From: Alexei Starovoitov <ast@fb.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Andrii Nakryiko <andriin@fb.com>, bpf <bpf@vger.kernel.org>,
Networking <netdev@vger.kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH bpf-next 5/6] libbpf: support libbpf-provided extern variables
Date: Wed, 20 Nov 2019 21:39:13 +0000 [thread overview]
Message-ID: <11d4fde2-6cf5-72eb-9c04-b424f7314672@fb.com> (raw)
In-Reply-To: <CAEf4BzaW4-XTxZTt2ZLvzuc2UsmmPa3Bkoej7B0pUJWcM--eVQ@mail.gmail.com>
On 11/19/19 7:44 PM, Andrii Nakryiko wrote:
> So, to summarize, we proceed with uint64_t for everything, with added
> bits of weak vs strong handling. Then in parallel we'll work on adding
> BTF for externs and __builtin_extern_resolved (and corresponding new
> kind of BTF relocation) and will keep making this whole API even
> better, while already having something useful and extensible.
I didn't know extern can be weak. That was a good find.
Indeed undefined config_* can be represented as uint64 zero value.
But I still have an issue with 'proceed uint64_t for everything',
since strings and tri-state don't fit into uint64.
How about strtol be applied by libbpf only for things that parse
successfully (like decimal and hex) and everything else will be
represented raw ?
Like CONFIG=y will be 121.
CONFIG=m will be 109
CONFIG="abc" will be 0x636261
In other words CONFIG_A is an address and
'extern weak uint64_t CONFIG_A' reads raw bytes from that location.
When that CONFIG_A is undefined in /boot/config.gz the u64 read
from that address will return zero.
u8 read from that address will return zero too.
next prev parent reply other threads:[~2019-11-20 21:39 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-17 7:08 [PATCH bpf-next 0/6] Add libbpf-provided extern variables support Andrii Nakryiko
2019-11-17 7:08 ` [PATCH bpf-next 1/6] selftests/bpf: ensure no DWARF relocations for BPF object files Andrii Nakryiko
2019-11-17 7:08 ` [PATCH bpf-next 2/6] libbpf: refactor relocation handling Andrii Nakryiko
2019-11-17 7:08 ` [PATCH bpf-next 3/6] libbpf: fix various errors and warning reported by checkpatch.pl Andrii Nakryiko
2019-11-17 7:08 ` [PATCH bpf-next 4/6] libbpf: support initialized global variables Andrii Nakryiko
2019-11-17 7:08 ` [PATCH bpf-next 5/6] libbpf: support libbpf-provided extern variables Andrii Nakryiko
2019-11-19 3:21 ` Alexei Starovoitov
2019-11-19 6:57 ` Andrii Nakryiko
2019-11-19 15:42 ` Andrii Nakryiko
2019-11-19 15:58 ` Alexei Starovoitov
2019-11-19 23:32 ` Daniel Borkmann
2019-11-20 3:17 ` Andrii Nakryiko
2019-11-20 3:44 ` Andrii Nakryiko
2019-11-20 21:39 ` Alexei Starovoitov [this message]
2019-11-20 22:47 ` Andrii Nakryiko
2019-11-21 0:18 ` Alexei Starovoitov
2019-11-21 2:13 ` Andrii Nakryiko
2019-11-21 4:39 ` Alexei Starovoitov
2019-11-17 7:08 ` [PATCH bpf-next 6/6] selftests/bpf: add tests for libbpf-provided externs Andrii Nakryiko
2019-11-17 7:12 ` [PATCH bpf-next 0/6] Add libbpf-provided extern variables support Andrii Nakryiko
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