[PATCH v4 05/13] gdb: Update x86 FreeBSD architectures to support XSAVE layouts.

[John Baldwin <jhb@FreeBSD.org>]

Refactor i386fbsd_core_read_xcr0 to fetch and return a corresponding
x86_xsave_layout as well as xcr0 using the size of an existing
NT_X86_XSTATE core dump to determine the offsets via
i387_set_xsave_layout.  Use this to add an implementation of
gdbarch_core_xfer_x86_xsave_layout.

Use tdep->xsave_layout.sizeof_xsave as the size of the XSTATE register
set and only fetch/store the register set if this size is non-zero.
---
 gdb/amd64-fbsd-tdep.c | 13 +++++--
 gdb/i386-fbsd-tdep.c  | 81 ++++++++++++++++++++++++++-----------------
 gdb/i386-fbsd-tdep.h  | 11 ++++--
 3 files changed, 69 insertions(+), 36 deletions(-)

diff --git a/gdb/amd64-fbsd-tdep.c b/gdb/amd64-fbsd-tdep.c
index 0d5ce004fb1..87b36d8bb10 100644
--- a/gdb/amd64-fbsd-tdep.c
+++ b/gdb/amd64-fbsd-tdep.c
@@ -224,7 +224,10 @@ amd64fbsd_core_read_description (struct gdbarch *gdbarch,
 				 struct target_ops *target,
 				 bfd *abfd)
 {
-  return amd64_target_description (i386fbsd_core_read_xcr0 (abfd), true);
+  x86_xsave_layout layout;
+  return amd64_target_description (i386_fbsd_core_read_xsave_info (abfd,
+								   &layout),
+				   true);
 }
 
 /* Similar to amd64_supply_fpregset, but use XSAVE extended state.  */
@@ -271,8 +274,10 @@ amd64fbsd_iterate_over_regset_sections (struct gdbarch *gdbarch,
   cb (".reg-x86-segbases", AMD64_FBSD_SIZEOF_SEGBASES_REGSET,
       AMD64_FBSD_SIZEOF_SEGBASES_REGSET, &amd64_fbsd_segbases_regset,
       "segment bases", cb_data);
-  cb (".reg-xstate", X86_XSTATE_SIZE (tdep->xcr0), X86_XSTATE_SIZE (tdep->xcr0),
-      &amd64fbsd_xstateregset, "XSAVE extended state", cb_data);
+  if (tdep->xsave_layout.sizeof_xsave != 0)
+    cb (".reg-xstate", tdep->xsave_layout.sizeof_xsave,
+	tdep->xsave_layout.sizeof_xsave, &amd64fbsd_xstateregset,
+	"XSAVE extended state", cb_data);
 }
 
 /* Implement the get_thread_local_address gdbarch method.  */
@@ -313,6 +318,8 @@ 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_layout
+    (gdbarch, i386_fbsd_core_xfer_x86_xsave_layout);
 
   /* 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 fb9030413ab..2c315b8f945 100644
--- a/gdb/i386-fbsd-tdep.c
+++ b/gdb/i386-fbsd-tdep.c
@@ -18,13 +18,13 @@
    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"
 #include "trad-frame.h"
 #include "tramp-frame.h"
 #include "i386-fbsd-tdep.h"
-#include "gdbsupport/x86-xstate.h"
 
 #include "i386-tdep.h"
 #include "i387-tdep.h"
@@ -241,43 +241,58 @@ static const struct tramp_frame i386_fbsd64_sigframe =
   i386_fbsd_sigframe_init
 };
 
-/* Get XSAVE extended state xcr0 from core dump.  */
+/* See i386-fbsd-tdep.h.  */
 
 uint64_t
-i386fbsd_core_read_xcr0 (bfd *abfd)
+i386_fbsd_core_read_xsave_info (bfd *abfd, x86_xsave_layout *layout)
 {
   asection *xstate = bfd_get_section_by_name (abfd, ".reg-xstate");
-  uint64_t xcr0;
+  if (xstate == nullptr)
+    return X86_XSTATE_SSE_MASK;
 
