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

From: Guo Ren
Date: Sun Sep 04 2022 - 07:55:45 EST

On Sun, Sep 4, 2022 at 7:13 PM <Conor.Dooley@xxxxxxxxxxxxx> wrote:
>
> 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>
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@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
> >>
> >
> >



--
Best Regards
Guo Ren