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Groups > linux.kernel > #1530628 > unrolled thread

[PATCH v3 00/30] perf clang: Builtin clang and perfhook support

Started byWang Nan <wangnan0@huawei.com>
First post2016-11-26 08:20 +0100
Last post2016-12-02 11:40 +0100
Articles 10 — 3 participants

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Contents

  [PATCH v3 00/30] perf clang: Builtin clang and perfhook support Wang Nan <wangnan0@huawei.com> - 2016-11-26 08:20 +0100
    [PATCH v3 08/30] tools build: Add feature detection for clang Wang Nan <wangnan0@huawei.com> - 2016-11-26 08:20 +0100
      [tip:perf/core] tools build: Add feature detection for clang tip-bot for Wang Nan <tipbot@zytor.com> - 2016-12-06 09:30 +0100
    [PATCH v3 11/30] perf clang: Use real file system for #include Wang Nan <wangnan0@huawei.com> - 2016-11-26 08:20 +0100
      [tip:perf/core] perf clang: Use real file system for #include tip-bot for Wang Nan <tipbot@zytor.com> - 2016-12-06 09:30 +0100
    [PATCH v3 15/30] perf clang: Compile BPF script use builtin clang support Wang Nan <wangnan0@huawei.com> - 2016-11-26 08:20 +0100
      [tip:perf/core] perf clang: Compile BPF script using builtin clang  support tip-bot for Wang Nan <tipbot@zytor.com> - 2016-12-06 09:50 +0100
    [PATCH v3 03/30] tools lib bpf: Retrive bpf_map through offset of bpf_map_def Wang Nan <wangnan0@huawei.com> - 2016-11-26 08:20 +0100
      Re: [PATCH v3 03/30] tools lib bpf: Retrive bpf_map through offset  of bpf_map_def Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2016-11-26 18:20 +0100
      [tip:perf/core] tools lib bpf: Retrive bpf_map through offset of  bpf_map_def tip-bot for Wang Nan <tipbot@zytor.com> - 2016-12-02 11:40 +0100

#1530628 — [PATCH v3 00/30] perf clang: Builtin clang and perfhook support

FromWang Nan <wangnan0@huawei.com>
Date2016-11-26 08:20 +0100
Subject[PATCH v3 00/30] perf clang: Builtin clang and perfhook support
Message-ID<sHFhv-3nx-5@gated-at.bofh.it>
This is version 3 of perf builtin clang and perfhook patch series.
Compare to v2 there is only minor changes:
 1. BPF map helpers in perf hooks now called 'perf_map_...',
    instead of 'jit_helper_map_...'.
    (Alexei Starovoitov)
 2. Rename bpf_map_{pin,get} to bpf_obj_{pin,get}, make them consist
    with kernel.
    (Joe Stringer).

Example in v2 should be changed accordingly:

  $ cat ./count_syscalls.c
  typedef unsigned long u64;
  
  #define BPF_MAP_TYPE_HASH 1
  #define BPF_MAP_TYPE_ARRAY 2
  
  enum GVAL {
      G_perf_pid,
      NR_GVALS
  };
  
  struct bpf_map_def SEC("maps") GVALS = {
      .type = BPF_MAP_TYPE_ARRAY,
      .key_size = sizeof(int),
      .value_size = sizeof(u64),
      .max_entries = NR_GVALS,
  };
  
  struct bpf_map_def SEC("maps") syscall_counter = {
      .type = BPF_MAP_TYPE_HASH,
      .key_size = sizeof(u64),
      .value_size = sizeof(u64),
      .max_entries = 512,
  };
  
  SEC("raw_syscalls:sys_enter")
  int func(void *ctx)
  {
      int key = G_perf_pid;
      u64 id = *((u64 *)(ctx + 8));
      int self_pid = bpf_get_current_pid_tgid() & 0xffffffff;
      int *perf_pid = bpf_map_lookup_elem(&GVALS, &key);
      u64 *counter;
  
      if (!perf_pid)
          return 0;
      if (*perf_pid == self_pid)
          return 0;
      counter = bpf_map_lookup_elem(&syscall_counter, &id);
      if (!counter) {
          u64 value = 1;
          bpf_map_update_elem(&syscall_counter, &id, &value, 0);
          return 0;
      }
      __sync_fetch_and_add(counter, 1);
      return 0;
  }
  
  SEC("perfhook:record_start")
  void record_start(void *ctx)
  {
      int perf_pid = getpid(), key = G_perf_pid;
      printf("Start count, perfpid=%d\n", perf_pid);
      perf_map_update_elem(ctx, &GVALS, &key, &perf_pid, 0);
  }
  
  SEC("perfhook:record_end")
  void record_end(void *ctx)
  {
      u64 key = -1, value;
      while (!perf_map_get_next_key(ctx, &syscall_counter, &key, &key)) {
          perf_map_lookup_elem(ctx, &syscall_counter, &key, &value);
          printf("syscall %ld\tcount: %ld\n", (long)key, (long)value);
      }
  }
  char _license[] SEC("license") = "GPL";
  int _version SEC("version") = LINUX_VERSION_CODE;
  $ sudo -s
  # ulimit -l unlimited
  # perf record -e ./count_syscalls.c echo "Haha"
  Start count, perfpid=25209
  Haha
  [ perf record: Woken up 1 times to write data ]
  syscall 293	count: 2
  syscall 8	count: 7
  syscall 11	count: 763
  syscall 4	count: 43
  syscall 21	count: 48
  syscall 86	count: 1
  syscall 5	count: 791
  ...

