[rfa] Attach vsyscall support for GNU/Linux

Daniel Jacobowitz
2004-10-24T18:53:48Z

This patch, based on a patch Andrew posted earlier this year, connects
vsyscall support to the inferior_created observer.

As before, I have adjusted the i386-linux sigtramp code to recognize
the names of the kernel trampolines (both of them this time - I forgot
the RT case when I first did this). And I have adjusted the i386
target to recognize signal trampolines before searching for DWARF-2
unwind information, as previously discussed. Other architectures which
now have a vsyscall DSO may need to make the same change.

I re-added the inferior_created observer to child_attach; it got lost
in the change to remove ATTACH_DETACH.

I ended up not using from_tty after all. Instead, I arrange for the
right message to be printed out by the core symfile code. This causes
the message for reading the DSO's symbols to be printed out iff the
messages for reading other shared libraries are.

Tested on i686-pc-linux-gnu. There are no changes in testsuite
results, but a couple of places in the logs look better; instead of
getting lucky when trying to backtrace from 0xffffe410, we get a proper
backtrace from __kernel_vsyscall.

OK? How about for the branch? I think this patch needs both i386 and
symtab approval.

--
Daniel Jacobowitz

2004-10-24 Andrew Cagney <cagney@redhat.com>
Daniel Jacobowitz <dan@debian.org>
Roland McGrath <roland@redhat.com>

* Makefile.in (symfile-mem.o): Update dependencies.
* i386-linux-tdep.c (i386_linux_sigtramp_p): Handle
__kernel_sigreturn and __kernel_rt_sigreturn.
* i386-tdep.c (i386_gdbarch_init): Check for signal frames
before dwarf2 frames.
* inf-ptrace.c (inf_ptrace_attach): Call
observer_notify_inferior_created.
* inftarg.c (child_attach): Likewise.
* symfile-mem.c: Include "observer.h", "auxv.h", and "elf/common.h".
(symbol_file_add_from_memory): Take NAME argument. Use it for
the new BFD's filename.
(add_symbol_file_from_memory_command): Update call to
symbol_file_add_from_memory.
(struct symbol_file_add_from_memory_args, add_vsyscall_page)
(symbol_file_add_from_memory_wrapper): New.
(_initialize_symfile_mem): Register add_vsyscall_page as an
inferior_created observer.

Index: gdb/Makefile.in
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/Makefile.in,v
retrieving revision 1.643
diff -u -p -r1.643 Makefile.in
--- gdb/Makefile.in 15 Oct 2004 16:17:34 -0000 1.643
+++ gdb/Makefile.in 24 Oct 2004 17:25:24 -0000
@@ -2600,7 +2600,8 @@ symfile.o: symfile.c $(defs_h) $(bfdlink
$(hashtab_h) $(readline_h) $(gdb_assert_h) $(block_h) \
$(gdb_string_h) $(gdb_stat_h)
symfile-mem.o: symfile-mem.c $(defs_h) $(symtab_h) $(gdbcore_h) \
- $(objfiles_h) $(gdbcmd_h) $(target_h) $(value_h) $(symfile_h)
+ $(objfiles_h) $(gdbcmd_h) $(target_h) $(value_h) $(symfile_h) \
+ $(observer_h) $(auxv_h) $(elf_common_h)
symmisc.o: symmisc.c $(defs_h) $(symtab_h) $(gdbtypes_h) $(bfd_h) \
$(symfile_h) $(objfiles_h) $(breakpoint_h) $(command_h) \
$(gdb_obstack_h) $(language_h) $(bcache_h) $(block_h) $(gdb_regex_h) \
Index: gdb/i386-linux-tdep.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/i386-linux-tdep.c,v
retrieving revision 1.41
diff -u -p -r1.41 i386-linux-tdep.c
--- gdb/i386-linux-tdep.c 6 Aug 2004 20:58:28 -0000 1.41
+++ gdb/i386-linux-tdep.c 24 Oct 2004 17:48:46 -0000
@@ -231,6 +231,12 @@ i386_linux_sigtramp_p (struct frame_info

find_pc_partial_function (pc, &name, NULL, NULL);

