From 08b12344149080c5f71deae8d8f63662d1a7be2d Mon Sep 17 00:00:00 2001 From: Alexander Potapenko Date: Wed, 10 Sep 2025 15:36:25 +0200 Subject: executor: introduce __no_stack_protector and use it for guest code When compiling the executor in syz-env-old, -fstack-protector may kick in and introduce global accesses that tools/check-syzos.sh reports. To prevent this, introduce the __no_stack_protector macro attribute that disable stack protection for the function in question, and use it for guest code. While at it, factor out some common definitions into common_kvm_syzos.h --- executor/common_kvm_syzos.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) create mode 100644 executor/common_kvm_syzos.h (limited to 'executor/common_kvm_syzos.h') diff --git a/executor/common_kvm_syzos.h b/executor/common_kvm_syzos.h new file mode 100644 index 000000000..a635d517b --- /dev/null +++ b/executor/common_kvm_syzos.h @@ -0,0 +1,33 @@ +// Copyright 2025 syzkaller project authors. All rights reserved. +// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file. + +// Common SYZOS definitions. + +// Prevent function inlining. This attribute is applied to every guest_handle_* function, +// making sure they remain small so that the compiler does not attempt to be too clever +// (e.g. generate switch tables). +#define noinline __attribute__((noinline)) + +// __no_stack_protector disables -fstack-protector which may introduce unwanted global accesses. +// TODO(glider): once syz-env-old migrates to GCC>11 we can just use +// __attribute__((no_stack_protector)). +#if defined(__clang__) +// Clang supports the no_stack_protector attribute. +#define __no_stack_protector __attribute__((no_stack_protector)) +#elif defined(__GNUC__) +// The no_stack_protector attribute was introduced in GCC 11.1. +#if __GNUC__ > 11 +#define __no_stack_protector __attribute__((no_stack_protector)) +#else +// Fallback to the optimize attribute for older GCC versions. +#define __no_stack_protector __attribute__((__optimize__("-fno-stack-protector"))) +#endif +#else +#define __no_stack_protector +#endif + +// Host will map the code in this section into the guest address space. +#define GUEST_CODE __attribute__((section("guest"))) __no_stack_protector + +// Start/end of the guest section. +extern char *__start_guest, *__stop_guest; -- cgit mrf-deployment