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* [Tarantool-patches] [PATCH luajit] sysprof: replace `backtrace` with libunwind
@ 2022-06-11 22:40 Maxim Kokryashkin via Tarantool-patches
  2022-11-29 11:02 ` Sergey Kaplun via Tarantool-patches
  0 siblings, 1 reply; 4+ messages in thread
From: Maxim Kokryashkin via Tarantool-patches @ 2022-06-11 22:40 UTC (permalink / raw)
  To: tarantool-patches, imun, skaplun

`backtrace` fails to unwind the host stack in LuaJIT, since there is
no frame pointers during the vm calls. Sometimes, those failures cause
crashes. This commit replaces it with the libunwind-based unwinder,
which makes use of additional runtime info to provide robust unwinding
without any frame pointers.

Also, this commit enables C API tests, which used to crash with
`backtrace`.

Part of tarantool/tarantool#781
---
Branch: https://github.com/tarantool/luajit/tree/fckxorg/sysprof-libunwind
PR: https://github.com/tarantool/tarantool/pull/7198

 CMakeLists.txt                                | 38 ++++++--
 cmake/FindLibUnwind.cmake                     | 86 +++++++++++++++++++
 cmake/GetLibUnwindVersion.cmake               | 12 +++
 src/CMakeLists.txt                            |  4 +
 src/lj_sysprof.c                              | 51 ++++++++---
 test/luajit-test-init.lua                     | 41 +++++++++
 test/tarantool-tests/CMakeLists.txt           |  6 ++
 .../misclib-sysprof-capi.test.lua             | 12 +--
 .../misclib-sysprof-lapi.test.lua             |  5 +-
 9 files changed, 225 insertions(+), 30 deletions(-)
 create mode 100644 cmake/FindLibUnwind.cmake
 create mode 100644 cmake/GetLibUnwindVersion.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 659ee879..d62d5b34 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -89,12 +89,7 @@ if(CMAKE_LIBRARY_ARCHITECTURE)
   AppendFlags(TARGET_C_FLAGS -DLUA_MULTILIB='"lib/${CMAKE_LIBRARY_ARCHITECTURE}"')
 endif()
 
-# Since the assembler part does NOT maintain a frame pointer, it's
-# pointless to slow down the C part by not omitting it. Debugging,
-# tracebacks and unwinding are not affected -- the assembler part
-# has frame unwind information and GCC emits it where needed (x64)
-# or with -g.
-AppendFlags(CMAKE_C_FLAGS -fomit-frame-pointer -fno-stack-protector)
+AppendFlags(CMAKE_C_FLAGS -fno-stack-protector)
 
 # Redefined to benefit from expanding macros in gdb.
 set(CMAKE_C_FLAGS_DEBUG "-g -ggdb3")
@@ -188,6 +183,37 @@ endif()
 option(LUAJIT_DISABLE_SYSPROF "LuaJIT platform and Lua profiler support" OFF)
 if(LUAJIT_DISABLE_SYSPROF)
   AppendFlags(TARGET_C_FLAGS -DLUAJIT_DISABLE_SYSPROF)
+  AppendFlags(CMAKE_C_FLAGS -fomit-frame-pointer)
+else()
+  if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND
+    (
+      CMAKE_SYSTEM_PROCESSOR STREQUAL "i386" OR
+      CMAKE_SYSTEM_PROCESSOR STREQUAL "i686" OR
+      CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64"
+    )
+  )
+    # XXX: Libunwind can be provided externally.
+    if(NOT LIBUNWIND_LIBRARIES)
+      find_package(LibUnwind MODULE QUIET)
+    endif()
+
+    if(NOT LIBUNWIND_FOUND AND NOT LIBUNWIND_LIBRARIES)
+      set(LUAJIT_DISABLE_SYSPROF ON)
+      AppendFlags(TARGET_C_FLAGS -DLUAJIT_DISABLE_SYSPROF)
+      AppendFlags(CMAKE_C_FLAGS -fomit-frame-pointer)
+      message(STATUS "Libunwind was not found, sysprof is disabled")
+
+      # XXX: CMake sets those variables globally, so using the `unset` here
+      # doesn't really clear them out of the parent scope. As stated in the
+      # `unset` documentation, to force a variable reference of the form ${VAR}
+      # to return an empty string, you need to use `set(<variable> "")`.
+      set(LIBUNWIND_INCLUDE_DIR "" PARENT_SCOPE)
+      set(LIBUNWIND_LIBRARIES "" PARENT_SCOPE)
+      set(LIBUNWIND_FOUND FALSE PARENT_SCOPE)
+    else()
+      AppendFlags(CMAKE_C_FLAGS -fno-omit-frame-pointer -fasynchronous-unwind-tables)
+    endif()
+  endif()
 endif()
 