Wang Nan (30):
  tools lib bpf: Add missing BPF functions
  tools lib bpf: Add private field for bpf_object
  tools lib bpf: Retrive bpf_map through offset of bpf_map_def
  perf tools: Introduce perf hooks
  perf tools: Pass context to perf hook functions
  perf llvm: Extract helpers in llvm-utils.c
  tools build: Add feature detection for LLVM
  tools build: Add feature detection for clang
  perf build: Add clang and llvm compile and linking support
  perf clang: Add builtin clang support ant test case
  perf clang: Use real file system for #include
  perf clang: Allow passing CFLAGS to builtin clang
  perf clang: Update test case to use real BPF script
  perf clang: Support compile IR to BPF object and add testcase
  perf clang: Compile BPF script use builtin clang support
  perf clang: Pass full path to builtin clang
  perf clang: Pass CFLAGS to builtin clang
  perf clang jit: Wrap llvm::Module using PerfModule
  perf clang jit: Insignt BPF and JIT functions in a Module
  perf clang jit: add PerfModule::doJIT to JIT perfhook functions
  perf clang jit: Export functions for jitted code
  perf clang jit: Actually JIT and hook in bpf loader
  perf clang jit: Collect the lowest address in maps section as map_base
  perf clang jit: Retrive fd of BPF map from its offset
  perf clang jit: Allow jitted perf hook access BPF maps
  perf clang: Link BPF functions declaration into perf
  perf clang: Declare BPF functions for BPF scripts automatically
  perf clang: Include helpers to BPF scripts
  perf clang builtin: Define hook helpers by default
  perf clang jit: Export getpid() to perf hook

 tools/build/feature/Makefile                  |  18 +
 tools/build/feature/test-clang.cpp            |  21 ++
 tools/build/feature/test-llvm.cpp             |   8 +
 tools/lib/bpf/bpf.c                           |  56 +++
 tools/lib/bpf/bpf.h                           |   7 +
 tools/lib/bpf/libbpf.c                        |  35 ++
 tools/lib/bpf/libbpf.h                        |  13 +
 tools/perf/Makefile.config                    |  62 +++-
 tools/perf/Makefile.perf                      |  23 +-
 tools/perf/builtin-record.c                   |  11 +
 tools/perf/tests/Build                        |   4 +-
 tools/perf/tests/bpf-script-example.c         |  30 +-
 tools/perf/tests/bpf-script-test-kbuild.c     |   2 +
 tools/perf/tests/bpf-script-test-prologue.c   |   6 +-
 tools/perf/tests/bpf-script-test-relocation.c |  17 +-
 tools/perf/tests/builtin-test.c               |  13 +
 tools/perf/tests/clang.c                      |  50 +++
 tools/perf/tests/llvm.h                       |   7 +
 tools/perf/tests/make                         |   2 +
 tools/perf/tests/perf-hooks.c                 |  48 +++
 tools/perf/tests/tests.h                      |   4 +
 tools/perf/util/Build                         |   5 +
 tools/perf/util/bpf-loader.c                  | 102 +++++-
 tools/perf/util/bpf-loader.h                  |  19 +
 tools/perf/util/c++/Build                     |   4 +
 tools/perf/util/c++/bpf-funcs-str.c           | 228 ++++++++++++
 tools/perf/util/c++/bpf-helper-str.c          |  23 ++
 tools/perf/util/c++/clang-bpf-includes.h      |  13 +
 tools/perf/util/c++/clang-c.h                 |  63 ++++
 tools/perf/util/c++/clang-test.cpp            |  99 +++++
 tools/perf/util/c++/clang.cpp                 | 497 ++++++++++++++++++++++++++
 tools/perf/util/c++/clang.h                   |  61 ++++
 tools/perf/util/jit-helpers.c                 |  57 +++
 tools/perf/util/jit-helpers.h                 |  28 ++
 tools/perf/util/llvm-utils.c                  |  76 +++-
 tools/perf/util/llvm-utils.h                  |  15 +-
 tools/perf/util/perf-hooks-list.h             |   3 +
 tools/perf/util/perf-hooks.c                  |  88 +++++
 tools/perf/util/perf-hooks.h                  |  39 ++
 tools/perf/util/util-cxx.h                    |  26 ++
 40 files changed, 1830 insertions(+), 53 deletions(-)
 create mode 100644 tools/build/feature/test-clang.cpp
 create mode 100644 tools/build/feature/test-llvm.cpp
 create mode 100644 tools/perf/tests/clang.c
 create mode 100644 tools/perf/tests/perf-hooks.c
 create mode 100644 tools/perf/util/c++/Build
 create mode 100644 tools/perf/util/c++/bpf-funcs-str.c
 create mode 100644 tools/perf/util/c++/bpf-helper-str.c
 create mode 100644 tools/perf/util/c++/clang-bpf-includes.h
 create mode 100644 tools/perf/util/c++/clang-c.h
 create mode 100644 tools/perf/util/c++/clang-test.cpp
 create mode 100644 tools/perf/util/c++/clang.cpp
 create mode 100644 tools/perf/util/c++/clang.h
 create mode 100644 tools/perf/util/jit-helpers.c
 create mode 100644 tools/perf/util/jit-helpers.h
 create mode 100644 tools/perf/util/perf-hooks-list.h
 create mode 100644 tools/perf/util/perf-hooks.c
 create mode 100644 tools/perf/util/perf-hooks.h
 create mode 100644 tools/perf/util/util-cxx.h

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Joe Stringer <joe@ovn.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com

-- 
2.10.1

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#1530629 — [PATCH v3 08/30] tools build: Add feature detection for clang

FromWang Nan <wangnan0@huawei.com>
Date2016-11-26 08:20 +0100
Subject[PATCH v3 08/30] tools build: Add feature detection for clang
Message-ID<sHFrc-3qJ-29@gated-at.bofh.it>
In reply to#1530628
Check if basic clang compiling environment is ready.

