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SubjectRe: [PATCH] libbpf: Support raw btf placed in the default path
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Hi Nakryiko, thank you for your reply. Yes, i happed to put the raw
BTF made by myself in /boot on kernel4.19, unluckly it reported error.
So is it possible to allow the raw BTF in /boot directly, athough we
can set the specified btf location again to solve the problem with the
bpf_object_open_opts interface. 


As you say, maybe we can remove the locations[i].raw_btf check, just
use the btf__parse. It looks more concise.


在 2022/8/26 上午4:26, Andrii Nakryiko 写道:
> On Wed, Aug 24, 2022 at 7:05 AM chentao.ct
> <chentao.kernel@linux.alibaba.com> wrote:
>>
>> Now only elf btf can be placed in the default path, raw btf should
>> also can be there.
>>
>
> It's not clear what you are trying to achieve. Do you want libbpf to
> attempt to load /boot/vmlinux-%1$s as raw BTF as well (so you can sort
> of sneak in pregenerated BTF), or what exactly?
> btf__load_vmlinux_btf() code already supports loading raw BTF, it just
> needs to be explicitly specified in locations table.
>
> So with your change locations[i].raw_btf check doesn't make sense and
> we need to clean this up.
>
> But first, let's discuss the use case, instead of your specific solution.
>
>
>> Signed-off-by: chentao.ct <chentao.kernel@linux.alibaba.com>
>> ---
>> tools/lib/bpf/btf.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
>> index bb1e06e..b22b5b3 100644
>> --- a/tools/lib/bpf/btf.c
>> +++ b/tools/lib/bpf/btf.c
>> @@ -4661,7 +4661,7 @@ struct btf *btf__load_vmlinux_btf(void)
>> } locations[] = {
>> /* try canonical vmlinux BTF through sysfs first */
>> { "/sys/kernel/btf/vmlinux", true /* raw BTF */ },
>> - /* fall back to trying to find vmlinux ELF on disk otherwise */
>> + /* fall back to trying to find vmlinux RAW/ELF on disk otherwise */
>> { "/boot/vmlinux-%1$s" },
>> { "/lib/modules/%1$s/vmlinux-%1$s" },
>> { "/lib/modules/%1$s/build/vmlinux" },
>> @@ -4686,7 +4686,7 @@ struct btf *btf__load_vmlinux_btf(void)
>> if (locations[i].raw_btf)
>> btf = btf__parse_raw(path);
>> else
>> - btf = btf__parse_elf(path, NULL);
>> + btf = btf__parse(path, NULL);
>> err = libbpf_get_error(btf);
>> pr_debug("loading kernel BTF '%s': %d\n", path, err);
>> if (err)
>> --
>> 2.2.1
>>

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