 # Switch to harder (and slower) hash function when a collision
diff --git a/cmake/FindLibUnwind.cmake b/cmake/FindLibUnwind.cmake
new file mode 100644
index 00000000..70221c12
--- /dev/null
+++ b/cmake/FindLibUnwind.cmake
@@ -0,0 +1,86 @@
+#[========================================================================[.rst:
+FindLibUnwind
+--------
+Finds the libunwind library.
+
+Result Variables
+^^^^^^^^^^^^^^^^
+``LIBUNWIND_FOUND``
+  True if the system has the libunwind library.
+``LIBUNWIND_VERSION``
+  The version of the libunwind library which was found.
+``LIBUNWIND_INCLUDE_DIR``
+  Include directory needed to use libunwind.
+``LIBUNWIND_LIBRARIES``
+  Libraries needed to link to libunwind.
+
+Cache Variables
+^^^^^^^^^^^^^^^
+``LIBUNWIND_INCLUDE_DIR``
+  The directory containing ``libunwind.h``.
+``LIBUNWIND_LIBRARIES``
+  The paths to the libunwind libraries.
+#]========================================================================]
+
+include(FindPackageHandleStandardArgs)
+include(GetLibUnwindVersion)
+
+find_package(PkgConfig QUIET)
+pkg_check_modules(PC_LIBUNWIND QUIET libunwind)
+
+find_path(LIBUNWIND_INCLUDE_DIR libunwind.h ${PC_LIBUNWIND_INCLUDE_DIRS})
+if(LIBUNWIND_INCLUDE_DIR)
+    include_directories(${LIBUNWIND_INCLUDE_DIR})
+endif()
+
+if(BUILD_STATIC AND NOT APPLE)
+    set(LIBUNWIND_LIBRARY_NAME libunwind.a)
+else()
+    # Only a dynamic version of libunwind is available on macOS: also, we
+    # should link against the umbrella framework `System` — otherwise `ld` will
+    # complain that it cannot link directly with libunwind.tbd.
+    set(LIBUNWIND_LIBRARY_NAME System unwind)
+endif()
+find_library(LIBUNWIND_LIBRARY NAMES ${LIBUNWIND_LIBRARY_NAME}
+             PATHS ${PC_LIBUNWIND_LIBRARY_DIRS})
+
+if(APPLE)
+    set(LIBUNWIND_LIBRARIES ${LIBUNWIND_LIBRARY})
+else()
+    if(BUILD_STATIC)
+        set(LIBUNWIND_PLATFORM_LIBRARY_NAME
+            "libunwind-${CMAKE_SYSTEM_PROCESSOR}.a")
+    else()
+        set(LIBUNWIND_PLATFORM_LIBRARY_NAME
+            "unwind-${CMAKE_SYSTEM_PROCESSOR}")
+    endif()
+    find_library(LIBUNWIND_PLATFORM_LIBRARY ${LIBUNWIND_PLATFORM_LIBRARY_NAME}
+                 ${PC_LIBUNWIND_LIBRARY_DIRS})
+    set(LIBUNWIND_LIBRARIES ${LIBUNWIND_LIBRARY} ${LIBUNWIND_PLATFORM_LIBRARY})
+endif()
+
+if(BUILD_STATIC)
+    # libunwind could have been built with liblzma dependency:
+    # https://github.com/libunwind/libunwind/blob/4feb1152d1c4aaafbb2d504dbe34c6db5b6fe9f2/configure.ac#L302-L317
+    pkg_check_modules(PC_LIBLZMA QUIET liblzma)
+    find_library(LIBLZMA_LIBRARY liblzma.a ${PC_LIBLZMA_LIBRARY_DIRS})
+    if(NOT LIBLZMA_LIBRARY STREQUAL "LIBLZMA_LIBRARY-NOTFOUND")
+        message(STATUS "liblzma found")
+        set(LIBUNWIND_LIBRARIES ${LIBUNWIND_LIBRARIES} ${LIBLZMA_LIBRARY})
+    endif()
+    # Ditto,
+    # https://github.com/libunwind/libunwind/blob/4feb1152d1c4aaafbb2d504dbe34c6db5b6fe9f2/configure.ac#L319-L334
+    set(LIBUNWIND_LIBRARIES ${LIBUNWIND_LIBRARIES} ZLIB::ZLIB)
+endif()
+
+if(PC_LIBUNWIND_VERSION)
+    set(LIBUNWIND_VERSION ${PC_LIBUNWIND_VERSION})
+else()
+    GetLibUnwindVersion(LIBUNWIND_VERSION)
+endif()
+
+find_package_handle_standard_args(LibUnwind
+      VERSION_VAR LIBUNWIND_VERSION
+      REQUIRED_VARS LIBUNWIND_INCLUDE_DIR LIBUNWIND_LIBRARIES)
+
+mark_as_advanced(LIBUNWIND_INCLUDE_DIR LIBUNWIND_LIBRARIES)
diff --git a/cmake/GetLibUnwindVersion.cmake b/cmake/GetLibUnwindVersion.cmake
new file mode 100644
index 00000000..af833478
--- /dev/null
+++ b/cmake/GetLibUnwindVersion.cmake
@@ -0,0 +1,12 @@
+function(GetLibUnwindVersion _LIBUNWIND_VERSION)
+    set(_LIBUNWIND_VERSION_HEADER "${LIBUNWIND_INCLUDE_DIR}/libunwind-common.h")
+    if(LIBUNWIND_LIBRARY AND EXISTS ${_LIBUNWIND_VERSION_HEADER})
+        file(READ ${_LIBUNWIND_VERSION_HEADER}
+             _LIBUNWIND_VERSION_HEADER_CONTENTS)
+        string(REGEX MATCH
+               "#define UNW_VERSION_MAJOR[ \t]+([0-9]+)\n#define UNW_VERSION_MINOR[ \t]+([0-9]+)"
+               _VERSION_REGEX "${_LIBUNWIND_VERSION_HEADER_CONTENTS}")
+        set(${_LIBUNWIND_VERSION} "${CMAKE_MATCH_1}.${CMAKE_MATCH_2}"
+            PARENT_SCOPE)
+    endif()
+endfunction()
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 1a3f106a..9e004a44 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -283,6 +283,10 @@ add_dependencies(core_shared buildvm_output)
 
