[PATCH v6a 06/15] 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_guess_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 | 15 +++++++--
  gdb/i386-fbsd-tdep.c  | 71 ++++++++++++++++++++++++-------------------
  gdb/i386-fbsd-tdep.h  | 14 +++++++--
  3 files changed, 64 insertions(+), 36 deletions(-)

diff --git a/gdb/amd64-fbsd-tdep.c b/gdb/amd64-fbsd-tdep.c
index 0d5ce004fb1..2b633cd479c 100644
--- a/gdb/amd64-fbsd-tdep.c
+++ b/gdb/amd64-fbsd-tdep.c
@@ -224,7 +224,12 @@ 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;
+  uint64_t xcr0 = i386_fbsd_core_read_xsave_info (abfd, layout);
+  if (xcr0 == 0)
+    xcr0 = X86_XSTATE_SSE_MASK;
+
+  return amd64_target_description (xcr0, true);
  }
  
  /* Similar to amd64_supply_fpregset, but use XSAVE extended state.  */
@@ -271,8 +276,10 @@ 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 +320,8 @@ 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_read_x86_xsave_layout
+    (gdbarch, i386_fbsd_core_read_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..f8c2758c2b0 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 +241,46 @@ 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 0;
  
-  if (xstate)
+  /* Check extended state size.  */
+  size_t size = bfd_section_size (xstate);
+  if (size < X86_XSTATE_AVX_SIZE)
+    return 0;
+
+  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 0;
      }
-  else
-    xcr0 = X86_XSTATE_SSE_MASK;
+
+  uint64_t xcr0 = bfd_get_64 (abfd, contents);
+
+  if (!i387_guess_xsave_layout (xcr0, size, layout))
+    return 0;
  
    return xcr0;
  }
  
+/* See i386-fbsd-tdep.h.  */
+
+bool
+i386_fbsd_core_read_x86_xsave_layout (struct gdbarch *gdbarch,
+				      x86_xsave_layout &layout)
+{
+  return i386_fbsd_core_read_xsave_info (core_bfd, layout) != 0;
+}
+
  /* Implement the core_read_description gdbarch method.  */
  
  static const struct target_desc *
@@ -285,7 +288,11 @@ 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;
+  uint64_t xcr0 = i386_fbsd_core_read_xsave_info (abfd, layout);
+  if (xcr0 == 0)
+    xcr0 = X86_XSTATE_X87_MASK;
+  return i386_target_description (xcr0, true);
  }
  
  /* Similar to i386_supply_fpregset, but use XSAVE extended state.  */
@@ -335,9 +342,9 @@ 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 +393,8 @@ 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_read_x86_xsave_layout
+    (gdbarch, i386_fbsd_core_read_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..c49cb1eba68 100644
--- a/gdb/i386-fbsd-tdep.h
+++ b/gdb/i386-fbsd-tdep.h
@@ -20,10 +20,20 @@
  #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);
+/* Read the XSAVE extended state xcr0 value from the ABFD core file.
+   If it appears to be valid, return it and fill LAYOUT with values
+   inferred from that value.
+
+   Otherwise, return 0 to indicate no state was found and leave LAYOUT
+   untouched.  */
+uint64_t i386_fbsd_core_read_xsave_info (bfd *abfd, x86_xsave_layout &layout);
+
+/* Implement the core_read_x86_xsave_layout gdbarch method.  */
+bool i386_fbsd_core_read_x86_xsave_layout (struct gdbarch *gdbarch,
+					   x86_xsave_layout &layout);
  
  /* The format of the XSAVE extended area is determined by hardware.
     Cores store the XSAVE extended area in a NT_X86_XSTATE note that
-- 
2.40.0