: sbi: Respect scounteren when emulating the time CSR This optimization creates a correctness issue, as it prevents supervisor software from restricting VS-mode or U-mode access to the time CSR for its own purposes. Closes: https://github.com/riscv-software-src/opensbi/issues/370 Fixes: ebc8ebc0f846 ("lib: sbi: Improve HPM CSR read/write emulation") Signed-off-by: Samuel Holland Reviewed-by: Anup Patel --- lib/sbi/sbi_emulate_csr.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/lib/sbi/sbi_emulate_csr.c b/lib/sbi/sbi_emulate_csr.c index 869c81f4..3adec78d 100644 --- a/lib/sbi/sbi_emulate_csr.c +++ b/lib/sbi/sbi_emulate_csr.c @@ -66,12 +66,11 @@ int sbi_emulate_csr_read(int csr_num, struct sbi_trap_regs *regs, *csr_val = csr_read(CSR_MCYCLE); break; case CSR_TIME: + if (!hpm_allowed(csr_num - CSR_CYCLE, prev_mode, virt)) + return SBI_ENOTSUPP; /* * We emulate TIME CSR for both Host (HS/U-mode) and * Guest (VS/VU-mode). - * - * Faster TIME CSR reads are critical for good performance - * in S-mode software so we don't check CSR permissions. */ *csr_val = (virt) ? sbi_timer_virt_value(): sbi_timer_value();