Re: gdb and PIE binaries
AFAIK gdb does not use fancy information like file-mapping stuff. NT_FILE is probably hard to support on the Hurd, since we don't have a way to go backwards from a memory object port to a file (let alone a file name). All GDB needs is to know where the PIE was loaded, so it can find the DT_DEBUG and bootstrap the link_map list from there. On Linux, NT_AUXV in a core file has AT_ENTRY and from that and the ELF file, you can figure out where the PIE was loaded. In a live process, you read the same info from /proc/$pid/auxv. On the Hurd, we don't really have auxv at all. But to simplify things with GDB, we could have our core dumps include an NT_AUXV containing just an AT_ENTRY value synthesized by other means. Off hand I don't recall anything we store that can be used to compute such a value. Probably the right thing is to have the proc server keep that state like it does arg_locations, with the exec server writing it and the debugger and core-writer reading it.
Re: Time for another round of releases
Hello Samuel On 11/09/16 13:54, Samuel Thibault wrote: > Manolis Ragkousis, on Wed 09 Nov 2016 13:02:14 +0200, wrote: >> Now I only have problems with linking http://paste.lisp.org/display/330765 > > __gsync_wait and __gsync_wake are gnumach RPCs. They have been added to > gnumach quite a long time ago, don't you have them in > gnumach/include/mach/gnumach.defs? > > Samuel > Yes I do have them in gnumach/include/mach/gnumach.defs. The linking errors appears both when building from Guix and on debian/hurd. But I have managed to bypass the linking by first running make mach/subdir_lib, make hurd/subdir_lib, make libpthread/subdir_lib and then make all. It seems there is an issue with the order of subdirs building. Manolis
Re: gdb and PIE binaries
Samuel Thibault, on Fri 11 Nov 2016 18:17:43 +0100, wrote: > AIUI, what gdb misses is simply the name of the files being mapped: > since the mappings may be random, it can't invent the file names. I forgot to mention: on Linux, its provided in the core file through an NT_FILE note. Samuel
gdb and PIE binaries
Hello, Debian is pushing more and more PIE builds, so that address randomization can be done. However, on GNU/Hurd, gdb can't work with core files from processes running PIE programs, so one has to pass CFLAGS=-no-pie etc. to be able to debug programs, it'll become more and more problematic. AIUI, what gdb misses is simply the name of the files being mapped: since the mappings may be random, it can't invent the file names. It has been also raised several times that it'd be nice that running vminfo $pid (and /proc/$pid/maps) would show file names. AIUI, it'd be a matter of adding a char[] field to struct vm_object inside mach, that the creator of the VM object would set to whatever it seems fit, here the file name. What do people think about it? Could somebody have a look at implementing it? Samuel
