[PATCH 6/9] Support TLS variables on FreeBSD/amd64.

John Baldwin
2019-01-22T18:43:49Z

Use the fs_base register to fetch the address of a thread's tcb and
calculate the address of the DTV array. This value is then passed to
fbsd_get_thread_local_address to compute the final variable address.

Note that fs_base is currently only available via the native target as
core dumps on FreeBSD do not store the value of fs_base.

gdb/ChangeLog:

* amd64-fbsd-tdep.c (amd64fbsd_get_thread_local_address): New.
(amd64fbsd_init_abi): Install gdbarch
"fetch_tls_load_module_address" and "get_thread_local_address"
methods.
---
gdb/ChangeLog | 7 +++++++
gdb/amd64-fbsd-tdep.c | 25 +++++++++++++++++++++++++
2 files changed, 32 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 09e57e7474..7e97fae997 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2019-01-22 John Baldwin <jhb@FreeBSD.org>
+
+ * amd64-fbsd-tdep.c (amd64fbsd_get_thread_local_address): New.
+ (amd64fbsd_init_abi): Install gdbarch
+ "fetch_tls_load_module_address" and "get_thread_local_address"
+ methods.
+
2019-01-22 John Baldwin <jhb@FreeBSD.org>

* fbsd-tdep.c (fbsd_pspace_data_handle): New variable.
diff --git a/gdb/amd64-fbsd-tdep.c b/gdb/amd64-fbsd-tdep.c
index 628d42f7a0..32bda5741c 100644
--- a/gdb/amd64-fbsd-tdep.c
+++ b/gdb/amd64-fbsd-tdep.c
@@ -204,6 +204,26 @@ amd64fbsd_iterate_over_regset_sections (struct gdbarch *gdbarch,
&amd64fbsd_xstateregset, "XSAVE extended state", cb_data);
}

+/* Implement the get_thread_local_address gdbarch method. */
+
+static CORE_ADDR
+amd64fbsd_get_thread_local_address (struct gdbarch *gdbarch, ptid_t ptid,
+ CORE_ADDR lm_addr, CORE_ADDR offset)
+{
+ struct regcache *regcache;
+
+ regcache = get_thread_arch_regcache (ptid, gdbarch);
+
+ target_fetch_registers (regcache, AMD64_FSBASE_REGNUM);
+
+ ULONGEST fsbase;
+ if (regcache->cooked_read (AMD64_FSBASE_REGNUM, &fsbase) != REG_VALID)
+ error (_("Unable to fetch %%fsbase"));
+
+ CORE_ADDR dtv_addr = fsbase + gdbarch_ptr_bit (gdbarch) / 8;
+ return fbsd_get_thread_local_address (gdbarch, dtv_addr, lm_addr, offset);
+}
+
static void
amd64fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
@@ -241,6 +261,11 @@ amd64fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
/* FreeBSD uses SVR4-style shared libraries. */
set_solib_svr4_fetch_link_map_offsets
(gdbarch, svr4_lp64_fetch_link_map_offsets);
+
+ set_gdbarch_fetch_tls_load_module_address (gdbarch,
+ svr4_fetch_objfile_link_map);
+ set_gdbarch_get_thread_local_address (gdbarch,
+ amd64fbsd_get_thread_local_address);
}

void
--
2.19.2