Hi, Huacai
On 2025/8/11 22:07, Huacai Chen wrote:
Hi, Youling,

On Mon, Aug 11, 2025 at 5:28 PM Youling Tang <youling.t...@linux.dev> wrote:
From: Youling Tang <tangyoul...@kylinos.cn>

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 <tangyoul...@kylinos.cn>
---
  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/Kconfig b/arch/loongarch/Kconfig
index f0abc38c40ac..fd50c83f7827 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -625,6 +625,14 @@ config CPU_HAS_PREFETCH
  config ARCH_SUPPORTS_KEXEC
         def_bool y

+config ARCH_SUPPORTS_KEXEC_FILE
+       def_bool 64BIT
+
+config ARCH_SELECTS_KEXEC_FILE
+       def_bool y
+       depends on KEXEC_FILE
+       select HAVE_IMA_KEXEC if IMA
+
  config ARCH_SUPPORTS_CRASH_DUMP
         def_bool y

diff --git a/arch/loongarch/include/asm/image.h 
b/arch/loongarch/include/asm/image.h
index 1f090736e71d..829e1ecb1f5d 100644
--- a/arch/loongarch/include/asm/image.h
+++ b/arch/loongarch/include/asm/image.h
@@ -36,5 +36,23 @@ struct loongarch_image_header {
         uint32_t pe_header;
  };

+static const uint8_t loongarch_image_pe_sig[2] = {'M', 'Z'};
+static const uint8_t loongarch_pe_machtype[6] = {'P', 'E', 0x0, 0x0, 0x64, 
0x62};
+
+/**
+ * loongarch_header_check_pe_sig - Helper to check the loongarch image header.
+ *
+ * Returns non-zero if 'MZ' signature is found.
+ */
+
+static inline int loongarch_header_check_pe_sig(const struct 
loongarch_image_header *h)
+{
+       if (!h)
+               return 0;
+
+       return (h->pe_sig[0] == loongarch_image_pe_sig[0]
+               && h->pe_sig[1] == loongarch_image_pe_sig[1]);
+}
+
  #endif /* __ASSEMBLY__ */
  #endif /* __ASM_IMAGE_H */
diff --git a/arch/loongarch/include/asm/kexec.h 
b/arch/loongarch/include/asm/kexec.h
index cf95cd3eb2de..3ef8517a3670 100644
--- a/arch/loongarch/include/asm/kexec.h
+++ b/arch/loongarch/include/asm/kexec.h
@@ -41,6 +41,18 @@ struct kimage_arch {
         unsigned long systable_ptr;
  };

+#ifdef CONFIG_KEXEC_FILE
+extern const struct kexec_file_ops kexec_image_ops;
+
+int arch_kimage_file_post_load_cleanup(struct kimage *image);
+#define arch_kimage_file_post_load_cleanup arch_kimage_file_post_load_cleanup
+
+extern int load_other_segments(struct kimage *image,
+               unsigned long kernel_load_addr, unsigned long kernel_size,
+               char *initrd, unsigned long initrd_len,
+               char *cmdline, unsigned long cmdline_len);
I think the RISC-V naming "load_extra_segments" is better.
This name is also fine, but I prefer it to be consistent with
that in kexec-tools.

+#endif
+
  typedef void (*do_kexec_t)(unsigned long efi_boot,
                            unsigned long cmdline_ptr,
                            unsigned long systable_ptr,
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 6f5a4574a911..bd9405ee3888 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -62,6 +62,7 @@ obj-$(CONFIG_MAGIC_SYSRQ)     += sysrq.o
  obj-$(CONFIG_RELOCATABLE)      += relocate.o

  obj-$(CONFIG_KEXEC_CORE)       += machine_kexec.o relocate_kernel.o
+obj-$(CONFIG_KEXEC_FILE)       += machine_kexec_file.o kexec_image.o
We only support the efi format, so we don't need to split a
kexec_image.c like RISC-V, just put everything into
machine_kexec_file.c is OK.
I hope it is separated and consistent with other architectures.
For instance, arm64 only supports one type.

Youling.

