Merge bitcoin/bitcoin#23724: build: add systemtap's sys/sdt.h as depends for GUIX builds with USDT tracepoints

6200fbf build: rename --enable-ebpf to --enable-usdt (0xb10c)
e158a2a build: add systemtap's sys/sdt.h as depends (0xb10c)

Pull request description:

  There has been light conceptual agreement on including the Userspace, Statically Defined Tracing tracepoints in Bitcoin Core release builds. This, for example, enables user to hook into production deployments, if they need to. Binaries don't have to be switched out. This is possible because we don't do [expensive computations](https://github.com/bitcoin/bitcoin/blob/master/doc/tracing.md#no-expensive-computations-for-tracepoints) only needed for the tracepoints. The tracepoints are NOPs when not used.

  Systemtap's `sys/sdt.h` header is required to build Bitcoin Core with USDT support. The header file defines the `DTRACE_PROBE` macros used in [`src/util/trace.h`](https://github.com/bitcoin/bitcoin/blob/master/src/util/trace.h). This PR adds Systemtap 4.5 (May 2021) as dependency. GUIX builds for Linux hosts now include the tracepoints.

  Closes bitcoin/bitcoin#23297.

ACKs for top commit:
  fanquake:
    ACK 6200fbf - tested enabling / disabling and with/without SDT from depends. We can follow up with #23819, #23907 and #23296, and if any serious issues arise before feature freeze, it is easy for us to flip depends such that USDT becomes opt-in, rather than opt-out, and thus, releases would be tracepoint free.

Tree-SHA512: 0263f44892bf8450e8a593e4de7a498243687f8d81269e1c3283fa8354922c7cf93fddef4b92cf5192d33798424aa5812e03e68ef8de31af078a32dd34021382

Author: fanquake

configure.ac

@@ -137,11 +137,11 @@ AC_ARG_WITH([bdb],
   [use_bdb=$withval],
   [use_bdb=auto])
 
-AC_ARG_ENABLE([ebpf],
-  [AS_HELP_STRING([--enable-ebpf],
-  [enable eBPF tracing (default is yes if sys/sdt.h is found)])],
-  [use_ebpf=$enableval],
-  [use_ebpf=yes])
+AC_ARG_ENABLE([usdt],
+  [AS_HELP_STRING([--enable-usdt],
+  [enable tracepoints for Userspace, Statically Defined Tracing (default is yes if sys/sdt.h is found)])],
+  [use_usdt=$enableval],
+  [use_usdt=yes])
 
 AC_ARG_WITH([miniupnpc],
   [AS_HELP_STRING([--with-miniupnpc],
@@ -1337,15 +1337,15 @@ if test "$enable_wallet" != "no"; then
     fi
 fi
 
-if test "$use_ebpf" != "no"; then
-  AC_MSG_CHECKING([whether eBPF tracepoints are supported])
+if test "$use_usdt" != "no"; then
+  AC_MSG_CHECKING([whether Userspace, Statically Defined Tracing tracepoints are supported])
   AC_COMPILE_IFELSE([
     AC_LANG_PROGRAM(
       [#include <sys/sdt.h>],
       [DTRACE_PROBE("context", "event");]
     )],
-    [AC_MSG_RESULT([yes]); have_sdt=yes; AC_DEFINE([ENABLE_TRACING], [1], [Define to 1 to enable eBPF user static defined tracepoints])],
-    [AC_MSG_RESULT([no]); have_sdt=no;]
+    [AC_MSG_RESULT([yes]); AC_DEFINE([ENABLE_TRACING], [1], [Define to 1 to enable tracepoints for Userspace, Statically Defined Tracing])],
+    [AC_MSG_RESULT([no]); use_usdt=no;]
   )
 fi
 
@@ -1759,7 +1759,6 @@ AM_CONDITIONAL([TARGET_WINDOWS], [test "$TARGET_OS" = "windows"])
 AM_CONDITIONAL([ENABLE_WALLET], [test "$enable_wallet" = "yes"])
 AM_CONDITIONAL([USE_SQLITE], [test "$use_sqlite" = "yes"])
 AM_CONDITIONAL([USE_BDB], [test "$use_bdb" = "yes"])
-AM_CONDITIONAL([ENABLE_TRACING], [test "$have_sdt" = "yes"])
 AM_CONDITIONAL([ENABLE_TESTS], [test "$BUILD_TEST" = "yes"])
 AM_CONDITIONAL([ENABLE_FUZZ], [test "$enable_fuzz" = "yes"])
 AM_CONDITIONAL([ENABLE_FUZZ_BINARY], [test "$enable_fuzz_binary" = "yes"])
@@ -1929,7 +1928,7 @@ echo "  with bench      = $use_bench"
 echo "  with upnp       = $use_upnp"
 echo "  with natpmp     = $use_natpmp"
 echo "  use asm         = $use_asm"
-echo "  ebpf tracing    = $have_sdt"
+echo "  USDT tracing    = $use_usdt"
 echo "  sanitizers      = $use_sanitizers"
 echo "  debug enabled   = $enable_debug"
 echo "  gprof enabled   = $enable_gprof"

depends/Makefile

@@ -39,6 +39,7 @@ NO_SQLITE ?=
 NO_WALLET ?=
 NO_ZMQ ?=
 NO_UPNP ?=
+NO_USDT ?=
 NO_NATPMP ?=
 MULTIPROCESS ?=
 FALLBACK_DOWNLOAD_PATH ?= https://bitcoincore.org/depends-sources
@@ -149,8 +150,9 @@ natpmp_packages_$(NO_NATPMP) = $(natpmp_packages)
 
 zmq_packages_$(NO_ZMQ) = $(zmq_packages)
 multiprocess_packages_$(MULTIPROCESS) = $(multiprocess_packages)
+usdt_packages_$(NO_USDT) = $(usdt_$(host_os)_packages)
 
