Support the fs_base and gs_base registers on i386.

As on amd64, these registers hold the base address of the fs and gs
segments, respectively.  For i386 these two registers are 32 bits.

gdb/ChangeLog:

	* amd64-fbsd-nat.c (amd64_fbsd_nat_target::read_description):
	Update calls to i386_target_description to add 'segments'
	parameter.
	* amd64-tdep.c (amd64_init_abi): Set tdep->fsbase_regnum.  Don't
	add segment base registers.
	* arch/i386.c (i386_create_target_description): Add 'segments'
	parameter to enable segment base registers.
	* arch/i386.h (i386_create_target_description): Likewise.
	* features/i386/32bit-segments.xml: New file.
	* features/i386/32bit-segments.c: Generate.
	* i386-fbsd-nat.c (i386_fbsd_nat_target::read_description): Update
	call to i386_target_description to add 'segments' parameter.
	* i386-fbsd-tdep.c (i386fbsd_core_read_description): Likewise.
	* i386-go32-tdep.c (i386_go32_init_abi): Likewise.
	* i386-linux-tdep.c (i386_linux_read_description): Likewise.
	* i386-tdep.c (i386_validate_tdesc_p): Add segment base registers
	if feature is present.
	(i386_gdbarch_init): Pass I386_NUM_REGS to set_gdbarch_num_regs.
	Add 'segments' parameter to call to i386_target_description.
	(i386_target_description): Add 'segments' parameter to enable
	segment base registers.
	(_initialize_i386_tdep) [GDB_SELF_TEST]: Add 'segments' parameter
	to call to i386_target_description.
	* i386-tdep.h (struct gdbarch_tdep): Add 'fsbase_regnum'.
	(enum i386_regnum): Add I386_FSBASE_REGNUM and I386_GSBASE_REGNUM.
	Define I386_NUM_REGS.
	(i386_target_description): Add 'segments' parameter to enable
	segment base registers.

gdb/gdbserver/ChangeLog:

	* linux-x86-tdesc.c (i386_linux_read_description): Update call to
	i386_create_target_description for 'segments' parameter.
	* lynx-i386-low.c (lynx_i386_arch_setup): Likewise.
	* nto-x86-low.c (nto_x86_arch_setup): Likewise.
	* win32-i386-low.c (i386_arch_setup): Likewise.

18 files changed, 119 insertions, 31 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4e592a3..79ba941 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,34 @@
+2019-03-12  John Baldwin  <jhb@FreeBSD.org>
+
+	* amd64-fbsd-nat.c (amd64_fbsd_nat_target::read_description):
+	Update calls to i386_target_description to add 'segments'
+	parameter.
+	* amd64-tdep.c (amd64_init_abi): Set tdep->fsbase_regnum.  Don't
+	add segment base registers.
+	* arch/i386.c (i386_create_target_description): Add 'segments'
+	parameter to enable segment base registers.
+	* arch/i386.h (i386_create_target_description): Likewise.
+	* features/i386/32bit-segments.xml: New file.
+	* features/i386/32bit-segments.c: Generate.
+	* i386-fbsd-nat.c (i386_fbsd_nat_target::read_description): Update
+	call to i386_target_description to add 'segments' parameter.
+	* i386-fbsd-tdep.c (i386fbsd_core_read_description): Likewise.
+	* i386-go32-tdep.c (i386_go32_init_abi): Likewise.
+	* i386-linux-tdep.c (i386_linux_read_description): Likewise.
+	* i386-tdep.c (i386_validate_tdesc_p): Add segment base registers
+	if feature is present.
+	(i386_gdbarch_init): Pass I386_NUM_REGS to set_gdbarch_num_regs.
+	Add 'segments' parameter to call to i386_target_description.
+	(i386_target_description): Add 'segments' parameter to enable
+	segment base registers.
+	(_initialize_i386_tdep) [GDB_SELF_TEST]: Add 'segments' parameter
+	to call to i386_target_description.
+	* i386-tdep.h (struct gdbarch_tdep): Add 'fsbase_regnum'.
+	(enum i386_regnum): Add I386_FSBASE_REGNUM and I386_GSBASE_REGNUM.
+	Define I386_NUM_REGS.
+	(i386_target_description): Add 'segments' parameter to enable
+	segment base registers.
+
 2019-03-12  Eli Zaretskii  <eliz@gnu.org>
 
