Ptrace support for Aarch64 SVE

Add support for reading and writing registers for Aarch64 SVE.

We need to support the cases where the kernel only gives us a
fpsimd structure. This occurs when there is no active SVE state
in the kernel (for example, after starting a new process).

Added checks to make sure the vector length has not changed whilst
the process is running.

gdb/
	* aarch64-linux-nat.c (fetch_sveregs_from_thread): New function.
	(store_sveregs_to_thread): Likewise.
	(aarch64_linux_fetch_inferior_registers): Check for SVE.
	(aarch64_linux_store_inferior_registers): Likewise.
	* nat/aarch64-sve-linux-ptrace.c (aarch64_sve_get_sveregs): New
	function.
	(aarch64_sve_regs_copy_to_regcache): Likewise.
	(aarch64_sve_regs_copy_from_regcache): Likewise.
	* nat/aarch64-sve-linux-ptrace.h (aarch64_sve_get_sveregs): New
	declaration.
	(aarch64_sve_regs_copy_to_regcache): Likewise.
	(aarch64_sve_regs_copy_from_regcache): Likewise.
	(sve_context): Structure from Linux headers.
	(SVE_SIG_ZREGS_SIZE): Define from Linux headers.
	(SVE_SIG_ZREG_SIZE): Likewise.
	(SVE_SIG_PREG_SIZE): Likewise.
	(SVE_SIG_FFR_SIZE): Likewise.
	(SVE_SIG_REGS_OFFSET): Likewise.
	(SVE_SIG_ZREGS_OFFSET): Likewise.
	(SVE_SIG_ZREG_OFFSET): Likewise.
	(SVE_SIG_ZREGS_SIZE): Likewise.
	(SVE_SIG_PREGS_OFFSET): Likewise.
	(SVE_SIG_PREG_OFFSET): Likewise.
	(SVE_SIG_PREGS_SIZE): Likewise.
	(SVE_SIG_FFR_OFFSET): Likewise.
	(SVE_SIG_REGS_SIZE): Likewise.
	(SVE_SIG_CONTEXT_SIZE): Likewise.
	(SVE_PT_REGS_MASK): Likewise.
	(SVE_PT_REGS_FPSIMD): Likewise.
	(SVE_PT_REGS_SVE): Likewise.
	(SVE_PT_VL_INHERIT): Likewise.
	(SVE_PT_VL_ONEXEC): Likewise.
	(SVE_PT_REGS_OFFSET): Likewise.
	(SVE_PT_FPSIMD_OFFSET): Likewise.
	(SVE_PT_FPSIMD_SIZE): Likewise.
	(SVE_PT_SVE_ZREG_SIZE): Likewise.
	(SVE_PT_SVE_PREG_SIZE): Likewise.
	(SVE_PT_SVE_FFR_SIZE): Likewise.
	(SVE_PT_SVE_FPSR_SIZE): Likewise.
	(SVE_PT_SVE_FPCR_SIZE): Likewise.
	(__SVE_SIG_TO_PT): Likewise.
	(SVE_PT_SVE_OFFSET): Likewise.
	(SVE_PT_SVE_ZREGS_OFFSET): Likewise.
	(SVE_PT_SVE_ZREG_OFFSET): Likewise.
	(SVE_PT_SVE_ZREGS_SIZE): Likewise.
	(SVE_PT_SVE_PREGS_OFFSET): Likewise.
	(SVE_PT_SVE_PREG_OFFSET): Likewise.
	(SVE_PT_SVE_PREGS_SIZE): Likewise.
	(SVE_PT_SVE_FFR_OFFSET): Likewise.
	(SVE_PT_SVE_FPSR_OFFSET): Likewise.
	(SVE_PT_SVE_FPCR_OFFSET): Likewise.
	(SVE_PT_SVE_SIZE): Likewise.
	(SVE_PT_SIZE): Likewise.
	(HAS_SVE_STATE): New define.

gdbserver/
	* Makefile.in: Add aarch64-sve-linux-ptrace.c.

1 files changed, 52 insertions, 2 deletions

diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index 1e4f937..1e7db29 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -384,19 +384,62 @@ store_fpregs_to_thread (const struct regcache *regcache)
     }
 }
 
+/* Fill GDB's register array with the sve register values
+   from the current thread.  */
+
+static void
+fetch_sveregs_from_thread (struct regcache *regcache)
+{
+  std::unique_ptr<gdb_byte[]> base
+    = aarch64_sve_get_sveregs (ptid_get_lwp (regcache->ptid ()));
+  aarch64_sve_regs_copy_to_reg_buf (regcache, base.get ());
+}
+
+/* Store to the current thread the valid sve register
+   values in the GDB's register array.  */
+
+static void
+store_sveregs_to_thread (struct regcache *regcache)
+{
+  int ret;
+  struct iovec iovec;
+  int tid = ptid_get_lwp (regcache->ptid ());
+
+  /* Obtain a dump of SVE registers from ptrace.  */
+  std::unique_ptr<gdb_byte[]> base = aarch64_sve_get_sveregs (tid);
+
+  /* Overwrite with regcache state.  */
+  aarch64_sve_regs_copy_from_reg_buf (regcache, base.get ());
+
+  /* Write back to the kernel.  */
+  iovec.iov_base = base.get ();
+  iovec.iov_len = ((struct user_sve_header *) base.get ())->size;
+  ret = ptrace (PTRACE_SETREGSET, tid, NT_ARM_SVE, &iovec);
+
+  if (ret < 0)
+    perror_with_name (_("Unable to store sve registers"));
+}
+
 /* Implement the "fetch_registers" target_ops method.  */
 
 void
 aarch64_linux_nat_target::fetch_registers (struct regcache *regcache,
 					   int regno)
 {
+  struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
+
   if (regno == -1)
     {
       fetch_gregs_from_thread (regcache);
-      fetch_fpregs_from_thread (regcache);
+      if (tdep->has_sve ())
+	fetch_sveregs_from_thread (regcache);
+      else
+	fetch_fpregs_from_thread (regcache);
     }
   else if (regno < AARCH64_V0_REGNUM)
     fetch_gregs_from_thread (regcache);
+  else if (tdep->has_sve ())
+    fetch_sveregs_from_thread (regcache);
   else
     fetch_fpregs_from_thread (regcache);
 }
@@ -407,13 +450,20 @@ void
 aarch64_linux_nat_target::store_registers (struct regcache *regcache,
 					   int regno)
 {
+  struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
+
   if (regno == -1)
     {
       store_gregs_to_thread (regcache);
-      store_fpregs_to_thread (regcache);
+      if (tdep->has_sve ())
+	store_sveregs_to_thread (regcache);
+      else
+	store_fpregs_to_thread (regcache);
     }
   else if (regno < AARCH64_V0_REGNUM)
     store_gregs_to_thread (regcache);
+  else if (tdep->has_sve ())
+    store_sveregs_to_thread (regcache);
   else
     store_fpregs_to_thread (regcache);
 }