Commit 2fde1747 authored by John Fastabend's avatar John Fastabend Committed by Daniel Borkmann
Browse files

selftests/bpf: Add variable-length data concat pattern less than test 



Extend original variable-length tests with a case to catch a common
existing pattern of testing for < 0 for errors. Note because
verifier also tracks upper bounds and we know it can not be greater
than MAX_LEN here we can skip upper bound check.

In ALU64 enabled compilation converting from long->int return types
in probe helpers results in extra instruction pattern, <<= 32, s >>= 32.
The trade-off is the non-ALU64 case works. If you really care about
every extra insn (XDP case?) then you probably should be using original
int type.

In addition adding a sext insn to bpf might help the verifier in the
general case to avoid these types of tricks.

Signed-off-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200623032224.4020118-3-andriin@fb.com
parent 5e85c6bb

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

+12 −0
Original line number Diff line number Diff line
@@ -51,6 +51,18 @@ void test_varlen(void) 
	CHECK_VAL(data->total2, size1 + size2);

	CHECK(memcmp(data->payload2, exp_str, size1 + size2), "content_check",

	      "doesn't match!");



	CHECK_VAL(data->payload3_len1, size1);

	CHECK_VAL(data->payload3_len2, size2);

	CHECK_VAL(data->total3, size1 + size2);

	CHECK(memcmp(data->payload3, exp_str, size1 + size2), "content_check",

	      "doesn't match!");



	CHECK_VAL(data->payload4_len1, size1);

	CHECK_VAL(data->payload4_len2, size2);

	CHECK_VAL(data->total4, size1 + size2);

	CHECK(memcmp(data->payload4, exp_str, size1 + size2), "content_check",

	      "doesn't match!");

cleanup:

	test_varlen__destroy(skel);

}

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

+66 −4
Original line number Diff line number Diff line
@@ -26,8 +26,18 @@ int payload2_len2 = -1; 
int total2 = -1;

char payload2[MAX_LEN + MAX_LEN] = { 1 };



int payload3_len1 = -1;

int payload3_len2 = -1;

int total3= -1;

char payload3[MAX_LEN + MAX_LEN] = { 1 };



int payload4_len1 = -1;

int payload4_len2 = -1;

int total4= -1;

char payload4[MAX_LEN + MAX_LEN] = { 1 };



SEC("raw_tp/sys_enter")

int handler64(void *regs)

int handler64_unsigned(void *regs)

{

	int pid = bpf_get_current_pid_tgid() >> 32;

	void *payload = payload1;
@@ -54,8 +64,34 @@ int handler64(void *regs) 
	return 0;

}



SEC("tp_btf/sys_enter")

int handler32(void *regs)

SEC("raw_tp/sys_exit")

int handler64_signed(void *regs)

{

	int pid = bpf_get_current_pid_tgid() >> 32;

	void *payload = payload3;

	long len;



	/* ignore irrelevant invocations */

	if (test_pid != pid || !capture)

		return 0;



	len = bpf_probe_read_kernel_str(payload, MAX_LEN, &buf_in1[0]);

	if (len >= 0) {

		payload += len;

		payload3_len1 = len;

	}

	len = bpf_probe_read_kernel_str(payload, MAX_LEN, &buf_in2[0]);

	if (len >= 0) {

		payload += len;

		payload3_len2 = len;

	}

	total3 = payload - (void *)payload3;



	return 0;

}



SEC("tp/raw_syscalls/sys_enter")

int handler32_unsigned(void *regs)

{

	int pid = bpf_get_current_pid_tgid() >> 32;

	void *payload = payload2;
@@ -82,7 +118,33 @@ int handler32(void *regs) 
	return 0;

}



SEC("tp_btf/sys_exit")

SEC("tp/raw_syscalls/sys_exit")

int handler32_signed(void *regs)

{

	int pid = bpf_get_current_pid_tgid() >> 32;

	void *payload = payload4;

	int len;



	/* ignore irrelevant invocations */

	if (test_pid != pid || !capture)

		return 0;



	len = bpf_probe_read_kernel_str(payload, MAX_LEN, &buf_in1[0]);

	if (len >= 0) {

		payload += len;

		payload4_len1 = len;

	}

	len = bpf_probe_read_kernel_str(payload, MAX_LEN, &buf_in2[0]);

	if (len >= 0) {

		payload += len;

		payload4_len2 = len;

	}

	total4 = payload - (void *)payload4;



	return 0;

}



SEC("tp/syscalls/sys_exit_getpid")

int handler_exit(void *regs)

{

	long bla;

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