[binutils-gdb] Revert "gdbserver: update target description creation for x86/linux"

[Andrew Burgess <aburgess@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=cba2791ca6a984bd533ab643f4d92e3f5b278b43

commit cba2791ca6a984bd533ab643f4d92e3f5b278b43
Author: Andrew Burgess <aburgess@redhat.com>
Date:   Tue Mar 26 18:52:27 2024 +0000

    Revert "gdbserver: update target description creation for x86/linux"
    
    This reverts commit 61bb321605fc74703adc994fd7a78e9d2495ca7a.

Diff:
---
 gdbserver/linux-amd64-ipa.cc |  43 ++++--
 gdbserver/linux-i386-ipa.cc  |  23 +++-
 gdbserver/linux-x86-low.cc   |  15 +--
 gdbserver/linux-x86-tdesc.cc | 315 ++++++++++++-------------------------------
 gdbserver/linux-x86-tdesc.h  |  49 ++++---
 5 files changed, 168 insertions(+), 277 deletions(-)

diff --git a/gdbserver/linux-amd64-ipa.cc b/gdbserver/linux-amd64-ipa.cc
index 42de7d2da16..f97b0d6a1d9 100644
--- a/gdbserver/linux-amd64-ipa.cc
+++ b/gdbserver/linux-amd64-ipa.cc
@@ -169,21 +169,47 @@ supply_static_tracepoint_registers (struct regcache *regcache,
 
 #endif /* HAVE_UST */
 
+#if !defined __ILP32__
+/* Map the tdesc index to xcr0 mask.  */
+static uint64_t idx2mask[X86_TDESC_LAST] = {
+  X86_XSTATE_X87_MASK,
+  X86_XSTATE_SSE_MASK,
+  X86_XSTATE_AVX_MASK,
+  X86_XSTATE_MPX_MASK,
+  X86_XSTATE_AVX_MPX_MASK,
+  X86_XSTATE_AVX_AVX512_MASK,
+  X86_XSTATE_AVX_MPX_AVX512_PKU_MASK,
+};
+#endif
+
 /* Return target_desc to use for IPA, given the tdesc index passed by
    gdbserver.  */
 
 const struct target_desc *
 get_ipa_tdesc (int idx)
 {
-  uint64_t xcr0 = x86_linux_tdesc_idx_to_xcr0 (idx);
+  if (idx >= X86_TDESC_LAST)
+    {
+      internal_error ("unknown ipa tdesc index: %d", idx);
+    }
 
 #if defined __ILP32__
-  bool is_x32 = true;
+  switch (idx)
+    {
+    case X86_TDESC_SSE:
+      return amd64_linux_read_description (X86_XSTATE_SSE_MASK, true);
+    case X86_TDESC_AVX:
+      return amd64_linux_read_description (X86_XSTATE_AVX_MASK, true);
+    case X86_TDESC_AVX_AVX512:
+      return amd64_linux_read_description (X86_XSTATE_AVX_AVX512_MASK, true);
+    default:
+      break;
+    }
 #else
-  bool is_x32 = false;
+  return amd64_linux_read_description (idx2mask[idx], false);
 #endif
 
-  return amd64_linux_read_description (xcr0, is_x32);
+  internal_error ("unknown ipa tdesc index: %d", idx);
 }
 
 /* Allocate buffer for the jump pads.  The branch instruction has a
@@ -251,10 +277,11 @@ void
 initialize_low_tracepoint (void)
 {
 #if defined __ILP32__
-  for (auto i = 0; i < x86_linux_x32_ipa_tdesc_count (); i++)
-    amd64_linux_read_description (x86_linux_tdesc_idx_to_xcr0 (i), true);
+  amd64_linux_read_description (X86_XSTATE_SSE_MASK, true);
+  amd64_linux_read_description (X86_XSTATE_AVX_MASK, true);
+  amd64_linux_read_description (X86_XSTATE_AVX_AVX512_MASK, true);
 #else
-  for (auto i = 0; i < x86_linux_amd64_ipa_tdesc_count (); i++)
-    amd64_linux_read_description (x86_linux_tdesc_idx_to_xcr0 (i), false);
+  for (auto i = 0; i < X86_TDESC_LAST; i++)
+    amd64_linux_read_description (idx2mask[i], false);
 #endif
 }
diff --git a/gdbserver/linux-i386-ipa.cc b/gdbserver/linux-i386-ipa.cc
index 246bcb9813b..459b8055b5c 100644
--- a/gdbserver/linux-i386-ipa.cc
+++ b/gdbserver/linux-i386-ipa.cc
@@ -246,15 +246,28 @@ initialize_fast_tracepoint_trampoline_buffer (void)
     }
 }
 
