linux/lib/buildid.c

// SPDX-License-Identifier: GPL-2.0

#include <linux/buildid.h>
#include <linux/cache.h>
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/pagemap.h>
#include <linux/secretmem.h>

#define BUILD_ID …

#define MAX_PHDR_CNT …

struct freader { … };

static void freader_init_from_file(struct freader *r, void *buf, u32 buf_sz,
				   struct file *file, bool may_fault)
{ … }

static void freader_init_from_mem(struct freader *r, const char *data, u64 data_sz)
{ … }

static void freader_put_folio(struct freader *r)
{ … }

static int freader_get_folio(struct freader *r, loff_t file_off)
{ … }

static const void *freader_fetch(struct freader *r, loff_t file_off, size_t sz)
{ … }

static void freader_cleanup(struct freader *r)
{ … }

/*
 * Parse build id from the note segment. This logic can be shared between
 * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
 * identical.
 */
static int parse_build_id(struct freader *r, unsigned char *build_id, __u32 *size,
			  loff_t note_off, Elf32_Word note_size)
{ … }

/* Parse build ID from 32-bit ELF */
static int get_build_id_32(struct freader *r, unsigned char *build_id, __u32 *size)
{ … }

/* Parse build ID from 64-bit ELF */
static int get_build_id_64(struct freader *r, unsigned char *build_id, __u32 *size)
{ … }

/* enough for Elf64_Ehdr, Elf64_Phdr, and all the smaller requests */
#define MAX_FREADER_BUF_SZ …

static int __build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
			    __u32 *size, bool may_fault)
{ … }

/*
 * Parse build ID of ELF file mapped to vma
 * @vma:      vma object
 * @build_id: buffer to store build id, at least BUILD_ID_SIZE long
 * @size:     returns actual build id size in case of success
 *
 * Assumes no page fault can be taken, so if relevant portions of ELF file are
 * not already paged in, fetching of build ID fails.
 *
 * Return: 0 on success; negative error, otherwise
 */
int build_id_parse_nofault(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size)
{ … }

/*
 * Parse build ID of ELF file mapped to VMA
 * @vma:      vma object
 * @build_id: buffer to store build id, at least BUILD_ID_SIZE long
 * @size:     returns actual build id size in case of success
 *
 * Assumes faultable context and can cause page faults to bring in file data
 * into page cache.
 *
 * Return: 0 on success; negative error, otherwise
 */
int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size)
{ … }

/**
 * build_id_parse_buf - Get build ID from a buffer
 * @buf:      ELF note section(s) to parse
 * @buf_size: Size of @buf in bytes
 * @build_id: Build ID parsed from @buf, at least BUILD_ID_SIZE_MAX long
 *
 * Return: 0 on success, -EINVAL otherwise
 */
int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size)
{ … }

#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID) || IS_ENABLED(CONFIG_VMCORE_INFO)
unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX] __ro_after_init;

/**
 * init_vmlinux_build_id - Compute and stash the running kernel's build ID
 */
void __init init_vmlinux_build_id(void)
{ … }
#endif