 list(APPEND TARGET_LIBS m)
 
+if(NOT LUAJIT_DISABLE_SYSPROF)
+  list(APPEND TARGET_LIBS ${LIBUNWIND_LIBRARIES})
+endif()
+
 set(LIB_OBJECTS_STATIC
   $<TARGET_OBJECTS:vm_static>
   $<TARGET_OBJECTS:core_static>
diff --git a/src/lj_sysprof.c b/src/lj_sysprof.c
index a4a70146..20604b90 100644
--- a/src/lj_sysprof.c
+++ b/src/lj_sysprof.c
@@ -26,7 +26,9 @@
 
 #include <pthread.h>
 #include <errno.h>
-#include <execinfo.h>
+
+#define UNW_LOCAL_ONLY
+#include <libunwind.h>
 
 /*
 ** Number of profiler frames we need to omit during stack
@@ -85,6 +87,34 @@ static struct sysprof sysprof = {0};
 
 /* --- Stream ------------------------------------------------------------- */
 
+static ssize_t collect_stack(void **buffer, int size)
+{
+  int frame_no = 0;
+  unw_context_t unw_ctx;
+  unw_cursor_t unw_cur;
+
+  int rc = unw_getcontext(&unw_ctx);
+  if (rc != 0)
+    return -1;
+
+  rc = unw_init_local(&unw_cur, &unw_ctx);
+  if (rc != 0)
+    return -1;
+
+  for (; frame_no < size; ++frame_no) {
+    unw_word_t ip;
+    rc = unw_get_reg(&unw_cur, UNW_REG_IP, &ip);
+    if (rc != 0)
+      return -1;
+
+    buffer[frame_no] = (void *)ip;
+    rc = unw_step(&unw_cur);
+    if (rc <= 0)
+    break;
+  }
+  return frame_no;
+}
+
 static const uint8_t ljp_header[] = {'l', 'j', 'p', LJP_FORMAT_VERSION,
                                       0x0, 0x0, 0x0};
 
