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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: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200623032224.4020118-3-andriin@fb.com
This commit is contained in:
John Fastabend 2020-06-22 20:22:23 -07:00 committed by Daniel Borkmann
parent 5e85c6bb8e
commit 2fde1747c9
2 changed files with 78 additions and 4 deletions
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12
tools/testing/selftests/bpf/prog_tests/varlen.c
View File

@ -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);
}

70
tools/testing/selftests/bpf/progs/test_varlen.c
View File

@ -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;