[PATCH] xtensa: implement NPTL helpers

[Max Filippov <jcmvbkbc at gmail dot com>]

These changes allow debugging multithreaded NPTL xtensa applications.

2015-08-20  Max Filippov  <jcmvbkbc@gmail.com>
gdb/
	* xtensa-linux-nat.c (gdb_proc_service.h): New #include.
	(ps_get_thread_area): New function.
	* xtensa-linux-tdep.c (xtensa_linux_init_abi): Add call to
	set_gdbarch_fetch_tls_load_module_address to enable TLS support.
	* xtensa-tdep.c (xtensa_gdbarch_init): Call gdbarch_init_osabi
	to register xtensa-specific hooks.
	* xtensa-tdep.h (struct xtensa_elf_gregset_t): Add threadptr
	member.
---
 gdb/xtensa-linux-nat.c  | 19 +++++++++++++++++++
 gdb/xtensa-linux-tdep.c |  4 ++++
 gdb/xtensa-tdep.c       |  3 +++
 gdb/xtensa-tdep.h       |  3 ++-
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/gdb/xtensa-linux-nat.c b/gdb/xtensa-linux-nat.c
index 77ad3e0..3e5ad5c 100644
--- a/gdb/xtensa-linux-nat.c
+++ b/gdb/xtensa-linux-nat.c
@@ -37,6 +37,9 @@
 #include "gregset.h"
 #include "xtensa-tdep.h"
 
+/* Defines ps_err_e, struct ps_prochandle.  */
+#include "gdb_proc_service.h"
+
 /* Extended register set depends on hardware configs.
    Keeping these definitions separately allows to introduce
    hardware-specific overlays.  */
@@ -280,6 +283,22 @@ xtensa_linux_store_inferior_registers (struct target_ops *ops,
     store_xtregs (regcache, regnum);
 }
 
+ps_err_e
+ps_get_thread_area (const struct ps_prochandle *ph,
+                    lwpid_t lwpid, int idx, void **base)
+{
+  xtensa_elf_gregset_t regs;
+  if (ptrace (PTRACE_GETREGS, lwpid, NULL, &regs) != 0)
+    return PS_ERR;
+
+  /* IDX is the bias from the thread pointer to the beginning of the
+     thread descriptor.  It has to be subtracted due to implementation
+     quirks in libthread_db.  */
+  *base = (void *) ((char *)regs.threadptr - idx);
+
+  return PS_OK;
+}
+
 void _initialize_xtensa_linux_nat (void);
 
 void
diff --git a/gdb/xtensa-linux-tdep.c b/gdb/xtensa-linux-tdep.c
index 61ea9b0..99e0d3e 100644
--- a/gdb/xtensa-linux-tdep.c
+++ b/gdb/xtensa-linux-tdep.c
@@ -106,6 +106,10 @@ xtensa_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 				      xtensa_linux_gdb_signal_from_target);
   set_gdbarch_gdb_signal_to_target (gdbarch,
 				    xtensa_linux_gdb_signal_to_target);
+
+  /* Enable TLS support.  */
+  set_gdbarch_fetch_tls_load_module_address (gdbarch,
+                                             svr4_fetch_objfile_link_map);
 }
 
 /* Provide a prototype to silence -Wmissing-prototypes.  */
diff --git a/gdb/xtensa-tdep.c b/gdb/xtensa-tdep.c
index 55e7d98..07b7773 100644
--- a/gdb/xtensa-tdep.c
+++ b/gdb/xtensa-tdep.c
@@ -3273,6 +3273,9 @@ xtensa_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   set_solib_svr4_fetch_link_map_offsets
     (gdbarch, svr4_ilp32_fetch_link_map_offsets);
 
+  /* Hook in the ABI-specific overrides, if they have been registered.  */
+  gdbarch_init_osabi (info, gdbarch);
+
   return gdbarch;
 }
 
diff --git a/gdb/xtensa-tdep.h b/gdb/xtensa-tdep.h
index caa2988..1d476ad 100644
--- a/gdb/xtensa-tdep.h
+++ b/gdb/xtensa-tdep.h
@@ -96,7 +96,8 @@ typedef struct
   xtensa_elf_greg_t sar;
   xtensa_elf_greg_t windowstart;
   xtensa_elf_greg_t windowbase;
-  xtensa_elf_greg_t reserved[8+48];
+  xtensa_elf_greg_t threadptr;
+  xtensa_elf_greg_t reserved[7+48];
   xtensa_elf_greg_t ar[64];
 } xtensa_elf_gregset_t;
 
-- 
1.8.1.4