diff options
Diffstat (limited to 'include/accel/tcg/helper-retaddr.h')
| -rw-r--r-- | include/accel/tcg/helper-retaddr.h | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/include/accel/tcg/helper-retaddr.h b/include/accel/tcg/helper-retaddr.h new file mode 100644 index 0000000000..037fda2b83 --- /dev/null +++ b/include/accel/tcg/helper-retaddr.h @@ -0,0 +1,43 @@ +/* + * Get user helper pc for memory unwinding. + * SPDX-License-Identifier: LGPL-2.1-or-later + */ + +#ifndef ACCEL_TCG_HELPER_RETADDR_H +#define ACCEL_TCG_HELPER_RETADDR_H + +/* + * For user-only, helpers that use guest to host address translation + * must protect the actual host memory access by recording 'retaddr' + * for the signal handler. This is required for a race condition in + * which another thread unmaps the page between a probe and the + * actual access. + */ +#ifdef CONFIG_USER_ONLY +extern __thread uintptr_t helper_retaddr; + +static inline void set_helper_retaddr(uintptr_t ra) +{ + helper_retaddr = ra; + /* + * Ensure that this write is visible to the SIGSEGV handler that + * may be invoked due to a subsequent invalid memory operation. + */ + signal_barrier(); +} + +static inline void clear_helper_retaddr(void) +{ + /* + * Ensure that previous memory operations have succeeded before + * removing the data visible to the signal handler. + */ + signal_barrier(); + helper_retaddr = 0; +} +#else +#define set_helper_retaddr(ra) do { } while (0) +#define clear_helper_retaddr() do { } while (0) +#endif + +#endif /* ACCEL_TCG_HELPER_RETADDR_H */ |