Make sure ELF is present when looking up call sites

fwsGonzo · Oct 26, 2023 · 5930903 · 5930903
1 parent 2f04d96
commit 5930903
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Showing 2 changed files with 18 additions and 4 deletions.
diff --git a/lib/libriscv/elf.hpp b/lib/libriscv/elf.hpp
@@ -47,8 +47,11 @@ namespace riscv
 #endif
 
 	template <typename Class>
-	inline bool validate_header(const Class* hdr)
+	inline bool validate_header(std::string_view binary)
 	{
+		if (binary.size() < sizeof(Class))
+			return false;
+		auto* hdr = (Class *)binary.data();
 		if (hdr->e_ident[EI_MAG0] != 0x7F ||
 			hdr->e_ident[EI_MAG1] != 'E'  ||
 			hdr->e_ident[EI_MAG2] != 'L'  ||

diff --git a/lib/libriscv/memory.cpp b/lib/libriscv/memory.cpp
@@ -298,10 +298,11 @@ namespace riscv
 		if (UNLIKELY(m_binary.size() < sizeof(Ehdr))) {
 			throw MachineException(INVALID_PROGRAM, "ELF program too short");
 		}
-		const auto* elf = (Ehdr*) m_binary.data();
-		if (UNLIKELY(!validate_header<Ehdr> (elf))) {
-			throw MachineException(INVALID_PROGRAM, "Invalid ELF header! Mixup between 32- and 64-bit?", elf->e_ident[EI_CLASS]);
+		if (UNLIKELY(!validate_header<Ehdr> (m_binary))) {
+			throw MachineException(INVALID_PROGRAM, "Invalid ELF header! Mixup between 32- and 64-bit?");
 		}
+
+		const auto* elf = (Ehdr*) m_binary.data();
 		if (UNLIKELY(elf->e_type != ET_EXEC)) {
 			throw MachineException(INVALID_PROGRAM, "ELF program is not an executable type. Trying to load a dynamic library?");
 		}
@@ -477,6 +478,9 @@ namespace riscv
 	template <int W>
 	typename Memory<W>::Callsite Memory<W>::lookup(address_t address) const
 	{
+		if (!validate_header<Ehdr>(this->m_binary))
+			return {};
+
 		const auto* sym_hdr = section_by_name(".symtab");
 		if (sym_hdr == nullptr) return {};
 		const auto* str_hdr = section_by_name(".strtab");
@@ -539,6 +543,13 @@ namespace riscv
 			[this, print_function] (const int N, const address_type<W> addr) {
 				// get information about the callsite
 				const auto site = this->lookup(addr);
+				if (site.address == 0 && site.offset == 0 && site.size == 0) {
+					// if there is nothing to print, indicate that this is
+					// an unknown/empty location by "printing" a zero-length string.
+					print_function({});
+					return;
+				}
+
 				// write information directly to stdout
 				char buffer[8192];
 				int len = 0;