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charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <27513334-3086-4353-bf6c-fdee082a8ce8@linux.dev> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250813_042445_667944_83A9898C X-CRM114-Status: GOOD ( 54.85 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On Wed, Aug 13, 2025 at 10:18:12AM +0800, Youling Tang wrote: > Hi, Yao > On 2025/8/12 17:43, Yao Zi wrote: > > On Tue, Aug 12, 2025 at 03:06:23PM +0800, Youling Tang wrote: > > > On 2025/8/12 14:15, Youling Tang wrote: > > > > Hi, Yao > > > > On 2025/8/12 01:06, Yao Zi wrote: > > > > > On Mon, Aug 11, 2025 at 05:26:55PM +0800, Youling Tang wrote: > > > > > > From: Youling Tang > > > > > > > > > > > > This patch adds support for kexec_file on LoongArch. > > > > > > > > > > > > The image_load() as two parts: > > > > > > - the first part loads the kernel image (vmlinuz.efi or vmlinux.efi) > > > > > > - the second part loads other segments (eg: initrd, cmdline) > > > > > > > > > > > > Currently, pez(vmlinuz.efi) and pei(vmlinux.efi) format images > > > > > > are supported, > > > > > > but ELF format is not supported. > > > > > > > > > > > > Signed-off-by: Youling Tang > > > > > > --- > > > > > >   arch/loongarch/Kconfig                     |   8 ++ > > > > > >   arch/loongarch/include/asm/image.h         |  18 ++++ > > > > > >   arch/loongarch/include/asm/kexec.h         |  12 +++ > > > > > >   arch/loongarch/kernel/Makefile             |   1 + > > > > > >   arch/loongarch/kernel/kexec_image.c        | 112 > > > > > > +++++++++++++++++++++ > > > > > >   arch/loongarch/kernel/machine_kexec.c      |  33 ++++-- > > > > > >   arch/loongarch/kernel/machine_kexec_file.c |  46 +++++++++ > > > > > >   7 files changed, 219 insertions(+), 11 deletions(-) > > > > > >   create mode 100644 arch/loongarch/kernel/kexec_image.c > > > > > >   create mode 100644 arch/loongarch/kernel/machine_kexec_file.c > > ... > > > > > > > > diff --git a/arch/loongarch/kernel/kexec_image.c > > > > > > b/arch/loongarch/kernel/kexec_image.c > > > > > > new file mode 100644 > > > > > > index 000000000000..fdd1845b4e2e > > > > > > --- /dev/null > > > > > > +++ b/arch/loongarch/kernel/kexec_image.c > > ... > > > > > > > > +    /* > > > > > > +     * The location of the kernel segment may make it > > > > > > impossible to satisfy > > > > > > +     * the other segment requirements, so we try repeatedly to find a > > > > > > +     * location that will work. > > > > > > +     */ > > > > > > +    while ((ret = kexec_add_buffer(&kbuf)) == 0) { > > > > > > +        /* Try to load additional data */ > > > > > > +        kernel_segment = &image->segment[kernel_segment_number]; > > > > > > +        ret = load_other_segments(image, kernel_segment->mem, > > > > > > +                      kernel_segment->memsz, initrd, > > > > > > +                      initrd_len, cmdline, cmdline_len); > > > > > > +        if (!ret) > > > > > > +            break; > > > > > > + > > > > > > +        /* > > > > > > +         * We couldn't find space for the other segments; erase the > > > > > > +         * kernel segment and try the next available hole. > > > > > > +         */ > > > > > > +        image->nr_segments -= 1; > > > > > > +        kbuf.buf_min = kernel_segment->mem + kernel_segment->memsz; > > > > > > +        kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; > > > > > > +    } > > > > > > + > > > > > > +    if (ret) { > > > > > > +        pr_err("Could not find any suitable kernel location!"); > > > > > > +        return ERR_PTR(ret); > > > > > > +    } > > > > > > + > > > > > > +    kernel_segment = &image->segment[kernel_segment_number]; > > > > > > + > > > > > > +    /* Make sure the second kernel jumps to the correct > > > > > > "kernel_entry". */ > > > > > > +    image->start = kernel_segment->mem + h->kernel_entry - > > > > > > text_offset; > > > > > A non-relocatable loongarch kernel cannot be loaded to arbitrary > > > > > address. Thus this loading function seems to only work for relocatable > > > > > kernels, maybe it's better to leave a comment indicating the limitation. > > > > > > > > > > For now, we don't seem to have a way to find out whether the kernel is > > > > > relocatable (for example, a flag in kernel image header), so it's > > > > > impossible to point out whether the loaded kernel boots fine with > > > > > arbitrary loading address... > > > > LoongArch enables the relocation of the kernel when the kdump > > > > feature is enabled. > > > > > > > > config ARCH_SELECTS_CRASH_DUMP > > > >         def_bool y > > > >         depends on CRASH_DUMP > > > >         select RELOCATABLE > > > > > > This only means the currently-running kernel is relocatable, not the one > > being exec'ed, right? > No. > > > When enabling KEXEC_FILE, the RELOCATABLE configuration should > > > also be enabled. Both kexec and kdump require this. > > I'm not sure whether you're talking about the running kernel or the one > > that is going to be exec'ed. This method of kernel loading requires the > > exec'ed kernel being relocatable, not the currently running one. > > > > And I think it's totally reasonable to use KEXEC_FILE for non-crash-dump > > purpose, for example, linuxboot. It'll be confusing to the user if the > > system just hangs after booting a non-relocatable kernel, which is hard > > to debug. > > > > Thus IMHO we should ideally refuse to load non-relocatable kernels, or > > add a FIXME comment to indicate the situation that it's impossible to > > determine whether the exec'ed image is relocatable. > The first kernel and the second kernel are generally the same kernel > (the same image). This isn't true. There're real-world cases using kexec-file to load and boot an unrelated kernel image. Please refer to petitboot[1] and linuxboot[2] which uses kexec to act as a bootloader. > When KEXEC_FILE is enabled and RELOCATEABLE > is enabled by default, it has been forcibly guaranteed that both the > first kernel and the second kernel are relocatable kernels regardless > of kexec/kdump operations. This cannot be guaranteed since the first and second kernel could be completely unrelated. Please see my previous comment. > Unless the second kernel it loads is an older version of the kernel (the > older version of the kernel does not use the default configuration, with > CONFIG_KEXEC enabled but CONFIG_CRASH_DUMP disabled, > this is not acorrect usage). This may be incorrect for kdump's use case, but kexec-file isn't only meant to be used with kdump: it just loads an arbitrary kernel image and executes it, no matter whether it's for capturing a dump, booting a newer or older kernel, or etc, and there's no guarantee about features enabled in the second kernel. It's incorrect to assume the user only loads relocatable images with kexec-file. > Thanks, > Youling. > > > Youling. > > > > After enabling the relocation, LoongArch is the PIE kernel. For > > > > more details, please refer to commit d8da19fbdedd ("LoongArch: > > > > Add support for kernel relocation") > > Best regards. > > Yao Zi > Thanks, Yao Zi [1]: https://github.com/open-power/petitboot [2]: https://github.com/linuxboot/linuxboot