@@ -197,10 +227,11 @@ static void default_backtrace_host(void *(writer)(int frame_no, void *addr))
   int max_depth = sp->opt.mode == LUAM_SYSPROF_LEAF
                   ? SYSPROF_HANDLER_STACK_DEPTH + 1
                   : SYSPROF_BACKTRACE_FRAME_MAX;
-  const int depth = backtrace(backtrace_buf, max_depth);
+  const int depth = collect_stack(backtrace_buf, max_depth);
   int level;
 
   lua_assert(depth <= max_depth);
+  lua_assert(depth != -1);
   for (level = SYSPROF_HANDLER_STACK_DEPTH; level < depth; ++level) {
     if (!writer(level - SYSPROF_HANDLER_STACK_DEPTH + 1, backtrace_buf[level]))
       return;
@@ -410,20 +441,12 @@ int lj_sysprof_set_backtracer(luam_Sysprof_backtracer backtracer) {
 
   if (sp->state != SPS_IDLE)
     return PROFILE_ERRUSE;
-  if (backtracer == NULL) {
+
+  if (backtracer == NULL)
     sp->backtracer = default_backtrace_host;
-    /*
-    ** XXX: `backtrace` is not signal-safe, according to man,
-    ** because it is lazy loaded on the first call, which triggers
-    ** allocations. We need to call `backtrace` before starting profiling
-    ** to avoid lazy loading.
-    */
-    void *dummy = NULL;
-    backtrace(&dummy, 1);
-  }
-  else {
+  else
     sp->backtracer = backtracer;
-  }
+
   if (!is_unconfigured(sp)) {
     sp->state = SPS_IDLE;
   }
diff --git a/test/luajit-test-init.lua b/test/luajit-test-init.lua
index acd3d60e..37606e49 100644
--- a/test/luajit-test-init.lua
+++ b/test/luajit-test-init.lua
@@ -18,3 +18,44 @@ end
 function _dofile(filename)
   return dofile(path_to_sources..filename)
 end
+
+-- XXX: Some tests need more complicated skipconds that can be implemented
+-- in Lua, so this function checks if the test was marked as excluded via CLI
+-- arg.
+
+-- luacheck: no global
+ function is_excluded()
+  if #arg == 0 then
+    return false
+  end
+
+  local exclusions = nil
+  for i = 1, #arg do
+    local excl_arg = string.match(arg[i], '--exclude=({.+})')
+
+    if excl_arg == nil then
+      break
+    end
+
+    assert(exclusions == nil, '--exclude was already provided')
+
+    local excl_f, err = loadstring('return ' .. excl_arg)
+    assert(excl_f, err)
+
+    local excl = excl_f()
+    assert(type(excl) == 'table', '--exclude option must provide a valid array')
+    exclusions = excl
+  end
+
+  if exclusions == nil then
+    return false
+  end
+
+  local basename = string.match(arg[0], '[%w%-]+%.test%.lua')
+  for _, name in ipairs(exclusions) do
+    if basename == name .. '.test.lua' then
+      return true
+    end
+  end
+  return false
+end
diff --git a/test/tarantool-tests/CMakeLists.txt b/test/tarantool-tests/CMakeLists.txt
index e4d7134a..7bb07251 100644
--- a/test/tarantool-tests/CMakeLists.txt
+++ b/test/tarantool-tests/CMakeLists.txt
@@ -84,6 +84,11 @@ set(LUA_TEST_ENV
   "LUA_CPATH=\"${LUA_CPATH}\;\;\""
 )
 
+if(LUAJIT_DISABLE_SYSPROF)
+  string(CONCAT LUA_EXCLUDE_TESTS [[\{\"misclib-sysprof-lapi\",]]
+                                  [[\"misclib-sysprof-capi\"\}]])
+endif()
+
 if(CMAKE_VERBOSE_MAKEFILE)
   list(APPEND LUA_TEST_FLAGS --verbose)
 endif()
@@ -132,6 +137,7 @@ add_custom_command(TARGET tarantool-tests
       --exec '${LUAJIT_TEST_COMMAND}'
       --ext ${LUA_TEST_SUFFIX}
       ${LUA_TEST_FLAGS}
+      :: --exclude=${LUA_EXCLUDE_TESTS}
   WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
 )
 
