lib/perf: add support for perf based profiling

Signed-off-by: Balazs Scheidler <[email protected]>

configure.ac

@@ -466,6 +466,7 @@ dnl Checks for programs.
 AC_PROG_CC
 AC_PROG_CC_C99
 AM_PROG_CC_C_O
+AM_PROG_AS
 if test "x$ac_cv_prog_cc_c99" = "xno"; then
 	AC_MSG_ERROR([C99 standard compliant C compiler required. Try GCC 3.x or later.])
 fi

lib/Makefile.am

@@ -29,6 +29,7 @@ include lib/logthrsource/Makefile.am
 include lib/logthrdest/Makefile.am
 include lib/signal-slot-connector/Makefile.am
 include lib/multi-line/Makefile.am
+include lib/perf/Makefile.am
 
 LSNG_RELEASE		= $(shell echo @PACKAGE_VERSION@ | cut -d. -f1,2)
 
@@ -307,7 +308,8 @@ lib_libsyslog_ng_la_SOURCES		= \
 	$(multiline_sources)		\
 	$(logthrsource_sources)		\
 	$(logthrdest_sources) \
-	$(signal_slot_connector_sources)
+	$(signal_slot_connector_sources) \
+	$(perf_sources)
 
 lib_libsyslog_ng_la_CFLAGS		= \
 	$(AM_CFLAGS) \

lib/apphook.c

@@ -49,6 +49,7 @@
 #include "timeutils/cache.h"
 #include "multi-line/multi-line-factory.h"
 #include "filterx/filterx-globals.h"
+#include "perf/perf.h"
 
 #include <iv.h>
 #include <iv_work.h>
@@ -215,6 +216,7 @@ construct_nondumpable_logger(msg_fatal);
 void
 app_startup(void)
 {
+  perf_global_init();
   msg_init(FALSE);
   iv_set_fatal_msg_handler(app_fatal);
   iv_init();
@@ -293,6 +295,7 @@ app_shutdown(void)
   hostname_global_deinit();
   crypto_deinit();
   msg_deinit();
+  perf_global_deinit();
 
 
   /* NOTE: the iv_deinit() call should come here, but there's some exit

lib/perf/Makefile.am

@@ -0,0 +1,8 @@
+perfincludedir			= ${pkgincludedir}/perf
+
+perfinclude_HEADERS = \
+	lib/perf/perf.h
+
+perf_sources = \
+	lib/perf/perf.c \
+	lib/perf/trampoline.S

