| 1 | /* |
| 2 | * Get user helper pc for memory unwinding. |
| 3 | * SPDX-License-Identifier: LGPL-2.1-or-later |
| 4 | */ |
| 5 | |
| 6 | #ifndef ACCEL_TCG_HELPER_RETADDR_H |
| 7 | #define ACCEL_TCG_HELPER_RETADDR_H |
| 8 | |
| 9 | #ifndef CONFIG_TCG |
| 10 | #error Can only include this header with TCG |
| 11 | #endif |
| 12 | |
| 13 | /* |
| 14 | * For user-only, helpers that use guest to host address translation |
| 15 | * must protect the actual host memory access by recording 'retaddr' |
| 16 | * for the signal handler. This is required for a race condition in |
| 17 | * which another thread unmaps the page between a probe and the |
| 18 | * actual access. |
| 19 | */ |
| 20 | #ifdef CONFIG_USER_ONLY |
| 21 | extern __thread uintptr_t helper_retaddr; |
| 22 | |
| 23 | static inline void set_helper_retaddr(uintptr_t ra) |
| 24 | { |
| 25 | helper_retaddr = ra; |
| 26 | /* |
| 27 | * Ensure that this write is visible to the SIGSEGV handler that |
| 28 | * may be invoked due to a subsequent invalid memory operation. |
| 29 | */ |
| 30 | signal_barrier(); |
| 31 | } |
| 32 | |
| 33 | static inline void clear_helper_retaddr(void) |
| 34 | { |
| 35 | /* |
| 36 | * Ensure that previous memory operations have succeeded before |
| 37 | * removing the data visible to the signal handler. |
| 38 | */ |
| 39 | signal_barrier(); |
| 40 | helper_retaddr = 0; |
| 41 | } |
| 42 | #else |
| 43 | #define set_helper_retaddr(ra) do { } while (0) |
| 44 | #define clear_helper_retaddr() do { } while (0) |
| 45 | #endif |
| 46 | |
| 47 | #endif /* ACCEL_TCG_HELPER_RETADDR_H */ |