linux-kernel - Re: [PATCH V2 5/6] riscv: elf

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Message-ID: <98efc4d8-f846-1ff1-2635-d18b7fca4ac8@microchip.com>
Date:   Sun, 4 Sep 2022 10:36:37 +0000
From:   <Conor.Dooley@...rochip.com>
To:     <guoren@...nel.org>, <arnd@...db.de>, <palmer@...osinc.com>,
        <tglx@...utronix.de>, <peterz@...radead.org>, <luto@...nel.org>,
        <heiko@...ech.de>, <jszhang@...nel.org>, <lazyparser@...il.com>,
        <falcon@...ylab.org>, <chenhuacai@...nel.org>,
        <apatel@...tanamicro.com>, <atishp@...shpatra.org>,
        <palmer@...belt.com>, <paul.walmsley@...ive.com>
CC:     <linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-riscv@...ts.infradead.org>, <guoren@...ux.alibaba.com>,
        <lkp@...el.com>
Subject: Re: [PATCH V2 5/6] riscv: elf_kexec: Fixup compile warning

On 04/09/2022 08:26, guoren@...nel.org wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> From: Guo Ren <guoren@...ux.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@...ux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@...nel.org>
> Reported-by: kernel test robot <lkp@...el.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):

-- >8 --
From: Conor Dooley <conor.dooley@...rochip.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@...rochip.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