[PATCH v4 02/13] core: Support fetching TARGET_OBJECT_X86_XSAVE_LAYOUT from architectures.

[John Baldwin <jhb@FreeBSD.org>]

Add gdbarch_core_xfer_x86_xsave_layout to fetch the x86 XSAVE layout
structure from a core file.

Current OS's do not export the offsets of XSAVE state components in
core dumps, so provide an i387_set_xsave_layout helper function to set
offsets based on known combinations of XCR0 masks and total state
sizes.  Eventually when core dumps do contain this information this
function should only be used as a fall back for older core dumps.
---
 gdb/corelow.c             | 22 ++++++++++++++++
 gdb/gdbarch-gen.h         | 10 +++++++
 gdb/gdbarch.c             | 32 +++++++++++++++++++++++
 gdb/gdbarch_components.py | 13 +++++++++
 gdb/i386-tdep.c           |  2 +-
 gdb/i387-tdep.c           | 55 +++++++++++++++++++++++++++++++++++++++
 gdb/i387-tdep.h           |  8 ++++++
 7 files changed, 141 insertions(+), 1 deletion(-)

diff --git a/gdb/corelow.c b/gdb/corelow.c
index db489b4280e..c1fe73c09d8 100644
--- a/gdb/corelow.c
+++ b/gdb/corelow.c
@@ -1049,6 +1049,28 @@ core_target::xfer_partial (enum target_object object, const char *annex,
 	}
       return TARGET_XFER_E_IO;
 
+    case TARGET_OBJECT_X86_XSAVE_LAYOUT:
+      if (readbuf)
+	{
+	  if (m_core_gdbarch != nullptr
+	      && gdbarch_core_xfer_x86_xsave_layout_p (m_core_gdbarch))
+	    {
+	      LONGEST l = gdbarch_core_xfer_x86_xsave_layout  (m_core_gdbarch,
+							       readbuf, offset,
+							       len);
+
+	      if (l >= 0)
+		{
+		  *xfered_len = l;
+		  if (l == 0)
+		    return TARGET_XFER_EOF;
+		  else
+		    return TARGET_XFER_OK;
+		}
+	    }
+	}
+      return TARGET_XFER_E_IO;
+
     default:
       return this->beneath ()->xfer_partial (object, annex, readbuf,
 					     writebuf, offset, len,
diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h
index 76d12a15317..c6de67597fb 100644
--- a/gdb/gdbarch-gen.h
+++ b/gdb/gdbarch-gen.h
@@ -992,6 +992,16 @@ typedef LONGEST (gdbarch_core_xfer_siginfo_ftype) (struct gdbarch *gdbarch, gdb_
 extern LONGEST gdbarch_core_xfer_siginfo (struct gdbarch *gdbarch, gdb_byte *readbuf, ULONGEST offset, ULONGEST len);
 extern void set_gdbarch_core_xfer_siginfo (struct gdbarch *gdbarch, gdbarch_core_xfer_siginfo_ftype *core_xfer_siginfo);
 
+/* Read offset OFFSET of TARGET_OBJECT_X86_XSAVE_LAYOUT from core file
+   into buffer READBUF with length LEN.  Return the number of bytes read
+   (zero indicates EOF, a negative value indicates failure). */
+
+extern bool gdbarch_core_xfer_x86_xsave_layout_p (struct gdbarch *gdbarch);
+
+typedef LONGEST (gdbarch_core_xfer_x86_xsave_layout_ftype) (struct gdbarch *gdbarch, gdb_byte *readbuf, ULONGEST offset, ULONGEST len);
+extern LONGEST gdbarch_core_xfer_x86_xsave_layout (struct gdbarch *gdbarch, gdb_byte *readbuf, ULONGEST offset, ULONGEST len);
+extern void set_gdbarch_core_xfer_x86_xsave_layout (struct gdbarch *gdbarch, gdbarch_core_xfer_x86_xsave_layout_ftype *core_xfer_x86_xsave_layout);
+
 /* BFD target to use when generating a core file. */
 
