linux-kernel - Re: [PATCH v2 -next 0/6] riscv: kexec: add kexec_file

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Date:   Thu, 31 Mar 2022 19:37:33 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     lizhengyu3@...wei.com
CC:     liaochang1@...wei.com, alex@...ti.fr, aou@...s.berkeley.edu,
        Bjorn Topel <bjorn.topel@...il.com>, changbin.du@...el.com,
        ebiederm@...ssion.com, guoren@...ux.alibaba.com,
        jszhang@...nel.org, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        mick@....forth.gr, Paul Walmsley <paul.walmsley@...ive.com>,
        penberg@...nel.org, sunnanyong@...wei.com,
        wangkefeng.wang@...wei.com
Subject:     Re: [PATCH v2 -next 0/6] riscv: kexec: add kexec_file_load() support

On Wed, 30 Mar 2022 01:16:55 PDT (-0700), lizhengyu3@...wei.com wrote:
> This patchset implement kexec_file_load() support on riscv, Most of the
> code is based on the kexec-tool-patch repo developed by Nick Kossifids.
>
> This patch series enables us to load the riscv vmlinux by specifying
> its file decriptor, instead of user-filled buffer via kexec_file_load()
> syscall.
> ``
> Contrary to kexec_load() system call, we reuse the dt blob of the first
> kernel to the 2nd explicitly.
>
> To use kexec_file_load() system call, instead of kexec_load(), at kexec
> command, '-s' options must be specified. The patch for kexec_tools has
> to be apply to riscv architecture source like this:
>
> int elf_riscv_load(int argc, char **argv, const char *buf, off_t len,
> 	...
> 	if (info->file_mode) {
> 		return prepare_kexec_file_options(info);
> 	}
> 	...
>
> Add following routine to prepare cmdline_ptr, cmdline_len and initrd_fd
> for syscall kexec_file_load:
>
> int prepare_kexec_file_options(struct kexec_info *info)
> {
> 	int fd;
> 	ssize_t result;
> 	struct stat stats;
>
> 	if (arch_options.cmdline) {
> 		info->command_line = (char *)arch_options.cmdline;
> 		info->command_line_len = strlen(info->command_line) + 1;
> 	}
>
> 	if (!arch_options.initrd_path) {
> 		info->initrd_fd = -1;
> 		return 0;
> 	}
>
> 	fd = open(arch_options.initrd_path, O_RDONLY | _O_BINARY);
> 	if (fd < 0) {
> 		fprintf(stderr, "Cannot open `%s': %s\n", arch_options.initrd_path,
> 				strerror(errno));
> 		return -EINVAL;
> 	}
> 	result = fstat(fd, &stats);
> 	if (result < 0) {
> 		close(fd);
> 		fprintf(stderr, "Cannot stat: %s: %s\n", arch_options.initrd_path,
> 				strerror(errno));
> 		return -EINVAL;
> 	}
> 	info->initrd_fd = fd;
> 	return 0;
> }
>
> The basic usage of kexec_file is:
> 1) Reload capture kernel image:
> $ kexec -s -l <riscv-vmlinux> --reuse-cmdline
>
> 2) Startup capture kernel:
> $ kexec -e
>
> For kdump:
> 1) Reload capture kernel image:
> $ kexec -s -p <riscv-vmlinux> --reuse-cmdline
>
> 2) Do something to crash, like:
> $ echo c > /proc/sysrq-trigger
>
> v2:
>  * Support kdump
>  * Support purgatory
>  * Minor cleanups
>
> Li Zhengyu (3):
>   RISC-V: Support for kexec_file on panic
>   RISC-V: Add purgatory
>   RISC-V: Load purgatory in kexec_file
>
> Liao Chang (3):
>   kexec_file: Fix kexec_file.c build error for riscv platform
>   RISC-V: use memcpy for kexec_file mode
>   RISC-V: Add kexec_file support
>
>  arch/riscv/Kbuild                      |   2 +
>  arch/riscv/Kconfig                     |  17 +
>  arch/riscv/include/asm/kexec.h         |   4 +
>  arch/riscv/kernel/Makefile             |   1 +
>  arch/riscv/kernel/elf_kexec.c          | 448 +++++++++++++++++++++++++
>  arch/riscv/kernel/machine_kexec.c      |   4 +-
>  arch/riscv/kernel/machine_kexec_file.c |  14 +
>  arch/riscv/purgatory/.gitignore        |   4 +
>  arch/riscv/purgatory/Makefile          |  95 ++++++
>  arch/riscv/purgatory/entry.S           |  47 +++
>  arch/riscv/purgatory/purgatory.c       |  42 +++
>  include/linux/kexec.h                  |   2 +-
>  kernel/kexec_file.c                    |   4 +-
>  13 files changed, 680 insertions(+), 4 deletions(-)
>  create mode 100644 arch/riscv/kernel/elf_kexec.c
>  create mode 100644 arch/riscv/kernel/machine_kexec_file.c
>  create mode 100644 arch/riscv/purgatory/.gitignore
>  create mode 100644 arch/riscv/purgatory/Makefile
>  create mode 100644 arch/riscv/purgatory/entry.S
>  create mode 100644 arch/riscv/purgatory/purgatory.c

This seems like a reasonable way to do things, but I haven't looked over 
the code yet.  Looks like the autobuilders are finding some failures, 
and it's way too late for 5.18.  If you have time to fix the failures 
then it'd be great to have a version based on rc1 with these fixed, so 
we can target the next merge window.  That'll also make it easier to 
look this over on my end.

Thanks!