Re: [bpf-next v3 05/12] selftests/bpf: Allow passing more information to BPF prog test run

From: Andrii Nakryiko
Date: Wed Jul 10 2019 - 21:17:43 EST

On Mon, Jul 8, 2019 at 3:42 PM Krzesimir Nowak <krzesimir@xxxxxxxxxx> wrote:
>
> The test case can now specify a custom length of the data member,
> context data and its length, which will be passed to
> bpf_prog_test_run_xattr. For backward compatilibity, if the data
> length is 0 (which is what will happen when the field is left
> unspecified in the designated initializer of a struct), then the
> length passed to the bpf_prog_test_run_xattr is TEST_DATA_LEN.
>
> Also for backward compatilibity, if context data length is 0, NULL is
> passed as a context to bpf_prog_test_run_xattr. This is to avoid
> breaking other tests, where context data being NULL and context data
> length being 0 is handled differently from the case where context data
> is not NULL and context data length is 0.
>
> Custom lengths still can't be greater than hardcoded 64 bytes for data
> and 192 for context data.
>
> 192 for context data was picked to allow passing struct
> bpf_perf_event_data as a context for perf event programs. The struct
> is quite large, because it contains struct pt_regs.
>
> Test runs for perf event programs will not allow the copying the data
> back to data_out buffer, so they require data_out_size to be zero and
> data_out to be NULL. Since test_verifier hardcodes it, make it
> possible to override the size. Overriding the size to zero will cause
> the buffer to be NULL.
>
> Changes since v2:
> - Allow overriding the data out size and buffer.
>
> Signed-off-by: Krzesimir Nowak <krzesimir@xxxxxxxxxx>
> ---
> tools/testing/selftests/bpf/test_verifier.c | 105 +++++++++++++++++---
> 1 file changed, 93 insertions(+), 12 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> index 1640ba9f12c1..6f124cc4ee34 100644
> --- a/tools/testing/selftests/bpf/test_verifier.c
> +++ b/tools/testing/selftests/bpf/test_verifier.c
> @@ -54,6 +54,7 @@
> #define MAX_TEST_RUNS 8
> #define POINTER_VALUE 0xcafe4all
> #define TEST_DATA_LEN 64
> +#define TEST_CTX_LEN 192
>
> #define F_NEEDS_EFFICIENT_UNALIGNED_ACCESS (1 << 0)
> #define F_LOAD_WITH_STRICT_ALIGNMENT (1 << 1)
> @@ -96,7 +97,12 @@ struct bpf_test {
> enum bpf_prog_type prog_type;
> uint8_t flags;
> __u8 data[TEST_DATA_LEN];
> + __u32 data_len;
> + __u8 ctx[TEST_CTX_LEN];
> + __u32 ctx_len;
> void (*fill_helper)(struct bpf_test *self);
> + bool override_data_out_len;
> + __u32 overridden_data_out_len;
> uint8_t runs;
> struct {
> uint32_t retval, retval_unpriv;
> @@ -104,6 +110,9 @@ struct bpf_test {
> __u8 data[TEST_DATA_LEN];
> __u64 data64[TEST_DATA_LEN / 8];
> };
> + __u32 data_len;
> + __u8 ctx[TEST_CTX_LEN];
> + __u32 ctx_len;
> } retvals[MAX_TEST_RUNS];
> };
>
> @@ -818,21 +827,35 @@ static int set_admin(bool admin)
> }
>
> static int do_prog_test_run(int fd_prog, bool unpriv, uint32_t expected_val,
> - void *data, size_t size_data)
> + void *data, size_t size_data, void *ctx,
> + size_t size_ctx, u32 *overridden_data_out_size)
> {
> - __u8 tmp[TEST_DATA_LEN << 2];
> - __u32 size_tmp = sizeof(tmp);
> - int saved_errno;
> - int err;
> struct bpf_prog_test_run_attr attr = {
> .prog_fd = fd_prog,
> .repeat = 1,
> .data_in = data,
> .data_size_in = size_data,
> - .data_out = tmp,
> - .data_size_out = size_tmp,
> + .ctx_in = ctx,
> + .ctx_size_in = size_ctx,
> };
> + __u8 tmp[TEST_DATA_LEN << 2];
> + __u32 size_tmp = sizeof(tmp);
> + __u32 size_buf = size_tmp;
> + __u8 *buf = tmp;
> + int saved_errno;
> + int err;
>
> + if (overridden_data_out_size)
> + size_buf = *overridden_data_out_size;
> + if (size_buf > size_tmp) {
> + printf("FAIL: out data size (%d) greater than a buffer size (%d) ",
> + size_buf, size_tmp);
> + return -EINVAL;
> + }
> + if (!size_buf)
> + buf = NULL;
> + attr.data_size_out = size_buf;
> + attr.data_out = buf;
> if (unpriv)
> set_admin(true);
> err = bpf_prog_test_run_xattr(&attr);
> @@ -956,13 +979,45 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
> if (!alignment_prevented_execution && fd_prog >= 0) {
> uint32_t expected_val;
> int i;
> + __u32 size_data;
> + __u32 size_ctx;
> + bool bad_size;
> + void *ctx;
> + __u32 *overridden_data_out_size;
>
> if (!test->runs) {
> + if (test->data_len > 0)
> + size_data = test->data_len;
> + else
> + size_data = sizeof(test->data);
> + if (test->override_data_out_len)
> + overridden_data_out_size = &test->overridden_data_out_len;
> + else
> + overridden_data_out_size = NULL;
> + size_ctx = test->ctx_len;
> + bad_size = false;

