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

Guo Ren
2022-09-04T10:57:10Z

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:

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,

>
> -- >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