Check mmap_min_addr only if using NaCl bootstrap

Check the Linux sysctl vm.mmap_min_addr only when using the NaCl
bootstrap (rather than always when using NaCl). Or equivalently, check
it only with 32-bit NaCl runtimes. The bootstrap fails to start when the
value is too high to due low fixed address mappings. On ARM at least,
sel_ldr proper would also fail with a too-high min address since that
disturbs the address space layout. On 64-bit there is neither the
bootstrap nor 0-based address space layout so it always works.

Co-authored-by: Thomas Debesse <dev@illwieckz.net>

Author: slipher

src/engine/framework/VirtualMachine.cpp

@@ -447,7 +447,6 @@ static ExeSupport CheckExeSupport(Str::StringRef probe)
 
 #if defined(DAEMON_NACL_RUNTIME_ENABLED)
 static std::pair<Sys::OSHandle, IPC::Socket> CreateNaClVM(std::pair<IPC::Socket, IPC::Socket> pair, Str::StringRef name, bool debug, bool extract, int debugLoader) {
-	CheckMinAddressSysctlTooLarge();
 	const std::string& libPath = FS::GetLibPath();
 	std::vector<const char*> args;
 	char rootSocketRedir[32];
@@ -579,6 +578,8 @@ static std::pair<Sys::OSHandle, IPC::Socket> CreateNaClVM(std::pair<IPC::Socket,
 	}
 
 	if (useBootstrap) {
+		CheckMinAddressSysctlTooLarge();
+
 		bootstrapPath = FS::Path::Build(naclPath, Str::Format("nacl_helper_bootstrap-%s", arch));
 
 		if (FS::RawPath::FileExists(bootstrapPath)) {