+ /* If a vsyscall DSO is in use, the signal trampolines may have these
+ names. */
+ if (name && (strcmp (name, "__kernel_sigreturn") == 0
+ || strcmp (name, "__kernel_rt_sigreturn") == 0))
+ return 1;
+
/* If we have NAME, we can optimize the search. The trampolines are
named __restore and __restore_rt. However, they aren't dynamically
exported from the shared C library, so the trampoline may appear to
Index: gdb/i386-tdep.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/i386-tdep.c,v
retrieving revision 1.201
diff -u -p -r1.201 i386-tdep.c
--- gdb/i386-tdep.c 18 Sep 2004 20:16:37 -0000 1.201
+++ gdb/i386-tdep.c 24 Oct 2004 17:22:27 -0000
@@ -2216,6 +2216,10 @@ i386_gdbarch_init (struct gdbarch_info i
/* Helper for function argument information. */
set_gdbarch_fetch_pointer_argument (gdbarch, i386_fetch_pointer_argument);

+ /* The signal handler might have dwarf2 CFI, via the vsyscall DSO, so check
+ for this first. */
+ frame_unwind_append_sniffer (gdbarch, i386_sigtramp_frame_sniffer);
+
/* Hook in the DWARF CFI frame unwinder. */
frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);

@@ -2224,7 +2228,6 @@ i386_gdbarch_init (struct gdbarch_info i
/* Hook in ABI-specific overrides, if they have been registered. */
gdbarch_init_osabi (info, gdbarch);

- frame_unwind_append_sniffer (gdbarch, i386_sigtramp_frame_sniffer);
frame_unwind_append_sniffer (gdbarch, i386_frame_sniffer);

/* If we have a register mapping, enable the generic core file
Index: gdb/inf-ptrace.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/inf-ptrace.c,v
retrieving revision 1.11
diff -u -p -r1.11 inf-ptrace.c
--- gdb/inf-ptrace.c 15 Oct 2004 13:29:33 -0000 1.11
+++ gdb/inf-ptrace.c 24 Oct 2004 17:23:11 -0000
@@ -220,6 +220,10 @@ inf_ptrace_attach (char *args, int from_

inferior_ptid = pid_to_ptid (pid);
push_target (ptrace_ops_hack);
+
+ /* Do this first, before anything has had a chance to query the
+ inferior's symbol table or similar. */
+ observer_notify_inferior_created (&current_target, from_tty);
}

static void
Index: gdb/inftarg.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/inftarg.c,v
retrieving revision 1.34
diff -u -p -r1.34 inftarg.c
--- gdb/inftarg.c 8 Oct 2004 20:29:47 -0000 1.34
+++ gdb/inftarg.c 24 Oct 2004 17:23:15 -0000
@@ -211,6 +211,10 @@ child_attach (char *args, int from_tty)

inferior_ptid = pid_to_ptid (pid);
push_target (&deprecated_child_ops);
+
+ /* Do this first, before anything has had a chance to query the
+ inferior's symbol table or similar. */
+ observer_notify_inferior_created (&current_target, from_tty);
}

#if !defined(CHILD_POST_ATTACH)
Index: gdb/symfile-mem.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/symfile-mem.c,v
retrieving revision 1.3
diff -u -p -r1.3 symfile-mem.c
--- gdb/symfile-mem.c 17 Jul 2004 14:24:07 -0000 1.3
+++ gdb/symfile-mem.c 24 Oct 2004 18:02:15 -0000
@@ -52,13 +52,19 @@
#include "target.h"
#include "value.h"
#include "symfile.h"
+#include "observer.h"
+#include "auxv.h"
+#include "elf/common.h"

