• Wang Nan's avatar
    perf test: Test the BPF prologue adding infrastructure · bbb7d492
    Wang Nan authored
    This patch introduces a new BPF script to test the BPF prologue adding
    routines. The new script probes at null_lseek, which is the function pointer
    used when we try to lseek on '/dev/null'.
    
    The null_lseek function is chosen because it is used by function pointers, so
    we don't need to consider inlining and LTO.
    
    By extracting file->f_mode, bpf-script-test-prologue.c should know whether the
    file is writable or readonly. According to llseek_loop() and
    bpf-script-test-prologue.c, one fourth of total lseeks should be collected.
    
    Committer note:
    
    Testing it:
    
      # perf test -v BPF
      <SNIP>
      Kernel build dir is set to /lib/modules/4.3.0+/build
      set env: KBUILD_DIR=/lib/modules/4.3.0+/build
      unset env: KBUILD_OPTS
      include option is set to  -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/4.9.2/include -I/home/git/linux/arch/x86/include -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated  -I/home/git/linux/include -Iinclude -I/home/git/linux/arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I/home/git/linux/include/uapi -Iinclude/generated/uapi -include /home/git/linux/include/linux/kconfig.h
      set env: NR_CPUS=4
      set env: LINUX_VERSION_CODE=0x40300
      set env: CLANG_EXEC=/usr/libexec/icecc/bin/clang
      set env: CLANG_OPTIONS=-xc
      set env: KERNEL_INC_OPTIONS= -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/4.9.2/include -I/home/git/linux/arch/x86/include -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated  -I/home/git/linux/include -Iinclude -I/home/git/linux/arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I/home/git/linux/include/uapi -Iinclude/generated/uapi -include /home/git/linux/include/linux/kconfig.h
      set env: WORKING_DIR=/lib/modules/4.3.0+/build
      set env: CLANG_SOURCE=-
      llvm compiling command template: echo '/*
       * bpf-script-test-prologue.c
       * Test BPF prologue
       */
      #ifndef LINUX_VERSION_CODE
      # error Need LINUX_VERSION_CODE
      # error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
      #endif
      #define SEC(NAME) __attribute__((section(NAME), used))
    
      #include <uapi/linux/fs.h>
    
      #define FMODE_READ		0x1
      #define FMODE_WRITE		0x2
    
      static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) =
    	  (void *) 6;
    
      SEC("func=null_lseek file->f_mode offset orig")
      int bpf_func__null_lseek(void *ctx, int err, unsigned long f_mode,
    			   unsigned long offset, unsigned long orig)
      {
    	  if (err)
    		  return 0;
    	  if (f_mode & FMODE_WRITE)
    		  return 0;
    	  if (offset & 1)
    		  return 0;
    	  if (orig == SEEK_CUR)
    		  return 0;
    	  return 1;
      }
    
      char _license[] SEC("license") = "GPL";
      int _version SEC("version") = LINUX_VERSION_CODE;
      ' | $CLANG_EXEC -D__KERNEL__ -D__NR_CPUS__=$NR_CPUS -DLINUX_VERSION_CODE=$LINUX_VERSION_CODE $CLANG_OPTIONS $KERNEL_INC_OPTIONS -Wno-unused-value -Wno-pointer-sign -working-directory $WORKING_DIR -c "$CLANG_SOURCE" -target bpf -O2 -o -
      libbpf: loading object '[bpf_prologue_test]' from buffer
      libbpf: section .strtab, size 135, link 0, flags 0, type=3
      libbpf: section .text, size 0, link 0, flags 6, type=1
      libbpf: section .data, size 0, link 0, flags 3, type=1
      libbpf: section .bss, size 0, link 0, flags 3, type=8
      libbpf: section func=null_lseek file->f_mode offset orig, size 112, link 0, flags 6, type=1
      libbpf: found program func=null_lseek file->f_mode offset orig
      libbpf: section license, size 4, link 0, flags 3, type=1
      libbpf: license of [bpf_prologue_test] is GPL
      libbpf: section version, size 4, link 0, flags 3, type=1
      libbpf: kernel version of [bpf_prologue_test] is 40300
      libbpf: section .symtab, size 168, link 1, flags 0, type=2
      bpf: config program 'func=null_lseek file->f_mode offset orig'
      symbol:null_lseek file:(null) line:0 offset:0 return:0 lazy:(null)
      parsing arg: file->f_mode into file, f_mode(1)
      parsing arg: offset into offset
      parsing arg: orig into orig
      bpf: config 'func=null_lseek file->f_mode offset orig' is ok
      Looking at the vmlinux_path (7 entries long)
      Using /lib/modules/4.3.0+/build/vmlinux for symbols
      Open Debuginfo file: /lib/modules/4.3.0+/build/vmlinux
      Try to find probe point from debuginfo.
      Matched function: null_lseek
      Probe point found: null_lseek+0
      Searching 'file' variable in context.
      Converting variable file into trace event.
      converting f_mode in file
      f_mode type is unsigned int.
      Searching 'offset' variable in context.
      Converting variable offset into trace event.
      offset type is long long int.
      Searching 'orig' variable in context.
      Converting variable orig into trace event.
      orig type is int.
      Found 1 probe_trace_events.
      Opening /sys/kernel/debug/tracing//kprobe_events write=1
      Writing event: p:perf_bpf_probe/func _text+4840528 f_mode=+68(%di):u32 offset=%si:s64 orig=%dx:s32
      libbpf: don't need create maps for [bpf_prologue_test]
      prologue: pass validation
      prologue: slow path
      prologue: fetch arg 0, base reg is %di
      prologue: arg 0: offset 68
      prologue: fetch arg 1, base reg is %si
      prologue: fetch arg 2, base reg is %dx
      add bpf event perf_bpf_probe:func and attach bpf program 3
      adding perf_bpf_probe:func
      adding perf_bpf_probe:func to 0x51672c0
      mmap size 1052672B
      Opening /sys/kernel/debug/tracing//kprobe_events write=1
      Opening /sys/kernel/debug/tracing//uprobe_events write=1
      Parsing probe_events: p:perf_bpf_probe/func _text+4840528 f_mode=+68(%di):u32 offset=%si:s64 orig=%dx:s32
      Group:perf_bpf_probe Event:func probe:p
      Writing event: -:perf_bpf_probe/func
      test child finished with 0
      ---- end ----
      Test BPF filter: Ok
      #
    Signed-off-by: default avatarWang Nan <wangnan0@huawei.com>
    Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Alexei Starovoitov <ast@kernel.org>
    Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Cc: Zefan Li <lizefan@huawei.com>
    Cc: pi3orama@163.com
    Link: http://lkml.kernel.org/r/1447675815-166222-13-git-send-email-wangnan0@huawei.com
    [ Added tools/perf/tests/llvm-src-prologue.c to .gitignore ]
    Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    bbb7d492
llvm.h 535 Bytes