diff --git a/test/tarantool-tests/misclib-sysprof-capi.test.lua b/test/tarantool-tests/misclib-sysprof-capi.test.lua
index afb99cf2..a5c5b77d 100644
--- a/test/tarantool-tests/misclib-sysprof-capi.test.lua
+++ b/test/tarantool-tests/misclib-sysprof-capi.test.lua
@@ -1,10 +1,11 @@
 -- Sysprof is implemented for x86 and x64 architectures only.
 local ffi = require("ffi")
+-- luacheck: globals is_excluded
 require("utils").skipcond(
   jit.arch ~= "x86" and jit.arch ~= "x64" or jit.os ~= "Linux"
-    or ffi.abi("gc64"),
+    or ffi.abi("gc64") or is_excluded(),
   jit.arch.." architecture or "..jit.os..
-  " OS is NIY for sysprof"
+  " OS is NIY for sysprof, or the test suite was excluded"
 )
 
 local testsysprof = require("testsysprof")
@@ -15,15 +16,11 @@ local jit = require('jit')
 jit.off()
 
 local test = tap.test("clib-misc-sysprof")
-test:plan(2)
+test:plan(4)
 
 test:ok(testsysprof.base())
 test:ok(testsysprof.validation())
 
--- FIXME: The following two tests are disabled because sometimes
--- `backtrace` dynamically loads a platform-specific unwinder, which is
--- not signal-safe.
---[[
 local function lua_payload(n)
   if n <= 1 then
     return n
@@ -56,5 +53,4 @@ jit.on()
 jit.flush()
 
 test:ok(testsysprof.profile_func(payload))
---]]
 os.exit(test:check() and 0 or 1)
diff --git a/test/tarantool-tests/misclib-sysprof-lapi.test.lua b/test/tarantool-tests/misclib-sysprof-lapi.test.lua
index 2f53d771..2e1fa2c9 100644
--- a/test/tarantool-tests/misclib-sysprof-lapi.test.lua
+++ b/test/tarantool-tests/misclib-sysprof-lapi.test.lua
@@ -1,10 +1,11 @@
 -- Sysprof is implemented for x86 and x64 architectures only.
 local ffi = require("ffi")
+-- luacheck: globals is_excluded
 require("utils").skipcond(
   jit.arch ~= "x86" and jit.arch ~= "x64" or jit.os ~= "Linux"
-    or ffi.abi("gc64"),
+    or ffi.abi("gc64") or is_excluded(),
   jit.arch.." architecture or "..jit.os..
-  " OS is NIY for sysprof"
+  " OS is NIY for sysprof, or the test suite was excluded"
 )
 
 local tap = require("tap")
-- 
2.36.1


^ permalink raw reply	[flat|nested] 4+ messages in thread
* [Tarantool-patches] [PATCH luajit] symtab: check the _GNU_SOURCE definition
@ 2022-05-18 12:31 Maxim Kokryashkin via Tarantool-patches
  2022-05-18 12:31 ` [Tarantool-patches] [PATCH luajit] sysprof: replace `backtrace` with libunwind Maxim Kokryashkin via Tarantool-patches
  0 siblings, 1 reply; 4+ messages in thread
From: Maxim Kokryashkin via Tarantool-patches @ 2022-05-18 12:31 UTC (permalink / raw)
  To: tarantool-patches, imun, skaplun

Now the `_GNU_SOURCE` in `lj_symtab.c` is only defined when it wasn't
defined yet. That chnage fixes the macro redifinition warning.

Part of tarantool/tarantool#5813
---
Branch: https://github.com/tarantool/luajit/tree/fckxorg/sysprof-rc-full-ci

 src/lj_symtab.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/lj_symtab.c b/src/lj_symtab.c
index 57045765..2b2b205b 100644
--- a/src/lj_symtab.c
+++ b/src/lj_symtab.c
@@ -7,7 +7,10 @@
 
 #define lj_symtab_c
 #define LUA_CORE
+
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 
 #include "lj_symtab.h"
 
-- 
2.36.1


^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-11-29 11:05 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-06-11 22:40 [Tarantool-patches] [PATCH luajit] sysprof: replace `backtrace` with libunwind Maxim Kokryashkin via Tarantool-patches
2022-11-29 11:02 ` Sergey Kaplun via Tarantool-patches
  -- strict thread matches above, loose matches on Subject: below --
2022-05-18 12:31 [Tarantool-patches] [PATCH luajit] symtab: check the _GNU_SOURCE definition Maxim Kokryashkin via Tarantool-patches
2022-05-18 12:31 ` [Tarantool-patches] [PATCH luajit] sysprof: replace `backtrace` with libunwind Maxim Kokryashkin via Tarantool-patches
2022-05-26 16:33   ` Igor Munkin via Tarantool-patches

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