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From:   Emil Renner Berthing <emil.renner.berthing@canonical.com>
In-Reply-To: <20230914020044.1397356-3-songshuaishuai@tinylab.org>
References: <20230914020044.1397356-1-songshuaishuai@tinylab.org> <20230914020044.1397356-3-songshuaishuai@tinylab.org>
Mime-Version: 1.0
Date:   Thu, 14 Sep 2023 01:37:23 -0700
Message-ID: <CAJM55Z8D3yJREg0+UtecW3wpgrGKxZYP73Pvbi2oaQfsZf4Gfw@mail.gmail.com>
Subject: Re: [PATCH 2/2] riscv: kexec_file: Support loading Image binary file
To:     Song Shuai <songshuaishuai@tinylab.org>, paul.walmsley@sifive.com,
        palmer@dabbelt.com, aou@eecs.berkeley.edu, lihuafei1@huawei.com,
        conor.dooley@microchip.com, liaochang1@huawei.com,
        guoren@kernel.org, ajones@ventanamicro.com, alexghiti@rivosinc.com,
        evan@rivosinc.com, sunilvl@ventanamicro.com,
        xianting.tian@linux.alibaba.com, samitolvanen@google.com,
        masahiroy@kernel.org, apatel@ventanamicro.com, jszhang@kernel.org,
        duwe@suse.de, eric.devolder@oracle.com
Cc:     linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Song Shuai wrote:
> This patch creates image_kexec_ops to load Image binary file
> for kexec_file_load() syscall.
>
> Signed-off-by: Song Shuai <songshuaishuai@tinylab.org>
> ---
>  arch/riscv/include/asm/image.h         |  2 +
>  arch/riscv/include/asm/kexec.h         |  1 +
>  arch/riscv/kernel/Makefile             |  2 +-
>  arch/riscv/kernel/kexec_image.c        | 97 ++++++++++++++++++++++++++
>  arch/riscv/kernel/machine_kexec_file.c |  1 +
>  5 files changed, 102 insertions(+), 1 deletion(-)
>  create mode 100644 arch/riscv/kernel/kexec_image.c
>
> diff --git a/arch/riscv/include/asm/image.h b/arch/riscv/include/asm/image.h
> index e0b319af3681..8927a6ea1127 100644
> --- a/arch/riscv/include/asm/image.h
> +++ b/arch/riscv/include/asm/image.h
> @@ -30,6 +30,8 @@
>  			      RISCV_HEADER_VERSION_MINOR)
>
>  #ifndef __ASSEMBLY__
> +#define riscv_image_flag_field(flags, field)\
> +			       (((flags) >> field##_SHIFT) & field##_MASK)

Hi Song,

This macro is almost FIELD_GET from linux/bitfield.h ..

