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keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <4a707c58-2225-477f-936e-9f99ae616c44@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-purgate-ID: tlsNG-d62444/1787045184-1E07B757-EEF9512C/0/0 X-purgate-type: clean X-purgate-size: 3780 On 18.08.2026 11:14, Oleksii Kurochko wrote: > On 8/18/26 9:56 AM, Jan Beulich wrote: >> On 17.08.2026 13:33, Oleksii Kurochko wrote: >>> On 8/12/26 4:37 PM, Jan Beulich wrote: >>>> On 20.07.2026 18:02, Oleksii Kurochko wrote: >>>>> @@ -60,6 +68,40 @@ static void ex_handler_fixup(const struct exception_table_entry *ex, >>>>> regs->sepc = ex_fixup(ex); >>>>> } >>>>> >>>>> +static inline unsigned long regs_get_gpr(struct cpu_user_regs *regs, >>>>> + unsigned int offset) >>>>> +{ >>>>> + /* >>>>> + * The GPR number -> offset arithmetic below relies on x0..x31 being >>>>> + * laid out at the start of struct cpu_user_regs in architectural >>>>> + * order. >>>>> + */ >>>>> + BUILD_BUG_ON(offsetof(struct cpu_user_regs, ra) != >>>>> + sizeof(unsigned long)); >>>>> + BUILD_BUG_ON(offsetof(struct cpu_user_regs, t6) != >>>>> + 31 * sizeof(unsigned long)); >>>>> + >>>>> + if ( unlikely(!offset || (offset > MAX_REG_OFFSET)) ) >>>>> + return 0; >>>> >>>> And an offset not divisible by sizeof(unsigned long) is okay? >>> >>> No, it isn't okay. I will apply your comment ... >>> >>>> >>>> Returning 0 as error indicator also feels fragile. >>> >>> With what I suggested below returning could be just dropped. >>> >>>> >>>>> + return *(unsigned long *)((unsigned long)regs + offset); >>>>> +} >>>>> + >>>>> +static void ex_handler_trap_info(const struct exception_table_entry *ex, >>>>> + struct cpu_user_regs *regs) >>>>> +{ >>>>> + struct trap_info *trap_info = >>>>> + (struct trap_info *)regs_get_gpr(regs, ex->data * sizeof(unsigned long)); >>>> >>>> Related to the earlier comment: Simply pass just ex->data here, leaving the >>>> multiplication to regs_get_gpr()? >>> >>> ... It would be better to move the multiplication inside regs_get_gpr(). >>> >>> Your comment made me think about whether the multiplication is needed at >>> all (regardless of where it is done). In other words, ex->data contains >>> the register number, so we could just write: >>> >>> static unsigned long regs_get_gpr(const struct cpu_user_regs *regs, >>> unsigned int num) >>> { >>> /* >>> * The GPR number -> offset arithmetic below relies on x0..x31 being >>> * laid out at the start of struct cpu_user_regs in architectural >>> order. >>> */ >>> BUILD_BUG_ON(offsetof(struct cpu_user_regs, ra) != sizeof(unsigned >>> long)); >>> BUILD_BUG_ON(offsetof(struct cpu_user_regs, t6) != 31 * >>> sizeof(unsigned long)); >>> >>> ASSERT(num && (num < 32)); >>> >>> return ((const unsigned long *)regs)[num]; >>> } >>> >>> Probably, we want to consider this function out of context (for now >>> context is that we use it to recieve a pointer to trap_info which can't >>> be obviously stored in x0 as it should be always hardwired zero). In >>> that case, there is no need to check that num is 0. >>> >>> So, it probably makes sense to just have: >>> ASSERT(num < 32); >>> >>> ASSERT() is fine here as I don't think that compiler will use incorrect >>> number during register allocation. >> >> I agree. >> >> However, the x0 aspect is still odd. Why again is it that struct cpu_user_regs >> has a field for it, when the register value is always 0? > > zero field isn't there to hold a value, it's there so the first 32 slots > form an x0..x31 array indexed by GPR number. It is useful for SET_RD() > implementation, for example. But SET_RD() will need to avoid touching .zero anyway. Why waste the space, when something useful can be put there? Jan