+/* Map the tdesc index to xcr0 mask.  */
+static uint64_t idx2mask[X86_TDESC_LAST] = {
+  X86_XSTATE_X87_MASK,
+  X86_XSTATE_SSE_MASK,
+  X86_XSTATE_AVX_MASK,
+  X86_XSTATE_MPX_MASK,
+  X86_XSTATE_AVX_MPX_MASK,
+  X86_XSTATE_AVX_AVX512_MASK,
+  X86_XSTATE_AVX_MPX_AVX512_PKU_MASK,
+};
+
 /* Return target_desc to use for IPA, given the tdesc index passed by
    gdbserver.  */
 
 const struct target_desc *
 get_ipa_tdesc (int idx)
 {
-  uint64_t xcr0 = x86_linux_tdesc_idx_to_xcr0 (idx);
-
-  return i386_linux_read_description (xcr0);
+  if (idx >= X86_TDESC_LAST)
+    {
+      internal_error ("unknown ipa tdesc index: %d", idx);
+    }
+  return i386_linux_read_description (idx2mask[idx]);
 }
 
 /* Allocate buffer for the jump pads.  On i386, we can reach an arbitrary
@@ -276,6 +289,6 @@ void
 initialize_low_tracepoint (void)
 {
   initialize_fast_tracepoint_trampoline_buffer ();
-  for (auto i = 0; i < x86_linux_i386_ipa_tdesc_count (); i++)
-    i386_linux_read_description (x86_linux_tdesc_idx_to_xcr0 (i));
+  for (auto i = 0; i < X86_TDESC_LAST; i++)
+    i386_linux_read_description (idx2mask[i]);
 }
diff --git a/gdbserver/linux-x86-low.cc b/gdbserver/linux-x86-low.cc
index 6dbefdb2f26..9bf369f8a34 100644
--- a/gdbserver/linux-x86-low.cc
+++ b/gdbserver/linux-x86-low.cc
@@ -2892,17 +2892,14 @@ x86_target::get_ipa_tdesc_idx ()
   struct regcache *regcache = get_thread_regcache (current_thread, 0);
   const struct target_desc *tdesc = regcache->tdesc;
 
-  if (!use_xml)
-    {
-      if (tdesc == tdesc_i386_linux_no_xml.get ()
 #ifdef __x86_64__
-	  || tdesc == tdesc_amd64_linux_no_xml.get ()
-#endif /* __x86_64__ */
-	  )
-	return x86_linux_xcr0_to_tdesc_idx (X86_XSTATE_SSE_MASK);
-    }
+  return amd64_get_ipa_tdesc_idx (tdesc);
+#endif
+
+  if (tdesc == tdesc_i386_linux_no_xml.get ())
+    return X86_TDESC_SSE;
 
-  return x86_linux_xcr0_to_tdesc_idx (xcr0_storage);
+  return i386_get_ipa_tdesc_idx (tdesc);
 }
 
 /* The linux target ops object.  */
diff --git a/gdbserver/linux-x86-tdesc.cc b/gdbserver/linux-x86-tdesc.cc
index 87cf368a336..9fd64d8574b 100644
--- a/gdbserver/linux-x86-tdesc.cc
+++ b/gdbserver/linux-x86-tdesc.cc
@@ -28,277 +28,96 @@
 #include "x86-tdesc.h"
 #include "nat/x86-linux-tdesc.h"
 
-/* A structure used to describe a single cpu feature that might, or might
-   not, be checked for when creating a target description for one of i386,
-   amd64, or x32.  */
+/* Return the right x86_linux_tdesc index for a given XCR0.  Return
+   X86_TDESC_LAST if can't find a match.  */
 