I hated all this duplication of logic, which with this patch becomes
even more expansive, so I removed it. Please see [0]. Can you please
apply that patch and add all this new logic only once?

[0] https://patchwork.ozlabs.org/patch/1130601/

> expected_val = unpriv && test->retval_unpriv ?
> test->retval_unpriv : test->retval;
>
> - err = do_prog_test_run(fd_prog, unpriv, expected_val,
> - test->data, sizeof(test->data));
> + if (size_data > sizeof(test->data)) {
> + printf("FAIL: data size (%u) greater than TEST_DATA_LEN (%lu) ", size_data, sizeof(test->data));
> + bad_size = true;
> + }
> + if (size_ctx > sizeof(test->ctx)) {
> + printf("FAIL: ctx size (%u) greater than TEST_CTX_LEN (%lu) ", size_ctx, sizeof(test->ctx));

These look like way too long lines, wrap them?

> + bad_size = true;
> + }
> + if (size_ctx)
> + ctx = test->ctx;
> + else
> + ctx = NULL;

nit: single line:

ctx = size_ctx ? test->ctx : NULL;

> + if (bad_size)
> + err = 1;
> + else
> + err = do_prog_test_run(fd_prog, unpriv, expected_val,
> + test->data, size_data,
> + ctx, size_ctx,
> + overridden_data_out_size);
> if (err)
> run_errs++;
> else
> @@ -970,14 +1025,40 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
> }
>
> for (i = 0; i < test->runs; i++) {
> + if (test->retvals[i].data_len > 0)
> + size_data = test->retvals[i].data_len;
> + else
> + size_data = sizeof(test->retvals[i].data);
> + if (test->override_data_out_len)
> + overridden_data_out_size = &test->overridden_data_out_len;
> + else
> + overridden_data_out_size = NULL;
> + size_ctx = test->retvals[i].ctx_len;
> + bad_size = false;
> if (unpriv && test->retvals[i].retval_unpriv)
> expected_val = test->retvals[i].retval_unpriv;
> else
> expected_val = test->retvals[i].retval;
>
> - err = do_prog_test_run(fd_prog, unpriv, expected_val,
> - test->retvals[i].data,
> - sizeof(test->retvals[i].data));
> + if (size_data > sizeof(test->retvals[i].data)) {
> + printf("FAIL: data size (%u) at run %i greater than TEST_DATA_LEN (%lu) ", size_data, i + 1, sizeof(test->retvals[i].data));
> + bad_size = true;
> + }
> + if (size_ctx > sizeof(test->retvals[i].ctx)) {
> + printf("FAIL: ctx size (%u) at run %i greater than TEST_CTX_LEN (%lu) ", size_ctx, i + 1, sizeof(test->retvals[i].ctx));
> + bad_size = true;
> + }
> + if (size_ctx)
> + ctx = test->retvals[i].ctx;
> + else
> + ctx = NULL;
> + if (bad_size)
> + err = 1;
> + else
> + err = do_prog_test_run(fd_prog, unpriv, expected_val,
> + test->retvals[i].data, size_data,
> + ctx, size_ctx,
> + overridden_data_out_size);
> if (err) {
> printf("(run %d/%d) ", i + 1, test->runs);
> run_errs++;
> --
> 2.20.1
>