[thirdparty/kernel/linux.git] / lib / buildid.c

// SPDX-License-Identifier: GPL-2.0

#include <linux/buildid.h>
#include <linux/elf.h>
#include <linux/pagemap.h>

#define BUILD_ID 3
/*
 * 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 inline int parse_build_id(void *page_addr,
				 unsigned char *build_id,
				 __u32 *size,
				 void *note_start,
				 Elf32_Word note_size)
{
	Elf32_Word note_offs = 0, new_offs;

	/* check for overflow */
	if (note_start < page_addr || note_start + note_size < note_start)
		return -EINVAL;

	/* only supports note that fits in the first page */
	if (note_start + note_size > page_addr + PAGE_SIZE)
		return -EINVAL;

	while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
		Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);

		if (nhdr->n_type == BUILD_ID &&
		    nhdr->n_namesz == sizeof("GNU") &&
		    nhdr->n_descsz > 0 &&
		    nhdr->n_descsz <= BUILD_ID_SIZE_MAX) {
			memcpy(build_id,
			       note_start + note_offs +
			       ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
			       nhdr->n_descsz);
			memset(build_id + nhdr->n_descsz, 0,
			       BUILD_ID_SIZE_MAX - nhdr->n_descsz);
			if (size)
				*size = nhdr->n_descsz;
			return 0;
		}
		new_offs = note_offs + sizeof(Elf32_Nhdr) +
			ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
		if (new_offs <= note_offs)  /* overflow */
			break;
		note_offs = new_offs;
	}
	return -EINVAL;
}

/* Parse build ID from 32-bit ELF */
static int get_build_id_32(void *page_addr, unsigned char *build_id,
			   __u32 *size)
{
	Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
	Elf32_Phdr *phdr;
	int i;

	/* only supports phdr that fits in one page */
	if (ehdr->e_phnum >
	    (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
		return -EINVAL;

	phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));

	for (i = 0; i < ehdr->e_phnum; ++i) {
		if (phdr[i].p_type == PT_NOTE &&
		    !parse_build_id(page_addr, build_id, size,
				    page_addr + phdr[i].p_offset,
				    phdr[i].p_filesz))
			return 0;
	}
	return -EINVAL;
}

/* Parse build ID from 64-bit ELF */
static int get_build_id_64(void *page_addr, unsigned char *build_id,
			   __u32 *size)
{
	Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
	Elf64_Phdr *phdr;
	int i;

	/* only supports phdr that fits in one page */
	if (ehdr->e_phnum >
	    (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
		return -EINVAL;

	phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));

	for (i = 0; i < ehdr->e_phnum; ++i) {
		if (phdr[i].p_type == PT_NOTE &&
		    !parse_build_id(page_addr, build_id, size,
				    page_addr + phdr[i].p_offset,
				    phdr[i].p_filesz))
			return 0;
	}
	return -EINVAL;
}

/*
 * 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
 *
 * Returns 0 on success, otherwise error (< 0).
 */
int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
		   __u32 *size)
{
	Elf32_Ehdr *ehdr;
	struct page *page;
	void *page_addr;
	int ret;

	/* only works for page backed storage  */
	if (!vma->vm_file)
		return -EINVAL;

	page = find_get_page(vma->vm_file->f_mapping, 0);
	if (!page)
		return -EFAULT;	/* page not mapped */

	ret = -EINVAL;
	page_addr = kmap_atomic(page);
	ehdr = (Elf32_Ehdr *)page_addr;

	/* compare magic x7f "ELF" */
	if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
		goto out;

	/* only support executable file and shared object file */
	if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
		goto out;

