0001-Make-EXEC_BACKEND-work-reliably-on-Linux-and-FreeBSD.patch

From e615dc88c89142a1b7ecf7ba6f6f01ea59c61be5 Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@b1f14.hub>
Date: Wed, 17 Nov 2021 20:25:19 +1300
Subject: [PATCH] Make EXEC_BACKEND work reliably on Linux and FreeBSD.

Try to disable ASLR when building in EXEC_BACKEND mode (developer only),
to avoid random memory mapping failures.

Suggested-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20210806032944.m4tz7j2w47mant26%40alap3.anarazel.de
---
 configure                     |  2 +-
 configure.ac                  |  1 +
 src/bin/pg_ctl/pg_ctl.c       |  4 ++++
 src/common/exec.c             | 32 ++++++++++++++++++++++++++++++++
 src/include/pg_config.h.in    |  3 +++
 src/include/port.h            | 11 +++++++++++
 src/test/regress/pg_regress.c |  4 ++++
 7 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index ded80be880..9b7033d7dd 100755
--- a/configure
+++ b/configure
@@ -13427,7 +13427,7 @@ $as_echo "#define HAVE_STDBOOL_H 1" >>confdefs.h
 fi
 
 
-for ac_header in atomic.h copyfile.h execinfo.h getopt.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/event.h sys/ipc.h sys/prctl.h sys/procctl.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/uio.h sys/un.h termios.h ucred.h wctype.h
+for ac_header in atomic.h copyfile.h execinfo.h getopt.h ifaddrs.h langinfo.h mbarrier.h poll.h sys/epoll.h sys/event.h sys/ipc.h sys/personality.h sys/prctl.h sys/procctl.h sys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/sockio.h sys/tas.h sys/uio.h sys/un.h termios.h ucred.h wctype.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"
diff --git a/configure.ac b/configure.ac
index 775e5c4436..9602b04e36 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1376,6 +1376,7 @@ AC_CHECK_HEADERS(m4_normalize([
 	sys/epoll.h
 	sys/event.h
 	sys/ipc.h
+	sys/personality.h
 	sys/prctl.h
 	sys/procctl.h
 	sys/pstat.h
diff --git a/src/bin/pg_ctl/pg_ctl.c b/src/bin/pg_ctl/pg_ctl.c
index 7fbbe7022e..eadb5c2297 100644
--- a/src/bin/pg_ctl/pg_ctl.c
+++ b/src/bin/pg_ctl/pg_ctl.c
@@ -451,6 +451,10 @@ start_postmaster(void)
 	fflush(stdout);
 	fflush(stderr);
 
+#ifdef EXEC_BACKEND
+	pg_disable_aslr();
+#endif
+
 	pm_pid = fork();
 	if (pm_pid < 0)
 	{
diff --git a/src/common/exec.c b/src/common/exec.c
index 81b810d4cf..e5d9174333 100644
--- a/src/common/exec.c
+++ b/src/common/exec.c
@@ -25,6 +25,14 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+#ifdef EXEC_BACKEND
+#if defined(HAVE_SYS_PERSONALITY_H)
+#include <sys/personality.h>
+#elif defined(HAVE_SYS_PROCCTL_H)
+#include <sys/procctl.h>
+#endif
+#endif
+
 /*
  * Hacky solution to allow expressing both frontend and backend error reports
  * in one macro call.  First argument of log_error is an errcode() call of
@@ -470,6 +478,30 @@ set_pglocale_pgservice(const char *argv0, const char *app)
 	}
 }
 
+#ifdef EXEC_BACKEND
+/*
+ * For the benefit of PostgreSQL developers testing EXEC_BACKEND code paths on
+ * Unix systems (ie paths normally exercised only on Windows), provide a way to
+ * disable ASLR so that we avoid memory map in developer-only builds, if we
+ * know how on this platform.  (See also the macOS-specific hack in
+ * sysv_shmem.c.)
+ */
+int
+pg_disable_aslr(void)
+{
+#if defined(HAVE_SYS_PERSONALITY_H)
+	return personality(ADDR_NO_RANDOMIZE);
+#elif defined(HAVE_SYS_PROCCTL_H) && defined(PROC_ASLR_FORCE_DISABLE)
+	int			data = PROC_ASLR_FORCE_DISABLE;
+
+	return procctl(P_PID, 0, PROC_ASLR_CTL, &data);
+#else
+	errno = ENOSYS;
+	return -1;
+#endif
+}
+#endif
+
 #ifdef WIN32
 
 /*
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index ca3592465e..a3d658644a 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -617,6 +617,9 @@
 /* Define to 1 if you have the <sys/ipc.h> header file. */
 #undef HAVE_SYS_IPC_H
 
+/* Define to 1 if you have the <sys/personality.h> header file. */
+#undef HAVE_SYS_PERSONALITY_H
+
 /* Define to 1 if you have the <sys/prctl.h> header file. */
 #undef HAVE_SYS_PRCTL_H
 
diff --git a/src/include/port.h b/src/include/port.h
index 49b4d38131..94b0f23837 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -42,6 +42,12 @@ typedef SOCKET pgsocket;
 typedef unsigned int socklen_t;
 #endif
 
+#ifdef EXEC_BACKEND
+#if defined(HAVE_SYS_PROCCTL_H)
+#include <sys/procctl.h>
+#endif
+#endif
+
 /* non-blocking */
 extern bool pg_set_noblock(pgsocket sock);
 extern bool pg_set_block(pgsocket sock);
@@ -140,6 +146,11 @@ extern char *pipe_read_line(char *cmd, char *line, int maxsize);
 /* Doesn't belong here, but this is used with find_other_exec(), so... */
 #define PG_BACKEND_VERSIONSTR "postgres (PostgreSQL) " PG_VERSION "\n"
 
+#ifdef EXEC_BACKEND
+/* Disable ASLR before exec, for developer builds only (in exec.c) */
+extern int pg_disable_aslr(void);
+#endif
+
 
 #if defined(WIN32) || defined(__CYGWIN__)
 #define EXE ".exe"
diff --git a/src/test/regress/pg_regress.c b/src/test/regress/pg_regress.c
index 2c8a600bad..67c78bccf2 100644
--- a/src/test/regress/pg_regress.c
+++ b/src/test/regress/pg_regress.c
@@ -1246,6 +1246,10 @@ spawn_process(const char *cmdline)
 	if (logfile)
 		fflush(logfile);
 
+#ifdef EXEC_BACKEND
+	pg_disable_aslr();
+#endif
+
 	pid = fork();
 	if (pid == -1)
 	{
-- 
2.33.1