Doesn't like 'llvm-config --libs' which can returns llvm libraries in
right order and duplicates some libraries if necessary, there's no
correspondence for clang libraries (-lclangxxx). to avoid extra
complexity and to avoid new clang breaking libraries ordering, use
--start-group and --end-group.

In this test case, manually identify required clang libs and hope it to
be stable. Putting all clang libraries here is possible (use make's
wildcard), but then feature checking becomes very slow.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1474874832-134786-5-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/build/feature/Makefile       | 10 ++++++++++
 tools/build/feature/test-clang.cpp | 21 +++++++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 tools/build/feature/test-clang.cpp

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index c09de59..871d553 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -237,6 +237,16 @@ $(OUTPUT)test-llvm.bin:
 		$(shell $(LLVM_CONFIG) --libs Core BPF)		\
 		$(shell $(LLVM_CONFIG) --system-libs)
 
+$(OUTPUT)test-clang.bin:
+	$(BUILDXX) -std=gnu++11 					\
+		-I$(shell $(LLVM_CONFIG) --includedir) 		\
+		-L$(shell $(LLVM_CONFIG) --libdir)		\
+		-Wl,--start-group -lclangBasic -lclangDriver	\
+		  -lclangFrontend -lclangEdit -lclangLex	\
+		  -lclangAST -Wl,--end-group 			\
+		$(shell $(LLVM_CONFIG) --libs Core option)	\
+		$(shell $(LLVM_CONFIG) --system-libs)
+
 -include $(OUTPUT)*.d
 
 ###############################
diff --git a/tools/build/feature/test-clang.cpp b/tools/build/feature/test-clang.cpp
new file mode 100644
index 0000000..e23c1b1
--- /dev/null
+++ b/tools/build/feature/test-clang.cpp
@@ -0,0 +1,21 @@
+#include "clang/Basic/VirtualFileSystem.h"
+#include "clang/Driver/Driver.h"
+#include "clang/Frontend/TextDiagnosticPrinter.h"
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang;
+using namespace clang::driver;
+
+int main()
+{
+	IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
+	IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
+
+	DiagnosticsEngine Diags(DiagID, &*DiagOpts);
+	Driver TheDriver("test", "bpf-pc-linux", Diags);
+
+	llvm::llvm_shutdown();
+	return 0;
+}
-- 
2.10.1

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#1536762 — [tip:perf/core] tools build: Add feature detection for clang

Fromtip-bot for Wang Nan <tipbot@zytor.com>
Date2016-12-06 09:30 +0100
Subject[tip:perf/core] tools build: Add feature detection for clang
Message-ID<sLjiq-84n-41@gated-at.bofh.it>
In reply to#1530629
Commit-ID:  c7fb4f62e2a97bd25d555263ef501fe053edcbb6
Gitweb:     http://git.kernel.org/tip/c7fb4f62e2a97bd25d555263ef501fe053edcbb6
Author:     Wang Nan <wangnan0@huawei.com>
AuthorDate: Sat, 26 Nov 2016 07:03:32 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 5 Dec 2016 15:51:43 -0300

tools build: Add feature detection for clang

Check if basic clang compiling environment is ready.

Doesn't like 'llvm-config --libs' which can returns llvm libraries in right
order and duplicates some libraries if necessary, there's no correspondence for
clang libraries (-lclangxxx). to avoid extra complexity and to avoid new clang
breaking libraries ordering, use --start-group and --end-group.

In this test case, manually identify required clang libs and hope it to be
stable. Putting all clang libraries here is possible (use make's wildcard), but
then feature checking becomes very slow.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Joe Stringer <joe@ovn.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/20161126070354.141764-9-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/build/feature/Makefile       | 10 ++++++++++
 tools/build/feature/test-clang.cpp | 21 +++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index c09de59..871d553 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -237,6 +237,16 @@ $(OUTPUT)test-llvm.bin:
 		$(shell $(LLVM_CONFIG) --libs Core BPF)		\
 		$(shell $(LLVM_CONFIG) --system-libs)
 
+$(OUTPUT)test-clang.bin:
+	$(BUILDXX) -std=gnu++11 					\
+		-I$(shell $(LLVM_CONFIG) --includedir) 		\
+		-L$(shell $(LLVM_CONFIG) --libdir)		\
+		-Wl,--start-group -lclangBasic -lclangDriver	\
+		  -lclangFrontend -lclangEdit -lclangLex	\
+		  -lclangAST -Wl,--end-group 			\
+		$(shell $(LLVM_CONFIG) --libs Core option)	\
+		$(shell $(LLVM_CONFIG) --system-libs)
+
 -include $(OUTPUT)*.d
 
