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[PATCH RFC 0/5] add arm64 cross compilation support to BPF samples

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  [PATCH RFC 0/5] add arm64 cross compilation support to BPF samples Joel Fernandes <joelaf@google.com> - 2017-08-07 15:10 +0200
    [PATCH RFC 1/5] samples/bpf: Use getppid instead of getpgrp for array map stress Joel Fernandes <joelaf@google.com> - 2017-08-07 15:10 +0200
    [PATCH RFC 2/5] samples/bpf: Enable cross compiler support Joel Fernandes <joelaf@google.com> - 2017-08-07 15:10 +0200

#1705483 — [PATCH RFC 0/5] add arm64 cross compilation support to BPF samples

The series adds cross compiler support for BPF samples and fixes issues
building for arm64.

Tested on my arm64 platform with good results, for x86 I have only build tested
it. There are no errors on building, however there is a build warning for x86
which I haven't yet gotten rid off (I believe the warning itself isn't of
consequence but rather a result of using the preprocessor in this way). I
appreciate any help testing for x86 and looking forward to any feedback on the
patches, thanks!

Joel Fernandes (5):
  samples/bpf: Use getppid instead of getpgrp for array map stress
  samples/bpf: Enable cross compiler support
  samples/bpf: Fix inline asm issues building samples on arm64
  samples/bpf: Fix pt_regs issues when cross-compiling
  samples/bpf: Add documentation on cross compilation

 samples/bpf/Makefile             | 46 +++++++++++++++++++++++++-----
 samples/bpf/README.rst           | 10 +++++++
 samples/bpf/arm64_asmstubs.h     |  3 ++
 samples/bpf/bpf_helpers.h        | 61 ++++++++++++++++++++++++++++++++--------
 samples/bpf/generic_asmstubs.h   |  4 +++
 samples/bpf/map_perf_test_kern.c |  2 +-
 samples/bpf/map_perf_test_user.c |  2 +-
 7 files changed, 107 insertions(+), 21 deletions(-)
 create mode 100644 samples/bpf/arm64_asmstubs.h
 create mode 100644 samples/bpf/generic_asmstubs.h

CC: Alexei Starovoitov <ast@kernel.org>
CC: Daniel Borkmann <daniel@iogearbox.net>

-- 
2.14.0.rc1.383.gd1ce394fe2-goog

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#1705495 — [PATCH RFC 1/5] samples/bpf: Use getppid instead of getpgrp for array map stress

When cross-compiling the bpf sample map_perf_test for aarch64, I find that
__NR_getpgrp is undefined. This causes build errors. This syscall is deprecated
and requires defining __ARCH_WANT_SYSCALL_DEPRECATED. To avoid having to define
that, just use a different syscall (getppid) for the array map stress test.

Signed-off-by: Joel Fernandes <joelaf@google.com>
---
 samples/bpf/map_perf_test_kern.c | 2 +-
 samples/bpf/map_perf_test_user.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/samples/bpf/map_perf_test_kern.c b/samples/bpf/map_perf_test_kern.c
index 245165817fbe..038ffec295cf 100644
--- a/samples/bpf/map_perf_test_kern.c
+++ b/samples/bpf/map_perf_test_kern.c
@@ -232,7 +232,7 @@ int stress_hash_map_lookup(struct pt_regs *ctx)
 	return 0;
 }
 
-SEC("kprobe/sys_getpgrp")
+SEC("kprobe/sys_getppid")
 int stress_array_map_lookup(struct pt_regs *ctx)
 {
 	u32 key = 1, i;
diff --git a/samples/bpf/map_perf_test_user.c b/samples/bpf/map_perf_test_user.c
index 1a8894b5ac51..1e9e68942197 100644
--- a/samples/bpf/map_perf_test_user.c
+++ b/samples/bpf/map_perf_test_user.c
@@ -232,7 +232,7 @@ static void test_array_lookup(int cpu)
 
 	start_time = time_get_ns();
 	for (i = 0; i < max_cnt; i++)
-		syscall(__NR_getpgrp, 0);
+		syscall(__NR_getppid, 0);
 	printf("%d:array_lookup %lld lookups per sec\n",
 	       cpu, max_cnt * 1000000000ll * 64 / (time_get_ns() - start_time));
 }
-- 
2.14.0.rc1.383.gd1ce394fe2-goog

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#1705498 — [PATCH RFC 2/5] samples/bpf: Enable cross compiler support

When cross compiling, bpf samples use HOSTCC, however what we really want is to
use the cross compiler to build for the cross target since that is what will
help run the BPF target code.  Detect this and also set -static as LDFLAGS
since often times we don't have control over what C library the cross target is
running and its not smart to rely on it.

Signed-off-by: Joel Fernandes <joelaf@google.com>
---
 samples/bpf/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 6c7468eb3684..e5642c8c144d 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -152,6 +152,12 @@ HOSTLOADLIBES_test_map_in_map += -lelf
 LLC ?= llc
 CLANG ?= clang
 
+# Detect that we're cross compiling and use the right compilers and flags
+ifdef CROSS_COMPILE
+HOSTCC = $(CROSS_COMPILE)gcc
+HOSTLDFLAGS += -static
+endif
+
 # Trick to allow make to be run from this directory
 all:
 	$(MAKE) -C ../../ $(CURDIR)/
-- 
2.14.0.rc1.383.gd1ce394fe2-goog

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