[PATCH v4 07/13] gdb: Update x86 Linux architectures to support XSAVE layouts.

[John Baldwin <jhb@FreeBSD.org>]

Refactor i386_linux_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.
---
 gdb/amd64-linux-tdep.c | 11 ++++--
 gdb/i386-linux-tdep.c  | 77 ++++++++++++++++++++++++++----------------
 gdb/i386-linux-tdep.h  | 23 +++++++------
 3 files changed, 69 insertions(+), 42 deletions(-)

diff --git a/gdb/amd64-linux-tdep.c b/gdb/amd64-linux-tdep.c
index cbbac1a0c64..63fc02e4eb1 100644
--- a/gdb/amd64-linux-tdep.c
+++ b/gdb/amd64-linux-tdep.c
@@ -1616,7 +1616,8 @@ amd64_linux_core_read_description (struct gdbarch *gdbarch,
 				  bfd *abfd)
 {
   /* Linux/x86-64.  */
-  uint64_t xcr0 = i386_linux_core_read_xcr0 (abfd);
+  x86_xsave_layout layout;
+  uint64_t xcr0 = i386_linux_core_read_xsave_info (abfd, &layout);
 
   return amd64_linux_read_description (xcr0 & X86_XSTATE_ALL_MASK,
 				       gdbarch_ptr_bit (gdbarch) == 32);
@@ -1661,8 +1662,10 @@ amd64_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
 
   cb (".reg", 27 * 8, 27 * 8, &i386_gregset, NULL, cb_data);
   cb (".reg2", 512, 512, &amd64_fpregset, NULL, cb_data);
-  cb (".reg-xstate", X86_XSTATE_SIZE (tdep->xcr0), X86_XSTATE_SIZE (tdep->xcr0),
-      &amd64_linux_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, &amd64_linux_xstateregset,
+	"XSAVE extended state", cb_data);
 }
 
 /* The instruction sequences used in x86_64 machines for a
@@ -1804,6 +1807,8 @@ amd64_linux_init_abi_common(struct gdbarch_info info, struct gdbarch *gdbarch,
   tdep->sc_num_regs = ARRAY_SIZE (amd64_linux_sc_reg_offset);
 
   tdep->xsave_xcr0_offset = I386_LINUX_XSAVE_XCR0_OFFSET;
+  set_gdbarch_core_xfer_x86_xsave_layout
+    (gdbarch, i386_linux_core_xfer_x86_xsave_layout);
 
   /* Add the %orig_rax register used for syscall restarting.  */
   set_gdbarch_write_pc (gdbarch, amd64_linux_write_pc);
diff --git a/gdb/i386-linux-tdep.c b/gdb/i386-linux-tdep.c
index a6adeca1b97..a91e6eecfc0 100644
--- a/gdb/i386-linux-tdep.c
+++ b/gdb/i386-linux-tdep.c
@@ -638,43 +638,59 @@ static int i386_linux_sc_reg_offset[] =
   0 * 4				/* %gs */
 };
 
-/* Get XSAVE extended state xcr0 from core dump.  */
+/* See i386-linux-tdep.h.  */
 
 uint64_t
-i386_linux_core_read_xcr0 (bfd *abfd)
+i386_linux_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_LINUX_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_LINUX_XSAVE_XCR0_OFFSET,
-					  8))
-	    {
-	      warning (_("Couldn't read `xcr0' bytes from "
-			 "`.reg-xstate' section in core file."));
-	      return 0;
-	    }
-
-	  xcr0 = bfd_get_64 (abfd, contents);
-	}
+      warning (_("Couldn't read `xcr0' bytes from "
+		 "`.reg-xstate' section in core file."));
+      return 0;
     }
-  else
-    xcr0 = 0;
+
+  uint64_t xcr0 = bfd_get_64 (abfd, contents);
+
+  if (!i387_set_xsave_layout (xcr0, size, layout))
+    return 0;
 
   return xcr0;
 }
 
+/* Implement the core_xfer_x86_xsave_layout gdbarch method.  */
+
+LONGEST
+i386_linux_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_linux_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;
+}
+
 /* See i386-linux-tdep.h.  */
 