 ###############################
diff --git a/tools/build/feature/test-clang.cpp b/tools/build/feature/test-clang.cpp
new file mode 100644
index 0000000..e23c1b1
--- /dev/null
+++ b/tools/build/feature/test-clang.cpp
@@ -0,0 +1,21 @@
+#include "clang/Basic/VirtualFileSystem.h"
+#include "clang/Driver/Driver.h"
+#include "clang/Frontend/TextDiagnosticPrinter.h"
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang;
+using namespace clang::driver;
+
+int main()
+{
+	IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
+	IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
+
+	DiagnosticsEngine Diags(DiagID, &*DiagOpts);
+	Driver TheDriver("test", "bpf-pc-linux", Diags);
+
+	llvm::llvm_shutdown();
+	return 0;
+}

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#1530630 — [PATCH v3 11/30] perf clang: Use real file system for #include

FromWang Nan <wangnan0@huawei.com>
Date2016-11-26 08:20 +0100
Subject[PATCH v3 11/30] perf clang: Use real file system for #include
Message-ID<sHFrc-3qJ-21@gated-at.bofh.it>
In reply to#1530628
Utilize clang's OverlayFileSystem facility, allow CompilerInstance to
access real file system.

With this patch '#include' directive can be used.

Add a new getModuleFromSource for real file.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/perf/util/c++/clang.cpp | 44 +++++++++++++++++++++++++++++++------------
 tools/perf/util/c++/clang.h   |  3 +++
 2 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp
index c17b117..cf96199 100644
--- a/tools/perf/util/c++/clang.cpp
+++ b/tools/perf/util/c++/clang.cpp
@@ -15,6 +15,7 @@
 #include "clang/Tooling/Tooling.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Option/Option.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/ManagedStatic.h"
 #include <memory>
 
@@ -27,14 +28,6 @@ static std::unique_ptr<llvm::LLVMContext> LLVMCtx;
 
 using namespace clang;
 
-static vfs::InMemoryFileSystem *
-buildVFS(StringRef& Name, StringRef& Content)
-{
-	vfs::InMemoryFileSystem *VFS = new vfs::InMemoryFileSystem(true);
-	VFS->addFile(Twine(Name), 0, llvm::MemoryBuffer::getMemBuffer(Content));
-	return VFS;
-}
-
 static CompilerInvocation *
 createCompilerInvocation(StringRef& Path, DiagnosticsEngine& Diags)
 {
@@ -60,17 +53,17 @@ createCompilerInvocation(StringRef& Path, DiagnosticsEngine& Diags)
 	return CI;
 }
 
-std::unique_ptr<llvm::Module>
-getModuleFromSource(StringRef Name, StringRef Content)
+static std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Path,
+		    IntrusiveRefCntPtr<vfs::FileSystem> VFS)
 {
 	CompilerInstance Clang;
 	Clang.createDiagnostics();
 
-	IntrusiveRefCntPtr<vfs::FileSystem> VFS = buildVFS(Name, Content);
 	Clang.setVirtualFileSystem(&*VFS);
 
 	IntrusiveRefCntPtr<CompilerInvocation> CI =
-		createCompilerInvocation(Name, Clang.getDiagnostics());
+		createCompilerInvocation(Path, Clang.getDiagnostics());
 	Clang.setInvocation(&*CI);
 
 	std::unique_ptr<CodeGenAction> Act(new EmitLLVMOnlyAction(&*LLVMCtx));
@@ -80,6 +73,33 @@ getModuleFromSource(StringRef Name, StringRef Content)
 	return Act->takeModule();
 }
 
+std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Name, StringRef Content)
+{
+	using namespace vfs;
+
+	llvm::IntrusiveRefCntPtr<OverlayFileSystem> OverlayFS(
+			new OverlayFileSystem(getRealFileSystem()));
+	llvm::IntrusiveRefCntPtr<InMemoryFileSystem> MemFS(
+			new InMemoryFileSystem(true));
+
+	/*
+	 * pushOverlay helps setting working dir for MemFS. Must call
+	 * before addFile.
+	 */
+	OverlayFS->pushOverlay(MemFS);
+	MemFS->addFile(Twine(Name), 0, llvm::MemoryBuffer::getMemBuffer(Content));
+
+	return getModuleFromSource(Name, OverlayFS);
+}
+
+std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Path)
+{
+	IntrusiveRefCntPtr<vfs::FileSystem> VFS(vfs::getRealFileSystem());
+	return getModuleFromSource(Path, VFS);
+}
+
 }
 
 extern "C" {
diff --git a/tools/perf/util/c++/clang.h b/tools/perf/util/c++/clang.h
index f64483b..90aff01 100644
--- a/tools/perf/util/c++/clang.h
+++ b/tools/perf/util/c++/clang.h
@@ -12,5 +12,8 @@ using namespace llvm;
 std::unique_ptr<Module>
 getModuleFromSource(StringRef Name, StringRef Content);
 
+std::unique_ptr<Module>
+getModuleFromSource(StringRef Path);
+
 }
 #endif
-- 
2.10.1

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#1536761 — [tip:perf/core] perf clang: Use real file system for #include

Fromtip-bot for Wang Nan <tipbot@zytor.com>
Date2016-12-06 09:30 +0100
Subject[tip:perf/core] perf clang: Use real file system for #include
Message-ID<sLjiq-84n-39@gated-at.bofh.it>
In reply to#1530630
Commit-ID:  77dfa84a843c0bc935a6c8664f2556573e30845f
Gitweb:     http://git.kernel.org/tip/77dfa84a843c0bc935a6c8664f2556573e30845f
Author:     Wang Nan <wangnan0@huawei.com>
AuthorDate: Sat, 26 Nov 2016 07:03:35 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 5 Dec 2016 15:51:44 -0300

perf clang: Use real file system for #include

Utilize clang's OverlayFileSystem facility, allow CompilerInstance to
access real file system.