 	PR/24325
diff --git a/gdb/amd64-fbsd-nat.c b/gdb/amd64-fbsd-nat.c
index 74ef240..9fff763 100644
--- a/gdb/amd64-fbsd-nat.c
+++ b/gdb/amd64-fbsd-nat.c
@@ -190,13 +190,13 @@ amd64_fbsd_nat_target::read_description ()
       if (is64)
 	return amd64_target_description (xcr0, true);
       else
-	return i386_target_description (xcr0);
+	return i386_target_description (xcr0, false);
     }
 #endif
   if (is64)
     return amd64_target_description (X86_XSTATE_SSE_MASK, true);
   else
-    return i386_target_description (X86_XSTATE_SSE_MASK);
+    return i386_target_description (X86_XSTATE_SSE_MASK, false);
 }
 
 #if defined(HAVE_PT_GETDBREGS) && defined(USE_SIGTRAP_SIGINFO)
diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index 3f61997..d589295 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -3107,15 +3107,7 @@ amd64_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch,
 
   if (tdesc_find_feature (tdesc, "org.gnu.gdb.i386.segments") != NULL)
     {
-      const struct tdesc_feature *feature =
-	  tdesc_find_feature (tdesc, "org.gnu.gdb.i386.segments");
-      struct tdesc_arch_data *tdesc_data_segments =
-	  (struct tdesc_arch_data *) info.tdep_info;
-
-      tdesc_numbered_register (feature, tdesc_data_segments,
-		       AMD64_FSBASE_REGNUM, "fs_base");
-      tdesc_numbered_register (feature, tdesc_data_segments,
-		       AMD64_GSBASE_REGNUM, "gs_base");
+      tdep->fsbase_regnum = AMD64_FSBASE_REGNUM;
     }
 
   if (tdesc_find_feature (tdesc, "org.gnu.gdb.i386.pkeys") != NULL)
diff --git a/gdb/arch/i386.c b/gdb/arch/i386.c
index 7d29013..ab24cf7 100644
--- a/gdb/arch/i386.c
+++ b/gdb/arch/i386.c
@@ -28,11 +28,12 @@
 #include "../features/i386/32bit-avx512.c"
 #include "../features/i386/32bit-mpx.c"
 #include "../features/i386/32bit-pkeys.c"
+#include "../features/i386/32bit-segments.c"
 
 /* Create i386 target descriptions according to XCR0.  */
 
 target_desc *
-i386_create_target_description (uint64_t xcr0, bool is_linux)
+i386_create_target_description (uint64_t xcr0, bool is_linux, bool segments)
 {
   target_desc *tdesc = allocate_target_description ();
 
@@ -53,6 +54,9 @@ i386_create_target_description (uint64_t xcr0, bool is_linux)
   if (is_linux)
     regnum = create_feature_i386_32bit_linux (tdesc, regnum);
 
+  if (segments)
+    regnum = create_feature_i386_32bit_segments (tdesc, regnum);
+
   if (xcr0 & X86_XSTATE_AVX)
     regnum = create_feature_i386_32bit_avx (tdesc, regnum);
 
diff --git a/gdb/arch/i386.h b/gdb/arch/i386.h
index fa85438..9a831ce 100644
--- a/gdb/arch/i386.h
+++ b/gdb/arch/i386.h
@@ -21,6 +21,7 @@
 #include "common/tdesc.h"
 #include <stdint.h>
 
-target_desc *i386_create_target_description (uint64_t xcr0, bool is_linux);
+target_desc *i386_create_target_description (uint64_t xcr0, bool is_linux,
+					     bool segments);
 
 #endif /* ARCH_I386_H */
diff --git a/gdb/features/i386/32bit-segments.c b/gdb/features/i386/32bit-segments.c
new file mode 100644
index 0000000..c22c3df
--- /dev/null
+++ b/gdb/features/i386/32bit-segments.c
@@ -0,0 +1,15 @@
+/* THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi:set ro:
+  Original: 32bit-segments.xml */
+
+#include "common/tdesc.h"
+
+static int
+create_feature_i386_32bit_segments (struct target_desc *result, long regnum)
+{
+  struct tdesc_feature *feature;
+
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.segments");
+  tdesc_create_reg (feature, "fs_base", regnum++, 1, NULL, 32, "int");
+  tdesc_create_reg (feature, "gs_base", regnum++, 1, NULL, 32, "int");
+  return regnum;
+}
diff --git a/gdb/features/i386/32bit-segments.xml b/gdb/features/i386/32bit-segments.xml
new file mode 100644
index 0000000..098948e
--- /dev/null
+++ b/gdb/features/i386/32bit-segments.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<!-- Copyright (C) 2016-2018 Free Software Foundation, Inc.
+
+     Copying and distribution of this file, with or without modification,
+     are permitted in any medium without royalty provided the copyright
+     notice and this notice are preserved.  -->
+
+<!DOCTYPE feature SYSTEM "gdb-target.dtd">
+<feature name="org.gnu.gdb.i386.segments">
+  <reg name="fs_base" bitsize="32" type="int"/>
+  <reg name="gs_base" bitsize="32" type="int"/>
+</feature>
diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 3eb9ec0..9879481 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,11 @@
+2019-03-12  John Baldwin  <jhb@FreeBSD.org>
+
+	* linux-x86-tdesc.c (i386_linux_read_description): Update call to
+	i386_create_target_description for 'segments' parameter.
+	* lynx-i386-low.c (lynx_i386_arch_setup): Likewise.
+	* nto-x86-low.c (nto_x86_arch_setup): Likewise.
+	* win32-i386-low.c (i386_arch_setup): Likewise.
+
 2019-03-12  Tom Tromey  <tromey@adacore.com>
 
