Hi Pingfan,
On Thu, 29 May 2025 12:17:40 +0800
Pingfan Liu <pi...@redhat.com> wrote:
> As UEFI becomes popular, a few architectures support to boot a PE format
> kernel image directly. But the internal of PE format varies, which means
> each parser for each format.
>
> This patch (with the rest in this series) introduces a common skeleton
> to all parsers, and leave the format parsing in
> bpf-prog, so the kernel code can keep relative stable.
>
> A new kexec_file_ops is implementation, named pe_image_ops.
>
> There are some place holder function in this patch. (They will take
> effect after the introduction of kexec bpf light skeleton and bpf
> helpers). Overall the parsing progress is a pipeline, the current
> bpf-prog parser is attached to bpf_handle_pefile(), and detatched at the
> end of the current stage 'disarm_bpf_prog()' the current parsed result
> by the current bpf-prog will be buffered in kernel 'prepare_nested_pe()'
> , and deliver to the next stage. For each stage, the bpf bytecode is
> extracted from the '.bpf' section in the PE file.
>
> Signed-off-by: Pingfan Liu <pi...@redhat.com>
> Cc: Baoquan He <b...@redhat.com>
> Cc: Dave Young <dyo...@redhat.com>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: Philipp Rudo <pr...@redhat.com>
> To: kexec@lists.infradead.org
> ---
> include/linux/kexec.h | 1 +
> kernel/Kconfig.kexec | 8 +
> kernel/Makefile | 1 +
> kernel/kexec_pe_image.c | 356 ++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 366 insertions(+)
> create mode 100644 kernel/kexec_pe_image.c
>
[...]
> diff --git a/kernel/kexec_pe_image.c b/kernel/kexec_pe_image.c
> new file mode 100644
> index 0000000000000..3097efccb8502
> --- /dev/null
> +++ b/kernel/kexec_pe_image.c
> @@ -0,0 +1,356 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Kexec PE image loader
> +
> + * Copyright (C) 2025 Red Hat, Inc
> + */
> +
> +#define pr_fmt(fmt) "kexec_file(Image): " fmt
> +
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/list.h>
> +#include <linux/kernel.h>
> +#include <linux/vmalloc.h>
> +#include <linux/kexec.h>
> +#include <linux/pe.h>
> +#include <linux/string.h>
> +#include <linux/bpf.h>
> +#include <linux/filter.h>
> +#include <asm/byteorder.h>
> +#include <asm/image.h>
> +#include <asm/memory.h>
> +
> +
> +static LIST_HEAD(phase_head);
> +
> +struct parsed_phase {
> + struct list_head head;
> + struct list_head res_head;
> +};
> +
> +static struct parsed_phase *cur_phase;
> +
> +static char *kexec_res_names[3] = {"kernel", "initrd", "cmdline"};
Wouldn't it be better to use a enum rather than strings for the
different resources? Especially as in prepare_nested_pe you are
comparing two strings using == instead of strcmp(). So IIUC it should
always return false.
> +struct kexec_res {
> + struct list_head node;
> + char *name;
> + /* The free of buffer is deferred to kimage_file_post_load_cleanup */
> + bool deferred_free;
> + struct mem_range_result *r;
> +};
> +
> +static struct parsed_phase *alloc_new_phase(void)
> +{
> + struct parsed_phase *phase = kzalloc(sizeof(struct parsed_phase),
> GFP_KERNEL);
> +
> + INIT_LIST_HEAD(&phase->head);
> + INIT_LIST_HEAD(&phase->res_head);
> + list_add_tail(&phase->head, &phase_head);
> +
> + return phase;
> +}
I must admit I don't fully understand how you are handling the
different phases. In particular I don't understand why you are keeping
all the resources a phase returned once it is finished. The way I see
it those resources are only needed once as input for the next phase. So
it should be sufficient to only keep a single kexec_context and update
it when a phase returns a new resource. The way I see it this should
simplify pe_image_load quite a bit. Or am I missing something?
> +static bool is_valid_pe(const char *kernel_buf, unsigned long kernel_len)
> +{
> + struct mz_hdr *mz;
> + struct pe_hdr *pe;
> +
> + if (!kernel_buf)
> + return false;
> + mz = (struct mz_hdr *)kernel_buf;
> + if (mz->magic != MZ_MAGIC)
> + return false;
> + pe = (struct pe_hdr *)(kernel_buf + mz->peaddr);
> + if (pe->magic != PE_MAGIC)
> + return false;
> + if (pe->opt_hdr_size == 0) {
> + pr_err("optional header is missing\n");
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static bool is_valid_format(const char *kernel_buf, unsigned long kernel_len)
> +{
> + return is_valid_pe(kernel_buf, kernel_len);
> +}
> +
> +/*
> + * The UEFI Terse Executable (TE) image has MZ header.