-struct x86_tdesc_feature {
-  /* The cpu feature mask.  This is a mask against an xcr0 value.  */
-  uint64_t feature;
-
-  /* Is this feature checked when creating an i386 target description.  */
-  bool is_i386;
-
-  /* Is this feature checked when creating an amd64 target description.  */
-  bool is_amd64;
-
-  /* Is this feature checked when creating an x32 target description.  */
-  bool is_x32;
-};
-
-/* A constant table that describes all of the cpu features that are
-   checked when building a target description for i386, amd64, or x32.  */
-
-static constexpr x86_tdesc_feature x86_linux_all_tdesc_features[] = {
-  /* Feature,           i386,	amd64,	x32.  */
-  { X86_XSTATE_PKRU,	true,	true, 	true },
-  { X86_XSTATE_AVX512,	true,	true, 	true },
-  { X86_XSTATE_AVX,	true,	true, 	true },
-  { X86_XSTATE_MPX,	true,	true, 	false },
-  { X86_XSTATE_SSE,	true,	false, 	false },
-  { X86_XSTATE_X87,	true,	false, 	false }
-};
-
-/* Return a compile time constant which is a mask of all the cpu features
-   that are checked for when building an i386 target description.  */
-
-static constexpr uint64_t
-x86_linux_i386_tdesc_feature_mask ()
-{
-  uint64_t mask = 0;
-
-  for (const auto &entry : x86_linux_all_tdesc_features)
-    if (entry.is_i386)
-      mask |= entry.feature;
-
-  return mask;
-}
-
-/* Return a compile time constant which is a mask of all the cpu features
-   that are checked for when building an amd64 target description.  */
-
-static constexpr uint64_t
-x86_linux_amd64_tdesc_feature_mask ()
-{
-  uint64_t mask = 0;
-
-  for (const auto &entry : x86_linux_all_tdesc_features)
-    if (entry.is_amd64)
-      mask |= entry.feature;
-
-  return mask;
-}
-
-/* Return a compile time constant which is a mask of all the cpu features
-   that are checked for when building an x32 target description.  */
-
-static constexpr uint64_t
-x86_linux_x32_tdesc_feature_mask ()
-{
-  uint64_t mask = 0;
-
-  for (const auto &entry : x86_linux_all_tdesc_features)
-    if (entry.is_x32)
-      mask |= entry.feature;
-
-  return mask;
-}
-
-/* Return a compile time constant which is a count of the number of cpu
-   features that are checked for when building an i386 target description.  */
-
-static constexpr int
-x86_linux_i386_tdesc_count ()
-{
-  uint64_t count = 0;
-
-  for (const auto &entry : x86_linux_all_tdesc_features)
-    if (entry.is_i386)
-      ++count;
-
-  gdb_assert (count > 0);
-
-  return (1 << count);
-}
-
-/* Return a compile time constant which is a count of the number of cpu
-   features that are checked for when building an amd64 target description.  */
-
-static constexpr int
-x86_linux_amd64_tdesc_count ()
-{
-  uint64_t count = 0;
-
-  for (const auto &entry : x86_linux_all_tdesc_features)
-    if (entry.is_amd64)
-      ++count;
-
-  gdb_assert (count > 0);
-
-  return (1 << count);
-}
-
-/* Return a compile time constant which is a count of the number of cpu
-   features that are checked for when building an x32 target description.  */
-
-static constexpr int
-x86_linux_x32_tdesc_count ()
-{
-  uint64_t count = 0;
-
-  for (const auto &entry : x86_linux_all_tdesc_features)
-    if (entry.is_x32)
-      ++count;
-
-  gdb_assert (count > 0);
-
-  return (1 << count);
-}
-
-#ifdef IN_PROCESS_AGENT
-
-/* See linux-x86-tdesc.h.  */
-
-int
-x86_linux_amd64_ipa_tdesc_count ()
-{
-  return x86_linux_amd64_tdesc_count ();
-}
-
-/* See linux-x86-tdesc.h.  */
-
-int
-x86_linux_x32_ipa_tdesc_count ()
-{
-  return x86_linux_x32_tdesc_count ();
-}
-
-/* See linux-x86-tdesc.h.  */
-
-int
-x86_linux_i386_ipa_tdesc_count ()
-{
-  return x86_linux_i386_tdesc_count ();
-}
-
-#endif /* IN_PROCESS_AGENT */
-
-/* Convert an xcr0 value into an integer.  The integer will be passed to
-   the in-process-agent where it will then be passed to
-   x86_linux_tdesc_idx_to_xcr0 to get back the xcr0 value.  */
-
-int
-x86_linux_xcr0_to_tdesc_idx (uint64_t xcr0)
+static enum x86_linux_tdesc
+xcr0_to_tdesc_idx (uint64_t xcr0, bool is_x32)
 {
-  /* The following table shows which features are checked for when creating
-     the target descriptions (see nat/x86-linux-tdesc.c), the feature order
-     represents the bit order within the generated index number.
-
-     i386  | x87 sse mpx avx avx512 pkru
-     amd64 |         mpx avx avx512 pkru
-     i32   |             avx avx512 pkru
-
-     The features are ordered so that for each mode (i386, amd64, i32) the
-     generated index will form a continuous range.  */
-
-  int idx = 0;
-
-  for (int i = 0; i < ARRAY_SIZE (x86_linux_all_tdesc_features); ++i)
+  if (xcr0 & X86_XSTATE_PKRU)
     {
-      if ((xcr0 & x86_linux_all_tdesc_features[i].feature) != 0)
-	idx |= (1 << i);
+      if (is_x32)
+	{
+	  /* No x32 MPX and PKU, fall back to avx_avx512.  */
+	  return X86_TDESC_AVX_AVX512;
+	}
+      else
+	return X86_TDESC_AVX_MPX_AVX512_PKU;
     }
-
-  return idx;
-}
-
-
-#ifdef IN_PROCESS_AGENT
-
-/* Convert an index number (as returned from x86_linux_xcr0_to_tdesc_idx)
-   into an xcr0 value which can then be used to create a target
-   description.  */
-
-uint64_t
-x86_linux_tdesc_idx_to_xcr0 (int idx)
-{
-  uint64_t xcr0 = 0;
-
-  for (int i = 0; i < ARRAY_SIZE (x86_linux_all_tdesc_features); ++i)
+  else if (xcr0 & X86_XSTATE_AVX512)
+    return X86_TDESC_AVX_AVX512;
+  else if ((xcr0 & X86_XSTATE_AVX_MPX_MASK) == X86_XSTATE_AVX_MPX_MASK)
     {
-      if ((idx & (1 << i)) != 0)
-	xcr0 |= x86_linux_all_tdesc_features[i].feature;
+      if (is_x32) /* No MPX on x32.  */
+	return X86_TDESC_AVX;
+      else
+	return X86_TDESC_AVX_MPX;
     }
-
-  return xcr0;
+  else if (xcr0 & X86_XSTATE_MPX)
+    {
+      if (is_x32) /* No MPX on x32.  */
+	return X86_TDESC_AVX;
+      else
+	return X86_TDESC_MPX;
+    }
+  else if (xcr0 & X86_XSTATE_AVX)
+    return X86_TDESC_AVX;
+  else if (xcr0 & X86_XSTATE_SSE)
+    return X86_TDESC_SSE;
+  else if (xcr0 & X86_XSTATE_X87)
+    return X86_TDESC_MMX;
+  else
+    return X86_TDESC_LAST;
 }
 
