[RFC PATCH 3/4] Update x86 FreeBSD architectures to support XSAVE offsets.

[John Baldwin <jhb@FreeBSD.org>]

Add an implementation of gdbarch_core_xfer_x86_xsave_offsets which
uses the size of an existing NT_X86_XSTATE core dump to determine
the offsets via i387_set_xsave_offsets.

The XSAVE register set is now also marked as variable size.  This is
not quite correct (and in particular, the maximum ("collect") size
still assumes the Intel layout.
---
 gdb/amd64-fbsd-tdep.c |  8 ++++++--
 gdb/i386-fbsd-tdep.c  | 33 +++++++++++++++++++++++++++++++--
 gdb/i386-fbsd-tdep.h  |  6 ++++++
 3 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/gdb/amd64-fbsd-tdep.c b/gdb/amd64-fbsd-tdep.c
index da5c297902d..19a86d40203 100644
--- a/gdb/amd64-fbsd-tdep.c
+++ b/gdb/amd64-fbsd-tdep.c
@@ -28,6 +28,7 @@
 
 #include "amd64-tdep.h"
 #include "amd64-fbsd-tdep.h"
+#include "i387-tdep.h"
 #include "fbsd-tdep.h"
 #include "solib-svr4.h"
 #include "inferior.h"
@@ -236,7 +237,8 @@ static const struct regset amd64fbsd_xstateregset =
   {
     NULL,
     amd64fbsd_supply_xstateregset,
-    amd64fbsd_collect_xstateregset
+    amd64fbsd_collect_xstateregset,
+    REGSET_VARIABLE_SIZE
   };
 
 /* Iterate over core file register note sections.  */
@@ -253,7 +255,7 @@ amd64fbsd_iterate_over_regset_sections (struct gdbarch *gdbarch,
       &amd64_fbsd_gregset, NULL, cb_data);
   cb (".reg2", tdep->sizeof_fpregset, tdep->sizeof_fpregset, &amd64_fpregset,
       NULL, cb_data);
-  cb (".reg-xstate", X86_XSTATE_SIZE (tdep->xcr0), X86_XSTATE_SIZE (tdep->xcr0),
+  cb (".reg-xstate", X86_XSTATE_SSE_SIZE, X86_XSTATE_SIZE (tdep->xcr0),
       &amd64fbsd_xstateregset, "XSAVE extended state", cb_data);
 }
 
@@ -295,6 +297,8 @@ amd64fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   tramp_frame_prepend_unwinder (gdbarch, &amd64_fbsd_sigframe);
 
   tdep->xsave_xcr0_offset = I386_FBSD_XSAVE_XCR0_OFFSET;
+  set_gdbarch_core_xfer_x86_xsave_offsets
+    (gdbarch, i386fbsd_core_xfer_x86_xsave_offsets);
 
   /* Iterate over core file register note sections.  */
   set_gdbarch_iterate_over_regset_sections
diff --git a/gdb/i386-fbsd-tdep.c b/gdb/i386-fbsd-tdep.c
index 16ffd576323..577eed06321 100644
--- a/gdb/i386-fbsd-tdep.c
+++ b/gdb/i386-fbsd-tdep.c
@@ -18,6 +18,7 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "defs.h"
+#include "gdbcore.h"
 #include "osabi.h"
 #include "regcache.h"
 #include "regset.h"
@@ -263,6 +264,31 @@ i386fbsd_core_read_xcr0 (bfd *abfd)
   return xcr0;
 }
 
+/* Implement the core_xfer_x86_xsave_offsets gdbarch method.  */
+
+LONGEST
+i386fbsd_core_xfer_x86_xsave_offsets (struct gdbarch *gdbarch,
+				      gdb_byte *readbuf, ULONGEST offset,
+				      ULONGEST len)
+{
+  asection *xstate = bfd_get_section_by_name (core_bfd, ".reg-xstate");
+  if (xstate == nullptr)
+    return -1;
+
+  if (offset > sizeof (struct xsave_offsets))
+    return -1;
+
+  i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  struct xsave_offsets xsave_offsets;
+  i387_set_xsave_offsets (tdep->xcr0, bfd_section_size (xstate), &xsave_offsets);
+
+  if (offset + len > sizeof (struct xsave_offsets))
+    len = sizeof (struct xsave_offsets) - offset;
+
+  memcpy (readbuf, ((gdb_byte *) &xsave_offsets) + offset, len);
+  return len;
+}
+
 /* Implement the core_read_description gdbarch method.  */
 
 static const struct target_desc *
@@ -299,7 +325,8 @@ static const struct regset i386fbsd_xstateregset =
   {
     NULL,
     i386fbsd_supply_xstateregset,
-    i386fbsd_collect_xstateregset
+    i386fbsd_collect_xstateregset,
+    REGSET_VARIABLE_SIZE
   };
 
 /* Iterate over core file register note sections.  */
@@ -318,7 +345,7 @@ i386fbsd_iterate_over_regset_sections (struct gdbarch *gdbarch,
       NULL, cb_data);
 
   if (tdep->xcr0 & X86_XSTATE_AVX)
-    cb (".reg-xstate", X86_XSTATE_SIZE (tdep->xcr0),
+    cb (".reg-xstate", X86_XSTATE_SSE_SIZE,
 	X86_XSTATE_SIZE (tdep->xcr0), &i386fbsd_xstateregset,
 	"XSAVE extended state", cb_data);
 }
@@ -372,6 +399,8 @@ i386fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   i386_elf_init_abi (info, gdbarch);
 
   tdep->xsave_xcr0_offset = I386_FBSD_XSAVE_XCR0_OFFSET;
+  set_gdbarch_core_xfer_x86_xsave_offsets
+    (gdbarch, i386fbsd_core_xfer_x86_xsave_offsets);
 
   /* Iterate over core file register note sections.  */
   set_gdbarch_iterate_over_regset_sections
diff --git a/gdb/i386-fbsd-tdep.h b/gdb/i386-fbsd-tdep.h
index 76f4c20f657..ed8e8285f88 100644
--- a/gdb/i386-fbsd-tdep.h
+++ b/gdb/i386-fbsd-tdep.h
@@ -25,6 +25,12 @@
 /* Get XSAVE extended state xcr0 from core dump.  */
 extern uint64_t i386fbsd_core_read_xcr0 (bfd *abfd);
 
+/* Implement the core_xfer_x86_xsave_offsets gdbarch method.  */
+extern LONGEST i386fbsd_core_xfer_x86_xsave_offsets (struct gdbarch *gdbarch,
+						     gdb_byte *readbuf,
+						     ULONGEST offset,
+						     ULONGEST len);
+
 /* The format of the XSAVE extended area is determined by hardware.
    Cores store the XSAVE extended area in a NT_X86_XSTATE note that
    matches the layout on Linux.  */
-- 
2.34.1