With this patch the '#include' directive can be used.

Add a new getModuleFromSource for real file.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Joe Stringer <joe@ovn.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/20161126070354.141764-12-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/c++/clang.cpp | 44 +++++++++++++++++++++++++++++++------------
 tools/perf/util/c++/clang.h   |  3 +++
 2 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp
index c17b117..cf96199 100644
--- a/tools/perf/util/c++/clang.cpp
+++ b/tools/perf/util/c++/clang.cpp
@@ -15,6 +15,7 @@
 #include "clang/Tooling/Tooling.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Option/Option.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/ManagedStatic.h"
 #include <memory>
 
@@ -27,14 +28,6 @@ static std::unique_ptr<llvm::LLVMContext> LLVMCtx;
 
 using namespace clang;
 
-static vfs::InMemoryFileSystem *
-buildVFS(StringRef& Name, StringRef& Content)
-{
-	vfs::InMemoryFileSystem *VFS = new vfs::InMemoryFileSystem(true);
-	VFS->addFile(Twine(Name), 0, llvm::MemoryBuffer::getMemBuffer(Content));
-	return VFS;
-}
-
 static CompilerInvocation *
 createCompilerInvocation(StringRef& Path, DiagnosticsEngine& Diags)
 {
@@ -60,17 +53,17 @@ createCompilerInvocation(StringRef& Path, DiagnosticsEngine& Diags)
 	return CI;
 }
 
-std::unique_ptr<llvm::Module>
-getModuleFromSource(StringRef Name, StringRef Content)
+static std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Path,
+		    IntrusiveRefCntPtr<vfs::FileSystem> VFS)
 {
 	CompilerInstance Clang;
 	Clang.createDiagnostics();
 
-	IntrusiveRefCntPtr<vfs::FileSystem> VFS = buildVFS(Name, Content);
 	Clang.setVirtualFileSystem(&*VFS);
 
 	IntrusiveRefCntPtr<CompilerInvocation> CI =
-		createCompilerInvocation(Name, Clang.getDiagnostics());
+		createCompilerInvocation(Path, Clang.getDiagnostics());
 	Clang.setInvocation(&*CI);
 
 	std::unique_ptr<CodeGenAction> Act(new EmitLLVMOnlyAction(&*LLVMCtx));
@@ -80,6 +73,33 @@ getModuleFromSource(StringRef Name, StringRef Content)
 	return Act->takeModule();
 }
 
+std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Name, StringRef Content)
+{
+	using namespace vfs;
+
+	llvm::IntrusiveRefCntPtr<OverlayFileSystem> OverlayFS(
+			new OverlayFileSystem(getRealFileSystem()));
+	llvm::IntrusiveRefCntPtr<InMemoryFileSystem> MemFS(
+			new InMemoryFileSystem(true));
+
+	/*
+	 * pushOverlay helps setting working dir for MemFS. Must call
+	 * before addFile.
+	 */
+	OverlayFS->pushOverlay(MemFS);
+	MemFS->addFile(Twine(Name), 0, llvm::MemoryBuffer::getMemBuffer(Content));
+
+	return getModuleFromSource(Name, OverlayFS);
+}
+
+std::unique_ptr<llvm::Module>
+getModuleFromSource(StringRef Path)
+{
+	IntrusiveRefCntPtr<vfs::FileSystem> VFS(vfs::getRealFileSystem());
+	return getModuleFromSource(Path, VFS);
+}
+
 }
 
 extern "C" {
diff --git a/tools/perf/util/c++/clang.h b/tools/perf/util/c++/clang.h
index f64483b..90aff01 100644
--- a/tools/perf/util/c++/clang.h
+++ b/tools/perf/util/c++/clang.h
@@ -12,5 +12,8 @@ using namespace llvm;
 std::unique_ptr<Module>
 getModuleFromSource(StringRef Name, StringRef Content);
 
+std::unique_ptr<Module>
+getModuleFromSource(StringRef Path);
+
 }
 #endif

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#1530631 — [PATCH v3 15/30] perf clang: Compile BPF script use builtin clang support

FromWang Nan <wangnan0@huawei.com>
Date2016-11-26 08:20 +0100
Subject[PATCH v3 15/30] perf clang: Compile BPF script use builtin clang support
Message-ID<sHFrc-3qJ-23@gated-at.bofh.it>
In reply to#1530628
After this patch, perf utilizes builtin clang support to build BPF
script, no longer depend on external clang.

