[PATCH v5 08/19] *-linux-nat: Handle null inferior in read_description.

[John Baldwin <jhb@FreeBSD.org>]

Don't invoke ptrace in the target read_description method if there is
not an active inferior to query via ptrace.  Instead, use the default
register set for the architecture.
---
 gdb/aarch64-linux-nat.c | 3 +++
 gdb/arm-linux-nat.c     | 3 +++
 gdb/mips-linux-nat.c    | 3 +++
 gdb/ppc-linux-nat.c     | 3 +++
 gdb/riscv-linux-nat.c   | 3 +++
 gdb/s390-linux-nat.c    | 3 +++
 gdb/x86-linux-nat.c     | 3 +++
 7 files changed, 21 insertions(+)

diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index ecb2eeb9540..62f8825b9c8 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -785,6 +785,9 @@ aarch64_linux_nat_target::read_description ()
   gdb_byte regbuf[ARM_VFP3_REGS_SIZE];
   struct iovec iovec;
 
+  if (inferior_ptid == null_ptid)
+    return nullptr;
+
   tid = inferior_ptid.pid ();
 
   iovec.iov_base = regbuf;
diff --git a/gdb/arm-linux-nat.c b/gdb/arm-linux-nat.c
index ef3fa008adf..70c6bc684fa 100644
--- a/gdb/arm-linux-nat.c
+++ b/gdb/arm-linux-nat.c
@@ -531,6 +531,9 @@ ps_get_thread_area (struct ps_prochandle *ph,
 const struct target_desc *
 arm_linux_nat_target::read_description ()
 {
+  if (inferior_ptid == null_ptid)
+    return this->beneath ()->read_description ();
+
   CORE_ADDR arm_hwcap = linux_get_hwcap ();
 
   if (have_ptrace_getregset == TRIBOOL_UNKNOWN)
diff --git a/gdb/mips-linux-nat.c b/gdb/mips-linux-nat.c
index 972b5db8e76..1fa0e8c479c 100644
--- a/gdb/mips-linux-nat.c
+++ b/gdb/mips-linux-nat.c
@@ -454,6 +454,9 @@ mips_linux_nat_target::register_u_offset (struct gdbarch *gdbarch,
 const struct target_desc *
 mips_linux_nat_target::read_description ()
 {
+  if (inferior_ptid == null_ptid)
+    return _MIPS_SIM == _ABIO32 ? tdesc_mips_linux : tdesc_mips64_linux;
+
   static int have_dsp = -1;
 
   if (have_dsp < 0)
diff --git a/gdb/ppc-linux-nat.c b/gdb/ppc-linux-nat.c
index 42885deb45e..2f4799aa73a 100644
--- a/gdb/ppc-linux-nat.c
+++ b/gdb/ppc-linux-nat.c
@@ -1941,6 +1941,9 @@ ppc_linux_nat_target::auxv_parse (const gdb_byte **readptr,
 const struct target_desc *
 ppc_linux_nat_target::read_description ()
 {
+  if (inferior_ptid == null_ptid)
+    return ppc_linux_match_description (ppc_linux_no_features);
+
   int tid = inferior_ptid.pid ();
 
   if (have_ptrace_getsetevrregs)
diff --git a/gdb/riscv-linux-nat.c b/gdb/riscv-linux-nat.c
index 8be4a5ac3e5..5d325e633da 100644
--- a/gdb/riscv-linux-nat.c
+++ b/gdb/riscv-linux-nat.c
@@ -201,6 +201,9 @@ fill_fpregset (const struct regcache *regcache, prfpregset_t *fpregs,
 const struct target_desc *
 riscv_linux_nat_target::read_description ()
 {
+  if (inferior_ptid == null_ptid)
+    return nullptr;
+
   const struct riscv_gdbarch_features features
     = riscv_linux_read_features (inferior_ptid.pid ());
   return riscv_lookup_target_description (features);
diff --git a/gdb/s390-linux-nat.c b/gdb/s390-linux-nat.c
index fc3917d30be..7d3b3cfe78b 100644
--- a/gdb/s390-linux-nat.c
+++ b/gdb/s390-linux-nat.c
@@ -987,6 +987,9 @@ s390_linux_nat_target::auxv_parse (const gdb_byte **readptr,
 const struct target_desc *
 s390_linux_nat_target::read_description ()
 {
+  if (inferior_ptid == null_ptid)
+    return nullptr;
+
   int tid = inferior_ptid.pid ();
 
   have_regset_last_break
diff --git a/gdb/x86-linux-nat.c b/gdb/x86-linux-nat.c
index fd2145244cc..87862b89eab 100644
--- a/gdb/x86-linux-nat.c
+++ b/gdb/x86-linux-nat.c
@@ -115,6 +115,9 @@ x86_linux_nat_target::read_description ()
   static uint64_t xcr0;
   uint64_t xcr0_features_bits;
 
+  if (inferior_ptid == null_ptid)
+    return nullptr;
+
   tid = inferior_ptid.pid ();
 
 #ifdef __x86_64__
-- 
2.40.0