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Subject[PATCH v2 4/4] perf augmented_raw_syscalls: Document clang configuration
Date
To build this program successfully with clang, there have three
compiler options need to be specified:

- Header file path: tools/perf/include/bpf;
- Specify architecture;
- Define macro __NR_CPUS__.

This patch add comments to explain the reasons for building failure and
give two examples for llvm.clang-opt variable, one is for x86_64
architecture and another is for aarch64 architecture.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
.../examples/bpf/augmented_raw_syscalls.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/tools/perf/examples/bpf/augmented_raw_syscalls.c b/tools/perf/examples/bpf/augmented_raw_syscalls.c
index a3701a4daf2e..fb6987edab2c 100644
--- a/tools/perf/examples/bpf/augmented_raw_syscalls.c
+++ b/tools/perf/examples/bpf/augmented_raw_syscalls.c
@@ -6,6 +6,25 @@
*
* perf trace -e tools/perf/examples/bpf/augmented_raw_syscalls.c cat /etc/passwd > /dev/null
*
+ * This program include two header files 'unistd.h' and 'pid_filter.h', which
+ * are placed in the folder tools/perf/include/bpf, but this folder is not
+ * included in env $KERNEL_INC_OPTIONS and it leads to compilation failure.
+ * For building this code, we also need to specify architecture and define macro
+ * __NR_CPUS__. To resolve these issues, variable llvm.clang-opt can be set in
+ * the file ~/.perfconfig:
+ *
+ * E.g. Test on a platform with 8 CPUs with x86_64 architecture:
+ *
+ * [llvm]
+ * clang-opt = "-D__NR_CPUS__=8 -D__x86_64__ \
+ * -I./tools/perf/include/bpf"
+ *
+ * E.g. Test on a platform with 5 CPUs with aarch64 architecture:
+ *
+ * [llvm]
+ * clang-opt = "-D__NR_CPUS__=5 -D__aarch64__ \
+ * -I./tools/perf/include/bpf"
+
* This exactly matches what is marshalled into the raw_syscall:sys_enter
* payload expected by the 'perf trace' beautifiers.
*
--
2.17.1
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