[Tarantool-patches] [PATCH luajit] symtab: check the _GNU_SOURCE definition

[Tarantool-patches] [PATCH luajit] symtab: check the _GNU_SOURCE definition

[Maxim Kokryashkin via Tarantool-patches]

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

[Tarantool-patches] [PATCH luajit] sysprof: replace `backtrace` with libunwind

[Maxim Kokryashkin via Tarantool-patches]

`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-rc-full-ci

 CMakeLists.txt                                | 20 +++--
 cmake/FindLibUnwind.cmake                     | 86 +++++++++++++++++++
 cmake/GetLibUnwindVersion.cmake               | 12 +++
 src/CMakeLists.txt                            | 17 ++++
 src/lj_sysprof.c                              | 51 ++++++++---
 .../misclib-sysprof-capi.test.lua             |  7 +-
 6 files changed, 167 insertions(+), 26 deletions(-)
 create mode 100644 cmake/FindLibUnwind.cmake
 create mode 100644 cmake/GetLibUnwindVersion.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 659ee879..63db42c2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -89,12 +89,20 @@ 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)
+
+if(NOT LUAJIT_DISABLE_SYSPROF AND
+    CMAKE_SYSTEM_NAME STREQUAL "Linux" AND
+    (
+    CMAKE_SYSTEM_PROCESSOR STREQUAL "i386" OR
+    CMAKE_SYSTEM_PROCESSOR STREQUAL "i686" OR
+    CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64"
+    )
+  )
+  AppendFlags(CMAKE_C_FLAGS -fno-omit-frame-pointer -fasynchronous-unwind-tables)
+else()
+  AppendFlags(CMAKE_C_FLAGS -fomit-frame-pointer)
+endif()
 
 # Redefined to benefit from expanding macros in gdb.
 set(CMAKE_C_FLAGS_DEBUG "-g -ggdb3")
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..4f9ad1de 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -283,6 +283,23 @@ add_dependencies(core_shared buildvm_output)
 
 list(APPEND TARGET_LIBS m)
 
+if(NOT LUAJIT_DISABLE_SYSPROF AND
+    CMAKE_SYSTEM_NAME STREQUAL "Linux" AND
+    (
+    CMAKE_SYSTEM_PROCESSOR STREQUAL "i386" OR
+    CMAKE_SYSTEM_PROCESSOR STREQUAL "i686" OR
+    CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64"
+    )
+  )
+  find_package(LibUnwind MODULE REQUIRED)
+
+  if(NOT LIBUNWIND_FOUND)
+    message(FATAL_ERROR "Libunwind is required for build with sysprof")
+  else()
+    list(APPEND TARGET_LIBS ${LIBUNWIND_LIBRARIES})
+  endif()
+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 55cea203..04509f68 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(sp_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/tarantool-tests/misclib-sysprof-capi.test.lua b/test/tarantool-tests/misclib-sysprof-capi.test.lua
index afb99cf2..1117ff73 100644
--- a/test/tarantool-tests/misclib-sysprof-capi.test.lua
+++ b/test/tarantool-tests/misclib-sysprof-capi.test.lua
@@ -15,15 +15,11 @@ 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 +52,4 @@ jit.on()
 jit.flush()
 
 test:ok(testsysprof.profile_func(payload))
---]]
 os.exit(test:check() and 0 or 1)
-- 
2.36.1

Re: [Tarantool-patches] [PATCH luajit] symtab: check the _GNU_SOURCE definition

[Igor Munkin via Tarantool-patches]

Max,

Thanks for the patch! LGTM as trivial.

On 18.05.22, Maxim Kokryashkin wrote:
> Now the `_GNU_SOURCE` in `lj_symtab.c` is only defined when it wasn't
> defined yet. That chnage fixes the macro redifinition warning.

Typo: s/chnage/change/.

> 
> 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(+)
> 

<snipped>

> -- 
> 2.36.1
> 

-- 
Best regards,
IM

Re: [Tarantool-patches] [PATCH luajit] symtab: check the _GNU_SOURCE definition

[Sergey Kaplun via Tarantool-patches]

Hi, Maxim!

Thanks for the patch!
LGTM.

On 18.05.22, Maxim Kokryashkin wrote:
> Now the `_GNU_SOURCE` in `lj_symtab.c` is only defined when it wasn't
> defined yet. That chnage fixes the macro redifinition warning.

Typo: s/chnage/change/

> 
> Part of tarantool/tarantool#5813
> ---

<snipped>

-- 
Best regards,
Sergey Kaplun

Re: [Tarantool-patches] [PATCH luajit] symtab: check the _GNU_SOURCE definition

[Igor Munkin via Tarantool-patches]

Max,

I've checked the patchset into tarantool branch in tarantool/luajit and
bumped a new version in master.

On 18.05.22, Maxim Kokryashkin wrote:
> 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(+)
> 

<snipped>

> -- 
> 2.36.1
> 

-- 
Best regards,
IM

Re: [Tarantool-patches] [PATCH luajit] sysprof: replace `backtrace` with libunwind

[Igor Munkin via Tarantool-patches]

Ignoring this patch, since we decided to resolve this in a separate
series.

-- 
Best regards,
IM