 	* linux-low.c (iterate_over_lwps): Update.
diff --git a/gdb/gdbserver/linux-x86-tdesc.c b/gdb/gdbserver/linux-x86-tdesc.c
index 04bccc8..8f24a3d 100644
--- a/gdb/gdbserver/linux-x86-tdesc.c
+++ b/gdb/gdbserver/linux-x86-tdesc.c
@@ -87,7 +87,7 @@ i386_linux_read_description (uint64_t xcr0)
 
   if (*tdesc == NULL)
     {
-      *tdesc = i386_create_target_description (xcr0, true);
+      *tdesc = i386_create_target_description (xcr0, true, false);
 
       init_target_desc (*tdesc, i386_expedite_regs);
     }
diff --git a/gdb/gdbserver/lynx-i386-low.c b/gdb/gdbserver/lynx-i386-low.c
index bc1027d..e47f6b9 100644
--- a/gdb/gdbserver/lynx-i386-low.c
+++ b/gdb/gdbserver/lynx-i386-low.c
@@ -331,7 +331,7 @@ static void
 lynx_i386_arch_setup (void)
 {
   struct target_desc *tdesc
-    = i386_create_target_description (X86_XSTATE_SSE_MASK, false);
+    = i386_create_target_description (X86_XSTATE_SSE_MASK, false, false);
 
   init_target_desc (tdesc, i386_expedite_regs);
 
diff --git a/gdb/gdbserver/nto-x86-low.c b/gdb/gdbserver/nto-x86-low.c
index 1b00f7f..cfbe7ba 100644
--- a/gdb/gdbserver/nto-x86-low.c
+++ b/gdb/gdbserver/nto-x86-low.c
@@ -89,7 +89,7 @@ nto_x86_arch_setup (void)
 {
   the_low_target.num_regs = 16;
   struct target_desc *tdesc
-    = i386_create_target_description (X86_XSTATE_SSE_MASK, false);
+    = i386_create_target_description (X86_XSTATE_SSE_MASK, false, false);
 
   init_target_desc (tdesc, i386_expedite_regs);
 
diff --git a/gdb/gdbserver/win32-i386-low.c b/gdb/gdbserver/win32-i386-low.c
index 3be75d2..7b187d3 100644
--- a/gdb/gdbserver/win32-i386-low.c
+++ b/gdb/gdbserver/win32-i386-low.c
@@ -439,7 +439,7 @@ i386_arch_setup (void)
 					   false, false);
   const char **expedite_regs = amd64_expedite_regs;
 #else
-  tdesc = i386_create_target_description (X86_XSTATE_SSE_MASK, false);
+  tdesc = i386_create_target_description (X86_XSTATE_SSE_MASK, false, false);
   const char **expedite_regs = i386_expedite_regs;
 #endif
 
diff --git a/gdb/i386-fbsd-nat.c b/gdb/i386-fbsd-nat.c
index 2309b76..7106e90 100644
--- a/gdb/i386-fbsd-nat.c
+++ b/gdb/i386-fbsd-nat.c
@@ -160,7 +160,7 @@ i386_fbsd_nat_target::read_description ()
   if (x86bsd_xsave_len == 0)
     xcr0 = X86_XSTATE_SSE_MASK;
 
