From b63a5e38efa2dc6df46eafb0bbad3f48472e1bef Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Fri, 27 Nov 2020 15:41:37 +0000 Subject: [PATCH] bfd/binutils: support for gdb target descriptions in the core file This commit lays the ground work for allowing GDB to write its target description into a generated core file. The goal of this work is to allow a user to connect to a remote target, capture a core file from within GDB, then pass the executable and core file to another user and have the user be able to examine the state of the machine without needing to connect to a running target. Different remote targets can have different register sets and this information is communicated from the target to GDB in the target description. It is possible for a user to extract the target description from GDB and pass this along with the core file so that when the core file is used the target description can be fed back into GDB, however this is not a great user experience. It would be nicer, I think, if GDB could write the target description directly into the core file, and then make use of this description when loading a core file. This commit performs the binutils/bfd side of this task, adding the boiler plate functions to access the target description from within a core file note, and reserving a new number for a note containing the target description. Later commits will extend GDB to make use of this. The new note is given the name 'GDB' and a type NT_GDB_TDESC. This should hopefully protect us if there's ever a reuse of the number assigned to NT_GDB_TDESC by some other core file producer. It should also, hopefully, make it clearer to users that this note carries GDB specific information. bfd/ChangeLog: * elf-bfd.h (elfcore_write_gdb_tdesc): Declare new function. * elf.c (elfcore_grok_gdb_tdesc): New function. (elfcore_grok_note): Handle NT_GDB_TDESC. (elfcore_write_gdb_tdesc): New function. (elfcore_write_register_note): Handle NT_GDB_TDESC. binutils/ChangeLog: * readelf.c (get_note_type): Handle NT_GDB_TDESC. include/ChangeLog: * elf/common.h (NT_GDB_TDESC): Define. --- bfd/ChangeLog | 9 +++++++++ bfd/elf-bfd.h | 2 ++ bfd/elf.c | 35 +++++++++++++++++++++++++++++++++++ binutils/ChangeLog | 5 +++++ binutils/readelf.c | 2 ++ include/ChangeLog | 5 +++++ include/elf/common.h | 4 ++++ 7 files changed, 62 insertions(+) diff --git a/bfd/ChangeLog b/bfd/ChangeLog index d4525f1e696..31d0714da27 100644 --- a/bfd/ChangeLog +++ b/bfd/ChangeLog @@ -1,3 +1,12 @@ +2021-03-05 Craig Blackmore + Andrew Burgess + + * elf-bfd.h (elfcore_write_gdb_tdesc): Declare new function. + * elf.c (elfcore_grok_gdb_tdesc): New function. + (elfcore_grok_note): Handle NT_GDB_TDESC. + (elfcore_write_gdb_tdesc): New function. + (elfcore_write_register_note): Handle NT_GDB_TDESC. + 2021-03-05 Nick Clifton PR 27521 diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h index dd66d98883e..69e18036a49 100644 --- a/bfd/elf-bfd.h +++ b/bfd/elf-bfd.h @@ -2798,6 +2798,8 @@ extern char *elfcore_write_aarch_pauth (bfd *, char *, int *, const void *, int); extern char *elfcore_write_arc_v2 (bfd *, char *, int *, const void *, int); +extern char *elfcore_write_gdb_tdesc + (bfd *, char *, int *, const void *, int); extern char *elfcore_write_lwpstatus (bfd *, char *, int *, long, int, const void *); extern char *elfcore_write_register_note diff --git a/bfd/elf.c b/bfd/elf.c index 087f05e5cc8..2d66e9b999f 100644 --- a/bfd/elf.c +++ b/bfd/elf.c @@ -9912,6 +9912,15 @@ elfcore_grok_arc_v2 (bfd *abfd, Elf_Internal_Note *note) return