Huacai

  obj-$(CONFIG_CRASH_DUMP)       += crash_dump.o

  obj-$(CONFIG_UNWINDER_GUESS)   += unwind_guess.o
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
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Kexec image loader for LoongArch
+
+ * Author: Youling Tang <tangyoul...@kylinos.cn>
+ * Copyright (C) 2025 KylinSoft Corporation.
+ */
+
+#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/cpufeature.h>
+#include <asm/image.h>
+
+static int image_probe(const char *kernel_buf, unsigned long kernel_len)
+{
+       const struct loongarch_image_header *h =
+               (const struct loongarch_image_header *)(kernel_buf);
+
+       if (!h || (kernel_len < sizeof(*h))) {
+               pr_err("No loongarch image header.\n");
+               return -EINVAL;
+       }
+
+       if (!loongarch_header_check_pe_sig(h)) {
+               pr_err("Bad loongarch PE image header.\n");
+               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 loongarch_image_header *h;
+       struct kexec_buf kbuf;
+       unsigned long text_offset, kernel_segment_number;
+       struct kexec_segment *kernel_segment;
+       int ret;
+
+       h = (struct loongarch_image_header *)kernel;
+       if (!h->image_size)
+               return ERR_PTR(-EINVAL);
+
+       /* Load the kernel */
+       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);
+       text_offset = le64_to_cpu(h->text_offset);
+       kbuf.buf_align = SZ_2M;
+
+       kernel_segment_number = image->nr_segments;
+
+       /*
+        * 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;
+
+       kexec_dprintk("Loaded kernel at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+                     kernel_segment->mem, kbuf.bufsz,
+                     kernel_segment->memsz);
+
+       return NULL;
+}
+
+const struct kexec_file_ops kexec_image_ops = {
+       .probe = image_probe,
+       .load = image_load,
+};
diff --git a/arch/loongarch/kernel/machine_kexec.c 
b/arch/loongarch/kernel/machine_kexec.c
index f9381800e291..008f43e26120 100644
--- a/arch/loongarch/kernel/machine_kexec.c
+++ b/arch/loongarch/kernel/machine_kexec.c
@@ -70,18 +70,28 @@ int machine_kexec_prepare(struct kimage *kimage)
         kimage->arch.efi_boot = fw_arg0;
         kimage->arch.systable_ptr = fw_arg2;

-       /* Find the command line */
-       for (i = 0; i < kimage->nr_segments; i++) {
-               if (!strncmp(bootloader, (char __user *)kimage->segment[i].buf, 
strlen(bootloader))) {
-                       if (!copy_from_user(cmdline_ptr, 
kimage->segment[i].buf, COMMAND_LINE_SIZE))
-                               kimage->arch.cmdline_ptr = (unsigned 
long)cmdline_ptr;
-                       break;
+       if (kimage->file_mode == 1) {
+               /*
+                * kimage->cmdline_buf will be released in kexec_file_load, so 
copy to
+                * the KEXEC_CMDLINE_ADDR safe area.
+                */
+               memcpy((void *)KEXEC_CMDLINE_ADDR, (void 
*)kimage->arch.cmdline_ptr,
+                                       strlen((char 
*)kimage->arch.cmdline_ptr) + 1);
+               kimage->arch.cmdline_ptr = (unsigned long)KEXEC_CMDLINE_ADDR;
+       } else {
+               /* Find the command line */
+               for (i = 0; i < kimage->nr_segments; i++) {
+                       if (!strncmp(bootloader, (char __user 
*)kimage->segment[i].buf, strlen(bootloader))) {
+                               if (!copy_from_user(cmdline_ptr, 
kimage->segment[i].buf, COMMAND_LINE_SIZE))
+                                       kimage->arch.cmdline_ptr = (unsigned 
long)cmdline_ptr;
+                               break;
+                       }
                 }
-       }

-       if (!kimage->arch.cmdline_ptr) {
-               pr_err("Command line not included in the provided image\n");
-               return -EINVAL;
+               if (!kimage->arch.cmdline_ptr) {
+                       pr_err("Command line not included in the provided 
image\n");
+                       return -EINVAL;
+               }
         }

         /* kexec/kdump need a safe page to save reboot_code_buffer */
@@ -288,7 +298,8 @@ void machine_kexec(struct kimage *image)
         local_irq_disable();

         pr_notice("EFI boot flag 0x%lx\n", efi_boot);
-       pr_notice("Command line at 0x%lx\n", cmdline_ptr);
+       pr_notice("Command line addr at 0x%lx\n", cmdline_ptr);
+       pr_notice("Command line at %s\n", (char *)cmdline_ptr);
         pr_notice("System table at 0x%lx\n", systable_ptr);
         pr_notice("We will call new kernel at 0x%lx\n", start_addr);
         pr_notice("Bye ...\n");
diff --git a/arch/loongarch/kernel/machine_kexec_file.c 
b/arch/loongarch/kernel/machine_kexec_file.c
new file mode 100644
index 000000000000..bc91ae0afa4c
--- /dev/null
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * kexec_file for LoongArch
+ *
+ * Author: Youling Tang <tangyoul...@kylinos.cn>
+ * Copyright (C) 2025 KylinSoft Corporation.
+ *
+ * Most code is derived from LoongArch port of kexec-tools
+ */
+
+#define pr_fmt(fmt) "kexec_file: " fmt
+
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
+#include <linux/memblock.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+#include <asm/bootinfo.h>
+
+const struct kexec_file_ops * const kexec_file_loaders[] = {
+       &kexec_image_ops,
+       NULL
+};
+
+int arch_kimage_file_post_load_cleanup(struct kimage *image)
+{
+       vfree(image->elf_headers);
+       image->elf_headers = NULL;
+       image->elf_headers_sz = 0;
+
+       return kexec_image_post_load_cleanup_default(image);
+}
+
+int load_other_segments(struct kimage *image,
+                       unsigned long kernel_load_addr,
+                       unsigned long kernel_size,
+                       char *initrd, unsigned long initrd_len,
+                       char *cmdline, unsigned long cmdline_len)
+{
+       image->arch.cmdline_ptr = (unsigned long)cmdline;
+
+       return 0;
+}
--
2.34.1


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