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In-Reply-To: <8551463c-376c-8c64-6bf3-31dd5d9133d8@microchip.com>
From:   Guo Ren <guoren@kernel.org>
Date:   Sun, 4 Sep 2022 19:55:18 +0800
Message-ID: <CAJF2gTQuJDev3fBjVvycDvwnhUBgaHzkh_sp9=BJefmr=KfqXQ@mail.gmail.com>
Subject: Re: [PATCH V2 5/6] riscv: elf_kexec: Fixup compile warning
To:     Conor.Dooley@microchip.com
Cc:     arnd@arndb.de, palmer@rivosinc.com, tglx@linutronix.de,
        peterz@infradead.org, luto@kernel.org, heiko@sntech.de,
        jszhang@kernel.org, lazyparser@gmail.com, falcon@tinylab.org,
        chenhuacai@kernel.org, apatel@ventanamicro.com,
        atishp@atishpatra.org, palmer@dabbelt.com,
        paul.walmsley@sifive.com, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
        guoren@linux.alibaba.com, lkp@intel.com
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On Sun, Sep 4, 2022 at 7:13 PM <Conor.Dooley@microchip.com> wrote:
>
> On 04/09/2022 11:56, Guo Ren wrote:
> > On Sun, Sep 4, 2022 at 6:36 PM <Conor.Dooley@microchip.com> wrote:
> >>
> >> On 04/09/2022 08:26, guoren@kernel.org wrote:
> >>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >>>
> >>> From: Guo Ren <guoren@linux.alibaba.com>
> >>>
> >>> 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@linux.alibaba.com>
> >>> Signed-off-by: Guo Ren <guoren@kernel.org>
> >>> Reported-by: kernel test robot <lkp@intel.com>
> >>
> >> 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@microchip.com>
Thx, your idea is also awesome which let me know the benefit of
IS_ENABLED() than ifdef.

>
> >
> > 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@microchip.com>
> >> 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@microchip.com>
> >> ---
> >>  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
> >>
> >
> >


-- 
Best Regards
 Guo Ren