6def6de5e0
* Remove cmake/bindgen/llvm from wasmtime-runtime This commit removes the cmake/bindgen dependency (which removes the need for `llvm-config`) from the `wasmtime-runtime` crate. The C++ code is instead compiled with the `cc` crate (it's just one file anyway) and the interface is handwritten since it's quite small anyway. Some other changes are: * The `TrapContext` type in C++ was removed since it was unused, and it was moved to Rust with a `Cell` on each field. * Functions between Rust/C++ now return `int` instead of `bool` to make them a bit more FFI compatible portably. * The `jmp_buf` type has a workaround that will be fixed in the next commit. * Move setjmp/longjmp to C++ This commit moves the definition of setjmp and longjmp into C++. This is primarily done because it's [debatable whether it's possible to call `setjmp` from Rust][rfc]. The semantics of `setjmp` are that it returns twice but LLVM doesn't actually know about this because rustc isn't telling LLVM this information, so it's unclear whether it can ever be safe. Additionally this removes the need for Rust code to know the definition of `jmp_buf` which is a pretty hairy type to define in Rust across platforms. The solution in this commit is to move all setjmp/longjmp code to C++, and that way we should be able to guarantee that jumps over wasm JIT code should always go from C++ to C++, removing Rust from the equation for now from needing to get any fiddly bits working across platforms. This should overall help it be a bit more portable and also means Rust doesn't have to know about `jmp_buf` as a type. The previous `Vec` of `jmp_buf` is now replaced with one thread-local pointer where previous values are stored on the stack and restored when the function returns. This is intended to be functionally the same as the previous implementation. [rfc]: https://github.com/rust-lang/rfcs/issues/2625 * rustfmt * Use volatile loads/stores * Remove mention of cmake from README
38 lines
666 B
C++
38 lines
666 B
C++
#include <setjmp.h>
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#include "SignalHandlers.hpp"
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extern "C"
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int WasmtimeCallTrampoline(void *vmctx, void (*body)(void*, void*), void *args) {
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jmp_buf buf;
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void *volatile prev;
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if (setjmp(buf) != 0) {
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LeaveScope(prev);
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return 0;
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}
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prev = EnterScope(&buf);
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body(vmctx, args);
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LeaveScope(prev);
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return 1;
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}
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extern "C"
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int WasmtimeCall(void *vmctx, void (*body)(void*)) {
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jmp_buf buf;
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void *volatile prev;
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if (setjmp(buf) != 0) {
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LeaveScope(prev);
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return 0;
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}
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prev = EnterScope(&buf);
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body(vmctx);
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LeaveScope(prev);
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return 1;
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}
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extern "C"
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void Unwind() {
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jmp_buf *buf = (jmp_buf*) GetScope();
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longjmp(*buf, 1);
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}
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