 extern bool gdbarch_gcore_bfd_target_p (struct gdbarch *gdbarch);
diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
index b4763aa6bf4..6fe6199ce80 100644
--- a/gdb/gdbarch.c
+++ b/gdb/gdbarch.c
@@ -180,6 +180,7 @@ struct gdbarch
   gdbarch_core_pid_to_str_ftype *core_pid_to_str = nullptr;
   gdbarch_core_thread_name_ftype *core_thread_name = nullptr;
   gdbarch_core_xfer_siginfo_ftype *core_xfer_siginfo = nullptr;
+  gdbarch_core_xfer_x86_xsave_layout_ftype *core_xfer_x86_xsave_layout = nullptr;
   const char * gcore_bfd_target = 0;
   int vtable_function_descriptors = 0;
   int vbit_in_delta = 0;
@@ -439,6 +440,7 @@ verify_gdbarch (struct gdbarch *gdbarch)
   /* Skip verify of core_pid_to_str, has predicate.  */
   /* Skip verify of core_thread_name, has predicate.  */
   /* Skip verify of core_xfer_siginfo, has predicate.  */
+  /* Skip verify of core_xfer_x86_xsave_layout, has predicate.  */
   /* Skip verify of gcore_bfd_target, has predicate.  */
   /* Skip verify of vtable_function_descriptors, invalid_p == 0 */
   /* Skip verify of vbit_in_delta, invalid_p == 0 */
@@ -1060,6 +1062,12 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
   gdb_printf (file,
 	      "gdbarch_dump: core_xfer_siginfo = <%s>\n",
 	      host_address_to_string (gdbarch->core_xfer_siginfo));
+  gdb_printf (file,
+	      "gdbarch_dump: gdbarch_core_xfer_x86_xsave_layout_p() = %d\n",
+	      gdbarch_core_xfer_x86_xsave_layout_p (gdbarch));
+  gdb_printf (file,
+	      "gdbarch_dump: core_xfer_x86_xsave_layout = <%s>\n",
+	      host_address_to_string (gdbarch->core_xfer_x86_xsave_layout));
   gdb_printf (file,
 	      "gdbarch_dump: gdbarch_gcore_bfd_target_p() = %d\n",
 	      gdbarch_gcore_bfd_target_p (gdbarch));
@@ -3916,6 +3924,30 @@ set_gdbarch_core_xfer_siginfo (struct gdbarch *gdbarch,
   gdbarch->core_xfer_siginfo = core_xfer_siginfo;
 }
 
+bool
+gdbarch_core_xfer_x86_xsave_layout_p (struct gdbarch *gdbarch)
+{
+  gdb_assert (gdbarch != NULL);
+  return gdbarch->core_xfer_x86_xsave_layout != NULL;
+}
+
+LONGEST
+gdbarch_core_xfer_x86_xsave_layout (struct gdbarch *gdbarch, gdb_byte *readbuf, ULONGEST offset, ULONGEST len)
+{
+  gdb_assert (gdbarch != NULL);
+  gdb_assert (gdbarch->core_xfer_x86_xsave_layout != NULL);
+  if (gdbarch_debug >= 2)
+    gdb_printf (gdb_stdlog, "gdbarch_core_xfer_x86_xsave_layout called\n");
+  return gdbarch->core_xfer_x86_xsave_layout (gdbarch, readbuf, offset, len);
+}
+
+void
+set_gdbarch_core_xfer_x86_xsave_layout (struct gdbarch *gdbarch,
+					gdbarch_core_xfer_x86_xsave_layout_ftype core_xfer_x86_xsave_layout)
+{
+  gdbarch->core_xfer_x86_xsave_layout = core_xfer_x86_xsave_layout;
+}
+
 bool
 gdbarch_gcore_bfd_target_p (struct gdbarch *gdbarch)
 {
diff --git a/gdb/gdbarch_components.py b/gdb/gdbarch_components.py
index 92c501d2a72..0a1c5d927df 100644
--- a/gdb/gdbarch_components.py
+++ b/gdb/gdbarch_components.py
@@ -1666,6 +1666,19 @@ of bytes read (zero indicates EOF, a negative value indicates failure).
     predicate=True,
 )
 
