Use last read-only segment for rodata end

fwsGonzo · Nov 22, 2023 · 5e48e1d · 5e48e1d
1 parent 879b668
commit 5e48e1d
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Showing 2 changed files with 28 additions and 6 deletions.
diff --git a/lib/libriscv/memory.cpp b/lib/libriscv/memory.cpp
@@ -161,6 +161,10 @@ namespace riscv
 				attr.read, attr.write, attr.exec);
 		}
 
+		if (attr.read && !attr.write) {
+			this->m_initial_rodata_end =
+				std::max(m_initial_rodata_end, static_cast<address_t>(hdr->p_vaddr + len));
+		}
 		if (attr.exec && this->cached_execute_segments() == 0)
 		{
 			serialize_execute_segment(options, hdr);
@@ -181,12 +185,6 @@ namespace riscv
 				throw MachineException(INVALID_PROGRAM, "Execute segment must be execute-only");
 			}
 		}
-		if (attr.write) {
-			if (this->m_initial_rodata_end == RWREAD_BEGIN)
-				this->m_initial_rodata_end = hdr->p_vaddr;
-			else
-				this->m_initial_rodata_end = std::min(m_initial_rodata_end, static_cast<address_t>(hdr->p_vaddr));
-		}
 
 		// Load into virtual memory
 		this->memcpy(hdr->p_vaddr, src, len);

diff --git a/tests/unit/protections.cpp b/tests/unit/protections.cpp
@@ -99,6 +99,12 @@ TEST_CASE("Writes to read-only segment", "[Memory]")
 	int main() {
 		*(volatile int *)array = 1234;
 		return 666;
+	}
+	void write_to(char* dst) {
+		*dst = 1;
+	}
+	int read_from(char* dst) {
+		return *dst;
 	})M");
 
 	riscv::Machine<RISCV64> machine { binary, { .memory_max = MAX_MEMORY } };
@@ -119,4 +125,22 @@ TEST_CASE("Writes to read-only segment", "[Memory]")
 	}(), Catch::Matchers::ContainsSubstring("Protection fault"));
 
 	REQUIRE(machine.return_value<int>() != 666);
+
+	const auto write_addr = machine.address_of("write_to");
+	REQUIRE(write_addr != 0x0);
+	const auto read_addr = machine.address_of("read_from");
+	REQUIRE(read_addr != 0x0);
+
+	// Reads amd writes to invalid locations
+	REQUIRE_THROWS_WITH([&] {
+		machine.vmcall<MAX_INSTRUCTIONS>(read_addr, 0);
+	}(), Catch::Matchers::ContainsSubstring("Protection fault"));
+
+	machine.vmcall<MAX_INSTRUCTIONS>(read_addr, 0x1000);
+
+	for (uint64_t addr = machine.memory.start_address(); addr < machine.memory.initial_rodata_end(); addr += 0x1000) {
+		REQUIRE_THROWS_WITH([&] {
+			machine.vmcall<MAX_INSTRUCTIONS>(write_addr, addr);
+		}(), Catch::Matchers::ContainsSubstring("Protection fault"));
+	}
 }