From c1fc1a00ea9633961153451d0e927db49c1b268d Mon Sep 17 00:00:00 2001 From: Yuta Saito Date: Thu, 23 Nov 2023 01:59:54 +0900 Subject: [PATCH] [wasm] Fix Asyncify loop exit condition for normal return (#9007) [wasm] Fix Asyncify loop exit condition for normal return Stop calling `asyncify_stop_unwind` when the main function returns without any unwinding. In the era when Asyncify buffers were allocated on the stack, the `top` and `end` fields were remained in the stack space even after the main function returned, so buffer-overflow check in the `asyncify_stop_unwind` function passed. But now, the `top` and `end` fields are part of the jump buffer allocated on the heap and they are deallocated with `free` when the corresponding VM tag is popped. So, the buffer-overflow check in the `asyncify_stop_unwind` function failed when the main fuction returned without any unwinding, and we have to break the asyncify loop before calling `asyncify_stop_unwind`. Related commit: https://github.com/ruby/ruby.wasm/commit/bc46b12b127e4b6625a100f373504ed5ea45ae66 --- wasm/runtime.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/wasm/runtime.c b/wasm/runtime.c index b5b0a1a966..89b06be6ad 100644 --- a/wasm/runtime.c +++ b/wasm/runtime.c @@ -19,6 +19,13 @@ int rb_wasm_rt_start(int (main)(int argc, char **argv), int argc, char **argv) { result = main(argc, argv); } + extern void *rb_asyncify_unwind_buf; + // Exit Asyncify loop if there is no unwound buffer, which + // means that main function has returned normally. + if (rb_asyncify_unwind_buf == NULL) { + break; + } + // NOTE: it's important to call 'asyncify_stop_unwind' here instead in rb_wasm_handle_jmp_unwind // because unless that, Asyncify inserts another unwind check here and it unwinds to the root frame. asyncify_stop_unwind();