	if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
		ret = get_build_id_32(page_addr, build_id, size);
	else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
		ret = get_build_id_64(page_addr, build_id, size);
out:
	kunmap_atomic(page_addr);
	put_page(page);
	return ret;
}
Commit	Line	Data
bd7525da JO	1	// SPDX-License-Identifier: GPL-2.0
	2
	3	#include <linux/buildid.h>
	4	#include <linux/elf.h>
	5	#include <linux/pagemap.h>
	6
	7	#define BUILD_ID 3
	8	/*
	9	* Parse build id from the note segment. This logic can be shared between
	10	* 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
	11	* identical.
	12	*/
	13	static inline int parse_build_id(void *page_addr,
	14	unsigned char *build_id,
921f88fc	15	__u32 *size,
bd7525da JO	16	void *note_start,
	17	Elf32_Word note_size)
	18	{
	19	Elf32_Word note_offs = 0, new_offs;
	20
	21	/* check for overflow */
	22	if (note_start < page_addr \|\| note_start + note_size < note_start)
	23	return -EINVAL;
	24
	25	/* only supports note that fits in the first page */
	26	if (note_start + note_size > page_addr + PAGE_SIZE)
	27	return -EINVAL;
	28
	29	while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
	30	Elf32_Nhdr nhdr = (Elf32_Nhdr )(note_start + note_offs);
	31
	32	if (nhdr->n_type == BUILD_ID &&
	33	nhdr->n_namesz == sizeof("GNU") &&
	34	nhdr->n_descsz > 0 &&
	35	nhdr->n_descsz <= BUILD_ID_SIZE_MAX) {
	36	memcpy(build_id,
	37	note_start + note_offs +
	38	ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
	39	nhdr->n_descsz);
	40	memset(build_id + nhdr->n_descsz, 0,
	41	BUILD_ID_SIZE_MAX - nhdr->n_descsz);
921f88fc JO	42	if (size)
921f88fc JO	43	*size = nhdr->n_descsz;
bd7525da JO	44	return 0;
	45	}
	46	new_offs = note_offs + sizeof(Elf32_Nhdr) +
	47	ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
	48	if (new_offs <= note_offs) /* overflow */
	49	break;
	50	note_offs = new_offs;
	51	}
	52	return -EINVAL;
	53	}
	54
	55	/* Parse build ID from 32-bit ELF */
921f88fc JO	56	static int get_build_id_32(void page_addr, unsigned char build_id,
921f88fc JO	57	__u32 *size)
bd7525da JO	58	{
	59	Elf32_Ehdr ehdr = (Elf32_Ehdr )page_addr;
	60	Elf32_Phdr *phdr;
	61	int i;
	62
	63	/* only supports phdr that fits in one page */
	64	if (ehdr->e_phnum >
	65	(PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
	66	return -EINVAL;
	67
	68	phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
	69
	70	for (i = 0; i < ehdr->e_phnum; ++i) {
	71	if (phdr[i].p_type == PT_NOTE &&
921f88fc	72	!parse_build_id(page_addr, build_id, size,
bd7525da JO	73	page_addr + phdr[i].p_offset,
	74	phdr[i].p_filesz))
	75	return 0;
	76	}
	77	return -EINVAL;
	78	}
	79
	80	/* Parse build ID from 64-bit ELF */
921f88fc JO	81	static int get_build_id_64(void page_addr, unsigned char build_id,
921f88fc JO	82	__u32 *size)
bd7525da JO	83	{
	84	Elf64_Ehdr ehdr = (Elf64_Ehdr )page_addr;
	85	Elf64_Phdr *phdr;
	86	int i;
	87
	88	/* only supports phdr that fits in one page */
	89	if (ehdr->e_phnum >
	90	(PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
	91	return -EINVAL;
	92
	93	phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
	94
	95	for (i = 0; i < ehdr->e_phnum; ++i) {
	96	if (phdr[i].p_type == PT_NOTE &&
921f88fc	97	!parse_build_id(page_addr, build_id, size,
bd7525da JO	98	page_addr + phdr[i].p_offset,
	99	phdr[i].p_filesz))
	100	return 0;
	101	}
	102	return -EINVAL;
	103	}
	104
921f88fc JO	105	/*
	106	* Parse build ID of ELF file mapped to vma
	107	* @vma: vma object
	108	* @build_id: buffer to store build id, at least BUILD_ID_SIZE long
	109	* @size: returns actual build id size in case of success
	110	*
	111	* Returns 0 on success, otherwise error (< 0).
	112	*/
	113	int build_id_parse(struct vm_area_struct vma, unsigned char build_id,
	114	__u32 *size)
bd7525da JO	115	{
	116	Elf32_Ehdr *ehdr;
	117	struct page *page;
	118	void *page_addr;
	119	int ret;
	120
	121	/* only works for page backed storage */
	122	if (!vma->vm_file)
	123	return -EINVAL;
	124
	125	page = find_get_page(vma->vm_file->f_mapping, 0);
	126	if (!page)
	127	return -EFAULT; /* page not mapped */
	128
	129	ret = -EINVAL;
	130	page_addr = kmap_atomic(page);
	131	ehdr = (Elf32_Ehdr *)page_addr;
	132
	133	/* compare magic x7f "ELF" */
	134	if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
	135	goto out;
	136
	137	/* only support executable file and shared object file */
	138	if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
	139	goto out;
	140
	141	if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
921f88fc	142	ret = get_build_id_32(page_addr, build_id, size);
bd7525da	143	else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
921f88fc	144	ret = get_build_id_64(page_addr, build_id, size);
bd7525da JO	145	out:
	146	kunmap_atomic(page_addr);
	147	put_page(page);
	148	return ret;
	149	}