[ +Johan ]
On 11/25/21 2:36 AM, Tiezhu Yang wrote:
Add the __NR_bpf definitions to fix the following build errors for mips.
$ cd tools/bpf/bpftool
$ make
[...]
bpf.c:54:4: error: #error __NR_bpf not defined. libbpf does not support your arch.
# error __NR_bpf not defined. libbpf does not support your arch.
^~~~~
bpf.c: In function ‘sys_bpf’:
bpf.c:66:17: error: ‘__NR_bpf’ undeclared (first use in this function); did you mean ‘__NR_brk’?
return syscall(__NR_bpf, cmd, attr, size);
^~~~~~~~
__NR_brk
[...]
In file included from gen_loader.c:15:0:
skel_internal.h: In function ‘skel_sys_bpf’:
skel_internal.h:53:17: error: ‘__NR_bpf’ undeclared (first use in this function); did you mean ‘__NR_brk’?
return syscall(__NR_bpf, cmd, attr, size);
^~~~~~~~
__NR_brk
We can see the following generated definitions:
$ grep -r "#define __NR_bpf" arch/mips
arch/mips/include/generated/uapi/asm/unistd_o32.h:#define __NR_bpf (__NR_Linux + 355)
arch/mips/include/generated/uapi/asm/unistd_n64.h:#define __NR_bpf (__NR_Linux + 315)
arch/mips/include/generated/uapi/asm/unistd_n32.h:#define __NR_bpf (__NR_Linux + 319)
The __NR_Linux is defined in arch/mips/include/uapi/asm/unistd.h:
$ grep -r "#define __NR_Linux" arch/mips
arch/mips/include/uapi/asm/unistd.h:#define __NR_Linux 4000
arch/mips/include/uapi/asm/unistd.h:#define __NR_Linux 5000
arch/mips/include/uapi/asm/unistd.h:#define __NR_Linux 6000
That is to say, __NR_bpf is
4000 + 355 = 4355 for mips o32,
6000 + 319 = 6319 for mips n32,
5000 + 315 = 5315 for mips n64.
So use the GCC pre-defined macro _ABIO32, _ABIN32 and _ABI64 [1] to define
the corresponding __NR_bpf.
This patch is similar with commit bad1926dd2f6 ("bpf, s390: fix build for
libbpf and selftest suite").
[1] https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/mips/mips.h#l549
Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
v2: use a final number without __NR_Linux to define __NR_bpf
suggested by Andrii Nakryiko, thank you.
tools/build/feature/test-bpf.c | 6 ++++++
tools/lib/bpf/bpf.c | 6 ++++++
tools/lib/bpf/skel_internal.h | 10 ++++++++++
3 files changed, 22 insertions(+)
diff --git a/tools/build/feature/test-bpf.c b/tools/build/feature/test-bpf.c
index 82070ea..727d22e 100644
--- a/tools/build/feature/test-bpf.c
+++ b/tools/build/feature/test-bpf.c
@@ -14,6 +14,12 @@
# define __NR_bpf 349
# elif defined(__s390__)
# define __NR_bpf 351
+# elif defined(__mips__) && defined(_ABIO32)
+# define __NR_bpf 4355
+# elif defined(__mips__) && defined(_ABIN32)
+# define __NR_bpf 6319
+# elif defined(__mips__) && defined(_ABI64)
+# define __NR_bpf 5315
# else
# error __NR_bpf not defined. libbpf does not support your arch.
# endif
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 94560ba..17f9fe2 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -50,6 +50,12 @@
# define __NR_bpf 351
# elif defined(__arc__)
# define __NR_bpf 280
+# elif defined(__mips__) && defined(_ABIO32)
+# define __NR_bpf 4355
+# elif defined(__mips__) && defined(_ABIN32)
+# define __NR_bpf 6319
+# elif defined(__mips__) && defined(_ABI64)
+# define __NR_bpf 5315
# else
# error __NR_bpf not defined. libbpf does not support your arch.
# endif
diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
index 9cf6670..064da66 100644
--- a/tools/lib/bpf/skel_internal.h
+++ b/tools/lib/bpf/skel_internal.h
@@ -7,6 +7,16 @@
#include <sys/syscall.h>
#include <sys/mman.h>
+#ifndef __NR_bpf
+# if defined(__mips__) && defined(_ABIO32)
+# define __NR_bpf 4355
+# elif defined(__mips__) && defined(_ABIN32)
+# define __NR_bpf 6319
+# elif defined(__mips__) && defined(_ABI64)
+# define __NR_bpf 5315
+# endif
+#endif
Bit unfortunate that mips is the only arch where we run into this apparently? :/
Given we also redefine a skel_sys_bpf(), maybe libbpf should just provide something
like a `LIBBPF_API int libbpf_sys_bpf(enum bpf_cmd cmd, [...])` so we rely implicitly
only on the libbpf-internal __NR_bpf instead of duplicating again?
/* This file is a base header for auto-generated *.lskel.h files.
* Its contents will change and may become part of auto-generation in the future.
*