-packages += $($(host_arch)_$(host_os)_packages) $($(host_os)_packages) $(qt_packages_) $(wallet_packages_) $(upnp_packages_) $(natpmp_packages_)
+packages += $($(host_arch)_$(host_os)_packages) $($(host_os)_packages) $(qt_packages_) $(wallet_packages_) $(upnp_packages_) $(natpmp_packages_) $(usdt_packages_)
 native_packages += $($(host_arch)_$(host_os)_native_packages) $($(host_os)_native_packages)
 
 ifneq ($(zmq_packages_),)
@@ -228,6 +230,7 @@ $(host_prefix)/share/config.site : config.site.in $(host_prefix)/.stamp_$(final_
             -e 's|@no_bdb@|$(NO_BDB)|' \
             -e 's|@no_sqlite@|$(NO_SQLITE)|' \
             -e 's|@no_upnp@|$(NO_UPNP)|' \
+            -e 's|@no_usdt@|$(NO_USDT)|' \
             -e 's|@no_natpmp@|$(NO_NATPMP)|' \
             -e 's|@multiprocess@|$(MULTIPROCESS)|' \
             -e 's|@debug@|$(DEBUG)|' \

depends/config.site.in

@@ -70,6 +70,10 @@ if test -z "$enable_zmq" && test -n "@no_zmq@"; then
   enable_zmq=no
 fi
 
+if test -z "$enable_usdt" && test -n "@no_usdt@"; then
+  enable_usdt=no
+fi
+
 if test "@host_os@" = darwin; then
   BREW=no
 fi

depends/packages/packages.mk

@@ -19,6 +19,8 @@ natpmp_packages=libnatpmp
 multiprocess_packages = libmultiprocess capnp
 multiprocess_native_packages = native_libmultiprocess native_capnp
 
+usdt_linux_packages=systemtap
+
 darwin_native_packages = native_ds_store native_mac_alias
 
 $(host_arch)_$(host_os)_native_packages += native_b2

depends/packages/systemtap.mk

@@ -0,0 +1,12 @@
+package=systemtap
+$(package)_version=4.5
+$(package)_download_path=https://sourceware.org/systemtap/ftp/releases/
+$(package)_file_name=$(package)-$($(package)_version).tar.gz
+$(package)_sha256_hash=75078ed37e0dd2a769c9d1f9394170b2d9f4d7daa425f43ca80c13bad6cfc925
+$(package)_patches=remove_SDT_ASM_SECTION_AUTOGROUP_SUPPORT_check.patch
+
+define $(package)_preprocess_cmds
+  patch -p1 < $($(package)_patch_dir)/remove_SDT_ASM_SECTION_AUTOGROUP_SUPPORT_check.patch && \
+  mkdir -p $($(package)_staging_prefix_dir)/include/sys && \
+  cp includes/sys/sdt.h $($(package)_staging_prefix_dir)/include/sys/sdt.h
+endef

depends/patches/systemtap/remove_SDT_ASM_SECTION_AUTOGROUP_SUPPORT_check.patch

@@ -0,0 +1,31 @@
+commit b92d4c121486f3c6e8a2cea537c53eb09894479a
+Author: 0xb10c <[email protected]>
+Date:   Tue Dec 7 11:02:07 2021 +0100
+
+    Remove _SDT_ASM_SECTION_AUTOGROUP_SUPPORT check
+    
+    We assume that the assembler supports "?" in .pushsection directives.
+    This enables us to skip configure and make.
+    
+    See https://github.com/bitcoin/bitcoin/issues/23297.
+
+diff --git a/includes/sys/sdt.h b/includes/sys/sdt.h
+index 97766e710..352b4ee25 100644
+--- a/includes/sys/sdt.h
++++ b/includes/sys/sdt.h
+@@ -230,12 +230,10 @@ __extension__ extern unsigned long long __sdt_unsp;
+    nice with code in COMDAT sections, which comes up in C++ code.
+    Without that assembler support, some combinations of probe placements
+    in certain kinds of C++ code may produce link-time errors.  */
+-#include "sdt-config.h"
+-#if _SDT_ASM_SECTION_AUTOGROUP_SUPPORT
++/* PATCH: We assume that the assembler supports the feature. This
++   enables us to skip configure and make. In turn, this means we
++   require fewer dependencies and have shorter depend build times. */
+ # define _SDT_ASM_AUTOGROUP "?"
+-#else
+-# define _SDT_ASM_AUTOGROUP ""
+-#endif
+ 
+ #define _SDT_ASM_BODY(provider, name, pack_args, args)			      \
+   _SDT_ASM_1(990:	_SDT_NOP)					      \

doc/dependencies.md

@@ -23,7 +23,7 @@ These are the dependencies currently used by Bitcoin Core. You can find instruct
 | Qt | [5.12.11](https://download.qt.io/official_releases/qt/) | [5.9.5](https://github.com/bitcoin/bitcoin/issues/20104) | No |  |  |
 | SQLite | [3.32.1](https://sqlite.org/download.html) | [3.7.17](https://github.com/bitcoin/bitcoin/pull/19077) |  |  |  |
 | XCB |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) (Linux only) |
-| systemtap ([tracing](tracing.md))|  |  |  |  | |
+| systemtap ([tracing](tracing.md))| [4.5](https://sourceware.org/systemtap/ftp/releases/) |  |  |  | |
 | xkbcommon |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) (Linux only) |
 | ZeroMQ | [4.3.1](https://github.com/zeromq/libzmq/releases) | 4.0.0 | No |  |  |
 | zlib |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk) |