elfcore_make_note_pseudosection (abfd, ".reg-arc-v2", note); } +/* Convert NOTE into a bfd_section called ".gdb-tdesc". Return TRUE if + successful otherwise, return FALSE. */ + +static bfd_boolean +elfcore_grok_gdb_tdesc (bfd *abfd, Elf_Internal_Note *note) +{ + return elfcore_make_note_pseudosection (abfd, ".gdb-tdesc", note); +} + #if defined (HAVE_PRPSINFO_T) typedef prpsinfo_t elfcore_psinfo_t; #if defined (HAVE_PRPSINFO32_T) /* Sparc64 cross Sparc32 */ @@ -10570,6 +10579,13 @@ elfcore_grok_note (bfd *abfd, Elf_Internal_Note *note) else return TRUE; + case NT_GDB_TDESC: + if (note->namesz == 4 + && strcmp (note->namedata, "GDB") == 0) + return elfcore_grok_gdb_tdesc (abfd, note); + else + return TRUE; + case NT_PRPSINFO: case NT_PSINFO: if (bed->elf_backend_grok_psinfo) @@ -11951,6 +11967,23 @@ elfcore_write_arc_v2 (bfd *abfd, note_name, NT_ARC_V2, arc_v2, size); } +/* Write the target description (a string) pointed to by TDESC, length + SIZE, into the note buffer BUF, and update *BUFSIZ. ABFD is the bfd the + note is being written into. Return a pointer to the new start of the + note buffer, to replace BUF which may no longer be valid. */ + +char * +elfcore_write_gdb_tdesc (bfd *abfd, + char *buf, + int *bufsiz, + const void *tdesc, + int size) +{ + const char *note_name = "GDB"; + return elfcore_write_note (abfd, buf, bufsiz, + note_name, NT_GDB_TDESC, tdesc, size); +} + char * elfcore_write_register_note (bfd *abfd, char *buf, @@ -12035,6 +12068,8 @@ elfcore_write_register_note (bfd *abfd, return elfcore_write_aarch_pauth (abfd, buf, bufsiz, data, size); if (strcmp (section, ".reg-arc-v2") == 0) return elfcore_write_arc_v2 (abfd, buf, bufsiz, data, size); + if (strcmp (section, ".gdb-tdesc") == 0) + return elfcore_write_gdb_tdesc (abfd, buf, bufsiz, data, size); return NULL; } diff --git a/binutils/ChangeLog b/binutils/ChangeLog index da24027199e..80b6ea6a4c7 100644 --- a/binutils/ChangeLog +++ b/binutils/ChangeLog @@ -1,3 +1,8 @@ +2021-03-05 Craig Blackmore + Andrew Burgess + + * readelf.c (get_note_type): Handle NT_GDB_TDESC. + 2021-03-05 Nick Clifton PR 27387 diff --git a/binutils/readelf.c b/binutils/readelf.c index c862839b4cf..fe58ebf6ac4 100644 --- a/binutils/readelf.c +++ b/binutils/readelf.c @@ -18499,6 +18499,8 @@ get_note_type (Filedata * filedata, unsigned e_type) return _("NT_PRPSINFO (prpsinfo structure)"); case NT_TASKSTRUCT: return _("NT_TASKSTRUCT (task structure)"); + case NT_GDB_TDESC: + return _("NT_GDB_TDESC (GDB XML target description)"); case NT_PRXFPREG: return _("NT_PRXFPREG (user_xfpregs structure)"); case NT_PPC_VMX: diff --git a/include/ChangeLog b/include/ChangeLog index 7c53c21b9c3..08c45673be6 100644 --- a/include/ChangeLog +++ b/include/ChangeLog @@ -1,3 +1,8 @@ +2021-03-05 Craig Blackmore + Andrew Burgess + + * elf/common.h (NT_GDB_TDESC): Define. + 2021-03-03 Alan Modra * coff/internal.h: Delete obsolete relocation defines. Move used diff --git a/include/elf/common.h b/include/elf/common.h index e7d55ae0782..e6e9c278faa 100644 --- a/include/elf/common.h +++ b/include/elf/common.h @@ -677,6 +677,10 @@ #define NT_SIGINFO 0x53494749 /* Fields of siginfo_t. */ #define NT_FILE 0x46494c45 /* Description of mapped files. */ +/* The range 0xff000000 to 0xffffffff is set aside for notes that don't + originate from any particular operating system. */ +#define NT_GDB_TDESC 0xff000000 /* Contains copy of GDB's target description XML. */ + /* Note segments for core files on dir-style procfs systems. */ #define NT_PSTATUS 10 /* Has a struct pstatus */ -- 2.30.2