-  if (xstate)
+  /* Check extended state size.  */
+  size_t size = bfd_section_size (xstate);
+  if (size < X86_XSTATE_AVX_SIZE)
+    return X86_XSTATE_SSE_MASK;
+
+  char contents[8];
+  if (! bfd_get_section_contents (abfd, xstate, contents,
+				  I386_FBSD_XSAVE_XCR0_OFFSET, 8))
     {
-      size_t size = bfd_section_size (xstate);
-
-      /* Check extended state size.  */
-      if (size < X86_XSTATE_AVX_SIZE)
-	xcr0 = X86_XSTATE_SSE_MASK;
-      else
-	{
-	  char contents[8];
-
-	  if (! bfd_get_section_contents (abfd, xstate, contents,
-					  I386_FBSD_XSAVE_XCR0_OFFSET,
-					  8))
-	    {
-	      warning (_("Couldn't read `xcr0' bytes from "
-			 "`.reg-xstate' section in core file."));
-	      return X86_XSTATE_SSE_MASK;
-	    }
-
-	  xcr0 = bfd_get_64 (abfd, contents);
-	}
+      warning (_("Couldn't read `xcr0' bytes from "
+		 "`.reg-xstate' section in core file."));
+      return X86_XSTATE_SSE_MASK;
     }
-  else
-    xcr0 = X86_XSTATE_SSE_MASK;
+
+  uint64_t xcr0 = bfd_get_64 (abfd, contents);
+
+  if (!i387_set_xsave_layout (xcr0, size, layout))
+    return X86_XSTATE_SSE_MASK;
 
   return xcr0;
 }
 
+/* Implement the core_xfer_x86_xsave_layout gdbarch method.  */
+
+LONGEST
+i386_fbsd_core_xfer_x86_xsave_layout (struct gdbarch *gdbarch,
+				      gdb_byte *readbuf, ULONGEST offset,
+				      ULONGEST len)
+{
+  if (offset > sizeof (x86_xsave_layout))
+    return -1;
+
+  x86_xsave_layout layout;
+  if (i386_fbsd_core_read_xsave_info (core_bfd, &layout) == X86_XSTATE_SSE_MASK)
+    return -1;
+
+  if (offset + len > sizeof (layout))
+    len = sizeof (layout) - offset;
+
+  memcpy (readbuf, ((gdb_byte *) &layout) + offset, len);
+  return len;
+}
+
 /* Implement the core_read_description gdbarch method.  */
 
 static const struct target_desc *
@@ -285,7 +300,9 @@ i386fbsd_core_read_description (struct gdbarch *gdbarch,
 				struct target_ops *target,
 				bfd *abfd)
 {
-  return i386_target_description (i386fbsd_core_read_xcr0 (abfd), true);
+  x86_xsave_layout layout;
+  return i386_target_description (i386_fbsd_core_read_xsave_info (abfd, &layout),
+				  true);
 }
 
 /* Similar to i386_supply_fpregset, but use XSAVE extended state.  */
@@ -335,9 +352,9 @@ i386fbsd_iterate_over_regset_sections (struct gdbarch *gdbarch,
       I386_FBSD_SIZEOF_SEGBASES_REGSET, &i386_fbsd_segbases_regset,
       "segment bases", cb_data);
 
-  if (tdep->xcr0 & X86_XSTATE_AVX)
-    cb (".reg-xstate", X86_XSTATE_SIZE (tdep->xcr0),
-	X86_XSTATE_SIZE (tdep->xcr0), &i386fbsd_xstateregset,
+  if (tdep->xsave_layout.sizeof_xsave != 0)
+    cb (".reg-xstate", tdep->xsave_layout.sizeof_xsave,
+	tdep->xsave_layout.sizeof_xsave, &i386fbsd_xstateregset,
 	"XSAVE extended state", cb_data);
 }
 
@@ -386,6 +403,8 @@ 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_layout
+    (gdbarch, i386_fbsd_core_xfer_x86_xsave_layout);
 
   /* 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 cb991af9e49..edebabe138b 100644
--- a/gdb/i386-fbsd-tdep.h
+++ b/gdb/i386-fbsd-tdep.h
@@ -20,10 +20,17 @@
 #ifndef I386_FBSD_TDEP_H
 #define I386_FBSD_TDEP_H
 
+#include "gdbsupport/x86-xstate.h"
 #include "regset.h"
 
-/* Get XSAVE extended state xcr0 from core dump.  */
-extern uint64_t i386fbsd_core_read_xcr0 (bfd *abfd);
+/* Validate and fetch XSAVE extended state xcr0 and extended area
+   layout from core dump.  */
+uint64_t i386_fbsd_core_read_xsave_info (bfd *abfd, x86_xsave_layout *layout);
+
+/* Implement the core_xfer_x86_xsave_layout gdbarch method.  */
+LONGEST i386_fbsd_core_xfer_x86_xsave_layout (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
-- 
2.39.1