[PATCH 7/9] Support TLS variables on FreeBSD/i386.

[John Baldwin <jhb@FreeBSD.org>]

Derive the pointer to the DTV array from the gs_base register.  As
with FreeBSD/amd64, gs_base is currently only available via the native
target.

gdb/ChangeLog:

	* i386-fbsd-tdep.c (i386fbsd_get_thread_local_address): New.
	(i386fbsd_init_abi): Install gdbarch
	"fetch_tls_load_module_address" and "get_thread_local_address"
	methods.
---
 gdb/ChangeLog        |  7 +++++++
 gdb/i386-fbsd-tdep.c | 29 +++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 7e97fae997..06c637c80a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2019-01-22  John Baldwin  <jhb@FreeBSD.org>
+
+	* i386-fbsd-tdep.c (i386fbsd_get_thread_local_address): New.
+	(i386fbsd_init_abi): Install gdbarch
+	"fetch_tls_load_module_address" and "get_thread_local_address"
+	methods.
+
 2019-01-22  John Baldwin  <jhb@FreeBSD.org>
 
 	* amd64-fbsd-tdep.c (amd64fbsd_get_thread_local_address): New.
diff --git a/gdb/i386-fbsd-tdep.c b/gdb/i386-fbsd-tdep.c
index 239ca91abe..01141b9e14 100644
--- a/gdb/i386-fbsd-tdep.c
+++ b/gdb/i386-fbsd-tdep.c
@@ -320,6 +320,30 @@ i386fbsd_iterate_over_regset_sections (struct gdbarch *gdbarch,
 	"XSAVE extended state", cb_data);
 }
 
+/* Implement the get_thread_local_address gdbarch method.  */
+
+static CORE_ADDR
+i386fbsd_get_thread_local_address (struct gdbarch *gdbarch, ptid_t ptid,
+				   CORE_ADDR lm_addr, CORE_ADDR offset)
+{
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+  struct regcache *regcache;
+
+  if (tdep->fsbase_regnum == -1)
+    error (_("Unable to fetch %%gsbase"));
+
+  regcache = get_thread_arch_regcache (ptid, gdbarch);
+
+  target_fetch_registers (regcache, tdep->fsbase_regnum + 1);
+
+  ULONGEST gsbase;
+  if (regcache->cooked_read (tdep->fsbase_regnum + 1, &gsbase) != REG_VALID)
+    error (_("Unable to fetch %%gsbase"));
+
+  CORE_ADDR dtv_addr = gsbase + gdbarch_ptr_bit (gdbarch) / 8;
+  return fbsd_get_thread_local_address (gdbarch, dtv_addr, lm_addr, offset);
+}
+
 static void
 i386fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
@@ -418,6 +442,11 @@ i386fbsd4_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 
   set_gdbarch_core_read_description (gdbarch,
 				     i386fbsd_core_read_description);
+
+  set_gdbarch_fetch_tls_load_module_address (gdbarch,
+					     svr4_fetch_objfile_link_map);
+  set_gdbarch_get_thread_local_address (gdbarch,
+					i386fbsd_get_thread_local_address);
 }
 
 void
-- 
2.19.2