-  return i386_target_description (xcr0);
+  return i386_target_description (xcr0, false);
 }
 #endif
 
diff --git a/gdb/i386-fbsd-tdep.c b/gdb/i386-fbsd-tdep.c
index 236edd6..2f28bad 100644
--- a/gdb/i386-fbsd-tdep.c
+++ b/gdb/i386-fbsd-tdep.c
@@ -267,7 +267,7 @@ i386fbsd_core_read_description (struct gdbarch *gdbarch,
 				struct target_ops *target,
 				bfd *abfd)
 {
-  return i386_target_description (i386fbsd_core_read_xcr0 (abfd));
+  return i386_target_description (i386fbsd_core_read_xcr0 (abfd), false);
 }
 
 /* Similar to i386_supply_fpregset, but use XSAVE extended state.  */
diff --git a/gdb/i386-go32-tdep.c b/gdb/i386-go32-tdep.c
index 06833c3..30db72d 100644
--- a/gdb/i386-go32-tdep.c
+++ b/gdb/i386-go32-tdep.c
@@ -35,7 +35,7 @@ i386_go32_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 
   /* DJGPP does not support the SSE registers.  */
   if (!tdesc_has_registers (info.target_desc))
-    tdep->tdesc = i386_target_description (X86_XSTATE_X87_MASK);
+    tdep->tdesc = i386_target_description (X86_XSTATE_X87_MASK, false);
 
   /* Native compiler is GCC, which uses the SVR4 register numbering
      even in COFF and STABS.  See the comment in i386_gdbarch_init,
diff --git a/gdb/i386-linux-tdep.c b/gdb/i386-linux-tdep.c
index da81715..fa6b86f 100644
--- a/gdb/i386-linux-tdep.c
+++ b/gdb/i386-linux-tdep.c
@@ -694,7 +694,7 @@ i386_linux_read_description (uint64_t xcr0)
     [(xcr0 & X86_XSTATE_PKRU) ? 1 : 0];
 
   if (*tdesc == NULL)
-    *tdesc = i386_create_target_description (xcr0, true);
+    *tdesc = i386_create_target_description (xcr0, true, false);
 
   return *tdesc;
 }
diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index bc9ba75..4e63832 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -8175,7 +8175,7 @@ i386_validate_tdesc_p (struct gdbarch_tdep *tdep,
   const struct tdesc_feature *feature_core;
 
   const struct tdesc_feature *feature_sse, *feature_avx, *feature_mpx,
-			     *feature_avx512, *feature_pkeys;
+			     *feature_avx512, *feature_pkeys, *feature_segments;
   int i, num_regs, valid_p;
 
   if (! tdesc_has_registers (tdesc))
@@ -8198,6 +8198,9 @@ i386_validate_tdesc_p (struct gdbarch_tdep *tdep,
   /* Try AVX512 registers.  */
   feature_avx512 = tdesc_find_feature (tdesc, "org.gnu.gdb.i386.avx512");
 
+  /* Try segment base registers.  */
+  feature_segments = tdesc_find_feature (tdesc, "org.gnu.gdb.i386.segments");
+
   /* Try PKEYS  */
   feature_pkeys = tdesc_find_feature (tdesc, "org.gnu.gdb.i386.pkeys");
 
@@ -8307,6 +8310,16 @@ i386_validate_tdesc_p (struct gdbarch_tdep *tdep,
 	    tdep->mpx_register_names[i]);
     }
 
+  if (feature_segments)
+    {
+      if (tdep->fsbase_regnum < 0)
+	tdep->fsbase_regnum = I386_FSBASE_REGNUM;
+      valid_p &= tdesc_numbered_register (feature_segments, tdesc_data,
+					  tdep->fsbase_regnum, "fs_base");
+      valid_p &= tdesc_numbered_register (feature_segments, tdesc_data,
+					  tdep->fsbase_regnum + 1, "gs_base");
+    }
+
   if (feature_pkeys)
     {
       tdep->xcr0 |= X86_XSTATE_PKRU;
@@ -8543,14 +8556,14 @@ i386_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   /* Even though the default ABI only includes general-purpose registers,
      floating-point registers and the SSE registers, we have to leave a
      gap for the upper AVX, MPX and AVX512 registers.  */
-  set_gdbarch_num_regs (gdbarch, I386_PKEYS_NUM_REGS);
+  set_gdbarch_num_regs (gdbarch, I386_NUM_REGS);
 
   set_gdbarch_gnu_triplet_regexp (gdbarch, i386_gnu_triplet_regexp);
 
