[PATCH] Implement the skip_solib_resolver gdbarch hook for FreeBSD architectures.

[John Baldwin <jhb@FreeBSD.org>]

The ELF runtime linker on all FreeBSD architectures uses the
"_rtld_bind" entry point for unresolved PTL entries.  FreeBSD/mips has
an additional entry point called "_mips_rtld_bind".

gdb/ChangeLog:

	* fbsd-tdep.c (fbsd_skip_solib_resolver): New function.
	(fbsd_init_abi): Install gdbarch "skip_solib_resolver" method.
	* fbsd-tdep.h (fbsd_skip_solib_resolver): New prototype.
	* mips-fbsd-tdep.c (mips_fbsd_skip_solib_resolver): New function.
	(mips_fbsd_init_abi): Install gdbarch "skip_solib_resolver"
	method.
---
 gdb/ChangeLog        |  9 +++++++++
 gdb/fbsd-tdep.c      | 15 +++++++++++++++
 gdb/fbsd-tdep.h      |  3 +++
 gdb/mips-fbsd-tdep.c | 16 ++++++++++++++++
 4 files changed, 43 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index c292927e49..219c2b110b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2020-07-10  John Baldwin  <jhb@FreeBSD.org>
+
+	* fbsd-tdep.c (fbsd_skip_solib_resolver): New function.
+	(fbsd_init_abi): Install gdbarch "skip_solib_resolver" method.
+	* fbsd-tdep.h (fbsd_skip_solib_resolver): New prototype.
+	* mips-fbsd-tdep.c (mips_fbsd_skip_solib_resolver): New function.
+	(mips_fbsd_init_abi): Install gdbarch "skip_solib_resolver"
+	method.
+
 2020-07-10  John Baldwin  <jhb@FreeBSD.org>
 
 	* fbsd-nat.h (fbsd_nat_target::supports_multi_process): New
diff --git a/gdb/fbsd-tdep.c b/gdb/fbsd-tdep.c
index 557c5d3d73..02d1b1fd40 100644
--- a/gdb/fbsd-tdep.c
+++ b/gdb/fbsd-tdep.c
@@ -21,6 +21,7 @@
 #include "auxv.h"
 #include "gdbcore.h"
 #include "inferior.h"
+#include "objfiles.h"
 #include "regcache.h"
 #include "regset.h"
 #include "gdbthread.h"
@@ -2071,6 +2072,19 @@ fbsd_get_thread_local_address (struct gdbarch *gdbarch, CORE_ADDR dtv_addr,
   return addr + offset;
 }
 
+/* Implement the "skip_solib_resolver" gdbarch method.  */
+
+CORE_ADDR
+fbsd_skip_solib_resolver (struct gdbarch *gdbarch, CORE_ADDR pc)
+{
+  struct bound_minimal_symbol msym;
+
+  msym = lookup_minimal_symbol("_rtld_bind", NULL, NULL);
+  if (msym.minsym && BMSYMBOL_VALUE_ADDRESS (msym) == pc)
+    return frame_unwind_caller_pc (get_current_frame ());
+  return 0;
+}
+
 /* To be called from GDB_OSABI_FREEBSD handlers. */
 
 void
@@ -2085,6 +2099,7 @@ fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   set_gdbarch_get_siginfo_type (gdbarch, fbsd_get_siginfo_type);
   set_gdbarch_gdb_signal_from_target (gdbarch, fbsd_gdb_signal_from_target);
   set_gdbarch_gdb_signal_to_target (gdbarch, fbsd_gdb_signal_to_target);
+  set_gdbarch_skip_solib_resolver (gdbarch, fbsd_skip_solib_resolver);
 
   /* `catch syscall' */
   set_xml_syscall_file_name (gdbarch, "syscalls/freebsd.xml");
diff --git a/gdb/fbsd-tdep.h b/gdb/fbsd-tdep.h
index 5dd8203299..2e3f46186c 100644
--- a/gdb/fbsd-tdep.h
+++ b/gdb/fbsd-tdep.h
@@ -71,4 +71,7 @@ extern CORE_ADDR fbsd_get_thread_local_address (struct gdbarch *gdbarch,
 						CORE_ADDR lm_addr,
 						CORE_ADDR offset);
 
+extern CORE_ADDR fbsd_skip_solib_resolver (struct gdbarch *gdbarch,
+					   CORE_ADDR pc);
+
 #endif /* fbsd-tdep.h */
diff --git a/gdb/mips-fbsd-tdep.c b/gdb/mips-fbsd-tdep.c
index abaf7f2474..90ef466137 100644
--- a/gdb/mips-fbsd-tdep.c
+++ b/gdb/mips-fbsd-tdep.c
@@ -462,6 +462,20 @@ static const struct tramp_frame mips64_fbsd_sigframe =
 
 /* Shared library support.  */
 
+/* FreeBSD/mips can use an alternate routine in the runtime linker to
+   resolve functions.  */
+
+CORE_ADDR
+mips_fbsd_skip_solib_resolver (struct gdbarch *gdbarch, CORE_ADDR pc)
+{
+  struct bound_minimal_symbol msym;
+
+  msym = lookup_minimal_symbol("_mips_rtld_bind", NULL, NULL);
+  if (msym.minsym && BMSYMBOL_VALUE_ADDRESS (msym) == pc)
+    return frame_unwind_caller_pc (get_current_frame ());
+  return fbsd_skip_solib_resolver (gdbarch, pc);
+}
+
 /* FreeBSD/mips uses a slightly different `struct link_map' than the
    other FreeBSD platforms as it includes an additional `l_off'
    member.  */
@@ -546,6 +560,8 @@ mips_fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   set_gdbarch_iterate_over_regset_sections
     (gdbarch, mips_fbsd_iterate_over_regset_sections);
 
+  set_gdbarch_skip_solib_resolver (gdbarch, mips_fbsd_skip_solib_resolver);
+
   /* FreeBSD/mips has SVR4-style shared libraries.  */
   set_solib_svr4_fetch_link_map_offsets
     (gdbarch, (gdbarch_ptr_bit (gdbarch) == 32 ?
-- 
2.25.1