> + */
> +static int pe_image_probe(const char *kernel_buf, unsigned long kernel_len)
> +{
> + return is_valid_pe(kernel_buf, kernel_len) ? 0 : -1;
Every image, at least on x86, is a valid pe file. So we should check
for the .bpf section rather than the header.
> +}
> +
> +static int get_pe_section(char *file_buf, const char *sect_name,
s/get_pe_section/pe_get_section/ ?
that would make it more consistent with the other functions.
Thanks
Philipp
> + char **sect_start, unsigned long *sect_sz)
> +{
> + struct pe_hdr *pe_hdr;
> + struct pe32plus_opt_hdr *opt_hdr;
> + struct section_header *sect_hdr;
> + int section_nr, i;
> + struct mz_hdr *mz = (struct mz_hdr *)file_buf;
> +
> + *sect_start = NULL;
> + *sect_sz = 0;
> + pe_hdr = (struct pe_hdr *)(file_buf + mz->peaddr);
> + section_nr = pe_hdr->sections;
> + opt_hdr = (struct pe32plus_opt_hdr *)(file_buf + mz->peaddr +
> sizeof(struct pe_hdr));
> + sect_hdr = (struct section_header *)((char *)opt_hdr +
> pe_hdr->opt_hdr_size);
> +
> + for (i = 0; i < section_nr; i++) {
> + if (strcmp(sect_hdr->name, sect_name) == 0) {
> + *sect_start = file_buf + sect_hdr->data_addr;
> + *sect_sz = sect_hdr->raw_data_size;
> + return 0;
> + }
> + sect_hdr++;
> + }
> +
> + return -1;
> +}
> +
> +static bool pe_has_bpf_section(char *file_buf, unsigned long pe_sz)
> +{
> + char *sect_start = NULL;
> + unsigned long sect_sz = 0;
> + int ret;
> +
> + ret = get_pe_section(file_buf, ".bpf", §_start, §_sz);
> + if (ret < 0)
> + return false;
> + return true;
> +}
> +
> +/* Load a ELF */
> +static int arm_bpf_prog(char *bpf_elf, unsigned long sz)
> +{
> + return 0;
> +}
> +
> +static void disarm_bpf_prog(void)
> +{
> +}
> +
> +struct kexec_context {
> + bool kdump;
> + char *image;
> + int image_sz;
> + char *initrd;
> + int initrd_sz;
> + char *cmdline;
> + int cmdline_sz;
> +};
> +
> +void bpf_handle_pefile(struct kexec_context *context);
> +void bpf_post_handle_pefile(struct kexec_context *context);
> +
> +
> +/*
> + * optimize("O0") prevents inline, compiler constant propagation
> + */
> +__attribute__((used, optimize("O0"))) void bpf_handle_pefile(struct
> kexec_context *context)
> +{
> +}
> +
> +__attribute__((used, optimize("O0"))) void bpf_post_handle_pefile(struct
> kexec_context *context)
> +{
> +}
> +
> +/*
> + * PE file may be nested and should be unfold one by one.
> + * Query 'kernel', 'initrd', 'cmdline' in cur_phase, as they are inputs for
> the
> + * next phase.
> + */
> +static int prepare_nested_pe(char **kernel, unsigned long *kernel_len, char
> **initrd,
> + unsigned long *initrd_len, char **cmdline)
> +{
> + struct kexec_res *res;
> + int ret = -1;
> +
> + *kernel = NULL;
> + *kernel_len = 0;
> +
> + list_for_each_entry(res, &cur_phase->res_head, node) {
> + if (res->name == kexec_res_names[0]) {
> + *kernel = res->r->buf;
> + *kernel_len = res->r->data_sz;
> + ret = 0;
> + } else if (res->name == kexec_res_names[1]) {
> + *initrd = res->r->buf;
> + *initrd_len = res->r->data_sz;
> + } else if (res->name == kexec_res_names[2]) {
> + *cmdline = res->r->buf;
> + }
> + }
> +
> + return ret;
> +}
> +
> +static void *pe_image_load(struct kimage *image,
> + char *kernel, unsigned long kernel_len,
> + char *initrd, unsigned long initrd_len,
> + char *cmdline, unsigned long cmdline_len)
> +{
> + char *parsed_kernel = NULL;
> + unsigned long parsed_len;
> + char *linux_start, *initrd_start, *cmdline_start, *bpf_start;
> + unsigned long linux_sz, initrd_sz, cmdline_sz, bpf_sz;
> + struct parsed_phase *phase, *phase_tmp;
> + struct kexec_res *res, *res_tmp;
> + void *ldata;
> + int ret;
> +
> + linux_start = kernel;
> + linux_sz = kernel_len;
> + initrd_start = initrd;
> + initrd_sz = initrd_len;
> + cmdline_start = cmdline;
> + cmdline_sz = cmdline_len;
> +
> + while (is_valid_format(linux_start, linux_sz) &&
> + pe_has_bpf_section(linux_start, linux_sz)) {
> + struct kexec_context context;
> +
> + get_pe_section(linux_start, ".bpf", &bpf_start, &bpf_sz);
> + if (!!bpf_sz) {
> + /* load and attach bpf-prog */
> + ret = arm_bpf_prog(bpf_start, bpf_sz);
> + if (ret) {
> + pr_err("Fail to load .bpf section\n");
> + ldata = ERR_PTR(ret);
> + goto err;
> + }
> + }
> + cur_phase = alloc_new_phase();
> + if (image->type != KEXEC_TYPE_CRASH)
> + context.kdump = false;
> + else
> + context.kdump = true;
> + context.image = linux_start;
> + context.image_sz = linux_sz;
> + context.initrd = initrd_start;
> + context.initrd_sz = initrd_sz;
> + context.cmdline = cmdline_start;
> + context.cmdline_sz = strlen(cmdline_start);
> + /* bpf-prog fentry, which handle above buffers. */
> + bpf_handle_pefile(&context);
> +
> + prepare_nested_pe(&linux_start, &linux_sz, &initrd_start,
> + &initrd_sz, &cmdline_start);
> + /* bpf-prog fentry */
> + bpf_post_handle_pefile(&context);
> + /*
> + * detach the current bpf-prog from their attachment points.
