Implement the __builtin_nested_func_ptr_{created,deleted} functions
for the x86_64-linux platform. This serves to exercise the
infrastructure added in libgcc (--enable-off-stack-trampolines) and
gcc (-foff-stack-trampolines) in supporting off-stack trampoline
generation, and is intended primarily for demonstration and debugging
purposes.
Co-authored-by: Andrew Burgess <andrew.burg...@embecosm.com>
libgcc/ChangeLog:
* config/i386/heap-trampoline.c: New file: Implement off-stack
trampolines for x86_64.
* config/i386/t-heap-trampoline: Add rule to build
config/i386/heap-trampoline.c
* config.host (x86_64-*-linux*): Handle
--enable-off-stack-trampolines.
* configure.ac (--enable-off-stack-trampolines): Permit setting
for target x86_64-*-linux*.
* configure: Regenerate.
---
libgcc/config.host | 4 +
libgcc/config/i386/heap-trampoline.c | 143 +++++++++++++++++++++++++++
libgcc/config/i386/t-heap-trampoline | 21 ++++
libgcc/configure | 3 +
libgcc/configure.ac | 3 +
5 files changed, 174 insertions(+)
create mode 100644 libgcc/config/i386/heap-trampoline.c
create mode 100644 libgcc/config/i386/t-heap-trampoline
diff --git a/libgcc/config.host b/libgcc/config.host
index 168535b1780..163cd4c4161 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -753,6 +753,10 @@ x86_64-*-linux*)
tmake_file="${tmake_file} i386/t-crtpc t-crtfm i386/t-crtstuff
t-dfprules"
tm_file="${tm_file} i386/elf-lib.h"
md_unwind_header=i386/linux-unwind.h
+ if test x$off_stack_trampolines = xyes; then
+ extra_parts="${extra_parts} heap-trampoline.o"
+ tmake_file="${tmake_file} i386/t-heap-trampoline"
+ fi
;;
x86_64-*-kfreebsd*-gnu)
extra_parts="$extra_parts crtprec32.o crtprec64.o crtprec80.o
crtfastmath.o"
diff --git a/libgcc/config/i386/heap-trampoline.c
b/libgcc/config/i386/heap-trampoline.c
new file mode 100644
index 00000000000..6c202660c35
--- /dev/null
+++ b/libgcc/config/i386/heap-trampoline.c
@@ -0,0 +1,143 @@
+#include <unistd.h>
+#include <sys/mman.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+void *allocate_trampoline_page (void);
+int get_trampolines_per_page (void);
+struct tramp_ctrl_data *allocate_tramp_ctrl (struct tramp_ctrl_data *parent);
+void *allocate_trampoline_page (void);
+
+void __builtin_nested_func_ptr_created (void *chain, void *func, void **dst);
+void __builtin_nested_func_ptr_deleted (void);
+
+struct tramp_ctrl_data;
+struct tramp_ctrl_data
+{
+ struct tramp_ctrl_data *prev;
+
+ int free_trampolines;
+
+ /* This will be pointing to an executable mmap'ed page. */
+ union ix86_trampoline *trampolines;
+};
+
+static const uint8_t trampoline_insns[] = {
+ /* movabs $<chain>,%r11 */
+ 0x49, 0xbb,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+
+ /* movabs $<func>,%r10 */
+ 0x49, 0xba,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+
+ /* rex.WB jmpq *%r11 */
+ 0x41, 0xff, 0xe3
+};
+
+union ix86_trampoline {
+ uint8_t insns[sizeof(trampoline_insns)];
+
+ struct __attribute__((packed)) fields {
+ uint8_t insn_0[2];
+ void *func_ptr;
+ uint8_t insn_1[2];
+ void *chain_ptr;
+ uint8_t insn_2[3];
+ } fields;
+};
+
+int
+get_trampolines_per_page (void)
+{
+ return getpagesize() / sizeof(union ix86_trampoline);
+}
+
+static _Thread_local struct tramp_ctrl_data *tramp_ctrl_curr = NULL;
+
+void *
+allocate_trampoline_page (void)
+{
+ void *page;
+
+ page = mmap (0, getpagesize (), PROT_WRITE | PROT_EXEC,
+ MAP_ANON | MAP_PRIVATE, 0, 0);
