* [PATCH] tools/resolve_btfids: Fix build error with older host toolchains
@ 2021-02-23 1:20 Kun-Chuan Hsieh
2021-02-23 6:31 ` Andrii Nakryiko
2021-02-23 14:42 ` Jiri Olsa
0 siblings, 2 replies; 4+ messages in thread
From: Kun-Chuan Hsieh @ 2021-02-23 1:20 UTC (permalink / raw)
To: ast; +Cc: bpf, jolsa, andrii, Kun-Chuan Hsieh, stable
Older versions of libelf cannot recognize the compressed section.
However, it's only required to fix the compressed section info when
compiling with CONFIG_DEBUG_INFO_COMPRESSED flag is set.
Only compile the compressed_section_fix function when necessary will make
it easier to enable the BTF function. Since the tool resolve_btfids is
compiled with host toolchain. The host toolchain might be older than the
cross compile toolchain.
Cc: stable@vger.kernel.org
Signed-off-by: Kun-Chuan Hsieh <jetswayss@gmail.com>
---
tools/bpf/resolve_btfids/main.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
index 7409d7860aa6..ad40346c6631 100644
--- a/tools/bpf/resolve_btfids/main.c
+++ b/tools/bpf/resolve_btfids/main.c
@@ -260,6 +260,7 @@ static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
return btf_id__add(root, id, false);
}
+#ifdef CONFIG_DEBUG_INFO_COMPRESSED
/*
* The data of compressed section should be aligned to 4
* (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
@@ -292,6 +293,7 @@ static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
}
return 0;
}
+#endif
static int elf_collect(struct object *obj)
{
@@ -370,8 +372,10 @@ static int elf_collect(struct object *obj)
obj->efile.idlist_addr = sh.sh_addr;
}
+#ifdef CONFIG_DEBUG_INFO_COMPRESSED
if (compressed_section_fix(elf, scn, &sh))
return -1;
+#endif
}
return 0;
--
2.25.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] tools/resolve_btfids: Fix build error with older host toolchains
2021-02-23 1:20 [PATCH] tools/resolve_btfids: Fix build error with older host toolchains Kun-Chuan Hsieh
@ 2021-02-23 6:31 ` Andrii Nakryiko
2021-02-23 14:42 ` Jiri Olsa
1 sibling, 0 replies; 4+ messages in thread
From: Andrii Nakryiko @ 2021-02-23 6:31 UTC (permalink / raw)
To: Kun-Chuan Hsieh
Cc: Alexei Starovoitov, bpf, Jiri Olsa, Andrii Nakryiko, linux- stable
On Mon, Feb 22, 2021 at 5:20 PM Kun-Chuan Hsieh <jetswayss@gmail.com> wrote:
>
> Older versions of libelf cannot recognize the compressed section.
> However, it's only required to fix the compressed section info when
> compiling with CONFIG_DEBUG_INFO_COMPRESSED flag is set.
Is it possible to detect (at compilation time or at run time) if
libelf supports compressed ELF sections instead?
>
> Only compile the compressed_section_fix function when necessary will make
> it easier to enable the BTF function. Since the tool resolve_btfids is
> compiled with host toolchain. The host toolchain might be older than the
> cross compile toolchain.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Kun-Chuan Hsieh <jetswayss@gmail.com>
> ---
> tools/bpf/resolve_btfids/main.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> index 7409d7860aa6..ad40346c6631 100644
> --- a/tools/bpf/resolve_btfids/main.c
> +++ b/tools/bpf/resolve_btfids/main.c
> @@ -260,6 +260,7 @@ static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
> return btf_id__add(root, id, false);
> }
>
> +#ifdef CONFIG_DEBUG_INFO_COMPRESSED
> /*
> * The data of compressed section should be aligned to 4
> * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
> @@ -292,6 +293,7 @@ static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
> }
> return 0;
> }
> +#endif
>
> static int elf_collect(struct object *obj)
> {
> @@ -370,8 +372,10 @@ static int elf_collect(struct object *obj)
> obj->efile.idlist_addr = sh.sh_addr;
> }
>
> +#ifdef CONFIG_DEBUG_INFO_COMPRESSED
> if (compressed_section_fix(elf, scn, &sh))
> return -1;
> +#endif
> }
>
> return 0;
> --
> 2.25.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] tools/resolve_btfids: Fix build error with older host toolchains
2021-02-23 1:20 [PATCH] tools/resolve_btfids: Fix build error with older host toolchains Kun-Chuan Hsieh
2021-02-23 6:31 ` Andrii Nakryiko
@ 2021-02-23 14:42 ` Jiri Olsa
[not found] ` <CAAmO479hYwswvNvd4LBMQ7bjhYeDvFohpu9p=FzeUjZ-BY=5GA@mail.gmail.com>
1 sibling, 1 reply; 4+ messages in thread
From: Jiri Olsa @ 2021-02-23 14:42 UTC (permalink / raw)
To: Kun-Chuan Hsieh; +Cc: ast, bpf, jolsa, andrii, stable
On Tue, Feb 23, 2021 at 01:20:01AM +0000, Kun-Chuan Hsieh wrote:
> Older versions of libelf cannot recognize the compressed section.
so it's the SHF_COMPRESSED value the build fails on?
maybe we could do just this:
#ifndef SHF_COMPRESSED
#define SHF_COMPRESSED (1 << 11) /* Section with compressed data. */
#endif
jirka
> However, it's only required to fix the compressed section info when
> compiling with CONFIG_DEBUG_INFO_COMPRESSED flag is set.
