Re: [PATCH V2 5/6] riscv: elf_kexec: Fixup compile warning

[Conor.Dooley]

On 04/09/2022 11:56, Guo Ren wrote:
> On Sun, Sep 4, 2022 at 6:36 PM <Conor.Dooley@xxxxxxxxxxxxx> wrote:
>>
>> On 04/09/2022 08:26, guoren@xxxxxxxxxx wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>
>>> From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
>>>
>>> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1
>>> O=build_dir ARCH=riscv SHELL=/bin/bash arch/riscv/
>>>
>>> ../arch/riscv/kernel/elf_kexec.c: In function 'elf_kexec_load':
>>> ../arch/riscv/kernel/elf_kexec.c:185:23: warning: variable
>>> 'kernel_start' set but not used [-Wunused-but-set-variable]
>>>   185 |         unsigned long kernel_start;
>>>       |                       ^~~~~~~~~~~~
>>>
>>> Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
>>> Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
>>> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>>
>> Is this then a
>> Fixes: 838b3e28488f ("RISC-V: Load purgatory in kexec_file")
>> ?
>>
>> Could you also add something like:
>> "If CONFIG_CRYTPO is not enabled, ...." to explain why this
>> may be unused?
>>
>>> ---
>>>  arch/riscv/kernel/elf_kexec.c | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
>>> index 0cb94992c15b..bba3723a0914 100644
>>> --- a/arch/riscv/kernel/elf_kexec.c
>>> +++ b/arch/riscv/kernel/elf_kexec.c
>>> @@ -182,7 +182,9 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
>>>         unsigned long new_kernel_pbase = 0UL;
>>>         unsigned long initrd_pbase = 0UL;
>>>         unsigned long headers_sz;
>>> +#ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY
>>>         unsigned long kernel_start;
>>> +#endif /* CONFIG_ARCH_HAS_KEXEC_PURGATORY */
>>>         void *fdt, *headers;
>>>         struct elfhdr ehdr;
>>>         struct kexec_buf kbuf;
>>> @@ -197,7 +199,9 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
>>>                              &old_kernel_pbase, &new_kernel_pbase);
>>>         if (ret)
>>>                 goto out;
>>> +#ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY
>>>         kernel_start = image->start;
>>> +#endif /* CONFIG_ARCH_HAS_KEXEC_PURGATORY */
>>
>> Instead of adding more #ifdefs to the file, could we instead just drop the
>> kernel_start variable? For the sake of compilation coverage, we could then
>> also do the following (build-tested only):
> Em... I prefer:

Uh, that works for me. The below diff is:
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>

> 
> diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
> index 0cb94992c15b..4b9264340b78 100644
> --- a/arch/riscv/kernel/elf_kexec.c
> +++ b/arch/riscv/kernel/elf_kexec.c
> @@ -198,7 +198,7 @@ static void *elf_kexec_load(struct kimage *image,
> char *kernel_buf,
>         if (ret)
>                 goto out;
>         kernel_start = image->start;
> -       pr_notice("The entry point of kernel at 0x%lx\n", image->start);
> +       pr_notice("The entry point of kernel at 0x%lx\n", kernel_start);
> 
>         /* Add the kernel binary to the image */
>         ret = riscv_kexec_elf_load(image, &ehdr, &elf_info,
> 
> 
>>

Feel free to include this patch in your v3 then:
>> -- >8 --
>> From: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
>> Date: Sun, 4 Sep 2022 11:27:07 +0100
>> Subject: [PATCH] riscv: elf_kexec: replace ifdef with IS_ENABLED()
>>
>> IS_ENABLED() gives better compile time coverage than #ifdef.
>> Replace the ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY in elf_kexec_load()
>> since none of the code it guards uses a symbol that's missing if it
>> is not set.
>>
>> Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
>> ---
>>  arch/riscv/kernel/elf_kexec.c | 28 ++++++++++++++--------------
>>  1 file changed, 14 insertions(+), 14 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
>> index 0cb94992c15b..29cbf655c474 100644
>> --- a/arch/riscv/kernel/elf_kexec.c
>> +++ b/arch/riscv/kernel/elf_kexec.c
>> @@ -248,21 +248,21 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
>>                 cmdline = modified_cmdline;
>>         }
>>
>> -#ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY
>> -       /* Add purgatory to the image */
>> -       kbuf.top_down = true;
>> -       kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>> -       ret = kexec_load_purgatory(image, &kbuf);
>> -       if (ret) {
>> -               pr_err("Error loading purgatory ret=%d\n", ret);
>> -               goto out;
>> +       if (IS_ENABLED(CONFIG_ARCH_HAS_KEXEC_PURGATORY)) {
>> +               /* Add purgatory to the image */
>> +               kbuf.top_down = true;
>> +               kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>> +               ret = kexec_load_purgatory(image, &kbuf);
>> +               if (ret) {
>> +                       pr_err("Error loading purgatory ret=%d\n", ret);
>> +                       goto out;
>> +               }
>> +               ret = kexec_purgatory_get_set_symbol(image, "riscv_kernel_entry",
>> +                                                    &kernel_start,
>> +                                                    sizeof(kernel_start), 0);
>> +               if (ret)
>> +                       pr_err("Error update purgatory ret=%d\n", ret);
>>         }
>> -       ret = kexec_purgatory_get_set_symbol(image, "riscv_kernel_entry",
>> -                                            &kernel_start,
>> -                                            sizeof(kernel_start), 0);
>> -       if (ret)
>> -               pr_err("Error update purgatory ret=%d\n", ret);
>> -#endif /* CONFIG_ARCH_HAS_KEXEC_PURGATORY */
>>
>>         /* Add the initrd to the image */
>>         if (initrd != NULL) {
>> --
>> 2.37.1
>>
> 
>