-#endif /* IN_PROCESS_AGENT */
-
 #if defined __i386__ || !defined IN_PROCESS_AGENT
 
-/* A cache of all possible i386 target descriptions.  */
+static struct target_desc *i386_tdescs[X86_TDESC_LAST] = { };
 
-static struct target_desc *i386_tdescs[x86_linux_i386_tdesc_count ()] = { };
-
-/* See nat/x86-linux-tdesc.h.  */
+/* Return the target description according to XCR0.  */
 
 const struct target_desc *
 i386_linux_read_description (uint64_t xcr0)
 {
-  xcr0 &= x86_linux_i386_tdesc_feature_mask ();
-  int idx = x86_linux_xcr0_to_tdesc_idx (xcr0);
+  enum x86_linux_tdesc idx = xcr0_to_tdesc_idx (xcr0, false);
 
-  gdb_assert (idx >= 0 && idx < x86_linux_i386_tdesc_count ());
+  if (idx == X86_TDESC_LAST)
+    return NULL;
 
-  target_desc **tdesc = &i386_tdescs[idx];
+  struct target_desc **tdesc = &i386_tdescs[idx];
 
-  if (*tdesc == nullptr)
+  if (*tdesc == NULL)
     {
       *tdesc = i386_create_target_description (xcr0, true, false);
 
       init_target_desc (*tdesc, i386_expedite_regs);
     }
 
-  return *tdesc;
+  return *tdesc;;
 }
 #endif
 
 #ifdef __x86_64__
 
-/* A cache of all possible amd64 target descriptions.  */
-
-static target_desc *amd64_tdescs[x86_linux_amd64_tdesc_count ()] = { };
-
-/* A cache of all possible x32 target descriptions.  */
-
-static target_desc *x32_tdescs[x86_linux_x32_tdesc_count ()] = { };
-
-/* See nat/x86-linux-tdesc.h.  */
+static target_desc *amd64_tdescs[X86_TDESC_LAST] = { };
+static target_desc *x32_tdescs[X86_TDESC_LAST] = { };
 
 const struct target_desc *
 amd64_linux_read_description (uint64_t xcr0, bool is_x32)
 {
-  if (is_x32)
-    xcr0 &= x86_linux_x32_tdesc_feature_mask ();
-  else
-    xcr0 &= x86_linux_amd64_tdesc_feature_mask ();
-
-  int idx = x86_linux_xcr0_to_tdesc_idx (xcr0);
+  enum x86_linux_tdesc idx = xcr0_to_tdesc_idx (xcr0, is_x32);
 