>
> Only compile the compressed_section_fix function when necessary will make
> it easier to enable the BTF function. Since the tool resolve_btfids is
> compiled with host toolchain. The host toolchain might be older than the
> cross compile toolchain.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Kun-Chuan Hsieh <jetswayss@gmail.com>
> ---
> tools/bpf/resolve_btfids/main.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> index 7409d7860aa6..ad40346c6631 100644
> --- a/tools/bpf/resolve_btfids/main.c
> +++ b/tools/bpf/resolve_btfids/main.c
> @@ -260,6 +260,7 @@ static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
> return btf_id__add(root, id, false);
> }
>
> +#ifdef CONFIG_DEBUG_INFO_COMPRESSED
> /*
> * The data of compressed section should be aligned to 4
> * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
> @@ -292,6 +293,7 @@ static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
> }
> return 0;
> }
> +#endif
>
> static int elf_collect(struct object *obj)
> {
> @@ -370,8 +372,10 @@ static int elf_collect(struct object *obj)
> obj->efile.idlist_addr = sh.sh_addr;
> }
>
> +#ifdef CONFIG_DEBUG_INFO_COMPRESSED
> if (compressed_section_fix(elf, scn, &sh))
> return -1;
> +#endif
> }
>
> return 0;
> --
> 2.25.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] tools/resolve_btfids: Fix build error with older host toolchains
[not found] ` <CAAmO479hYwswvNvd4LBMQ7bjhYeDvFohpu9p=FzeUjZ-BY=5GA@mail.gmail.com>
@ 2021-02-23 17:26 ` Andrii Nakryiko
0 siblings, 0 replies; 4+ messages in thread
From: Andrii Nakryiko @ 2021-02-23 17:26 UTC (permalink / raw)
To: Kun-Chuan Hsieh
Cc: Jiri Olsa, Alexei Starovoitov, bpf, Jiri Olsa, Andrii Nakryiko, stable
On Tue, Feb 23, 2021 at 8:38 AM Kun-Chuan Hsieh <jetswayss@gmail.com> wrote:
>
> Hi Jiri Olsa,
>
> Yes, exactly. The missing SHF_COMPRESSED value causes build failure.
>
> Compared to conditional compilation, your suggestion seems to be a better
> solution. Thank you for your suggestion. I will submit the patch v2.
>
>
> Hi Andrii Nakryiko,
>
> Yes, it is possible to detect whether libelf supports compressed ELF
> sections at compilation time. I can think of two possible methods.
> 1. Check SHF_COMPRESSED is defined. (If libelf supports compressed ELF
> sections, SHF_COMPRESSED should be defined in libelf.h or elf.h)
> 2. Check the libelf version by _ELFUTILS_PREREQ (from elfutils/version.h)
>
> Best regards,
> Kun-Chuan Hsieh
>
> On Tue, Feb 23, 2021 at 10:43 PM Jiri Olsa <jolsa@redhat.com> wrote:
>>
>> On Tue, Feb 23, 2021 at 01:20:01AM +0000, Kun-Chuan Hsieh wrote:
>> > Older versions of libelf cannot recognize the compressed section.
>>
>> so it's the SHF_COMPRESSED value the build fails on?
>>
>> maybe we could do just this:
>>
>> #ifndef SHF_COMPRESSED
>> #define SHF_COMPRESSED (1 << 11) /* Section with compressed data. */
>> #endif
Yeah, I was hoping it would be something like this. Or we can just
#ifdef two regions of code that rely on SHF_COMPRESSED.
>>
>> jirka
>>
>> > However, it's only required to fix the compressed section info when
>> > compiling with CONFIG_DEBUG_INFO_COMPRESSED flag is set.
>> >
>> > Only compile the compressed_section_fix function when necessary will make
>> > it easier to enable the BTF function. Since the tool resolve_btfids is
>> > compiled with host toolchain. The host toolchain might be older than the
>> > cross compile toolchain.
>> >
>> > Cc: stable@vger.kernel.org
>> > Signed-off-by: Kun-Chuan Hsieh <jetswayss@gmail.com>
>> > ---
>> > tools/bpf/resolve_btfids/main.c | 4 ++++
>> > 1 file changed, 4 insertions(+)
>> >
>> > diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
>> > index 7409d7860aa6..ad40346c6631 100644
>> > --- a/tools/bpf/resolve_btfids/main.c
>> > +++ b/tools/bpf/resolve_btfids/main.c
>> > @@ -260,6 +260,7 @@ static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
>> > return btf_id__add(root, id, false);
>> > }
>> >
>> > +#ifdef CONFIG_DEBUG_INFO_COMPRESSED
>> > /*
>> > * The data of compressed section should be aligned to 4
>> > * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
>> > @@ -292,6 +293,7 @@ static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
>> > }
>> > return 0;
>> > }
>> > +#endif
>> >
>> > static int elf_collect(struct object *obj)
>> > {
>> > @@ -370,8 +372,10 @@ static int elf_collect(struct object *obj)
>> > obj->efile.idlist_addr = sh.sh_addr;
>> > }
>> >
>> > +#ifdef CONFIG_DEBUG_INFO_COMPRESSED
>> > if (compressed_section_fix(elf, scn, &sh))
>> > return -1;
>> > +#endif
>> > }
>> >
>> > return 0;
>> > --
>> > 2.25.1
>> >
>>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-02-23 1:20 [PATCH] tools/resolve_btfids: Fix build error with older host toolchains Kun-Chuan Hsieh
2021-02-23 6:31 ` Andrii Nakryiko
2021-02-23 14:42 ` Jiri Olsa
[not found] ` <CAAmO479hYwswvNvd4LBMQ7bjhYeDvFohpu9p=FzeUjZ-BY=5GA@mail.gmail.com>
2021-02-23 17:26 ` Andrii Nakryiko
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