Commit bd7525da authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov
Browse files

bpf: Move stack_map_get_build_id into lib 



Moving stack_map_get_build_id into lib with
declaration in linux/buildid.h header:

  int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id);

This function returns build id for given struct vm_area_struct.
There is no functional change to stack_map_get_build_id function.

Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210114134044.1418404-2-jolsa@kernel.org
parent 7064a734

include/linux/buildid.h

0 → 100644
+11 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _LINUX_BUILDID_H

#define _LINUX_BUILDID_H



#include <linux/mm_types.h>



#define BUILD_ID_SIZE_MAX 20



int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id);



#endif

kernel/bpf/stackmap.c

+4 −139
Original line number Diff line number Diff line
@@ -7,10 +7,9 @@ 
#include <linux/kernel.h>

#include <linux/stacktrace.h>

#include <linux/perf_event.h>

#include <linux/elf.h>

#include <linux/pagemap.h>

#include <linux/irq_work.h>

#include <linux/btf_ids.h>

#include <linux/buildid.h>

#include "percpu_freelist.h"



#define STACK_CREATE_FLAG_MASK					\
@@ -143,140 +142,6 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr) 
	return ERR_PTR(err);

}



#define BPF_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 stack_map_parse_build_id(void *page_addr,

					   unsigned char *build_id,

					   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 == BPF_BUILD_ID &&

		    nhdr->n_namesz == sizeof("GNU") &&

		    nhdr->n_descsz > 0 &&

		    nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {

			memcpy(build_id,

			       note_start + note_offs +

			       ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),

			       nhdr->n_descsz);

			memset(build_id + nhdr->n_descsz, 0,

			       BPF_BUILD_ID_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 stack_map_get_build_id_32(void *page_addr,

				     unsigned char *build_id)

{

	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 &&

		    !stack_map_parse_build_id(page_addr, build_id,

					      page_addr + phdr[i].p_offset,

					      phdr[i].p_filesz))

			return 0;

	}

	return -EINVAL;

}



/* Parse build ID from 64-bit ELF */

static int stack_map_get_build_id_64(void *page_addr,

				     unsigned char *build_id)

{

	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 &&

		    !stack_map_parse_build_id(page_addr, build_id,

					      page_addr + phdr[i].p_offset,

					      phdr[i].p_filesz))

			return 0;

	}

	return -EINVAL;

}



/* Parse build ID of ELF file mapped to vma */

static int stack_map_get_build_id(struct vm_area_struct *vma,

				  unsigned char *build_id)

{

	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 = stack_map_get_build_id_32(page_addr, build_id);

	else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)

		ret = stack_map_get_build_id_64(page_addr, build_id);

out:

	kunmap_atomic(page_addr);

	put_page(page);

	return ret;

}



static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,

					  u64 *ips, u32 trace_nr, bool user)

{
@@ -317,18 +182,18 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, 
		for (i = 0; i < trace_nr; i++) {

			id_offs[i].status = BPF_STACK_BUILD_ID_IP;

			id_offs[i].ip = ips[i];

			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);

			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);

		}

		return;

	}



	for (i = 0; i < trace_nr; i++) {

		vma = find_vma(current->mm, ips[i]);

		if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) {

		if (!vma || build_id_parse(vma, id_offs[i].build_id)) {

			/* per entry fall back to ips */

			id_offs[i].status = BPF_STACK_BUILD_ID_IP;

			id_offs[i].ip = ips[i];

			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);

			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);

			continue;

		}

		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]

lib/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -36,7 +36,8 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \ 
	 flex_proportions.o ratelimit.o show_mem.o \

	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \

	 earlycpio.o seq_buf.o siphash.o dec_and_lock.o \

	 nmi_backtrace.o nodemask.o win_minmax.o memcat_p.o

	 nmi_backtrace.o nodemask.o win_minmax.o memcat_p.o \

	 buildid.o



lib-$(CONFIG_PRINTK) += dump_stack.o

lib-$(CONFIG_SMP) += cpumask.o

lib/buildid.c

0 → 100644
+136 −0
Original line number Diff line number Diff line 
// 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,

				 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);

			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)

{

	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,

				    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)

{

	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,

				    page_addr + phdr[i].p_offset,

				    phdr[i].p_filesz))

			return 0;

	}

	return -EINVAL;

}



/* Parse build ID of ELF file mapped to vma */

int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id)

{

	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);

	else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)

		ret = get_build_id_64(page_addr, build_id);

out:

	kunmap_atomic(page_addr);

	put_page(page);

	return ret;

}