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Date:   Mon, 16 Oct 2023 13:19:42 +0800
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Subject: Re: [PATCH 2/2] riscv: kexec_file: Support loading Image binary file
To:     Emil Renner Berthing <emil.renner.berthing@canonical.com>,
        paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, lihuafei1@huawei.com,
        conor.dooley@microchip.com, liaochang1@huawei.com,
        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
References: <20230914020044.1397356-1-songshuaishuai@tinylab.org>
 <20230914020044.1397356-3-songshuaishuai@tinylab.org>
 <CAJM55Z8D3yJREg0+UtecW3wpgrGKxZYP73Pvbi2oaQfsZf4Gfw@mail.gmail.com>
 <22EFF2C197DC5C5A+f82966f5-90cf-09a5-214e-4b0e87bc6064@tinylab.org>
 <CAJM55Z8OebLJHg3mxk7y7Dw0z=JLgi4j17tQPf4-Mdd0BCQbaw@mail.gmail.com>
From:   Song Shuai <songshuaishuai@tinylab.org>
In-Reply-To: <CAJM55Z8OebLJHg3mxk7y7Dw0z=JLgi4j17tQPf4-Mdd0BCQbaw@mail.gmail.com>
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在 2023/10/11 18:48, Emil Renner Berthing 写道:
> Song Shuai wrote:
>>
>>
>> 在 2023/9/14 16:37, Emil Renner Berthing 写道:
>>> 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
>> Hi Emil,
>>
>> Sorry for the delayed response,
>>
>> The `flags` field currently only has bit-0 to indicate the kenrel
>> endianness, your comment looks good in this case.
>>
>> While considering the future extension of the `flags` feild, the
>> riscv_image_flag_field() is neccessiry to make callers to require the
>> bits they want.
> 
> Right, but please don't invent your own FIELD_GET then.

Hi Emil,

I tried to use FIELD_PREP/FIELD_GET to set/get the RISCV_IMAGE_FLAG_BE,
but using FIELD_PREP to define the __HEAD_FLAGS (used in head.S) emitted 
AS build error and the final .s file looked like:

  883  .dword _end - _start
  884  .dword (({ ({ do { } while (0); do { } while (0); do { } while 
(0); do { } while (0); do { } while (0); }); ((typeof((((1)) << 
(0))))(0) << (__builtin_ffsll((((1)) << (0))) - 1)) & ((((1)) << (0))); }))

IIUC the FIELD_PREP can't work well in this asm context, and using 
FILED_GET without FIELD_PREP paired looks not good to me.

The original riscv/*/image.h and the riscv_image_flag_filed() of this 
patch just do what arm64 does, so I still like to keep them.

I also found that Patch1 has a build issue due to my previous uncareful 
cherry-picking,
V2 will be sent to fix it if you're ok this patch without bitfield armed.

I would like to listen to your advice.

> 
>>
>> So I prefer to keep this snippet.
>>>
>>>> +	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
>>>>
>>>>
>>>> _______________________________________________
>>>> linux-riscv mailing list
>>>> linux-riscv@lists.infradead.org
>>>> http://lists.infradead.org/mailman/listinfo/linux-riscv
>>>
>>
>> --
>> Thanks
>> Song Shuai
>>
>>
>> _______________________________________________
>> linux-riscv mailing list
>> linux-riscv@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-riscv
> 

-- 
Thanks
Song Shuai