   /* Get the x86 target description from INFO.  */
   tdesc = info.target_desc;
   if (! tdesc_has_registers (tdesc))
-    tdesc = i386_target_description (X86_XSTATE_SSE_MASK);
+    tdesc = i386_target_description (X86_XSTATE_SSE_MASK, false);
   tdep->tdesc = tdesc;
 
   tdep->num_core_regs = I386_NUM_GREGS + I387_NUM_REGS;
@@ -8592,6 +8605,9 @@ i386_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   tdep->pkru_regnum = -1;
   tdep->num_pkeys_regs = 0;
 
+  /* No segment base registers.  */
+  tdep->fsbase_regnum = -1;
+
   tdesc_data = tdesc_data_alloc ();
 
   set_gdbarch_relocate_instruction (gdbarch, i386_relocate_instruction);
@@ -8717,20 +8733,21 @@ i386_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 /* Return the target description for a specified XSAVE feature mask.  */
 
 const struct target_desc *
-i386_target_description (uint64_t xcr0)
+i386_target_description (uint64_t xcr0, bool segments)
 {
   static target_desc *i386_tdescs \
-    [2/*SSE*/][2/*AVX*/][2/*MPX*/][2/*AVX512*/][2/*PKRU*/] = {};
+    [2/*SSE*/][2/*AVX*/][2/*MPX*/][2/*AVX512*/][2/*PKRU*/][2/*segments*/] = {};
   target_desc **tdesc;
 
   tdesc = &i386_tdescs[(xcr0 & X86_XSTATE_SSE) ? 1 : 0]
     [(xcr0 & X86_XSTATE_AVX) ? 1 : 0]
     [(xcr0 & X86_XSTATE_MPX) ? 1 : 0]
     [(xcr0 & X86_XSTATE_AVX512) ? 1 : 0]
-    [(xcr0 & X86_XSTATE_PKRU) ? 1 : 0];
+    [(xcr0 & X86_XSTATE_PKRU) ? 1 : 0]
+    [segments ? 1 : 0];
 
   if (*tdesc == NULL)
-    *tdesc = i386_create_target_description (xcr0, false);
+    *tdesc = i386_create_target_description (xcr0, false, segments);
 
   return *tdesc;
 }
@@ -9072,7 +9089,7 @@ Show Intel Memory Protection Extensions specific variables."),
 
   for (auto &a : xml_masks)
     {
-      auto tdesc = i386_target_description (a.mask);
+      auto tdesc = i386_target_description (a.mask, false);
 
       selftests::record_xml_tdesc (a.xml, tdesc);
     }
diff --git a/gdb/i386-tdep.h b/gdb/i386-tdep.h
index 2532306..c0d4948 100644
--- a/gdb/i386-tdep.h
+++ b/gdb/i386-tdep.h
@@ -200,6 +200,10 @@ struct gdbarch_tdep
   /* PKEYS register names.  */
   const char **pkeys_register_names;
 
+  /* Register number for %fsbase.  Set this to -1 to indicate the
+     absence of segment base registers.  */
+  int fsbase_regnum;
+
   /* Target description.  */
   const struct target_desc *tdesc;
 
@@ -296,7 +300,9 @@ enum i386_regnum
   I386_K7_REGNUM = I386_K0_REGNUM + 7,
   I386_ZMM0H_REGNUM,		/* %zmm0h */
   I386_ZMM7H_REGNUM = I386_ZMM0H_REGNUM + 7,
-  I386_PKRU_REGNUM
+  I386_PKRU_REGNUM,
+  I386_FSBASE_REGNUM,
+  I386_GSBASE_REGNUM
 };
 
 /* Register numbers of RECORD_REGMAP.  */
@@ -337,6 +343,7 @@ enum record_i386_regnum
 #define I386_MPX_NUM_REGS	(I386_BNDSTATUS_REGNUM + 1)
 #define I386_AVX512_NUM_REGS	(I386_ZMM7H_REGNUM + 1)
 #define I386_PKEYS_NUM_REGS	(I386_PKRU_REGNUM + 1)
+#define I386_NUM_REGS		(I386_GSBASE_REGNUM + 1)
 
 /* Size of the largest register.  */
 #define I386_MAX_REGISTER_SIZE	64
@@ -440,7 +447,8 @@ extern int i386_svr4_reg_to_regnum (struct gdbarch *gdbarch, int reg);
 
 extern int i386_process_record (struct gdbarch *gdbarch,
                                 struct regcache *regcache, CORE_ADDR addr);
-extern const struct target_desc *i386_target_description (uint64_t xcr0);
+extern const struct target_desc *i386_target_description (uint64_t xcr0,
+							  bool segments);
 
 /* Return true iff the current target is MPX enabled.  */
 extern int i386_mpx_enabled (void);