Test:

  $ type clang
  -bash: type: clang: not found
  $ cat ~/.perfconfig
  $ echo '#define LINUX_VERSION_CODE 0x040700' > ./test.c
  $ cat ./tools/perf/tests/bpf-script-example.c >> ./test.c
  $ ./perf record -v --dry-run -e ./test.c 2>&1 | grep builtin
  bpf: builtin compiling successful

Can't pass cflags so unable to include kernel headers now. Will be fixed
by following commits.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1474874832-134786-13-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/bpf-loader.c  | 15 +++++++++++----
 tools/perf/util/c++/clang-c.h | 26 ++++++++++++++++++++++++++
 tools/perf/util/c++/clang.cpp | 29 +++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index cf16b941..a0ea334f 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -14,11 +14,11 @@
 #include "debug.h"
 #include "bpf-loader.h"
 #include "bpf-prologue.h"
-#include "llvm-utils.h"
 #include "probe-event.h"
 #include "probe-finder.h" // for MAX_PROBES
 #include "parse-events.h"
 #include "llvm-utils.h"
+#include "c++/clang-c.h"
 
 #define DEFINE_PRINT_FN(name, level) \
 static int libbpf_##name(const char *fmt, ...)	\
@@ -86,9 +86,16 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
 		void *obj_buf;
 		size_t obj_buf_sz;
 
-		err = llvm__compile_bpf(filename, &obj_buf, &obj_buf_sz);
-		if (err)
-			return ERR_PTR(-BPF_LOADER_ERRNO__COMPILE);
+		perf_clang__init();
+		err = perf_clang__compile_bpf(filename, &obj_buf, &obj_buf_sz);
+		perf_clang__cleanup();
+		if (err) {
+			pr_warning("bpf: builtin compiling failed: %d, try external compiler\n", err);
+			err = llvm__compile_bpf(filename, &obj_buf, &obj_buf_sz);
+			if (err)
+				return ERR_PTR(-BPF_LOADER_ERRNO__COMPILE);
+		} else
+			pr_debug("bpf: builtin compiling successful\n");
 		obj = bpf_object__open_buffer(obj_buf, obj_buf_sz, filename);
 
 		if (!IS_ERR(obj) && llvm_param.dump_obj)
diff --git a/tools/perf/util/c++/clang-c.h b/tools/perf/util/c++/clang-c.h
index 22b3936..0eadd79 100644
--- a/tools/perf/util/c++/clang-c.h
+++ b/tools/perf/util/c++/clang-c.h
@@ -1,16 +1,42 @@
 #ifndef PERF_UTIL_CLANG_C_H
 #define PERF_UTIL_CLANG_C_H
 
+#include <stddef.h>	/* for size_t */
+#include <util-cxx.h>	/* for __maybe_unused */
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#ifdef HAVE_LIBCLANGLLVM_SUPPORT
 extern void perf_clang__init(void);
 extern void perf_clang__cleanup(void);
 
 extern int test__clang_to_IR(void);
 extern int test__clang_to_obj(void);
 
+extern int perf_clang__compile_bpf(const char *filename,
+				   void **p_obj_buf,
+				   size_t *p_obj_buf_sz);
+#else
+
+
+static inline void perf_clang__init(void) { }
+static inline void perf_clang__cleanup(void) { }
+
+static inline int test__clang_to_IR(void) { return -1; }
+static inline int test__clang_to_obj(void) { return -1;}
+
+static inline int
+perf_clang__compile_bpf(const char *filename __maybe_unused,
+			void **p_obj_buf __maybe_unused,
+			size_t *p_obj_buf_sz __maybe_unused)
+{
+	return -ENOTSUP;
+}
+
+#endif
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp
index 2a1a75d..1e97415 100644
--- a/tools/perf/util/c++/clang.cpp
+++ b/tools/perf/util/c++/clang.cpp
@@ -163,4 +163,33 @@ void perf_clang__cleanup(void)
 	perf::LLVMCtx.reset(nullptr);
 	llvm::llvm_shutdown();
 }
+
+int perf_clang__compile_bpf(const char *filename,
+			    void **p_obj_buf,
+			    size_t *p_obj_buf_sz)
+{
+	using namespace perf;
+
+	if (!p_obj_buf || !p_obj_buf_sz)
+		return -EINVAL;
+
+	llvm::opt::ArgStringList CFlags;
+	auto M = getModuleFromSource(std::move(CFlags), filename);
+	if (!M)
+		return  -EINVAL;
+	auto O = getBPFObjectFromModule(&*M);
+	if (!O)
+		return -EINVAL;
+
+	size_t size = O->size_in_bytes();
+	void *buffer;
+
+	buffer = malloc(size);
+	if (!buffer)
+		return -ENOMEM;
+	memcpy(buffer, O->data(), size);
+	*p_obj_buf = buffer;
+	*p_obj_buf_sz = size;
+	return 0;
+}
 }
-- 
2.10.1

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#1536779 — [tip:perf/core] perf clang: Compile BPF script using builtin clang support

Fromtip-bot for Wang Nan <tipbot@zytor.com>
Date2016-12-06 09:50 +0100
Subject[tip:perf/core] perf clang: Compile BPF script using builtin clang support
Message-ID<sLjBL-8aU-35@gated-at.bofh.it>
In reply to#1530631
Commit-ID:  edd695b032ba3a90c3bb07d934500b2c390a61ff
Gitweb:     http://git.kernel.org/tip/edd695b032ba3a90c3bb07d934500b2c390a61ff
Author:     Wang Nan <wangnan0@huawei.com>
AuthorDate: Sat, 26 Nov 2016 07:03:39 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 5 Dec 2016 15:51:45 -0300

perf clang: Compile BPF script using builtin clang support

After this patch, perf utilizes builtin clang support to build BPF
script, no longer depend on external clang, but fallbacking to it
if for some reason the builtin compiling framework fails.

