[PATCH] gdb/arm: Remove tpidruro register from non-FreeBSD target descriptions

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

Commit 92d48a1e4eac ("Add an arm-tls feature which includes the tpidruro
register from CP15.") introduced the org.gnu.gdb.arm.tls feature, which
adds the tpidruro register, and unconditionally enabled it in
aarch32_create_target_description.

In Linux, the tpidruro register isn't available via ptrace in the 32-bit
kernel but it is available for an aarch32 program running under an arm64
kernel via the ptrace compat interface.  This isn't currently implemented
however, which causes GDB on arm-linux with 64-bit kernel to list the
register but show it as unavailable, as reported by Tom de Vries:

  $ gdb -q -batch a.out -ex start -ex 'p $tpidruro'
  Temporary breakpoint 1 at 0x512

  Temporary breakpoint 1, 0xaaaaa512 in main ()
  $1 = <unavailable>

Simon Marchi then clarified:

> The only time we should be seeing some "unavailable" registers or memory
> is in the context of tracepoints, for things that are not collected.
> Seeing an unavailable register here is a sign that something is not
> right.

Therefore, disable the TLS feature in aarch32 target descriptions for Linux
and NetBSD targets (the latter also doesn't seem to support accessing
tpidruro either, based on a quick look at arm-netbsd-nat.c).

This patch fixes the following tests:

Running gdb.base/inline-frame-cycle-unwind.exp ...
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 3: backtrace when the unwind is broken at frame 3
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 5: backtrace when the unwind is broken at frame 5
FAIL: gdb.base/inline-frame-cycle-unwind.exp: cycle at level 1: backtrace when the unwind is broken at frame 1

Tested with Ubuntu 22.04.3 on armv8l-linux-gnueabihf in native,
native-gdbserver and native-extended-gdbserver targets with no regressions.

PR tdep/31418
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31418
---
 gdb/aarch32-tdep.c               | 4 ++--
 gdb/aarch32-tdep.h               | 2 +-
 gdb/aarch64-linux-nat.c          | 2 +-
 gdb/arch/aarch32.c               | 5 +++--
 gdb/arch/aarch32.h               | 2 +-
 gdb/arm-fbsd-tdep.c              | 2 +-
 gdb/arm-linux-nat.c              | 2 +-
 gdb/arm-linux-tdep.c             | 2 +-
 gdb/arm-netbsd-nat.c             | 2 +-
 gdbserver/linux-aarch32-tdesc.cc | 2 +-
 10 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/gdb/aarch32-tdep.c b/gdb/aarch32-tdep.c
index 9177b47d1481..f3ff3570c748 100644
--- a/gdb/aarch32-tdep.c
+++ b/gdb/aarch32-tdep.c
@@ -27,10 +27,10 @@ static struct target_desc *tdesc_aarch32;
 /* See aarch32-tdep.h.  */
 
 const target_desc *
-aarch32_read_description ()
+aarch32_read_description (bool tls)
 {
   if (tdesc_aarch32 == nullptr)
-    tdesc_aarch32 = aarch32_create_target_description ();
+    tdesc_aarch32 = aarch32_create_target_description (tls);
 
   return tdesc_aarch32;
 }
diff --git a/gdb/aarch32-tdep.h b/gdb/aarch32-tdep.h
index 654483438485..009ee61890e2 100644
--- a/gdb/aarch32-tdep.h
+++ b/gdb/aarch32-tdep.h
@@ -22,6 +22,6 @@ struct target_desc;
 
 /* Get the AArch32 target description.  */
 
-const target_desc *aarch32_read_description ();
+const target_desc *aarch32_read_description (bool tls);
 
 #endif /* aarch32-tdep.h.  */
diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index 11a41e1afae0..9dc45e1c1d96 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -887,7 +887,7 @@ aarch64_linux_nat_target::read_description ()
 
   ret = ptrace (PTRACE_GETREGSET, tid, NT_ARM_VFP, &iovec);
   if (ret == 0)
-    return aarch32_read_description ();
+    return aarch32_read_description (false);
 
   CORE_ADDR hwcap = linux_get_hwcap ();
   CORE_ADDR hwcap2 = linux_get_hwcap2 ();
diff --git a/gdb/arch/aarch32.c b/gdb/arch/aarch32.c
index c910e3b5a388..9f3e25088f41 100644
--- a/gdb/arch/aarch32.c
+++ b/gdb/arch/aarch32.c
@@ -25,7 +25,7 @@
 /* See aarch32.h.  */
 
 target_desc *
-aarch32_create_target_description ()
+aarch32_create_target_description (bool tls)
 {
   target_desc_up tdesc = allocate_target_description ();
 
