bpf: Treat first argument as return value for bpf_throw

Browse source

In case of the default exception callback, change the behavior of
bpf_throw, where the passed cookie value is no longer ignored, but
is instead the return value of the default exception callback. As
such, we need to place restrictions on the value being passed into
bpf_throw in such a case, only allowing those permitted by the
check_return_code function.

Thus, bpf_throw can now control the return value of the program from
each call site without having the user install a custom exception
callback just to override the return value when an exception is thrown.

We also modify the hidden subprog instructions to now move BPF_REG_1 to
BPF_REG_0, so as to set the return value before exit in the default
callback.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230912233214.1518551-9-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

...

This commit is contained in:

Kumar Kartikeya Dwivedi 2023-09-13 01:32:05 +02:00 • committed by Alexei Starovoitov

parent b62bf8a5e9

commit a923819fb2

1 changed files with 24 additions and 13 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

37

kernel/bpf/verifier.c

View file