[PATCH v4 08/13] gdb: Support XSAVE layouts for the current host in the Linux x86 targets.

[John Baldwin <jhb@FreeBSD.org>]

Note that this uses the CPUID instruction to determine the total size
of the XSAVE register set.  If there is a way to fetch the register set
size using ptrace that would probably be better.
---
 gdb/amd64-linux-nat.c |  6 ++++--
 gdb/configure.nat     |  3 ++-
 gdb/i386-linux-nat.c  |  8 ++++++--
 gdb/x86-linux-nat.c   | 33 +++++++++++++++++++++++++++++++++
 gdb/x86-linux-nat.h   | 11 +++++++++++
 5 files changed, 56 insertions(+), 5 deletions(-)

diff --git a/gdb/amd64-linux-nat.c b/gdb/amd64-linux-nat.c
index b5b0703879b..6571be40bb5 100644
--- a/gdb/amd64-linux-nat.c
+++ b/gdb/amd64-linux-nat.c
@@ -210,6 +210,7 @@ void
 amd64_linux_nat_target::fetch_registers (struct regcache *regcache, int regnum)
 {
   struct gdbarch *gdbarch = regcache->arch ();
+  const i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (gdbarch);
   int tid;
 
   /* GNU/Linux LWP ID's are process ID's.  */
@@ -235,7 +236,7 @@ amd64_linux_nat_target::fetch_registers (struct regcache *regcache, int regnum)
 
       if (have_ptrace_getregset == TRIBOOL_TRUE)
 	{
-	  char xstateregs[X86_XSTATE_MAX_SIZE];
+	  char xstateregs[tdep->xsave_layout.sizeof_xsave];
 	  struct iovec iov;
 
 	  /* Pre-4.14 kernels have a bug (fixed by commit 0852b374173b
@@ -270,6 +271,7 @@ void
 amd64_linux_nat_target::store_registers (struct regcache *regcache, int regnum)
 {
   struct gdbarch *gdbarch = regcache->arch ();
+  const i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (gdbarch);
   int tid;
 
   /* GNU/Linux LWP ID's are process ID's.  */
@@ -299,7 +301,7 @@ amd64_linux_nat_target::store_registers (struct regcache *regcache, int regnum)
 
       if (have_ptrace_getregset == TRIBOOL_TRUE)
 	{
-	  char xstateregs[X86_XSTATE_MAX_SIZE];
+	  char xstateregs[tdep->xsave_layout.sizeof_xsave];
 	  struct iovec iov;
 
 	  iov.iov_base = xstateregs;
diff --git a/gdb/configure.nat b/gdb/configure.nat
index b371ad89afe..2739d14a1c4 100644
--- a/gdb/configure.nat
+++ b/gdb/configure.nat
@@ -254,6 +254,7 @@ case ${gdb_host} in
 	    i386)
 		# Host: Intel 386 running GNU/Linux.
 		NATDEPFILES="${NATDEPFILES} x86-nat.o nat/x86-dregs.o \
+		nat/x86-xstate.o \
 		i386-linux-nat.o x86-linux-nat.o nat/linux-btrace.o \
 		nat/x86-linux.o nat/x86-linux-dregs.o"
 		;;
@@ -319,7 +320,7 @@ case ${gdb_host} in
 	    i386)
 		# Host: GNU/Linux x86-64
 		NATDEPFILES="${NATDEPFILES} x86-nat.o nat/x86-dregs.o \
-		amd64-nat.o amd64-linux-nat.o x86-linux-nat.o \
+		nat/x86-xstate.o amd64-nat.o amd64-linux-nat.o x86-linux-nat.o \
 		nat/linux-btrace.o \
 		nat/x86-linux.o nat/x86-linux-dregs.o \
 		nat/amd64-linux-siginfo.o"
diff --git a/gdb/i386-linux-nat.c b/gdb/i386-linux-nat.c
index a524fdc9a1d..7e0572e1907 100644
--- a/gdb/i386-linux-nat.c
+++ b/gdb/i386-linux-nat.c
@@ -330,7 +330,9 @@ store_fpregs (const struct regcache *regcache, int tid, int regno)
 static int
 fetch_xstateregs (struct regcache *regcache, int tid)
 {
-  char xstateregs[X86_XSTATE_MAX_SIZE];
+  struct gdbarch *gdbarch = regcache->arch ();
+  const i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (gdbarch);
+  char xstateregs[tdep->xsave_layout.sizeof_xsave];
   struct iovec iov;
 
