amd64-linux: expose system register FS_BASE and GS_BASE for Linux.

This patch allows examination of the registers FS_BASE and GS_BASE
for Linux Systems running on 64bit. Tests for simple read and write
of the new registers is also added with this patch.

2017-01-27  Walfred Tedeschi  <walfred.tedeschi@intel.com>
	    Richard Henderson  <rth@redhat.com>

gdb/ChangeLog:

	* amd64-linux-nat.c (PTRACE_ARCH_PRCTL): New define.
	(amd64_linux_fetch_inferior_registers): Add case to fetch FS_BASE
	GS_BASE for older kernels.
	(amd64_linux_store_inferior_registers): Add case to store FS_BASE
	GS_BASE for older kernels.
	* amd64-linux-tdep.c (amd64_linux_gregset_reg_offset): Add FS_BASE
	and GS_BASE to the offset table.
	(amd64_linux_register_reggroup_p): Add FS_BASE and GS_BASE to the
	system register group.
	* amd64-nat.c (amd64_native_gregset_reg_offset): Implements case
	for older kernels.
	* amd64-tdep.c (amd64_init_abi): Add segment registers for the
	amd64 ABI.
	* amd64-tdep.h (amd64_regnum): Add AMD64_FSBASE_REGNUM and
	AMD64_GSBASE_REGNUM.
	(AMD64_NUM_REGS): Set to AMD64_GSBASE_REGNUM + 1.
	* features/Makefile (amd64-linux.dat, amd64-avx-linux.dat)
	(amd64-mpx-linux.dat, amd64-avx512-linux.dat, x32-linux.dat)
	(x32-avx-linux.dat, x32-avx512-linux.dat): Add
	i386/64bit-segments.xml in those rules.
	* features/i386/64bit-segments.xml: New file.
	* features/i386/amd64-avx-mpx-linux.xml: Add 64bit-segments.xml.
	* features/i386/amd64-avx-linux.xml: Add 64bit-segments.xml.
	* features/i386/amd64-avx512-linux.xml: Add 64bit-segments.xml.
	* features/i386/amd64-mpx-linux.xml: Add 64bit-segments.xml.
	* features/i386/x32-avx512-linux.xml: Add 64bit-segments.xml.
	* features/i386/x32-avx-linux.xml: Add 64bit-segments.xml.
	* features/i386/amd64-linux.xml: Add 64bit-segments.xml.
	* features/i386/amd64-avx-linux.c: Regenerated.
	* features/i386/amd64-avx-mpx-linux.c: Regenerated.
	* features/i386/amd64-avx-mpx.c: Regenerated.
	* features/i386/amd64-avx512-linux.c: Regenerated.
	* features/i386/amd64-linux.c: Regenerated.
	* features/i386/amd64-mpx-linux.c: Regenerated.
	* features/i386/i386-avx-mpx-linux.c: Regenerated.
	* features/i386/i386-avx-mpx.c: Regenerated.
	* features/i386/x32-avx-linux.c: Regenerated.
	* features/i386/x32-avx512-linux.c: Regenerated.
	* regformats/i386/amd64-avx-linux.dat: Regenerated.
	* regformats/i386/amd64-avx-mpx-linux.dat: Regenerated.
	* regformats/i386/amd64-avx512-linux.dat: Regenerated.
	* regformats/i386/amd64-linux.dat: Regenerated.
	* regformats/i386/amd64-mpx-linux.dat: Regenerated.
	* regformats/i386/x32-avx-linux.dat: Regenerated.
	* regformats/i386/x32-avx512-linux.dat: Regenerated.
	* regformats/i386/x32-linux.dat: Regenerated.

gdb/doc/ChangeLog:

	* gdb.texinfo (i386 Features): Add system segment registers
	as feature.

gdb/gdbserver/ChangeLog:

	* linux-x86-low.c (x86_64_regmap): Add fs_base and gs_base
	to the register table.
	(x86_fill_gregset): Add support for old kernels for the
	fs_base and gs_base system registers.
	(x86_store_gregset): Likewise.
	* configure.srv (srv_i386_64bit_xmlfiles): Add 64bit-segments.xml.

gdb/testsuite/ChangeLog:

	* gdb.arch/amd64-gs_base.c: New file.
	* gdb.arch/amd64-gs_base.exp: New file.

