netdev - Re: [PATCH v6 bpf-next 04/14] libbpf: implement BPF CO-RE offset relocation algorithm

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Message-ID: <20190807221649.fiqo2kqj73qjcakr@ast-mbp>
Date:   Wed, 7 Aug 2019 15:16:51 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Andrii Nakryiko <andriin@...com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...com,
        daniel@...earbox.net, yhs@...com, andrii.nakryiko@...il.com,
        kernel-team@...com
Subject: Re: [PATCH v6 bpf-next 04/14] libbpf: implement BPF CO-RE offset
 relocation algorithm

On Wed, Aug 07, 2019 at 02:39:51PM -0700, Andrii Nakryiko wrote:
> This patch implements the core logic for BPF CO-RE offsets relocations.
> Every instruction that needs to be relocated has corresponding
> bpf_offset_reloc as part of BTF.ext. Relocations are performed by trying
> to match recorded "local" relocation spec against potentially many
> compatible "target" types, creating corresponding spec. Details of the
> algorithm are noted in corresponding comments in the code.
> 
> Signed-off-by: Andrii Nakryiko <andriin@...com>
> Acked-by: Song Liu <songliubraving@...com>
...
> +static struct btf *bpf_core_find_kernel_btf(void)
> +{
> +	const char *locations[] = {
> +		"/lib/modules/%1$s/vmlinux-%1$s",
> +		"/usr/lib/modules/%1$s/kernel/vmlinux",
> +	};

the vmlinux finding logic didn't work out of the box for me.
My vmlinux didn't have -`uname -r` suffix.
Probably worth adding /boot/vmlinux-uname too.
May be vmlinuz can have BTF as well?

Overall looks great. Applied to bpf-next. Thanks!