Test:

  $ type clang
  -bash: type: clang: not found
  $ cat ~/.perfconfig
  $ echo '#define LINUX_VERSION_CODE 0x040700' > ./test.c
  $ cat ./tools/perf/tests/bpf-script-example.c >> ./test.c
  $ ./perf record -v --dry-run -e ./test.c 2>&1 | grep builtin
  bpf: successfull builtin compilation
  $

Can't pass cflags so unable to include kernel headers now. Will be fixed
by following commits.

Committer notes:

Make sure '-v' comes before the '-e ./test.c' in the command line otherwise the
'verbose' variable will not be set when the bpf event is parsed and thus the
pr_debug indicating a 'successfull builtin compilation' will not be output, as
the debug level (1) will be less than what 'verbose' has at that point (0).

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Joe Stringer <joe@ovn.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/20161126070354.141764-16-wangnan0@huawei.com
[ Spell check/reflow successfull pr_debug string ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/bpf-loader.c  | 15 +++++++++++----
 tools/perf/util/c++/clang-c.h | 26 ++++++++++++++++++++++++++
 tools/perf/util/c++/clang.cpp | 29 +++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index cf16b941..36c8611 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -14,11 +14,11 @@
 #include "debug.h"
 #include "bpf-loader.h"
 #include "bpf-prologue.h"
-#include "llvm-utils.h"
 #include "probe-event.h"
 #include "probe-finder.h" // for MAX_PROBES
 #include "parse-events.h"
 #include "llvm-utils.h"
+#include "c++/clang-c.h"
 
 #define DEFINE_PRINT_FN(name, level) \
 static int libbpf_##name(const char *fmt, ...)	\
@@ -86,9 +86,16 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
 		void *obj_buf;
 		size_t obj_buf_sz;
 
-		err = llvm__compile_bpf(filename, &obj_buf, &obj_buf_sz);
-		if (err)
-			return ERR_PTR(-BPF_LOADER_ERRNO__COMPILE);
+		perf_clang__init();
+		err = perf_clang__compile_bpf(filename, &obj_buf, &obj_buf_sz);
+		perf_clang__cleanup();
+		if (err) {
+			pr_warning("bpf: builtin compilation failed: %d, try external compiler\n", err);
+			err = llvm__compile_bpf(filename, &obj_buf, &obj_buf_sz);
+			if (err)
+				return ERR_PTR(-BPF_LOADER_ERRNO__COMPILE);
+		} else
+			pr_debug("bpf: successfull builtin compilation\n");
 		obj = bpf_object__open_buffer(obj_buf, obj_buf_sz, filename);
 
 		if (!IS_ERR(obj) && llvm_param.dump_obj)
diff --git a/tools/perf/util/c++/clang-c.h b/tools/perf/util/c++/clang-c.h
index 22b3936..0eadd79 100644
--- a/tools/perf/util/c++/clang-c.h
+++ b/tools/perf/util/c++/clang-c.h
@@ -1,16 +1,42 @@
 #ifndef PERF_UTIL_CLANG_C_H
 #define PERF_UTIL_CLANG_C_H
 
+#include <stddef.h>	/* for size_t */
+#include <util-cxx.h>	/* for __maybe_unused */
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#ifdef HAVE_LIBCLANGLLVM_SUPPORT
 extern void perf_clang__init(void);
 extern void perf_clang__cleanup(void);
 
 extern int test__clang_to_IR(void);
 extern int test__clang_to_obj(void);
 
+extern int perf_clang__compile_bpf(const char *filename,
+				   void **p_obj_buf,
+				   size_t *p_obj_buf_sz);
+#else
+
+
+static inline void perf_clang__init(void) { }
+static inline void perf_clang__cleanup(void) { }
+
+static inline int test__clang_to_IR(void) { return -1; }
+static inline int test__clang_to_obj(void) { return -1;}
+
+static inline int
+perf_clang__compile_bpf(const char *filename __maybe_unused,
+			void **p_obj_buf __maybe_unused,
+			size_t *p_obj_buf_sz __maybe_unused)
+{
+	return -ENOTSUP;
+}
+
+#endif
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp
index 2a1a75d..1e97415 100644
--- a/tools/perf/util/c++/clang.cpp
+++ b/tools/perf/util/c++/clang.cpp
@@ -163,4 +163,33 @@ void perf_clang__cleanup(void)
 	perf::LLVMCtx.reset(nullptr);
 	llvm::llvm_shutdown();
 }
+
+int perf_clang__compile_bpf(const char *filename,
+			    void **p_obj_buf,
+			    size_t *p_obj_buf_sz)
+{
+	using namespace perf;
+
+	if (!p_obj_buf || !p_obj_buf_sz)
+		return -EINVAL;
+
+	llvm::opt::ArgStringList CFlags;
+	auto M = getModuleFromSource(std::move(CFlags), filename);
+	if (!M)
+		return  -EINVAL;
+	auto O = getBPFObjectFromModule(&*M);
+	if (!O)
+		return -EINVAL;
+
+	size_t size = O->size_in_bytes();
+	void *buffer;
+
+	buffer = malloc(size);
+	if (!buffer)
+		return -ENOMEM;
+	memcpy(buffer, O->data(), size);
+	*p_obj_buf = buffer;
+	*p_obj_buf_sz = size;
+	return 0;
+}
 }

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#1530632 — [PATCH v3 03/30] tools lib bpf: Retrive bpf_map through offset of bpf_map_def

FromWang Nan <wangnan0@huawei.com>
Date2016-11-26 08:20 +0100
Subject[PATCH v3 03/30] tools lib bpf: Retrive bpf_map through offset of bpf_map_def
Message-ID<sHFrc-3qJ-31@gated-at.bofh.it>
In reply to#1530628
Add a new API to libbpf, caller is able to get bpf_map through the
offset of bpf_map_def to 'maps' section.

