opensbi.git/lib/sbi/sbi_emulate_csr.c, branch master

lib: sbi: factorize previous mode computation

2024-10-25T18:23:18Z

Previous privilege mode retrieval from mstatus is done at different places, factorize it rather than copy/pasting it again. Signed-off-by: Clément Léger Reviewed-by: Samuel Holland

lib: sbi: factorize previous virtualization mode read from regs

2024-10-25T18:22:51Z

The same pattern is used at multiple places to verify in which mode the exception was actually taken. Factorize it. Signed-off-by: Clément Léger Reviewed-by: Samuel Holland

lib: sbi: Respect scounteren when emulating the time CSR

2024-09-23T12:42:39Z

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_emulate_csr: Do not log illegal CSR accesses

2024-07-04T05:12:16Z

Illegal CSR accesses from lower privilege modes are delegated to S-mode and do not necessarily indicate a bug. Supervisor software may want to emulate some CSRs, or may intentionally disable access to certain existing CSRs, and thus will expect traps when those CSRs are accessed. For example, Linux disables sstatus.VS by default in order to detect when userspace first accesses vector register state; this includes the CSRs defined by the V extesion. As a result, if the first vector instruction in a process is a CSR access, OpenSBI will log the illegal instruction exception, even though there is no unexpected or erroneous behavior occurring. Since the illegal instruction exception is delegated to S-mode, S-mode software should be responsible for reporting the exception, not OpenSBI. Signed-off-by: Samuel Holland Reviewed-by: Anup Patel

lib: sbi_pmu: remove mhpm_count field in hart feature

2023-08-22T07:56:09Z

After supporting noncontigous hpm event and counters in opensbi, the number of hpm counters can be calculated by the mhpm_mask. So this field is unnecessary and can be removed to save some space. Signed-off-by: Inochi Amaoto Reviewed-by: Anup Patel

lib: sbi: Remove unnecessary semicolon

2023-05-11T07:01:34Z

We have redundant semicolon at quite a few places so let's remove it. Signed-off-by: Xiang W Reviewed-by: Anup Patel

treewide: Replace TRUE/FALSE with true/false

2023-01-06T11:56:35Z

C language standard uses true/false for the boolean type. Let's switch to that for better language compatibility. Signed-off-by: Bin Meng Reviewed-by: Anup Patel Reviewed-by: Samuel Holland Tested-by: Samuel Holland

lib: sbi: Remove MCOUNTEREN and SCOUNTEREN hart features

2022-05-07T04:34:54Z

If a hart implements privileged spec v1.10 (or higher) then we can safely assume that [m|s]counteren CSR are present and we don't need MCOUNTEREN and SCOUNTEREN as hart features. Signed-off-by: Anup Patel Reviewed-by: Atish Patra

lib: sbi: illegal CSR 0x306 access in hpm_allowed()

2021-03-22T03:48:56Z

The trap handler sbi_emulate_csr_read() invokes hpm_allowed() which reads CSR 0x306 (mcounteren). The K210 does not support CSR 0x306. While trying to handle a trap occurring in S-mode code this creates an additional trap in M-mode. This results in failure to redirect to S-mode and the system hanging in sbi_hart_hang(). In hart_detect_features() we have already determined if CSR 0x306 is available and stored that information in the scratch area. We can use this information to decide if CSR 0x306 shall be accessed in hpm_allowed() and thus avoid the M-mode trap. Likewise if CSR scounteren is not available we have to avoid reading CSR 0x106. Signed-off-by: Heinrich Schuchardt Reviewed-by: Anup Patel

lib: sbi: Improve HPM CSR read/write emulation

2020-09-01T04:58:35Z

We improve HPM CSR read/write emulation as follows: 1. Fail for unimplemented counters so that trap is redirected to S-mode which can further help debugging S-mode software. 2. Check permissions in both MCOUNTEREN and SCOUNTEREN for HS-mode and U-mode. 3. Don't check permissions for TIME CSR because we emulate TIME CSR for both Host (HS/U-mode) and Guest (VS/VU-mode). Also, faster TIME CSR read is very helpful for good performance of S-mode software. 4. Don't emulate S-mode CSR read/write to M-mode HPM CSRs because these should not be accessible to S-mode software. Signed-off-by: Anup Patel Reviewed-by: Atish Patra