On Thu, Feb 26, 2026 at 9:37 PM Philipp Rudo <[email protected]> wrote: > > Hi Pingfan, > > On Mon, 19 Jan 2026 11:24:15 +0800 > Pingfan Liu <[email protected]> wrote: > > [...] > > > diff --git a/kernel/kexec_bpf_loader.c b/kernel/kexec_bpf_loader.c > > new file mode 100644 > > index 0000000000000..dc59e1389da94 > > --- /dev/null > > +++ b/kernel/kexec_bpf_loader.c > > @@ -0,0 +1,161 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * Kexec image bpf section helpers > > + * > > + * Copyright (C) 2025, 2026 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/elf.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> > > +#include "kexec_internal.h" > > + > > +/* 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 *kernel; > > + int kernel_sz; > > + char *initrd; > > + int initrd_sz; > > + char *cmdline; > > + int cmdline_sz; > > +}; > > + > > +void kexec_image_parser_anchor(struct kexec_context *context, > > + unsigned long parser_id); > > + > > +/* > > + * optimize("O0") prevents inline, compiler constant propagation > > + * > > + * Let bpf be the program context pointer so that it will not be spilled > > into > > + * stack. > > + */ > > +__attribute__((used, optimize("O0"))) void kexec_image_parser_anchor( > > + struct kexec_context *context, > > + unsigned long parser_id) > > +{ > > + /* > > + * To prevent linker from Identical Code Folding (ICF) with > > kexec_image_parser_anchor, > > + * making them have different code. > > + */ > > + volatile int dummy = 0; > > + > > + dummy += 1; > > +} > > + > > + > > +BTF_KFUNCS_START(kexec_modify_return_ids) > > +BTF_ID_FLAGS(func, kexec_image_parser_anchor, KF_SLEEPABLE) > > +BTF_KFUNCS_END(kexec_modify_return_ids) > > + > > +static const struct btf_kfunc_id_set kexec_modify_return_set = { > > + .owner = THIS_MODULE, > > + .set = &kexec_modify_return_ids, > > +}; > > + > > +static int __init kexec_bpf_prog_run_init(void) > > +{ > > + return register_btf_fmodret_id_set(&kexec_modify_return_set); > > +} > > +late_initcall(kexec_bpf_prog_run_init); > > + > > +static int kexec_buff_parser(struct bpf_parser_context *parser) > > +{ > > + return 0; > > +} > > + > > +/* At present, only PE format file with .bpf section is supported */ > > +#define file_has_bpf_section pe_has_bpf_section > > +#define file_get_section pe_get_section > > + > > +int decompose_kexec_image(struct kimage *image, int extended_fd) > > +{ > > + struct kexec_context context = { 0 }; > > + struct bpf_parser_context *bpf; > > + unsigned long kernel_sz, bpf_sz; > > + char *kernel_start, *bpf_start; > > + int ret = 0; > > + > > + if (image->type != KEXEC_TYPE_CRASH) > > + context.kdump = false; > > + else > > + context.kdump = true; > > + > > + kernel_start = image->kernel_buf; > > + kernel_sz = image->kernel_buf_len; > > + > > + while (file_has_bpf_section(kernel_start, kernel_sz)) { > > + > > + bpf = alloc_bpf_parser_context(kexec_buff_parser, &context); > > + if (!bpf) > > + return -ENOMEM; > > + file_get_section((const char *)kernel_start, ".bpf", > > &bpf_start, &bpf_sz); > > + if (!!bpf_sz) { > > + /* load and attach bpf-prog */ > > + ret = arm_bpf_prog(bpf_start, bpf_sz); > > + if (ret) { > > + put_bpf_parser_context(bpf); > > + pr_err("Fail to load .bpf section\n"); > > + goto err; > > + } > > + } > > I'm not sure this works as intended. In case a .bpf section exists but > bpf_sz is 0, the function will skip arming the bpf-prog but still > continue. That doesn't look right to me. IIUC a zero size bpf-prog > should be an error. Or am I missing something? >
Yes, you are right. It's better to treat a zero bpf_sz as an invalid format. Thanks, Pingfan
