make signal handler less greedy: only handle signals from expected memory ranges

include/eosio/vm/allocator.hpp

@@ -9,6 +9,7 @@
 #include <cstring>
 #include <map>
 #include <set>
+#include <span>
 #include <memory>
 #include <mutex>
 #include <utility>
@@ -372,6 +373,8 @@ namespace eosio { namespace vm {
 
       const void* get_code_start() const { return _code_base; }
 
+      std::span<std::byte> get_code_span() const {return {(std::byte*)_code_base, _code_size};}
+
       /* different semantics than free,
        * the memory must be at the end of the most recently allocated block.
        */
@@ -524,5 +527,7 @@ namespace eosio { namespace vm {
       inline T* create_pointer(uint32_t offset) { return reinterpret_cast<T*>(raw + offset); }
       inline int32_t get_current_page() const { return page; }
       bool is_in_region(char* p) { return p >= raw && p < raw + max_memory; }
+
+      std::span<std::byte> get_span() const {return {(std::byte*)raw, max_memory};}
    };
 }} // namespace eosio::vm

include/eosio/vm/execution_context.hpp

@@ -358,11 +358,11 @@ namespace eosio { namespace vm {
 
                   vm::invoke_with_signal_handler([&]() {
                      result = execute<sizeof...(Args)>(args_raw, fn, this, base_type::linear_memory(), stack);
-                  }, &handle_signal);
+                  }, &handle_signal, {_mod->allocator.get_code_span(),  base_type::get_wasm_allocator()->get_span()});
                } else {
                   vm::invoke_with_signal_handler([&]() {
                      result = execute<sizeof...(Args)>(args_raw, fn, this, base_type::linear_memory(), stack);
-                  }, &handle_signal);
+                  }, &handle_signal, {_mod->allocator.get_code_span(),  base_type::get_wasm_allocator()->get_span()});
                }
             }
          } catch(wasm_exit_exception&) {
@@ -800,7 +800,7 @@ namespace eosio { namespace vm {
             setup_locals(func_index);
             vm::invoke_with_signal_handler([&]() {
                execute(visitor);
-            }, &handle_signal);
+            }, &handle_signal, {_mod->allocator.get_code_span(),  base_type::get_wasm_allocator()->get_span()});
          }
 
          if (_mod->get_function_type(func_index).return_count && !_state.exiting) {

include/eosio/vm/signals.hpp

@@ -7,6 +7,7 @@
 #include <cstdlib>
 #include <exception>
 #include <utility>
+#include <span>
 #include <signal.h>
 #include <setjmp.h>
 
@@ -16,6 +17,9 @@ namespace eosio { namespace vm {
    __attribute__((visibility("default")))
    inline thread_local std::atomic<sigjmp_buf*> signal_dest{nullptr};
 
+   __attribute__((visibility("default")))
+   inline thread_local std::vector<std::span<std::byte>> protected_memory_ranges;
+
    // Fixes a duplicate symbol build issue when building with `-fvisibility=hidden`
    __attribute__((visibility("default")))
    inline thread_local std::exception_ptr saved_exception{nullptr};
@@ -25,7 +29,20 @@ namespace eosio { namespace vm {
 
    inline void signal_handler(int sig, siginfo_t* info, void* uap) {
       sigjmp_buf* dest = std::atomic_load(&signal_dest);
-      if (dest) {
+
+      auto in_protected_range = [&]() {
+         //empty protection list means legacy catch-all behavior; useful for some of the old tests
+         if(protected_memory_ranges.empty())
+            return true;
+
+         for(const std::span<std::byte>& range : protected_memory_ranges) {
+            if(info->si_addr >= range.data() && info->si_addr < range.data() + range.size())
+               return true;
+         }
+         return false;
+      };
+
+      if (dest && in_protected_range()) {
          siglongjmp(*dest, sig);
       } else {
          struct sigaction* prev_action;
@@ -98,7 +115,9 @@ namespace eosio { namespace vm {
       sigaddset(&sa.sa_mask, SIGPROF);
       sa.sa_flags = SA_NODEFER | SA_SIGINFO;
       sigaction(SIGSEGV, &sa, &prev_signal_handler<SIGSEGV>);
+#ifndef __linux__
       sigaction(SIGBUS, &sa, &prev_signal_handler<SIGBUS>);
+#endif
       sigaction(SIGFPE, &sa, &prev_signal_handler<SIGFPE>);
    }
 
@@ -114,16 +133,17 @@ namespace eosio { namespace vm {
    /// with non-trivial destructors, then it must mask the relevant signals
    /// during the lifetime of these objects or the behavior is undefined.
    ///
-   /// signals handled: SIGSEGV, SIGBUS, SIGFPE
+   /// signals handled: SIGSEGV, SIGBUS (except on Linux), SIGFPE
    ///
    // Make this noinline to prevent possible corruption of the caller's local variables.
    // It's unlikely, but I'm not sure that it can definitely be ruled out if both
    // this and f are inlined and f modifies locals from the caller.
    template<typename F, typename E>
-   [[gnu::noinline]] auto invoke_with_signal_handler(F&& f, E&& e) {
+   [[gnu::noinline]] auto invoke_with_signal_handler(F&& f, E&& e, const std::vector<std::span<std::byte>>& protect_ranges) {
       setup_signal_handler();
       sigjmp_buf dest;
       sigjmp_buf* volatile old_signal_handler = nullptr;
+      protected_memory_ranges = protect_ranges;
       int sig;
       if((sig = sigsetjmp(dest, 1)) == 0) {
          // Note: Cannot use RAII, as non-trivial destructors w/ longjmp

tests/signals_tests.cpp

@@ -15,7 +15,7 @@ TEST_CASE("Testing signals", "[invoke_with_signal_handler]") {
          std::raise(SIGSEGV);
       }, [](int sig) {
          throw test_exception{};
-      });
+      }, {});
    } catch(test_exception&) {
       okay = true;
    }
@@ -25,7 +25,7 @@ TEST_CASE("Testing signals", "[invoke_with_signal_handler]") {
 TEST_CASE("Testing throw", "[signal_handler_throw]") {
    CHECK_THROWS_AS(eosio::vm::invoke_with_signal_handler([](){
       eosio::vm::throw_<eosio::vm::wasm_exit_exception>( "Exiting" );
-   }, [](int){}), eosio::vm::wasm_exit_exception);
+   }, [](int){}, {}), eosio::vm::wasm_exit_exception);
 }
 
 static volatile sig_atomic_t sig_handled;
@@ -54,9 +54,11 @@ TEST_CASE("Test signal handler forwarding", "[signal_handler_forward]") {
       sig_handled = 0;
       std::raise(SIGSEGV);
       CHECK(sig_handled == 42 + SIGSEGV);
+#ifndef __linux__
       sig_handled = 0;
       std::raise(SIGBUS);
       CHECK(sig_handled == 42 + SIGBUS);
+#endif
       sig_handled = 0;
       std::raise(SIGFPE);
       CHECK(sig_handled == 42 + SIGFPE);
@@ -73,9 +75,11 @@ TEST_CASE("Test signal handler forwarding", "[signal_handler_forward]") {
       sig_handled = 0;
       std::raise(SIGSEGV);
       CHECK(sig_handled == 142 + SIGSEGV);
+#ifndef __linux__
       sig_handled = 0;
       std::raise(SIGBUS);
       CHECK(sig_handled == 142 + SIGBUS);
+#endif
       sig_handled = 0;
       std::raise(SIGFPE);
       CHECK(sig_handled == 142 + SIGFPE);