>  /**
>   * struct riscv_image_header - riscv kernel image header
>   * @code0:		Executable code
> diff --git a/arch/riscv/include/asm/kexec.h b/arch/riscv/include/asm/kexec.h
> index 518825fe4160..b9ee8346cc8c 100644
> --- a/arch/riscv/include/asm/kexec.h
> +++ b/arch/riscv/include/asm/kexec.h
> @@ -56,6 +56,7 @@ extern riscv_kexec_method riscv_kexec_norelocate;
>
>  #ifdef CONFIG_KEXEC_FILE
>  extern const struct kexec_file_ops elf_kexec_ops;
> +extern const struct kexec_file_ops image_kexec_ops;
>
>  struct purgatory_info;
>  int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index 1c62c639e875..9ecba3231a36 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -86,7 +86,7 @@ endif
>  obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
>  obj-$(CONFIG_KGDB)		+= kgdb.o
>  obj-$(CONFIG_KEXEC_CORE)	+= kexec_relocate.o crash_save_regs.o machine_kexec.o
> -obj-$(CONFIG_KEXEC_FILE)	+= kexec_elf.o machine_kexec_file.o
> +obj-$(CONFIG_KEXEC_FILE)	+= kexec_elf.o kexec_image.o machine_kexec_file.o
>  obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
>  obj-$(CONFIG_CRASH_CORE)	+= crash_core.o
>
> diff --git a/arch/riscv/kernel/kexec_image.c b/arch/riscv/kernel/kexec_image.c
> new file mode 100644
> index 000000000000..b6aa7f59bd53
> --- /dev/null
> +++ b/arch/riscv/kernel/kexec_image.c
> @@ -0,0 +1,97 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * RISC-V Kexec image loader
> + *
> + */
> +
> +#define pr_fmt(fmt)	"kexec_file(Image): " fmt
> +
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/kernel.h>
> +#include <linux/kexec.h>
> +#include <linux/pe.h>
> +#include <linux/string.h>
> +#include <asm/byteorder.h>
> +#include <asm/image.h>
> +
> +static int image_probe(const char *kernel_buf, unsigned long kernel_len)
> +{
> +	const struct riscv_image_header *h =
> +		(const struct riscv_image_header *)(kernel_buf);
> +
> +	if (!h || (kernel_len < sizeof(*h)))
> +		return -EINVAL;
> +
> +	/* According to Documentation/riscv/boot-image-header.rst,
> +	 * use "magic2" field to check when version >= 0.2.
> +	 */
> +
> +	if (h->version >= RISCV_HEADER_VERSION &&
> +	    memcmp(&h->magic2, RISCV_IMAGE_MAGIC2, sizeof(h->magic2)))
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static void *image_load(struct kimage *image,
> +				char *kernel, unsigned long kernel_len,
> +				char *initrd, unsigned long initrd_len,
> +				char *cmdline, unsigned long cmdline_len)
> +{
> +	struct riscv_image_header *h;
> +	u64 flags;
> +	bool be_image, be_kernel;
> +	struct kexec_buf kbuf;
> +	int ret;
> +
> +	/* Check Image header */
> +	h = (struct riscv_image_header *)kernel;
> +	if (!h->image_size) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	/* Check endianness */
> +	flags = le64_to_cpu(h->flags);
> +	be_image = riscv_image_flag_field(flags, RISCV_IMAGE_FLAG_BE);

..but here you're just testing a single bit, so since be_image is a bool it
could just be
	be_image = flags & RISCV_IMAGE_FLAG_BE_MASK;

/Emil

> +	be_kernel = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN);
> +	if (be_image != be_kernel) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	/* Load the kernel image */
> +	kbuf.image = image;
> +	kbuf.buf_min = 0;
> +	kbuf.buf_max = ULONG_MAX;
> +	kbuf.top_down = false;
> +
> +	kbuf.buffer = kernel;
> +	kbuf.bufsz = kernel_len;
> +	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
> +	kbuf.memsz = le64_to_cpu(h->image_size);
> +	kbuf.buf_align = le64_to_cpu(h->text_offset);
> +
> +	ret = kexec_add_buffer(&kbuf);
> +	if (ret) {
> +		pr_err("Error add kernel image ret=%d\n", ret);
> +		goto out;
> +	}
> +
> +	image->start = kbuf.mem;
> +
> +	pr_info("Loaded kernel at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
> +				kbuf.mem, kbuf.bufsz, kbuf.memsz);
> +
> +	ret = load_extra_segments(image, kbuf.mem, kbuf.memsz,
> +				  initrd, initrd_len, cmdline, cmdline_len);
> +
> +out:
> +	return ret ? ERR_PTR(ret) : NULL;
> +}
> +
> +const struct kexec_file_ops image_kexec_ops = {
> +	.probe = image_probe,
> +	.load = image_load,
> +};
> diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
> index aedb8c16a283..5dc700834f1e 100644
> --- a/arch/riscv/kernel/machine_kexec_file.c
> +++ b/arch/riscv/kernel/machine_kexec_file.c
> @@ -17,6 +17,7 @@
>
>  const struct kexec_file_ops * const kexec_file_loaders[] = {
>  	&elf_kexec_ops,
> +	&image_kexec_ops,
>  	NULL
>  };
>
> --
> 2.20.1
>
>
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