 const struct target_desc *
@@ -708,7 +724,8 @@ i386_linux_core_read_description (struct gdbarch *gdbarch,
 				  bfd *abfd)
 {
   /* Linux/i386.  */
-  uint64_t xcr0 = i386_linux_core_read_xcr0 (abfd);
+  x86_xsave_layout layout;
+  uint64_t xcr0 = i386_linux_core_read_xsave_info (abfd, &layout);
   const struct target_desc *tdesc = i386_linux_read_description (xcr0);
 
   if (tdesc != NULL)
@@ -768,8 +785,8 @@ i386_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
   cb (".reg", 68, 68, &i386_gregset, NULL, cb_data);
 
   if (tdep->xcr0 & X86_XSTATE_AVX)
-    cb (".reg-xstate", X86_XSTATE_SIZE (tdep->xcr0),
-	X86_XSTATE_SIZE (tdep->xcr0), &i386_linux_xstateregset,
+    cb (".reg-xstate", tdep->xsave_layout.sizeof_xsave,
+	tdep->xsave_layout.sizeof_xsave, &i386_linux_xstateregset,
 	"XSAVE extended state", cb_data);
   else if (tdep->xcr0 & X86_XSTATE_SSE)
     cb (".reg-xfp", 512, 512, &i386_fpregset, "extended floating-point",
@@ -872,6 +889,8 @@ i386_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
   tdep->sc_num_regs = ARRAY_SIZE (i386_linux_sc_reg_offset);
 
   tdep->xsave_xcr0_offset = I386_LINUX_XSAVE_XCR0_OFFSET;
+  set_gdbarch_core_xfer_x86_xsave_layout
+    (gdbarch, i386_linux_core_xfer_x86_xsave_layout);
 
   set_gdbarch_process_record (gdbarch, i386_process_record);
   set_gdbarch_process_record_signal (gdbarch, i386_linux_record_signal);
diff --git a/gdb/i386-linux-tdep.h b/gdb/i386-linux-tdep.h
index c0fd1f7f300..1eddb91097b 100644
--- a/gdb/i386-linux-tdep.h
+++ b/gdb/i386-linux-tdep.h
@@ -20,6 +20,8 @@
 #ifndef I386_LINUX_TDEP_H
 #define I386_LINUX_TDEP_H
 
+#include "gdbsupport/x86-xstate.h"
+
 /* The Linux kernel pretends there is an additional "orig_eax"
    register.  Since GDB needs access to that register to be able to
    properly restart system calls when necessary (see
@@ -34,8 +36,16 @@
 /* Total number of registers for GNU/Linux.  */
 #define I386_LINUX_NUM_REGS (I386_LINUX_ORIG_EAX_REGNUM + 1)
 
-/* Get XSAVE extended state xcr0 from core dump.  */
-extern uint64_t i386_linux_core_read_xcr0 (bfd *abfd);
+/* Validate and fetch XSAVE extended state xcr0 and extended area
+   layout from core dump.  */
+extern uint64_t i386_linux_core_read_xsave_info (bfd *abfd,
+						 x86_xsave_layout *layout);
+
+/* Implement the core_xfer_x86_xsave_layout gdbarch method.  */
+extern LONGEST i386_linux_core_xfer_x86_xsave_layout (struct gdbarch *gdbarch,
+						      gdb_byte *readbuf,
+						      ULONGEST offset,
+						      ULONGEST len);
 
 /* Handle and display information related to the MPX bound violation
    to the user.  */
@@ -52,14 +62,7 @@ extern const struct target_desc *i386_linux_read_description (uint64_t xcr0);
 	  fxsave_bytes[0..463]
 	  sw_usable_bytes[464..511]
 	  xstate_hdr_bytes[512..575]
-	  avx_bytes[576..831]
-	  mpx_bytes [960..1032]
-	  avx512_k_regs[1088..1152]
-	  avx512_zmmh_regs0-7[1153..1407]
-	  avx512_zmmh_regs8-15[1408..1663]
-	  avx512_zmm_regs16-31[1664..2687]
-	  pkru[2688..2752]
-	  future_state etc
+	  extended state regions (AVX, MPX, AVX512, PKRU, etc.)
 	};
 
   Same memory layout will be used for the coredump NT_X86_XSTATE
-- 
2.39.1