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Commit 84c0fa74 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Harshit Jain
Browse files

bpf: btf: Change how section is supported in btf_header 



There are currently unused section descriptions in the btf_header.  Those
sections are here to support future BTF use cases.  For example, the
func section (func_off) is to support function signature (e.g. the BPF
prog function signature).

Instead of spelling out all potential sections up-front in the btf_header.
This patch makes changes to btf_header such that extending it (e.g. adding
a section) is possible later.  The unused ones can be removed for now and
they can be added back later.

This patch:
1. adds a hdr_len to the btf_header.  It will allow adding
sections (and other info like parent_label and parent_name)
later.  The check is similar to the existing bpf_attr.
If a user passes in a longer hdr_len, the kernel
ensures the extra tailing bytes are 0.

2. allows the section order in the BTF object to be
different from its sec_off order in btf_header.

3. each sec_off is followed by a sec_len.  It must not have gap or
overlapping among sections.

The string section is ensured to be at the end due to the 4 bytes
alignment requirement of the type section.

The above changes will allow enough flexibility to
add new sections (and other info) to the btf_header later.

This patch also removes an unnecessary !err check
at the end of btf_parse().

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarCyber Knight <cyberknight755@gmail.com>
parent 74efcf39

include/uapi/linux/btf.h

+2 −6
Original line number Diff line number Diff line
@@ -12,15 +12,11 @@ struct btf_header { 
	__u16	magic;

	__u8	version;

	__u8	flags;



	__u32	parent_label;

	__u32	parent_name;

	__u32	hdr_len;



	/* All offsets are in bytes relative to the end of this header */

	__u32	label_off;	/* offset of label section	*/

	__u32	object_off;	/* offset of data object section*/

	__u32	func_off;	/* offset of function section	*/

	__u32	type_off;	/* offset of type section	*/

	__u32	type_len;	/* length of type section	*/

	__u32	str_off;	/* offset of string section	*/

	__u32	str_len;	/* length of string section	*/

};

kernel/bpf/btf.c

+158 −51
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/file.h>

#include <linux/uaccess.h>

#include <linux/kernel.h>

#include <linux/sort.h>

#include <linux/bpf_verifier.h>

#include <linux/btf.h>
@@ -180,15 +181,13 @@ 
	     i++, member++)



struct btf {

	union {

		struct btf_header *hdr;

	void *data;

	};

	struct btf_type **types;

	u32 *resolved_ids;

	u32 *resolved_sizes;

	const char *strings;

	void *nohdr_data;

	struct btf_header hdr;

	u32 nr_types;

	u32 types_size;

	u32 data_size;
@@ -222,6 +221,11 @@ enum resolve_mode { 


#define MAX_RESOLVE_DEPTH 32



struct btf_sec_info {

	u32 off;

	u32 len;

};



struct btf_verifier_env {

	struct btf *btf;

	u8 *visit_states;
@@ -412,14 +416,14 @@ static const struct btf_kind_operations *btf_type_ops(const struct btf_type *t) 
static bool btf_name_offset_valid(const struct btf *btf, u32 offset)

{

	return !BTF_STR_TBL_ELF_ID(offset) &&

		BTF_STR_OFFSET(offset) < btf->hdr->str_len;

		BTF_STR_OFFSET(offset) < btf->hdr.str_len;

}



static const char *btf_name_by_offset(const struct btf *btf, u32 offset)

{

	if (!BTF_STR_OFFSET(offset))

		return "(anon)";

	else if (BTF_STR_OFFSET(offset) < btf->hdr->str_len)

	else if (BTF_STR_OFFSET(offset) < btf->hdr.str_len)

		return &btf->strings[BTF_STR_OFFSET(offset)];

	else

		return "(invalid-name-offset)";
@@ -530,7 +534,8 @@ static void btf_verifier_log_member(struct btf_verifier_env *env, 
	__btf_verifier_log(log, "\n");

}



static void btf_verifier_log_hdr(struct btf_verifier_env *env)

static void btf_verifier_log_hdr(struct btf_verifier_env *env,

				 u32 btf_data_size)

{

	struct bpf_verifier_log *log = &env->log;

	const struct btf *btf = env->btf;
@@ -539,19 +544,16 @@ static void btf_verifier_log_hdr(struct btf_verifier_env *env) 
	if (!bpf_verifier_log_needed(log))

		return;



	hdr = btf->hdr;

	hdr = &btf->hdr;