-  if (is_x32)
-    gdb_assert (idx >= 0 && idx < x86_linux_x32_tdesc_count ());
-  else
-    gdb_assert (idx >= 0 && idx < x86_linux_amd64_tdesc_count ());
+  if (idx == X86_TDESC_LAST)
+    return NULL;
 
-  target_desc **tdesc = nullptr;
+  struct target_desc **tdesc = NULL;
 
   if (is_x32)
     tdesc = &x32_tdescs[idx];
   else
     tdesc = &amd64_tdescs[idx];
 
-  if (*tdesc == nullptr)
+  if (*tdesc == NULL)
     {
       *tdesc = amd64_create_target_description (xcr0, is_x32, true, true);
 
@@ -308,3 +127,39 @@ amd64_linux_read_description (uint64_t xcr0, bool is_x32)
 }
 
 #endif
+
+#ifndef IN_PROCESS_AGENT
+
+int
+i386_get_ipa_tdesc_idx (const struct target_desc *tdesc)
+{
+  for (int i = 0; i < X86_TDESC_LAST; i++)
+    {
+      if (tdesc == i386_tdescs[i])
+	return i;
+    }
+
+  /* If none tdesc is found, return the one with minimum features.  */
+  return X86_TDESC_MMX;
+}
+
+#if defined __x86_64__
+int
+amd64_get_ipa_tdesc_idx (const struct target_desc *tdesc)
+{
+  for (int i = 0; i < X86_TDESC_LAST; i++)
+    {
+      if (tdesc == amd64_tdescs[i])
+	return i;
+    }
+  for (int i = 0; i < X86_TDESC_LAST; i++)
+    {
+      if (tdesc == x32_tdescs[i])
+	return i;
+    }
+
+  return X86_TDESC_SSE;
+}
+
+#endif
+#endif
diff --git a/gdbserver/linux-x86-tdesc.h b/gdbserver/linux-x86-tdesc.h
index 70456e4be44..576aaf5e165 100644
--- a/gdbserver/linux-x86-tdesc.h
+++ b/gdbserver/linux-x86-tdesc.h
@@ -21,30 +21,29 @@
 #ifndef GDBSERVER_LINUX_X86_TDESC_H
 #define GDBSERVER_LINUX_X86_TDESC_H
 
-/* Convert an xcr0 value into an integer.  The integer will be passed to
-   the in-process-agent where it will then be passed to
-   x86_linux_tdesc_idx_to_xcr0 to get back the xcr0 value.  */
-
-extern int x86_linux_xcr0_to_tdesc_idx (uint64_t xcr0);
-
-#ifdef IN_PROCESS_AGENT
-
-/* Convert an index number (as returned from x86_linux_xcr0_to_tdesc_idx)
-   into an xcr0 value which can then be used to create a target
-   description.  */
-
-extern uint64_t x86_linux_tdesc_idx_to_xcr0 (int idx);
-
-/* Within the in-process-agent we need to pre-initialise all of the target
-   descriptions, to do this we need to know how many target descriptions
-   there are for each different target type.  These functions return the
-   target description count for the relevant target.  */
-
-extern int x86_linux_amd64_ipa_tdesc_count ();
-extern int x86_linux_x32_ipa_tdesc_count ();
-extern int x86_linux_i386_ipa_tdesc_count ();
-
-
-#endif /* IN_PROCESS_AGENT */
+/* Note: since IPA obviously knows what ABI it's running on (i386 vs x86_64
+   vs x32), it's sufficient to pass only the register set here.  This,
+   together with the ABI known at IPA compile time, maps to a tdesc.  */
+
+enum x86_linux_tdesc {
+  X86_TDESC_MMX = 0,
+  X86_TDESC_SSE = 1,
+  X86_TDESC_AVX = 2,
+  X86_TDESC_MPX = 3,
+  X86_TDESC_AVX_MPX = 4,
+  X86_TDESC_AVX_AVX512 = 5,
+  X86_TDESC_AVX_MPX_AVX512_PKU = 6,
+  X86_TDESC_LAST = 7,
+};
+
+#if defined __i386__ || !defined IN_PROCESS_AGENT
+int i386_get_ipa_tdesc_idx (const struct target_desc *tdesc);
+#endif
+
+#if defined __x86_64__ && !defined IN_PROCESS_AGENT
+int amd64_get_ipa_tdesc_idx (const struct target_desc *tdesc);
+#endif
+
+const struct target_desc *i386_get_ipa_tdesc (int idx);
 
 #endif /* GDBSERVER_LINUX_X86_TDESC_H */