2022-08-24 14:38:52

by Tao Chen

[permalink] [raw]
Subject: [PATCH] libbpf: Support raw btf placed in the default path

Now only elf btf can be placed in the default path, raw btf should
also can be there.

Signed-off-by: chentao.ct <[email protected]>
---
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


2022-08-25 20:42:34

by Andrii Nakryiko

[permalink] [raw]
Subject: Re: [PATCH] libbpf: Support raw btf placed in the default path

On Wed, Aug 24, 2022 at 7:05 AM chentao.ct
<[email protected]> 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 <[email protected]>
> ---
> 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
>

2022-08-29 06:25:58

by Tao Chen

[permalink] [raw]
Subject: Re: [PATCH] libbpf: Support raw btf placed in the default path

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
> <[email protected]> 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$s as raw BTF as well (so you can sort
> of sneak in pregenerated BTF), or what exactly?
> btf__load_vmlinux_btf() code already supports loading raw BTF, it just
> needs to be explicitly specified in locations table.
>
> So with your change locations[i].raw_btf check doesn't make sense and
> we need to clean this up.
>
> But first, let's discuss the use case, instead of your specific solution.
>
>
>> Signed-off-by: chentao.ct <[email protected]>
>> ---
>> tools/lib/bpf/btf.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
>> index bb1e06e..b22b5b3 100644
>> --- a/tools/lib/bpf/btf.c
>> +++ b/tools/lib/bpf/btf.c
>> @@ -4661,7 +4661,7 @@ struct btf *btf__load_vmlinux_btf(void)
>> } locations[] = {
>> /* try canonical vmlinux BTF through sysfs first */
>> { "/sys/kernel/btf/vmlinux", true /* raw BTF */ },
>> - /* fall back to trying to find vmlinux ELF on disk otherwise */
>> + /* fall back to trying to find vmlinux RAW/ELF on disk otherwise */
>> { "/boot/vmlinux-%1$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
>>

2022-09-09 19:15:00

by Andrii Nakryiko

[permalink] [raw]
Subject: Re: [PATCH] libbpf: Support raw btf placed in the default path

On Sun, Aug 28, 2022 at 10:36 PM Tao Chen
<[email protected]> wrote:
>
> 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.

Please don't top post, reply inline (that's kernel mail lists rules).

But yes, I think we can just use btf__parse and let libbpf figure out.
Please send a patch.

>
> 在 2022/8/26 上午4:26, Andrii Nakryiko 写道:
>
> On Wed, Aug 24, 2022 at 7:05 AM chentao.ct
> <[email protected]> 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$s as raw BTF as well (so you can sort
> of sneak in pregenerated BTF), or what exactly?
> btf__load_vmlinux_btf() code already supports loading raw BTF, it just
> needs to be explicitly specified in locations table.
>
> So with your change locations[i].raw_btf check doesn't make sense and
> we need to clean this up.
>
> But first, let's discuss the use case, instead of your specific solution.
>
>
> Signed-off-by: chentao.ct <[email protected]>
> ---
> tools/lib/bpf/btf.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index bb1e06e..b22b5b3 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -4661,7 +4661,7 @@ struct btf *btf__load_vmlinux_btf(void)
> } locations[] = {
> /* try canonical vmlinux BTF through sysfs first */
> { "/sys/kernel/btf/vmlinux", true /* raw BTF */ },
> - /* fall back to trying to find vmlinux ELF on disk otherwise */
> + /* fall back to trying to find vmlinux RAW/ELF on disk otherwise */
> { "/boot/vmlinux-%1$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
>

2022-09-12 16:18:39

by Tao Chen

[permalink] [raw]
Subject: Re: [PATCH] libbpf: Support raw btf placed in the default path

在 2022/9/10 上午3:00, Andrii Nakryiko 写道:
> On Sun, Aug 28, 2022 at 10:36 PM Tao Chen
> <[email protected]> wrote:
>>
>> 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.
>
> Please don't top post, reply inline (that's kernel mail lists rules).
>
> But yes, I think we can just use btf__parse and let libbpf figure out.
> Please send a patch.
>

Thank you, i will send the patch in v2.
>>
>> 在 2022/8/26 上午4:26, Andrii Nakryiko 写道:
>>
>> On Wed, Aug 24, 2022 at 7:05 AM chentao.ct
>> <[email protected]> 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$s as raw BTF as well (so you can sort
>> of sneak in pregenerated BTF), or what exactly?
>> btf__load_vmlinux_btf() code already supports loading raw BTF, it just
>> needs to be explicitly specified in locations table.
>>
>> So with your change locations[i].raw_btf check doesn't make sense and
>> we need to clean this up.
>>
>> But first, let's discuss the use case, instead of your specific solution.
>>
>>
>> Signed-off-by: chentao.ct <[email protected]>
>> ---
>> tools/lib/bpf/btf.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
>> index bb1e06e..b22b5b3 100644
>> --- a/tools/lib/bpf/btf.c
>> +++ b/tools/lib/bpf/btf.c
>> @@ -4661,7 +4661,7 @@ struct btf *btf__load_vmlinux_btf(void)
>> } locations[] = {
>> /* try canonical vmlinux BTF through sysfs first */
>> { "/sys/kernel/btf/vmlinux", true /* raw BTF */ },
>> - /* fall back to trying to find vmlinux ELF on disk otherwise */
>> + /* fall back to trying to find vmlinux RAW/ELF on disk otherwise */
>> { "/boot/vmlinux-%1$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
>>