+Method(
+    comment="""
+Read offset OFFSET of TARGET_OBJECT_X86_XSAVE_LAYOUT from core file
+into buffer READBUF with length LEN.  Return the number of bytes read
+(zero indicates EOF, a negative value indicates failure).
+""",
+    type="LONGEST",
+    name="core_xfer_x86_xsave_layout",
+    params=[("gdb_byte *", "readbuf"), ("ULONGEST", "offset"), ("ULONGEST", "len")],
+    predicate=True,
+    invalid=True,
+)
+
 Value(
     comment="""
 BFD target to use when generating a core file.
diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index 5c2d9e42d8d..50b57cb6497 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -8530,7 +8530,7 @@ i386_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
       /* Check that the XSAVE layout of ARCHES matches the layout for
 	 the current target.  */
       i386_gdbarch_tdep *other_tdep
-	= (i386_gdbarch_tdep *) gdbarch_tdep (arches->gdbarch);
+	= gdbarch_tdep<i386_gdbarch_tdep> (arches->gdbarch);
 
       if (other_tdep->xsave_layout != xsave_layout)
 	continue;
diff --git a/gdb/i387-tdep.c b/gdb/i387-tdep.c
index df0a6058adc..7026dfed6e4 100644
--- a/gdb/i387-tdep.c
+++ b/gdb/i387-tdep.c
@@ -898,6 +898,61 @@ static int xsave_pkeys_offset[] =
   (xsave + xsave_pkeys_offset[regnum - I387_PKRU_REGNUM (tdep)])
 
 
+/* See i387-tdep.h.  */
+
+bool
+i387_set_xsave_layout (uint64_t xcr0, size_t xsave_size,
+		       x86_xsave_layout *layout)
+{
+  if (HAS_PKRU(xcr0) && xsave_size == 2696)
+    {
+      /* Intel CPUs supporting PKRU.  */
+      layout->avx_offset = 576;
+      layout->bndregs_offset = 960;
+      layout->bndcfg_offset = 1024;
+      layout->k_offset = 1088;
+      layout->zmm_h_offset = 1152;
+      layout->zmm_offset = 1664;
+      layout->pkru_offset = 2688;
+    }
+  else if (HAS_PKRU(xcr0) && xsave_size == 2440)
+    {
+      /* AMD Ryzen 9 CPUs supporting PKRU.  */
+      layout->avx_offset = 576;
+      layout->k_offset = 832;
+      layout->zmm_h_offset = 896;
+      layout->zmm_offset = 1408;
+      layout->pkru_offset = 2432;
+    }
+  else if (HAS_AVX512(xcr0) && xsave_size == 2688)
+    {
+      /* Intel CPUs supporting AVX512.  */
+      layout->avx_offset = 576;
+      layout->bndregs_offset = 960;
+      layout->bndcfg_offset = 1024;
+      layout->k_offset = 1088;
+      layout->zmm_h_offset = 1152;
+      layout->zmm_offset = 1664;
+    }
+  else if (HAS_MPX(xcr0) && xsave_size == 1088)
+    {
+      /* Intel CPUs supporting MPX.  */
+      layout->avx_offset = 576;
+      layout->bndregs_offset = 960;
+      layout->bndcfg_offset = 1024;
+    }
+  else if (HAS_AVX(xcr0) && xsave_size == 832)
+    {
+      /* Intel and AMD CPUs supporting AVX.  */
+      layout->avx_offset = 576;
+    }
+  else
+    return false;
+
+  layout->sizeof_xsave = xsave_size;
+  return true;
+}
+
 /* Extract from XSAVE a bitset of the features that are available on the
    target, but which have not yet been enabled.  */
 
diff --git a/gdb/i387-tdep.h b/gdb/i387-tdep.h
index 2e890e71a2b..a9fc9442c01 100644
--- a/gdb/i387-tdep.h
+++ b/gdb/i387-tdep.h
@@ -25,6 +25,7 @@ class frame_info_ptr;
 struct regcache;
 struct type;
 struct ui_file;
+struct x86_xsave_layout;
 
 /* Number of i387 floating point registers.  */
 #define I387_NUM_REGS	16
@@ -138,6 +139,13 @@ extern void i387_collect_fsave (const struct regcache *regcache, int regnum,
 extern void i387_supply_fxsave (struct regcache *regcache, int regnum,
 				const void *fxsave);
 
+/* Select an XSAVE layout based on the XCR0 bitmask and total XSAVE
+   extended state size.  Returns true if the bitmask and size matched
+   a known layout.  */
+
+extern bool i387_set_xsave_layout (uint64_t xcr0, size_t xsave_size,
+				   x86_xsave_layout *layout);
+
 /* Similar to i387_supply_fxsave, but use XSAVE extended state.  */
 
 extern void i387_supply_xsave (struct regcache *regcache, int regnum,
-- 
2.39.1