> + * It also a point to free any registered interim resource.
> + * Any resource except attached to phase is interim.
> + */
> + disarm_bpf_prog();
> + }
> +
> + /* the rear of parsed phase contains the result */
> + list_for_each_entry_reverse(phase, &phase_head, head) {
> + if (initrd != NULL && cmdline != NULL && parsed_kernel != NULL)
> + break;
> + list_for_each_entry(res, &phase->res_head, node) {
> + if (!strcmp(res->name, "kernel") && !parsed_kernel) {
> + parsed_kernel = res->r->buf;
> + parsed_len = res->r->data_sz;
> + res->deferred_free = true;
> + } else if (!strcmp(res->name, "initrd") && !initrd) {
> + initrd = res->r->buf;
> + initrd_len = res->r->data_sz;
> + res->deferred_free = true;
> + } else if (!strcmp(res->name, "cmdline") && !cmdline) {
> + cmdline = res->r->buf;
> + cmdline_len = res->r->data_sz;
> + res->deferred_free = true;
> + }
> + }
> +
> + }
> +
> + if (initrd == NULL || cmdline == NULL || parsed_kernel == NULL) {
> + char *c, buf[64];
> +
> + c = buf;
> + if (parsed_kernel == NULL) {
> + strcpy(c, "kernel ");
> + c += strlen("kernel ");
> + }
> + if (initrd == NULL) {
> + strcpy(c, "initrd ");
> + c += strlen("initrd ");
> + }
> + if (cmdline == NULL) {
> + strcpy(c, "cmdline ");
> + c += strlen("cmdline ");
> + }
> + c = '\0';
> + pr_err("Can not extract data for %s", buf);
> + ldata = ERR_PTR(-EINVAL);
> + goto err;
> + }
> + /*
> + * image's kernel_buf, initrd_buf, cmdline_buf are set. Now they should
> + * be updated to the new content.
> + */
> + if (image->kernel_buf != parsed_kernel) {
> + vfree(image->kernel_buf);
> + image->kernel_buf = parsed_kernel;
> + image->kernel_buf_len = parsed_len;
> + }
> + if (image->initrd_buf != initrd) {
> + vfree(image->initrd_buf);
> + image->initrd_buf = initrd;
> + image->initrd_buf_len = initrd_len;
> + }
> + if (image->cmdline_buf != cmdline) {
> + kfree(image->cmdline_buf);
> + image->cmdline_buf = cmdline;
> + image->cmdline_buf_len = cmdline_len;
> + }
> + ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
> + image->kernel_buf_len);
> + if (ret) {
> + pr_err("Fail to find suitable image loader\n");
> + ldata = ERR_PTR(ret);
> + goto err;
> + }
> + ldata = kexec_image_load_default(image);
> + if (IS_ERR(ldata)) {
> + pr_err("architecture code fails to load image\n");
> + goto err;
> + }
> + image->image_loader_data = ldata;
> +
> +err:
> + list_for_each_entry_safe(phase, phase_tmp, &phase_head, head) {
> + list_for_each_entry_safe(res, res_tmp, &phase->res_head, node) {
> + list_del(&res->node);
> + /* defer to kimage_file_post_load_cleanup() */
> + if (res->deferred_free) {
> + res->r->buf = NULL;
> + res->r->buf_sz = 0;
> + }
> + mem_range_result_put(res->r);
> + kfree(res);
> + }
> + list_del(&phase->head);
> + kfree(phase);
> + }
> +
> + return ldata;
> +}
> +
> +const struct kexec_file_ops kexec_pe_image_ops = {
> + .probe = pe_image_probe,
> + .load = pe_image_load,
> +#ifdef CONFIG_KEXEC_IMAGE_VERIFY_SIG
> + .verify_sig = kexec_kernel_verify_pe_sig,
> +#endif
> +};