@@ -39,7 +39,8 @@ aarch32_create_target_description ()
   /* Create a vfpv3 feature, then a blank NEON feature.  */
   regnum = create_feature_arm_arm_vfpv3 (tdesc.get (), regnum);
   tdesc_create_feature (tdesc.get (), "org.gnu.gdb.arm.neon");
-  regnum = create_feature_arm_arm_tls (tdesc.get (), regnum);
+  if (tls)
+    regnum = create_feature_arm_arm_tls (tdesc.get (), regnum);
 
   return tdesc.release ();
 }
diff --git a/gdb/arch/aarch32.h b/gdb/arch/aarch32.h
index f7ee6faeea3c..1811b8a7a925 100644
--- a/gdb/arch/aarch32.h
+++ b/gdb/arch/aarch32.h
@@ -22,6 +22,6 @@
 
 /* Create the AArch32 target description.  */
 
-target_desc *aarch32_create_target_description ();
+target_desc *aarch32_create_target_description (bool tls);
 
 #endif /* aarch32.h.  */
diff --git a/gdb/arm-fbsd-tdep.c b/gdb/arm-fbsd-tdep.c
index b485951c3764..7b82de2166b5 100644
--- a/gdb/arm-fbsd-tdep.c
+++ b/gdb/arm-fbsd-tdep.c
@@ -228,7 +228,7 @@ arm_fbsd_read_description_auxv (const std::optional<gdb::byte_vector> &auxv,
   if (arm_hwcap & HWCAP_VFP)
     {
       if (arm_hwcap & HWCAP_NEON)
-	return aarch32_read_description ();
+	return aarch32_read_description (tls);
       else if ((arm_hwcap & (HWCAP_VFPv3 | HWCAP_VFPD32))
 	       == (HWCAP_VFPv3 | HWCAP_VFPD32))
 	return arm_read_description (ARM_FP_TYPE_VFPV3, tls);
diff --git a/gdb/arm-linux-nat.c b/gdb/arm-linux-nat.c
index 02994732563a..75f498cd5b3f 100644
--- a/gdb/arm-linux-nat.c
+++ b/gdb/arm-linux-nat.c
@@ -568,7 +568,7 @@ arm_linux_nat_target::read_description ()
       /* NEON implies VFPv3-D32 or no-VFP unit.  Say that we only support
 	 Neon with VFPv3-D32.  */
       if (arm_hwcap & HWCAP_NEON)
-	return aarch32_read_description ();
+	return aarch32_read_description (false);
       else if ((arm_hwcap & (HWCAP_VFPv3 | HWCAP_VFPv3D16)) == HWCAP_VFPv3)
 	return arm_read_description (ARM_FP_TYPE_VFPV3, false);
 
diff --git a/gdb/arm-linux-tdep.c b/gdb/arm-linux-tdep.c
index cc79247aaf12..a8b27a7463a6 100644
--- a/gdb/arm-linux-tdep.c
+++ b/gdb/arm-linux-tdep.c
@@ -740,7 +740,7 @@ arm_linux_core_read_description (struct gdbarch *gdbarch,
       /* NEON implies VFPv3-D32 or no-VFP unit.  Say that we only support
 	 Neon with VFPv3-D32.  */
       if (arm_hwcap & HWCAP_NEON)
-	return aarch32_read_description ();
+	return aarch32_read_description (false);
       else if ((arm_hwcap & (HWCAP_VFPv3 | HWCAP_VFPv3D16)) == HWCAP_VFPv3)
 	return arm_read_description (ARM_FP_TYPE_VFPV3, false);
 
diff --git a/gdb/arm-netbsd-nat.c b/gdb/arm-netbsd-nat.c
index df8b5ec7b03c..4b9f92946412 100644
--- a/gdb/arm-netbsd-nat.c
+++ b/gdb/arm-netbsd-nat.c
@@ -350,7 +350,7 @@ arm_netbsd_nat_target::read_description ()
 
   len = sizeof(flag);
   if (sysctlbyname("machdep.neon_present", &flag, &len, NULL, 0) == 0 && flag)
-    return aarch32_read_description ();
+    return aarch32_read_description (false);
 
   return arm_read_description (ARM_FP_TYPE_VFPV3, false);
 }
diff --git a/gdbserver/linux-aarch32-tdesc.cc b/gdbserver/linux-aarch32-tdesc.cc
index a696d8946e29..54c6f62e9965 100644
--- a/gdbserver/linux-aarch32-tdesc.cc
+++ b/gdbserver/linux-aarch32-tdesc.cc
@@ -32,7 +32,7 @@ aarch32_linux_read_description ()
 {
   if (tdesc_aarch32 == nullptr)
     {
-      tdesc_aarch32 = aarch32_create_target_description ();
+      tdesc_aarch32 = aarch32_create_target_description (false);
 
       static const char *expedite_regs[] = { "r11", "sp", "pc", 0 };
       init_target_desc (tdesc_aarch32, expedite_regs);