The API will be used to help jitted perf hook code find fd of a map.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
 tools/lib/bpf/libbpf.c | 12 ++++++++++++
 tools/lib/bpf/libbpf.h |  8 ++++++++
 2 files changed, 20 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 866d5cd..2e97459 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1524,3 +1524,15 @@ bpf_object__find_map_by_name(struct bpf_object *obj, const char *name)
 	}
 	return NULL;
 }
+
+struct bpf_map *
+bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset)
+{
+	int i;
+
+	for (i = 0; i < obj->nr_maps; i++) {
+		if (obj->maps[i].offset == offset)
+			return &obj->maps[i];
+	}
+	return ERR_PTR(-ENOENT);
+}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 0c0b012..a5a8b86 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -24,6 +24,7 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <linux/err.h>
+#include <sys/types.h>  // for size_t
 
 enum libbpf_errno {
 	__LIBBPF_ERRNO__START = 4000,
@@ -200,6 +201,13 @@ struct bpf_map;
 struct bpf_map *
 bpf_object__find_map_by_name(struct bpf_object *obj, const char *name);
 
+/*
+ * Get bpf_map through the offset of corresponding struct bpf_map_def
+ * in the bpf object file.
+ */
+struct bpf_map *
+bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset);
+
 struct bpf_map *
 bpf_map__next(struct bpf_map *map, struct bpf_object *obj);
 #define bpf_map__for_each(pos, obj)		\
-- 
2.10.1

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#1530694 — Re: [PATCH v3 03/30] tools lib bpf: Retrive bpf_map through offset of bpf_map_def

FromAlexei Starovoitov <alexei.starovoitov@gmail.com>
Date2016-11-26 18:20 +0100
SubjectRe: [PATCH v3 03/30] tools lib bpf: Retrive bpf_map through offset of bpf_map_def
Message-ID<sHONQ-11D-19@gated-at.bofh.it>
In reply to#1530632
On Sat, Nov 26, 2016 at 07:03:27AM +0000, Wang Nan wrote:
> Add a new API to libbpf, caller is able to get bpf_map through the
> offset of bpf_map_def to 'maps' section.
> 
> The API will be used to help jitted perf hook code find fd of a map.
> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
...
> +struct bpf_map *
> +bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset)
> +{
> +	int i;
> +
> +	for (i = 0; i < obj->nr_maps; i++) {
> +		if (obj->maps[i].offset == offset)
> +			return &obj->maps[i];
> +	}
> +	return ERR_PTR(-ENOENT);
> +}

Acked-by: Alexei Starovoitov <ast@kernel.org>

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#1534815 — [tip:perf/core] tools lib bpf: Retrive bpf_map through offset of bpf_map_def

Fromtip-bot for Wang Nan <tipbot@zytor.com>
Date2016-12-02 11:40 +0100
Subject[tip:perf/core] tools lib bpf: Retrive bpf_map through offset of bpf_map_def
Message-ID<sJTq2-2EV-27@gated-at.bofh.it>
In reply to#1530632
Commit-ID:  5a6acad17d2e81765dd4c2fce7346a6f045eab25
Gitweb:     http://git.kernel.org/tip/5a6acad17d2e81765dd4c2fce7346a6f045eab25
Author:     Wang Nan <wangnan0@huawei.com>
AuthorDate: Sat, 26 Nov 2016 07:03:27 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 29 Nov 2016 12:10:19 -0300

tools lib bpf: Retrive bpf_map through offset of bpf_map_def

Add a new API to libbpf, caller is able to get bpf_map through the
offset of bpf_map_def to 'maps' section.

The API will be used to help jitted perf hook code find fd of a map.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Joe Stringer <joe@ovn.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/20161126070354.141764-4-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/lib/bpf/libbpf.c | 12 ++++++++++++
 tools/lib/bpf/libbpf.h |  8 ++++++++
 2 files changed, 20 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 866d5cd..2e97459 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1524,3 +1524,15 @@ bpf_object__find_map_by_name(struct bpf_object *obj, const char *name)
 	}
 	return NULL;
 }
+
+struct bpf_map *
+bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset)
+{
+	int i;
+
+	for (i = 0; i < obj->nr_maps; i++) {
+		if (obj->maps[i].offset == offset)
+			return &obj->maps[i];
+	}
+	return ERR_PTR(-ENOENT);
+}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 0c0b012..a5a8b86 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -24,6 +24,7 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <linux/err.h>
+#include <sys/types.h>  // for size_t
 
 enum libbpf_errno {
 	__LIBBPF_ERRNO__START = 4000,
@@ -200,6 +201,13 @@ struct bpf_map;
 struct bpf_map *
 bpf_object__find_map_by_name(struct bpf_object *obj, const char *name);
 
+/*
+ * Get bpf_map through the offset of corresponding struct bpf_map_def
+ * in the bpf object file.
+ */
+struct bpf_map *
+bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset);
+
 struct bpf_map *
 bpf_map__next(struct bpf_map *map, struct bpf_object *obj);
 #define bpf_map__for_each(pos, obj)		\

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