2021-08-27 07:33:31

by Michal Suchánek

Subject: [PATCH] libbpf: Fix build with latest gcc/binutils with LTO

From: Patrick McCarty <[email protected]>

After updating to binutils 2.35, the build began to fail with an
assembler error. A bug was opened on the Red Hat Bugzilla a few days
later for the same issue.

Work around the problem by using the new `symver` attribute (introduced
in GCC 10) as needed, instead of the `COMPAT_VERSION` and
`DEFAULT_VERSION` macros, which expand to assembler directives.

Fixes: https://github.com/libbpf/libbpf/issues/338
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1863059
Fixes: https://bugzilla.opensuse.org/show_bug.cgi?id=1188749
Signed-off-by: Patrick McCarty <[email protected]>
Make the change conditional on GCC version
Signed-off-by: Michal Suchanek <[email protected]>
---
tools/lib/bpf/libbpf_internal.h | 23 +++++++++++++++++------
tools/lib/bpf/xsk.c | 4 ++--
2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 016ca7cb4f8a..af0f3fb102c0 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -86,20 +86,31 @@
(offsetof(TYPE, FIELD) + sizeof(((TYPE *)0)->FIELD))
#endif

+#ifdef __GNUC__
+# if __GNUC__ >= 10
+# define DEFAULT_VERSION(internal_name, api_name, version) \
+__attribute__((__symver__(#api_name "@@" #version)))
+# define COMPAT_VERSION(internal_name, api_name, version) \
+__attribute__((__symver__(#api_name "@" #version)))
+# endif
+#endif
+
+#if !defined(COMPAT_VERSION) || !defined(DEFAULT_VERSION)
/* Symbol versioning is different between static and shared library.
* Properly versioned symbols are needed for shared library, but
* only the symbol of the new version is needed for static library.
*/
-#ifdef SHARED
-# define COMPAT_VERSION(internal_name, api_name, version) \
+# ifdef SHARED
+# define COMPAT_VERSION(internal_name, api_name, version) \
asm(".symver " #internal_name "," #api_name "@" #version);
-# define DEFAULT_VERSION(internal_name, api_name, version) \
+# define DEFAULT_VERSION(internal_name, api_name, version) \
asm(".symver " #internal_name "," #api_name "@@" #version);
-#else
-# define COMPAT_VERSION(internal_name, api_name, version)
-# define DEFAULT_VERSION(internal_name, api_name, version) \
+# else
+# define COMPAT_VERSION(internal_name, api_name, version)
+# define DEFAULT_VERSION(internal_name, api_name, version) \
extern typeof(internal_name) api_name \
__attribute__((alias(#internal_name)));
+# endif
#endif

extern void libbpf_print(enum libbpf_print_level level,
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index e9b619aa0cdf..a2111696ba91 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -281,6 +281,7 @@ static int xsk_create_umem_rings(struct xsk_umem *umem, int fd,
return err;
}

+DEFAULT_VERSION(xsk_umem__create_v0_0_4, xsk_umem__create, LIBBPF_0.0.4)
int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
__u64 size, struct xsk_ring_prod *fill,
struct xsk_ring_cons *comp,
@@ -345,6 +346,7 @@ struct xsk_umem_config_v1 {
__u32 frame_headroom;
};

+COMPAT_VERSION(xsk_umem__create_v0_0_2, xsk_umem__create, LIBBPF_0.0.2)
int xsk_umem__create_v0_0_2(struct xsk_umem **umem_ptr, void *umem_area,
__u64 size, struct xsk_ring_prod *fill,
struct xsk_ring_cons *comp,
@@ -358,8 +360,6 @@ int xsk_umem__create_v0_0_2(struct xsk_umem **umem_ptr, void *umem_area,
return xsk_umem__create_v0_0_4(umem_ptr, umem_area, size, fill, comp,
&config);
}
-COMPAT_VERSION(xsk_umem__create_v0_0_2, xsk_umem__create, LIBBPF_0.0.2)
-DEFAULT_VERSION(xsk_umem__create_v0_0_4, xsk_umem__create, LIBBPF_0.0.4)

static enum xsk_prog get_xsk_prog(void)
{
--
2.31.1

2021-08-27 10:37:16

by Michal Suchánek

Subject: Re: [PATCH] libbpf: Fix build with latest gcc/binutils with LTO

Hello,

this is a duplicate of

https://patchwork.kernel.org/project/netdevbpf/patch/[email protected]/

Sorry aboit the noise.