	__btf_verifier_log(log, "magic: 0x%x\n", hdr->magic);

	__btf_verifier_log(log, "version: %u\n", hdr->version);

	__btf_verifier_log(log, "flags: 0x%x\n", hdr->flags);

	__btf_verifier_log(log, "parent_label: %u\n", hdr->parent_label);

	__btf_verifier_log(log, "parent_name: %u\n", hdr->parent_name);

	__btf_verifier_log(log, "label_off: %u\n", hdr->label_off);

	__btf_verifier_log(log, "object_off: %u\n", hdr->object_off);

	__btf_verifier_log(log, "func_off: %u\n", hdr->func_off);

	__btf_verifier_log(log, "hdr_len: %u\n", hdr->hdr_len);

	__btf_verifier_log(log, "type_off: %u\n", hdr->type_off);

	__btf_verifier_log(log, "type_len: %u\n", hdr->type_len);

	__btf_verifier_log(log, "str_off: %u\n", hdr->str_off);

	__btf_verifier_log(log, "str_len: %u\n", hdr->str_len);

	__btf_verifier_log(log, "btf_total_size: %u\n", btf->data_size);

	__btf_verifier_log(log, "btf_total_size: %u\n", btf_data_size);

}



static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
@@ -1708,9 +1710,9 @@ static int btf_check_all_metas(struct btf_verifier_env *env) 
	struct btf_header *hdr;

	void *cur, *end;



	hdr = btf->hdr;

	hdr = &btf->hdr;

	cur = btf->nohdr_data + hdr->type_off;

	end = btf->nohdr_data + hdr->str_off;

	end = btf->nohdr_data + hdr->type_len;



	env->log_type_id = 1;

	while (cur < end) {
@@ -1820,8 +1822,20 @@ static int btf_check_all_types(struct btf_verifier_env *env) 


static int btf_parse_type_sec(struct btf_verifier_env *env)

{

	const struct btf_header *hdr = &env->btf->hdr;

	int err;



	/* Type section must align to 4 bytes */

	if (hdr->type_off & (sizeof(u32) - 1)) {

		btf_verifier_log(env, "Unaligned type_off");

		return -EINVAL;

	}



	if (!hdr->type_len) {

		btf_verifier_log(env, "No type found");

		return -EINVAL;

	}



	err = btf_check_all_metas(env);

	if (err)

		return err;
@@ -1835,10 +1849,15 @@ static int btf_parse_str_sec(struct btf_verifier_env *env) 
	struct btf *btf = env->btf;

	const char *start, *end;



	hdr = btf->hdr;

	hdr = &btf->hdr;

	start = btf->nohdr_data + hdr->str_off;

	end = start + hdr->str_len;



	if (end != btf->data + btf->data_size) {

		btf_verifier_log(env, "String section is not at the end");

		return -EINVAL;

	}



	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET ||

	    start[0] || end[-1]) {

		btf_verifier_log(env, "Invalid string section");
@@ -1850,20 +1869,122 @@ static int btf_parse_str_sec(struct btf_verifier_env *env) 
	return 0;

}



static int btf_parse_hdr(struct btf_verifier_env *env)

static const size_t btf_sec_info_offset[] = {

	offsetof(struct btf_header, type_off),

	offsetof(struct btf_header, str_off),

};



static int btf_sec_info_cmp(const void *a, const void *b)

{

	const struct btf_sec_info *x = a;

	const struct btf_sec_info *y = b;



	return (int)(x->off - y->off) ? : (int)(x->len - y->len);

}



static int btf_check_sec_info(struct btf_verifier_env *env,

			      u32 btf_data_size)

{

	const unsigned int nr_secs = ARRAY_SIZE(btf_sec_info_offset);

	struct btf_sec_info secs[nr_secs];

	u32 total, expected_total, i;

	const struct btf_header *hdr;

	struct btf *btf = env->btf;

	u32 meta_left;

	const struct btf *btf;



	btf = env->btf;

	hdr = &btf->hdr;



	/* Populate the secs from hdr */

	for (i = 0; i < nr_secs; i++)

		secs[i] = *(struct btf_sec_info *)((void *)hdr +

						   btf_sec_info_offset[i]);



	sort(secs, nr_secs, sizeof(struct btf_sec_info),

	     btf_sec_info_cmp, NULL);



	/* Check for gaps and overlap among sections */

	total = 0;

	expected_total = btf_data_size - hdr->hdr_len;

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

		if (expected_total < secs[i].off) {

			btf_verifier_log(env, "Invalid section offset");

			return -EINVAL;

		}

		if (total < secs[i].off) {

			/* gap */

			btf_verifier_log(env, "Unsupported section found");

			return -EINVAL;

