Commit 502b0e3d authored by Andrii Nakryiko's avatar Andrii Nakryiko
Browse files

Merge branch 'libbpf: uprobe name-based attach followups' 

Alan Maguire says:

====================

Follow-up series to [1] to address some suggestions from Andrii to
improve parsing and make it more robust (patches 1, 2) and to improve
validation of u[ret]probe firing by validating expected argument
and return values (patch 3).

[1] https://lore.kernel.org/bpf/164903521182.13106.12656654142629368774.git-patchwork-notify@kernel.org/



Changes since v1:
- split library name, auto-attach parsing into separate patches (Andrii, patches 1, 2)
- made str_has_sfx() static inline, avoided repeated strlen()s by storing lengths,
  used strlen() instead of strnlen() (Andrii, patch 1)
- fixed sscanf() arg to use %li, switched logging to use "prog '%s'" format,
  used direct strcmp() on probe_type instead of prefix check (Andrii, patch 2)
- switched auto-attach tests to log parameter/return values to be checked by
  user-space side of tests. Needed to add pid filtering to avoid capturing
  stray malloc()s (Andrii, patch 3)
====================

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
parents 9fc4476a 1717e248

tools/lib/bpf/libbpf.c

+34 −49
Original line number Diff line number Diff line
@@ -10766,7 +10766,7 @@ static int resolve_full_path(const char *file, char *result, size_t result_sz) 
	const char *search_paths[3] = {};

	int i;



	if (strstr(file, ".so")) {

	if (str_has_sfx(file, ".so") || strstr(file, ".so.")) {

		search_paths[0] = getenv("LD_LIBRARY_PATH");

		search_paths[1] = "/usr/lib64:/usr/lib";

		search_paths[2] = arch_specific_lib_paths();
@@ -10913,60 +10913,45 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, 
static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link)

{

	DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts);

	char *func, *probe_name, *func_end;

	char *func_name, binary_path[512];

	unsigned long long raw_offset;

	size_t offset = 0;

	int n;

	char *probe_type = NULL, *binary_path = NULL, *func_name = NULL;

	int n, ret = -EINVAL;

	long offset = 0;



	*link = NULL;



	opts.retprobe = str_has_pfx(prog->sec_name, "uretprobe");

	if (opts.retprobe)

		probe_name = prog->sec_name + sizeof("uretprobe") - 1;

	else

		probe_name = prog->sec_name + sizeof("uprobe") - 1;

	if (probe_name[0] == '/')

		probe_name++;



	n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%m[a-zA-Z0-9_.]+%li",

		   &probe_type, &binary_path, &func_name, &offset);

	switch (n) {

	case 1:

		/* handle SEC("u[ret]probe") - format is valid, but auto-attach is impossible. */

	if (strlen(probe_name) == 0)

		return 0;



	snprintf(binary_path, sizeof(binary_path), "%s", probe_name);

	/* ':' should be prior to function+offset */

	func_name = strrchr(binary_path, ':');

	if (!func_name) {

		pr_warn("section '%s' missing ':function[+offset]' specification\n",

			prog->sec_name);

		return -EINVAL;

	}

	func_name[0] = '\0';

	func_name++;

	n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset);

	if (n < 1) {

		pr_warn("uprobe name '%s' is invalid\n", func_name);

		return -EINVAL;

	}

		ret = 0;

		break;

	case 2:

		pr_warn("prog '%s': section '%s' missing ':function[+offset]' specification\n",

			prog->name, prog->sec_name);

		break;

	case 3:

	case 4:

		opts.retprobe = strcmp(probe_type, "uretprobe") == 0;

		if (opts.retprobe && offset != 0) {

		free(func);

		pr_warn("uretprobes do not support offset specification\n");

		return -EINVAL;

			pr_warn("prog '%s': uretprobes do not support offset specification\n",

				prog->name);

			break;

		}



	/* Is func a raw address? */

	errno = 0;

	raw_offset = strtoull(func, &func_end, 0);

	if (!errno && !*func_end) {

		free(func);

		func = NULL;

		offset = (size_t)raw_offset;

		opts.func_name = func_name;

		*link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);

		ret = libbpf_get_error(*link);

		break;

	default:

		pr_warn("prog '%s': invalid format of section definition '%s'\n", prog->name,

			prog->sec_name);

		break;

	}

	opts.func_name = func;

	free(probe_type);

	free(binary_path);

	free(func_name);



	*link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);

	free(func);

	return libbpf_get_error(*link);

	return ret;

}



struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,

tools/lib/bpf/libbpf_internal.h

+11 −0
Original line number Diff line number Diff line
@@ -103,6 +103,17 @@ 
#define str_has_pfx(str, pfx) \

	(strncmp(str, pfx, __builtin_constant_p(pfx) ? sizeof(pfx) - 1 : strlen(pfx)) == 0)



/* suffix check */

static inline bool str_has_sfx(const char *str, const char *sfx)

{

	size_t str_len = strlen(str);

	size_t sfx_len = strlen(sfx);



	if (sfx_len <= str_len)

		return strcmp(str + str_len - sfx_len, sfx);

	return false;

}



/* Symbol versioning is different between static and shared library.