On Fri, Aug 27, 2021 at 09:28:55AM +0200, Michal Suchanek wrote:
> From: Patrick McCarty <[email protected]>
>
> After updating to binutils 2.35, the build began to fail with an
> assembler error. A bug was opened on the Red Hat Bugzilla a few days
> later for the same issue.
>
> Work around the problem by using the new `symver` attribute (introduced
> in GCC 10) as needed, instead of the `COMPAT_VERSION` and
> `DEFAULT_VERSION` macros, which expand to assembler directives.
>
> Fixes: https://github.com/libbpf/libbpf/issues/338
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1863059
> Fixes: https://bugzilla.opensuse.org/show_bug.cgi?id=1188749
> Signed-off-by: Patrick McCarty <[email protected]>
> Make the change conditional on GCC version
> Signed-off-by: Michal Suchanek <[email protected]>
> ---
> tools/lib/bpf/libbpf_internal.h | 23 +++++++++++++++++------
> tools/lib/bpf/xsk.c | 4 ++--
> 2 files changed, 19 insertions(+), 8 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
> index 016ca7cb4f8a..af0f3fb102c0 100644
> --- a/tools/lib/bpf/libbpf_internal.h
> +++ b/tools/lib/bpf/libbpf_internal.h
> @@ -86,20 +86,31 @@
> (offsetof(TYPE, FIELD) + sizeof(((TYPE *)0)->FIELD))
> #endif
>
> +#ifdef __GNUC__
> +# if __GNUC__ >= 10
> +# define DEFAULT_VERSION(internal_name, api_name, version) \
> +__attribute__((__symver__(#api_name "@@" #version)))
> +# define COMPAT_VERSION(internal_name, api_name, version) \
> +__attribute__((__symver__(#api_name "@" #version)))
> +# endif
> +#endif
> +
> +#if !defined(COMPAT_VERSION) || !defined(DEFAULT_VERSION)
> /* Symbol versioning is different between static and shared library.
> * Properly versioned symbols are needed for shared library, but
> * only the symbol of the new version is needed for static library.
> */
> -#ifdef SHARED
> -# define COMPAT_VERSION(internal_name, api_name, version) \
> +# ifdef SHARED
> +# define COMPAT_VERSION(internal_name, api_name, version) \
> asm(".symver " #internal_name "," #api_name "@" #version);
> -# define DEFAULT_VERSION(internal_name, api_name, version) \
> +# define DEFAULT_VERSION(internal_name, api_name, version) \
> asm(".symver " #internal_name "," #api_name "@@" #version);
> -#else
> -# define COMPAT_VERSION(internal_name, api_name, version)
> -# define DEFAULT_VERSION(internal_name, api_name, version) \
> +# else
> +# define COMPAT_VERSION(internal_name, api_name, version)
> +# define DEFAULT_VERSION(internal_name, api_name, version) \
> extern typeof(internal_name) api_name \
> __attribute__((alias(#internal_name)));
> +# endif
> #endif
>
> extern void libbpf_print(enum libbpf_print_level level,
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index e9b619aa0cdf..a2111696ba91 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -281,6 +281,7 @@ static int xsk_create_umem_rings(struct xsk_umem *umem, int fd,
> return err;
> }
>
> +DEFAULT_VERSION(xsk_umem__create_v0_0_4, xsk_umem__create, LIBBPF_0.0.4)
> int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
> __u64 size, struct xsk_ring_prod *fill,
> struct xsk_ring_cons *comp,
> @@ -345,6 +346,7 @@ struct xsk_umem_config_v1 {
> __u32 frame_headroom;
> };
>
> +COMPAT_VERSION(xsk_umem__create_v0_0_2, xsk_umem__create, LIBBPF_0.0.2)
> int xsk_umem__create_v0_0_2(struct xsk_umem **umem_ptr, void *umem_area,
> __u64 size, struct xsk_ring_prod *fill,
> struct xsk_ring_cons *comp,
> @@ -358,8 +360,6 @@ int xsk_umem__create_v0_0_2(struct xsk_umem **umem_ptr, void *umem_area,
> return xsk_umem__create_v0_0_4(umem_ptr, umem_area, size, fill, comp,
> &config);
> }
> -COMPAT_VERSION(xsk_umem__create_v0_0_2, xsk_umem__create, LIBBPF_0.0.2)
> -DEFAULT_VERSION(xsk_umem__create_v0_0_4, xsk_umem__create, LIBBPF_0.0.4)
>
> static enum xsk_prog get_xsk_prog(void)
> {
> --
> 2.31.1
>