selftests/bpf: Consolidate kernel modules into common directory

The selftests build four kernel modules which use copy-pasted Makefile
targets. This is a bit messy, and doesn't scale so well when we

selftests/bpf: Consolidate kernel modules into common directory

The selftests build four kernel modules which use copy-pasted Makefile
targets. This is a bit messy, and doesn't scale so well when we add more
modules, so let's consolidate these rules into a single rule generated
for each module name, and move the module sources into a single
directory.

To avoid parallel builds of the different modules stepping on each
other's toes during the 'modpost' phase of the Kbuild 'make modules',
the module files should really be a grouped target. However, make only
added explicit support for grouped targets in version 4.3, which is
newer than the minimum version supported by the kernel. However, make
implicitly treats pattern matching rules with multiple targets as a
grouped target, so we can work around this by turning the rule into a
pattern matching target. We do this by replacing '.ko' with '%ko' in the
targets with subst().

Signed-off-by: Toke Høiland-Jørgensen <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Acked-by: Viktor Malik <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

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selftests/bpf: Add struct_ops prog private stack tests

Add three tests for struct_ops using private stack.
./test_progs -t struct_ops_private_stack
#336/1 struct_ops_private_stack/private_stac

selftests/bpf: Add struct_ops prog private stack tests

Add three tests for struct_ops using private stack.
./test_progs -t struct_ops_private_stack
#336/1 struct_ops_private_stack/private_stack:OK
#336/2 struct_ops_private_stack/private_stack_fail:OK
#336/3 struct_ops_private_stack/private_stack_recur:OK
#336 struct_ops_private_stack:OK

The following is a snippet of a struct_ops check_member() implementation:

u32 moff = __btf_member_bit_offset(t, member) / 8;
switch (moff) {
case offsetof(struct bpf_testmod_ops3, test_1):
prog->aux->priv_stack_requested = true;
prog->aux->recursion_detected = test_1_recursion_detected;
fallthrough;
default:
break;
}
return 0;

The first test is with nested two different callback functions where the
first prog has more than 512 byte stack size (including subprogs) with
private stack enabled.

The second test is a negative test where the second prog has more than 512
byte stack size without private stack enabled.

The third test is the same callback function recursing itself. At run time,
the jit trampoline recursion check kicks in to prevent the recursion. The
recursion_detected() callback function is implemented by the bpf_testmod,
the following message in dmesg
bpf_testmod: oh no, recursing into test_1, recursion_misses 1
demonstrates the callback function is indeed triggered when recursion miss
happens.

Signed-off-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

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