 * Properly versioned symbols are needed for shared library, but

 * only the symbol of the new version is needed for static library.

tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c

+18 −7
Original line number Diff line number Diff line
@@ -5,14 +5,17 @@ 
#include "test_uprobe_autoattach.skel.h"



/* uprobe attach point */

static void autoattach_trigger_func(void)

static noinline int autoattach_trigger_func(int arg)

{

	asm volatile ("");

	return arg + 1;

}



void test_uprobe_autoattach(void)

{

	struct test_uprobe_autoattach *skel;

	int trigger_val = 100, trigger_ret;

	size_t malloc_sz = 1;

	char *mem;



	skel = test_uprobe_autoattach__open_and_load();
@@ -22,17 +25,25 @@ void test_uprobe_autoattach(void) 
	if (!ASSERT_OK(test_uprobe_autoattach__attach(skel), "skel_attach"))

		goto cleanup;



	skel->bss->test_pid = getpid();



	/* trigger & validate uprobe & uretprobe */

	autoattach_trigger_func();

	trigger_ret = autoattach_trigger_func(trigger_val);



	skel->bss->test_pid = getpid();



	/* trigger & validate shared library u[ret]probes attached by name */

	mem = malloc(1);

	mem = malloc(malloc_sz);

	free(mem);



	ASSERT_EQ(skel->bss->uprobe_byname_res, 1, "check_uprobe_byname_res");

	ASSERT_EQ(skel->bss->uretprobe_byname_res, 2, "check_uretprobe_byname_res");

	ASSERT_EQ(skel->bss->uprobe_byname2_res, 3, "check_uprobe_byname2_res");

	ASSERT_EQ(skel->bss->uretprobe_byname2_res, 4, "check_uretprobe_byname2_res");

	ASSERT_EQ(skel->bss->uprobe_byname_parm1, trigger_val, "check_uprobe_byname_parm1");

	ASSERT_EQ(skel->bss->uprobe_byname_ran, 1, "check_uprobe_byname_ran");

	ASSERT_EQ(skel->bss->uretprobe_byname_rc, trigger_ret, "check_uretprobe_byname_rc");

	ASSERT_EQ(skel->bss->uretprobe_byname_ran, 2, "check_uretprobe_byname_ran");

	ASSERT_EQ(skel->bss->uprobe_byname2_parm1, malloc_sz, "check_uprobe_byname2_parm1");

	ASSERT_EQ(skel->bss->uprobe_byname2_ran, 3, "check_uprobe_byname2_ran");

	ASSERT_EQ(skel->bss->uretprobe_byname2_rc, mem, "check_uretprobe_byname2_rc");

	ASSERT_EQ(skel->bss->uretprobe_byname2_ran, 4, "check_uretprobe_byname2_ran");

cleanup:

	test_uprobe_autoattach__destroy(skel);

}

tools/testing/selftests/bpf/progs/test_uprobe_autoattach.c

+32 −11
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2022, Oracle and/or its affiliates. */



#include <linux/ptrace.h>

#include <linux/bpf.h>

#include "vmlinux.h"



#include <bpf/bpf_core_read.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



int uprobe_byname_res = 0;

int uretprobe_byname_res = 0;

int uprobe_byname2_res = 0;

int uretprobe_byname2_res = 0;

int uprobe_byname_parm1 = 0;

int uprobe_byname_ran = 0;

int uretprobe_byname_rc = 0;

int uretprobe_byname_ran = 0;

size_t uprobe_byname2_parm1 = 0;

int uprobe_byname2_ran = 0;

char *uretprobe_byname2_rc = NULL;

int uretprobe_byname2_ran = 0;



int test_pid;



/* This program cannot auto-attach, but that should not stop other

 * programs from attaching.
@@ -23,14 +30,16 @@ int handle_uprobe_noautoattach(struct pt_regs *ctx) 
SEC("uprobe//proc/self/exe:autoattach_trigger_func")

int handle_uprobe_byname(struct pt_regs *ctx)

{

	uprobe_byname_res = 1;

	uprobe_byname_parm1 = PT_REGS_PARM1_CORE(ctx);

	uprobe_byname_ran = 1;

	return 0;

}



SEC("uretprobe//proc/self/exe:autoattach_trigger_func")

int handle_uretprobe_byname(struct pt_regs *ctx)

{

	uretprobe_byname_res = 2;

	uretprobe_byname_rc = PT_REGS_RC_CORE(ctx);

	uretprobe_byname_ran = 2;

	return 0;

}
@@ -38,14 +47,26 @@ int handle_uretprobe_byname(struct pt_regs *ctx) 
SEC("uprobe/libc.so.6:malloc")

int handle_uprobe_byname2(struct pt_regs *ctx)

{

	uprobe_byname2_res = 3;

	int pid = bpf_get_current_pid_tgid() >> 32;



	/* ignore irrelevant invocations */

	if (test_pid != pid)

		return 0;

	uprobe_byname2_parm1 = PT_REGS_PARM1_CORE(ctx);

	uprobe_byname2_ran = 3;

	return 0;

}



SEC("uretprobe/libc.so.6:free")

SEC("uretprobe/libc.so.6:malloc")

int handle_uretprobe_byname2(struct pt_regs *ctx)

{

	uretprobe_byname2_res = 4;

	int pid = bpf_get_current_pid_tgid() >> 32;



	/* ignore irrelevant invocations */

	if (test_pid != pid)

		return 0;

	uretprobe_byname2_rc = (char *)PT_REGS_RC_CORE(ctx);

	uretprobe_byname2_ran = 4;

	return 0;

}