lib/perf/perf.c

@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2024 Axoflow
+ * Copyright (c) 2024 Balázs Scheidler <[email protected]>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As an additional exemption you are allowed to compile & link against the
+ * OpenSSL libraries as published by the OpenSSL project. See the file
+ * COPYING for details.
+ *
+ */
+
+#include "perf.h"
+#include "messages.h"
+#include <sys/mman.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+typedef struct _PerfTrampolineArea
+{
+  guint8 *area;
+  gsize size;
+  gsize code_size;
+  struct
+  {
+    gint num;
+    gint alloc;
+  } trampolines;
+} PerfTrampolineArea;
+
+extern void _perf_trampoline_func_start(void);
+extern void _perf_trampoline_func_end(void);
+
+#define PAGE_SIZE 4096
+#define PAGE_MAX_INDEX ((PAGE_SIZE-1))
+
+#define SIZE_TO_PAGES(s) (((s + PAGE_MAX_INDEX) & ~PAGE_MAX_INDEX) / PAGE_SIZE)
+#define PAGE_TO_SIZE(p)  (p * PAGE_SIZE)
+
+#define MAX_TRAMPOLINES 16384
+
+static gboolean
+_allocate_trampoline_area(PerfTrampolineArea *self)
+{
+  guint8 *start = (guint8 *) &_perf_trampoline_func_start;
+  guint8 *end = (guint8 *) &_perf_trampoline_func_end;
+
+  self->code_size = end - start;
+  gsize code_pages = SIZE_TO_PAGES(self->code_size * MAX_TRAMPOLINES);
+
+  self->size = PAGE_TO_SIZE(code_pages);
+  self->area = mmap(NULL,
+                    self->size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS,
+                    -1, 0);
+  if (self->area == MAP_FAILED)
+    return FALSE;
+
+  self->trampolines.num = self->size / self->code_size;
+  self->trampolines.alloc = 0;
+
+  for (gint i = 0; i < self->trampolines.num; i++)
+    {
+      memcpy(self->area + i * self->code_size, start, self->code_size * sizeof(gchar));
+    }
+  return TRUE;
+}
+
+static gpointer
+_generate_trampoline(PerfTrampolineArea *self, gpointer target_address)
+{
+  if (self->trampolines.alloc >= self->trampolines.num)
+    return NULL;
+
+  gint res = mprotect(self->area, self->size, PROT_READ | PROT_WRITE);
+  if (res < 0)
+    return NULL;
+
+  guint8 *trampoline_start = self->area + (self->trampolines.alloc++) * self->code_size;
+  guint8 *trampoline_end = trampoline_start + self->code_size;
+  uintptr_t *value_p = (uintptr_t *) (trampoline_end - sizeof(target_address));
+  *value_p = (uintptr_t) target_address;
+
+  __builtin___clear_cache((gpointer) trampoline_start, (gpointer) trampoline_end);
+
+  res = mprotect(self->area, self->size, PROT_READ | PROT_EXEC);
+  if (res < 0)
+    return NULL;
+  return (gpointer) trampoline_start;
+}
+
+static gboolean
+_is_trampoline_address(PerfTrampolineArea *self, guint8 *address)
+{
+  return self->area <= address && self->area + self->size > address;
+}
+
+static gboolean
+_save_symbol(gpointer address, gsize size, const gchar *symbol_name)
+{
+  gchar filename[64];
+
+  g_snprintf(filename, sizeof(filename), "/tmp/perf-%d.map", (int) getpid());
+  FILE *mapfile = fopen(filename, "a");
+  if (!mapfile)
+    return FALSE;
+  fprintf(mapfile, "%0lx %ld %s\n", (uintptr_t) address, size, symbol_name);
+  fclose(mapfile);
+  return TRUE;
+}
+
+static PerfTrampolineArea trampolines;
+
+gpointer
+perf_generate_trampoline(gpointer target_address, const gchar *symbol_name)
+{
+  gpointer t = _generate_trampoline(&trampolines, target_address);
+
+  if (!t)
+    {
+      msg_warning_once("WARNING: out of free trampoline slots",
+                       evt_tag_int("max_trampolines", trampolines.trampolines.num));
+      return target_address;
+    }
+
+  _save_symbol(t, trampolines.code_size, symbol_name);
+  return t;
+}
+
+gboolean
+perf_is_trampoline_address(gpointer address)
+{
+  return _is_trampoline_address(&trampolines, address);
+}
+
+void
+perf_global_init(void)
+{
+  _allocate_trampoline_area(&trampolines);
+}
+
+void
+perf_global_deinit(void)
+{
+  /* we are never freeing the trampolines, as that would invalidate any
+   * function pointers that point into that area */
+}

lib/perf/perf.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2024 Axoflow
+ * Copyright (c) 2024 Balázs Scheidler <[email protected]>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As an additional exemption you are allowed to compile & link against the
+ * OpenSSL libraries as published by the OpenSSL project. See the file
+ * COPYING for details.
+ *
+ */
+
+#ifndef SYSLOG_NG_PERF_H_INCLUDED
+#define SYSLOG_NG_PERF_H_INCLUDED
+
+#include "syslog-ng.h"
+
+gpointer perf_generate_trampoline(gpointer target_address, const gchar *symbol_name);
+gboolean perf_is_trampoline_address(gpointer address);
+
+
+void perf_global_init(void);
+void perf_global_deinit(void);
+
+
+#endif

lib/perf/trampoline.S

@@ -0,0 +1,19 @@
+    .text
+    .global      _perf_trampoline_func_start
+    .align 16
+_perf_trampoline_func_start:
+#ifdef __x86_64__
+    endbr64
+    sub    $8, %rsp
+    mov    _perf_trampoline_target_address(%rip), %r11
+    call    *%r11
+    add    $8, %rsp
+    ret
+    .align 8
+_perf_trampoline_target_address:
+    .quad 0x0
+#endif // __x86_64__
+
+    .global      _perf_trampoline_func_end
+_perf_trampoline_func_end:
+    .section .note.GNU-stack,"",@progbits