1 #! @PERL@ 2 3 # This script handles linking the tool executables on Linux, 4 # statically and at an alternative load address. 5 # 6 # Linking statically sidesteps all sorts of complications to do with 7 # having two copies of the dynamic linker (valgrind's and the 8 # client's) coexisting in the same process. The alternative load 9 # address is needed because Valgrind itself will load the client at 10 # whatever address it specifies, which is almost invariably the 11 # default load address. Hence we can't allow Valgrind itself (viz, 12 # the tool executable) to be loaded at that address. 13 # 14 # Unfortunately there's no standard way to do 'static link at 15 # alternative address', so these link_tool_exe_*.in scripts handle 16 # the per-platform hoop-jumping. 17 # 18 # What we get passed here is: 19 # first arg 20 # the alternative load address 21 # all the rest of the args 22 # the gcc invocation to do the final link, that 23 # the build system would have done, left to itself 24 # 25 # We just let the script 'die' if something is wrong, rather than do 26 # proper error reporting. We don't expect the users to run this 27 # directly. It is only run as part of the build process, with 28 # carefully constrained inputs. 29 # 30 # Linux specific complications: 31 # 32 # - need to support both old GNU ld and gold: use -Ttext= to 33 # set the text segment address if that is all we have. We really 34 # need -Ttext-segment. Otherwise with GNU ld sections or notes 35 # (like the build-id) don't get at the desired address. But older 36 # linkers only know about -Ttext, not -Ttext-segment. So configure 37 # checks for us and sets FLAG_T_TEXT. 38 # 39 # - If all we have is -Ttext, then we need to pass --build-id=none 40 # (that is, -Wl,--build-id=none to gcc) if it accepts it, to ensure 41 # the linker doesn't add a notes section which ends up at the default 42 # load address and so defeats our attempts to keep that address clear 43 # for the client. However, older linkers don't support this flag, 44 # so it is tested for by configure.in and is shipped to us as part of 45 # argv[2 ..]. 46 # 47 # So: what we actually do: 48 # 49 # pass the specified command to the linker as-is, except, add 50 # "-static" and "-Ttext[-segment]=<argv[1]>" to it. 51 # Previously we did this by adding these options after the first 52 # word of the rest of the arguments, which works in the common case 53 # when it's something like "gcc". But the linker invocation itself 54 # might be multiple words, say if it's "ccache gcc". So we now put 55 # the new options at the end instead. 56 # 57 58 use warnings; 59 use strict; 60 61 # expect at least: alt-load-address gcc -o foo bar.o 62 die "Not enough arguments" 63 if (($#ARGV + 1) < 5); 64 65 my $ala = $ARGV[0]; 66 shift; # Remove $ala from @ARGV 67 68 # check for plausible-ish alt load address 69 die "Bogus alt-load address" 70 if (length($ala) < 3 || index($ala, "0x") != 0); 71 72 my $cmd = join(" ", @ARGV, "-static -Wl,@FLAG_T_TEXT@=$ala"); 73 74 #print "link_tool_exe_linux: $cmd\n"; 75 76 77 # Execute the command: 78 my $r = system($cmd); 79 80 if ($r == 0) { 81 exit 0; 82 } else { 83 exit 1; 84 } 85