   if (have_ptrace_getregset != TRIBOOL_TRUE)
@@ -353,7 +355,9 @@ fetch_xstateregs (struct regcache *regcache, int tid)
 static int
 store_xstateregs (const struct regcache *regcache, int tid, int regno)
 {
-  char xstateregs[X86_XSTATE_MAX_SIZE];
+  struct gdbarch *gdbarch = regcache->arch ();
+  const i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (gdbarch);
+  char xstateregs[tdep->xsave_layout.sizeof_xsave];
   struct iovec iov;
 
   if (have_ptrace_getregset != TRIBOOL_TRUE)
diff --git a/gdb/x86-linux-nat.c b/gdb/x86-linux-nat.c
index fd2145244cc..9201bc132f7 100644
--- a/gdb/x86-linux-nat.c
+++ b/gdb/x86-linux-nat.c
@@ -36,6 +36,7 @@
 #include "amd64-linux-tdep.h"
 #endif
 #include "gdbsupport/x86-xstate.h"
+#include "nat/x86-xstate.h"
 #include "nat/linux-btrace.h"
 #include "nat/linux-nat.h"
 #include "nat/x86-linux.h"
@@ -176,6 +177,8 @@ x86_linux_nat_target::read_description ()
 	  /* Get XCR0 from XSAVE extended state.  */
 	  xcr0 = xstateregs[(I386_LINUX_XSAVE_XCR0_OFFSET
 			     / sizeof (uint64_t))];
+
+	  x86_fetch_xsave_layout (xcr0, x86_xsave_length (), xsave_layout);
 	}
     }
 
@@ -207,6 +210,36 @@ x86_linux_nat_target::read_description ()
 
   gdb_assert_not_reached ("failed to return tdesc");
 }
+
+/* Implement the "xfer_partial" target_ops method.  */
+
+enum target_xfer_status
+x86_linux_nat_target::xfer_partial (enum target_object object,
+				    const char *annex, gdb_byte *readbuf,
+				    const gdb_byte *writebuf,
+				    ULONGEST offset, ULONGEST len,
+				    ULONGEST *xfered_len)
+{
+  switch (object)
+    {
+    case TARGET_OBJECT_X86_XSAVE_LAYOUT:
+      if (xsave_layout.sizeof_xsave == 0)
+	return TARGET_XFER_E_IO;
+
+      if (offset > sizeof (xsave_layout))
+	return TARGET_XFER_E_IO;
+
+      if (offset + len > sizeof (xsave_layout))
+	len = sizeof (xsave_layout) - offset;
+
+      memcpy (readbuf, ((gdb_byte *) &xsave_layout) + offset, len);
+      *xfered_len = len;
+      return len == 0 ? TARGET_XFER_EOF : TARGET_XFER_OK;
+    default:
+      return linux_nat_target::xfer_partial (object, annex, readbuf, writebuf,
+					    offset, len, xfered_len);
+    }
+}
 \f
 
 /* Enable branch tracing.  */
diff --git a/gdb/x86-linux-nat.h b/gdb/x86-linux-nat.h
index fcb5f08d251..7f6c6caf77b 100644
--- a/gdb/x86-linux-nat.h
+++ b/gdb/x86-linux-nat.h
@@ -22,6 +22,7 @@
 
 #include "gdb_proc_service.h"  /* For ps_err_e.  */
 #include "linux-nat.h"
+#include "gdbsupport/x86-xstate.h"
 #include "x86-nat.h"
 #include "nat/x86-linux.h"
 
@@ -32,6 +33,13 @@ struct x86_linux_nat_target : public x86_nat_target<linux_nat_target>
   /* Add the description reader.  */
   const struct target_desc *read_description () override;
 
+  enum target_xfer_status xfer_partial (enum target_object object,
+					const char *annex,
+					gdb_byte *readbuf,
+					const gdb_byte *writebuf,
+					ULONGEST offset, ULONGEST len,
+					ULONGEST *xfered_len) override;
+
   struct btrace_target_info *enable_btrace (thread_info *tp,
 					    const struct btrace_config *conf) override;
   void disable_btrace (struct btrace_target_info *tinfo) override;
@@ -74,6 +82,9 @@ struct x86_linux_nat_target : public x86_nat_target<linux_nat_target>
 protected:
   /* Override the GNU/Linux inferior startup hook.  */
   void post_startup_inferior (ptid_t) override;
+
+private:
+  x86_xsave_layout xsave_layout;
 };
 
 \f
-- 
2.39.1