+
+ return page;
+}
+
+struct tramp_ctrl_data *
+allocate_tramp_ctrl (struct tramp_ctrl_data *parent)
+{
+ struct tramp_ctrl_data *p = malloc (sizeof (struct tramp_ctrl_data));
+ if (p == NULL)
+ return NULL;
+
+ p->trampolines = allocate_trampoline_page ();
+
+ if (p->trampolines == MAP_FAILED)
+ return NULL;
+
+ p->prev = parent;
+ p->free_trampolines = get_trampolines_per_page();
+
+ return p;
+}
+
+void
+__builtin_nested_func_ptr_created (void *chain, void *func, void **dst)
+{
+ if (tramp_ctrl_curr == NULL)
+ {
+ tramp_ctrl_curr = allocate_tramp_ctrl (NULL);
+ if (tramp_ctrl_curr == NULL)
+ abort ();
+ }
+
+ if (tramp_ctrl_curr->free_trampolines == 0)
+ {
+ void *tramp_ctrl = allocate_tramp_ctrl (tramp_ctrl_curr);
+ if (!tramp_ctrl)
+ abort ();
+
+ tramp_ctrl_curr = tramp_ctrl;
+ }
+
+ union ix86_trampoline *trampoline
+ = &tramp_ctrl_curr->trampolines[get_trampolines_per_page ()
+ - tramp_ctrl_curr->free_trampolines];
+
+ memcpy (trampoline->insns, trampoline_insns,
+ sizeof(trampoline_insns));
+ trampoline->fields.func_ptr = func;
+ trampoline->fields.chain_ptr = chain;
+
+ tramp_ctrl_curr->free_trampolines -= 1;
+
+ __builtin___clear_cache ((void *)trampoline->insns,
+ ((void *)trampoline->insns +
sizeof(trampoline->insns)));
+
+ *dst = &trampoline->insns;
+}
+
+void
+__builtin_nested_func_ptr_deleted (void)
+{
+ if (tramp_ctrl_curr == NULL)
+ abort ();
+
+ tramp_ctrl_curr->free_trampolines += 1;
+
+ if (tramp_ctrl_curr->free_trampolines == get_trampolines_per_page ())
+ {
+ if (tramp_ctrl_curr->prev == NULL)
+ return;
+
+ munmap (tramp_ctrl_curr->trampolines, getpagesize());
+ struct tramp_ctrl_data *prev = tramp_ctrl_curr->prev;
+ free (tramp_ctrl_curr);
+ tramp_ctrl_curr = prev;
+ }
+}
diff --git a/libgcc/config/i386/t-heap-trampoline
b/libgcc/config/i386/t-heap-trampoline
new file mode 100644
index 00000000000..d9dc9cfeac4
--- /dev/null
+++ b/libgcc/config/i386/t-heap-trampoline
@@ -0,0 +1,21 @@
+# Machine description for AArch64 architecture.
+# Copyright (C) 2012-2021 Free Software Foundation, Inc.
+# Contributed by ARM Ltd.
+#
+# This file is part of GCC.
+#
+# GCC is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+#
+# GCC 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
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3. If not see
+# <http://www.gnu.org/licenses/>.
+
+LIB2ADD += $(srcdir)/config/i386/heap-trampoline.c
diff --git a/libgcc/configure b/libgcc/configure
index 2f469219e07..d9a74e3cc7c 100755
--- a/libgcc/configure
+++ b/libgcc/configure
@@ -2261,6 +2261,9 @@ fi
if test "${enable_off_stack_trampolines+set}" = set; then :
enableval=$enable_off_stack_trampolines;
case "$target" in
+ x86_64-*-linux* )
+ off_stack_trampolines=$enableval
+ ;;
*)
as_fn_error $? "Configure option --enable-off-stack-trampolines is not
supported \
for this platform" "$LINENO" 5
diff --git a/libgcc/configure.ac b/libgcc/configure.ac
index 97bbd4bd35c..4bec0a54493 100644
--- a/libgcc/configure.ac
+++ b/libgcc/configure.ac
@@ -72,6 +72,9 @@ AC_ARG_ENABLE([off-stack-trampolines],
[AS_HELP_STRING([--enable-off-stack-trampolines]
[Specify whether to support generating off-stack
trampolines])],[
case "$target" in
+ x86_64-*-linux* )
+ off_stack_trampolines=$enableval
+ ;;
*)
AC_MSG_ERROR([Configure option --enable-off-stack-trampolines is not
supported \
for this platform])
--
2.30.1 (Apple Git-130)