		}

		if (total > secs[i].off) {

			btf_verifier_log(env, "Section overlap found");

			return -EINVAL;

		}

		if (expected_total - total < secs[i].len) {

			btf_verifier_log(env,

					 "Total section length too long");

			return -EINVAL;

		}

		total += secs[i].len;

	}



	/* There is data other than hdr and known sections */

	if (expected_total != total) {

		btf_verifier_log(env, "Unsupported section found");

		return -EINVAL;

	}



	return 0;

}



static int btf_parse_hdr(struct btf_verifier_env *env, void __user *btf_data,

			 u32 btf_data_size)

{

	const struct btf_header *hdr;

	u32 hdr_len, hdr_copy;

	/*

	 * Minimal part of the "struct btf_header" that

	 * contains the hdr_len.

	 */

	struct btf_min_header {

		u16	magic;

		u8	version;

		u8	flags;

		u32	hdr_len;

	} __user *min_hdr;

	struct btf *btf;

	int err;



	btf = env->btf;

	min_hdr = btf_data;



	if (btf_data_size < sizeof(*min_hdr)) {

		btf_verifier_log(env, "hdr_len not found");

		return -EINVAL;

	}



	if (btf->data_size < sizeof(*hdr)) {

	if (get_user(hdr_len, &min_hdr->hdr_len))

		return -EFAULT;



	if (btf_data_size < hdr_len) {

		btf_verifier_log(env, "btf_header not found");

		return -EINVAL;

	}



	btf_verifier_log_hdr(env);

	err = bpf_check_uarg_tail_zero(btf_data, sizeof(btf->hdr), hdr_len);

	if (err) {

		if (err == -E2BIG)

			btf_verifier_log(env, "Unsupported btf_header");

		return err;

	}



	hdr_copy = min_t(u32, hdr_len, sizeof(btf->hdr));

	if (copy_from_user(&btf->hdr, btf_data, hdr_copy))

		return -EFAULT;



	hdr = &btf->hdr;



	btf_verifier_log_hdr(env, btf_data_size);



	hdr = btf->hdr;

	if (hdr->magic != BTF_MAGIC) {

		btf_verifier_log(env, "Invalid magic");

		return -EINVAL;
@@ -1879,26 +2000,14 @@ static int btf_parse_hdr(struct btf_verifier_env *env) 
		return -ENOTSUPP;

	}



	meta_left = btf->data_size - sizeof(*hdr);

	if (!meta_left) {

	if (btf_data_size == hdr->hdr_len) {

		btf_verifier_log(env, "No data");

		return -EINVAL;

	}



	if (meta_left < hdr->type_off || hdr->str_off <= hdr->type_off ||

	    /* Type section must align to 4 bytes */

	    hdr->type_off & (sizeof(u32) - 1)) {

		btf_verifier_log(env, "Invalid type_off");

		return -EINVAL;

	}



	if (meta_left < hdr->str_off ||

	    meta_left - hdr->str_off < hdr->str_len) {

		btf_verifier_log(env, "Invalid str_off or str_len");

		return -EINVAL;

	}



	btf->nohdr_data = btf->hdr + 1;

	err = btf_check_sec_info(env, btf_data_size);

	if (err)

		return err;



	return 0;

}
@@ -1941,6 +2050,11 @@ static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size, 
		err = -ENOMEM;

		goto errout;

	}

	env->btf = btf;



	err = btf_parse_hdr(env, btf_data, btf_data_size);

	if (err)

		goto errout;



	data = kvmalloc(btf_data_size, GFP_KERNEL | __GFP_NOWARN);

	if (!data) {
@@ -1950,18 +2064,13 @@ static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size, 


	btf->data = data;

	btf->data_size = btf_data_size;

	btf->nohdr_data = btf->data + btf->hdr.hdr_len;



	if (copy_from_user(data, btf_data, btf_data_size)) {

		err = -EFAULT;

		goto errout;

	}



	env->btf = btf;



	err = btf_parse_hdr(env);

	if (err)

		goto errout;



	err = btf_parse_str_sec(env);

	if (err)

		goto errout;
@@ -1970,16 +2079,14 @@ static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size, 
	if (err)

		goto errout;



	if (!err && log->level && bpf_verifier_log_full(log)) {

	if (log->level && bpf_verifier_log_full(log)) {

		err = -ENOSPC;

		goto errout;

	}



	if (!err) {

	btf_verifier_env_free(env);

	refcount_set(&btf->refcnt, 1);

	return btf;

	}



errout:

	btf_verifier_env_free(env);