/* Read inferior memory at ADDR to find the header of a loaded object file
and read its in-core symbols out of inferior memory. TEMPL is a bfd
- representing the target's format. */
+ representing the target's format. NAME is the name to use for this
+ symbol file in messages; it can be NULL or a malloc-allocated string
+ which will be attached to the BFD. */
static struct objfile *
-symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr, int from_tty)
+symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr, char *name,
+ int from_tty)
{
struct objfile *objf;
struct bfd *nbfd;
@@ -75,7 +81,10 @@ symbol_file_add_from_memory (struct bfd
if (nbfd == NULL)
error ("Failed to read a valid object file image from memory.");

- nbfd->filename = xstrdup ("shared object read from target memory");
+ if (name == NULL)
+ nbfd->filename = xstrdup ("shared object read from target memory");
+ else
+ nbfd->filename = name;

if (!bfd_check_format (nbfd, bfd_object))
{
@@ -129,7 +138,73 @@ add_symbol_file_from_memory_command (cha
error ("\
Must use symbol-file or exec-file before add-symbol-file-from-memory.");

- symbol_file_add_from_memory (templ, addr, from_tty);
+ symbol_file_add_from_memory (templ, addr, NULL, from_tty);
+}
+
+/* Arguments for symbol_file_add_from_memory_wrapper. */
+
+struct symbol_file_add_from_memory_args
+{
+ struct bfd *bfd;
+ CORE_ADDR sysinfo_ehdr;
+ char *name;
+ int from_tty;
+};
+
+/* Wrapper function for symbol_file_add_from_memory, for
+ catch_exceptions. */
+
+static int
+symbol_file_add_from_memory_wrapper (struct ui_out *uiout, void *data)
+{
+ struct symbol_file_add_from_memory_args *args = data;
+
+ symbol_file_add_from_memory (args->bfd, args->sysinfo_ehdr, args->name,
+ args->from_tty);
+ return 0;
+}
+
+/* Try to add the symbols for the vsyscall page, if there is one. This function
+ is called via the inferior_created observer. */
+
+static void
+add_vsyscall_page (struct target_ops *target, int from_tty)
+{
+ CORE_ADDR sysinfo_ehdr;
+
+ if (target_auxv_search (target, AT_SYSINFO_EHDR, &sysinfo_ehdr) > 0
+ && sysinfo_ehdr != (CORE_ADDR) 0)
+ {
+ struct bfd *bfd;
+ struct symbol_file_add_from_memory_args args;
+
+ if (core_bfd != NULL)
+ bfd = core_bfd;
+ else if (exec_bfd != NULL)
+ bfd = exec_bfd;
+ else
+ /* FIXME: cagney/2004-05-06: Should not require an existing
+ BFD when trying to create a run-time BFD of the VSYSCALL
+ page in the inferior. Unfortunately that's the current
+ interface so for the moment bail. Introducing a
+ ``bfd_runtime'' (a BFD created using the loaded image) file
+ format should fix this. */
+ {
+ warning ("could not load vsyscall page because no executable was specified");
+ warning ("try using the \"file\" command first");
+ return;
+ }
+ args.bfd = bfd;
+ args.sysinfo_ehdr = sysinfo_ehdr;
+ xasprintf (&args.name, "system-supplied DSO at 0x%s",
+ paddr_nz (sysinfo_ehdr));
+ /* Pass zero for FROM_TTY, because the action of loading the
+ vsyscall DSO was not triggered by the user, even if the user
+ typed "run" at the TTY. */
+ args.from_tty = 0;
+ catch_exceptions (uiout, symbol_file_add_from_memory_wrapper,
+ &args, NULL, RETURN_MASK_ALL);
+ }
}

\f
@@ -143,4 +218,7 @@ Load the symbols out of memory from a dy
Give an expression for the address of the file's shared object file header.",
&cmdlist);

+ /* Want to know of each new inferior so that it's vsyscall info can
+ be extracted. */
+ observer_attach_inferior_created (add_vsyscall_page);
}