| // Copyright (c) 2021, the Dart project authors. Please see the AUTHORS file | |
| // for details. All rights reserved. Use of this source code is governed by a | |
| // BSD-style license that can be found in the LICENSE file. | |
| // Work around for a bug in old kernels (only fixed in 3.18 Android kernel): | |
| // | |
| // Kernel does not clear If-Then execution state bits when entering ARM signal | |
| // handler which violates requirements imposed by ARM architecture reference. | |
| // Some CPUs look at these bits even while in ARM mode which causes them | |
| // to skip some instructions in the prologue of the signal handler. | |
| // | |
| // To work around the issue we insert enough NOPs in the prologue to ensure | |
| // that no actual instructions are skipped and then branch to the actual | |
| // signal handler. | |
| // | |
| // For the kernel patch that fixes the issue see: | |
| // http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6ecf830e5029598732e04067e325d946097519cb | |
| // | |
| // Note: can't use DART_* defines here because this file does not include | |
| // globals.h. | |
| #if !defined(PRODUCT) && defined(__ARMEL__) && defined(__ANDROID__) && \ | |
| !defined(__thumb__) | |
| .text | |
| .globl ThreadInterruptSignalHandlerTrampoline | |
| .hidden ThreadInterruptSignalHandlerTrampoline | |
| .type ThreadInterruptSignalHandlerTrampoline, %function | |
| ThreadInterruptSignalHandlerTrampoline: | |
| // IT (If-Then) instruction makes up to four instructions that follow it | |
| // conditional. | |
| nop | |
| nop | |
| nop | |
| nop | |
| // Tail-call the actual handler. | |
| // Note: no need to use interworking because we know that we are not | |
| // compiling for Thumb. | |
| b ThreadInterruptSignalHandler | |
| .size ThreadInterruptSignalHandlerTrampoline,.-ThreadInterruptSignalHandlerTrampoline | |
| #endif |