Change-Id: I2e0eeb93058a2320d4d3b045082643cfe4aff963
Signed-off-by: Walfred Tedeschi <walfred.tedeschi@intel.com>

1 files changed, 55 insertions, 5 deletions

diff --git a/gdb/amd64-linux-nat.c b/gdb/amd64-linux-nat.c
index 4a2036b0f9..528984cb4d 100644
--- a/gdb/amd64-linux-nat.c
+++ b/gdb/amd64-linux-nat.c
@@ -40,6 +40,12 @@
 #include "nat/linux-ptrace.h"
 #include "nat/amd64-linux-siginfo.h"
 
+/* This definition comes from prctl.h.  Kernels older than 2.5.64
+   do not have it.  */
+#ifndef PTRACE_ARCH_PRCTL
+#define PTRACE_ARCH_PRCTL      30
+#endif
+
 /* Mapping between the general-purpose registers in GNU/Linux x86-64
    `struct user' format and GDB's register cache layout for GNU/Linux
    i386.
@@ -171,6 +177,30 @@ amd64_linux_fetch_inferior_registers (struct target_ops *ops,
 
 	  amd64_supply_fxsave (regcache, -1, &fpregs);
 	}
+#ifndef HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE
+      {
+	/* PTRACE_ARCH_PRCTL is obsolete since 2.6.25, where the
+	   fs_base and gs_base fields of user_regs_struct can be
+	   used directly.  */
+	unsigned long base;
+
+	if (regnum == -1 || regnum == AMD64_FSBASE_REGNUM)
+	  {
+	    if (ptrace (PTRACE_ARCH_PRCTL, tid, &base, ARCH_GET_FS) < 0)
+	      perror_with_name (_("Couldn't get segment register fs_base"));
+
+	    regcache_raw_supply (regcache, AMD64_FSBASE_REGNUM, &base);
+	  }
+
+	if (regnum == -1 || regnum == AMD64_GSBASE_REGNUM)
+	  {
+	    if (ptrace (PTRACE_ARCH_PRCTL, tid, &base, ARCH_GET_GS) < 0)
+	      perror_with_name (_("Couldn't get segment register gs_base"));
+
+	    regcache_raw_supply (regcache, AMD64_GSBASE_REGNUM, &base);
+	  }
+      }
+#endif
     }
 }
 
@@ -237,6 +267,30 @@ amd64_linux_store_inferior_registers (struct target_ops *ops,
 	  if (ptrace (PTRACE_SETFPREGS, tid, 0, (long) &fpregs) < 0)
 	    perror_with_name (_("Couldn't write floating point status"));
 	}
+
+#ifndef HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE
+      {
+	/* PTRACE_ARCH_PRCTL is obsolete since 2.6.25, where the
+	   fs_base and gs_base fields of user_regs_struct can be
+	   used directly.  */
+	void *base;
+
+	if (regnum == -1 || regnum == AMD64_FSBASE_REGNUM)
+	  {
+	    regcache_raw_collect (regcache, AMD64_FSBASE_REGNUM, &base);
+
+	    if (ptrace (PTRACE_ARCH_PRCTL, tid, base, ARCH_SET_FS) < 0)
+	      perror_with_name (_("Couldn't write segment register fs_base"));
+	  }
+	if (regnum == -1 || regnum == AMD64_GSBASE_REGNUM)
+	  {
+
+	    regcache_raw_collect (regcache, AMD64_GSBASE_REGNUM, &base);
+	    if (ptrace (PTRACE_ARCH_PRCTL, tid, base, ARCH_SET_GS) < 0)
+	      perror_with_name (_("Couldn't write segment register gs_base"));
+	  }
+      }
+#endif
     }
 }
 
@@ -265,11 +319,7 @@ ps_get_thread_area (struct ps_prochandle *ph,
     }
   else
     {
-      /* This definition comes from prctl.h, but some kernels may not
-         have it.  */
-#ifndef PTRACE_ARCH_PRCTL
-#define PTRACE_ARCH_PRCTL      30
-#endif
+
       /* FIXME: ezannoni-2003-07-09 see comment above about include
 	 file order.  We could be getting bogus values for these two.  */
       gdb_assert (FS < ELF_NGREG);