gdb: change regcache interface to use array_view

Change most of regcache (and base classes) to use array_view when
possible, instead of raw pointers.  By propagating the use of array_view
further, it enables having some runtime checks to make sure the what we
read from or write to regcaches has the expected length (such as the one
in the `copy(array_view, array_view)` function.  It also integrates well
when connecting with other APIs already using gdb::array_view.

Add some overloads of the methods using raw pointers to avoid having to
change all call sites at once (which is both a lot of work and risky).

I tried to do this change in small increments, but since many of these
functions use each other, it ended up simpler to do it in one shot than
having a lot of intermediary / transient changes.

This change extends into gdbserver as well, because there is some part
of the regcache interface that is shared.

Changing the reg_buffer_common interface to use array_view caused some
build failures in nat/aarch64-scalable-linux-ptrace.c.  That file
currently "takes advantage" of the fact that
reg_buffer_common::{raw_supply,raw_collect} operates on `void *`, which
IMO is dangerous.  It uses raw_supply/raw_collect directly on
uint64_t's, which I guess is fine because it is expected that native
code will have the same endianness as the debugged process.  To
accomodate that, add some overloads of raw_collect and raw_supply that
work on uint64_t.

This file also uses raw_collect and raw_supply on `char` pointers.
Change it to use `gdb_byte` pointers instead.  Add overloads of
raw_collect and raw_supply that work on `gdb_byte *` and make an
array_view on the fly using the register's size.  Those call sites could
be converted to use array_view with not much work, in which case these
overloads could be removed, but I didn't want to do it in this patch, to
avoid starting to dig in arch-specific code.

During development, I inadvertently changed reg_buffer::raw_compare's
behavior to not accept an offset equal to the register size.  This
behavior (effectively comparing 0 bytes, returning true) change was
caught by the AArch64 SME core tests.  Add a selftest to make sure that
this raw_compare behavior is preserved in the future.

Change-Id: I9005f04114543ddff738949e12d85a31855304c2
Reviewed-By: John Baldwin <jhb@FreeBSD.org>

1 files changed, 12 insertions, 8 deletions

diff --git a/gdb/nat/aarch64-scalable-linux-ptrace.c b/gdb/nat/aarch64-scalable-linux-ptrace.c
index dc0e45f..b8fb317 100644
--- a/gdb/nat/aarch64-scalable-linux-ptrace.c
+++ b/gdb/nat/aarch64-scalable-linux-ptrace.c
@@ -613,7 +613,7 @@ aarch64_sve_regs_copy_to_reg_buf (int tid, struct reg_buffer_common *reg_buf)
 {
   gdb::byte_vector sve_state = aarch64_fetch_sve_regset (tid);
 
-  char *base = (char *) sve_state.data ();
+  gdb_byte *base = sve_state.data ();
   struct user_sve_header *header
     = (struct user_sve_header *) sve_state.data ();
 
@@ -684,8 +684,10 @@ aarch64_sve_regs_copy_to_reg_buf (int tid, struct reg_buffer_common *reg_buf)
 	  reg_buf->raw_supply (AARCH64_SVE_Z0_REGNUM + i, reg);
 	}
 
-      reg_buf->raw_supply (AARCH64_FPSR_REGNUM, &fpsimd->fpsr);
-      reg_buf->raw_supply (AARCH64_FPCR_REGNUM, &fpsimd->fpcr);
+      reg_buf->raw_supply (AARCH64_FPSR_REGNUM,
+			   (const gdb_byte *) &fpsimd->fpsr);
+      reg_buf->raw_supply (AARCH64_FPCR_REGNUM,
+			   (const gdb_byte *) &fpsimd->fpcr);
 
       /* Clear the SVE only registers.  */
       memset (reg, 0, SVE_PT_SVE_ZREG_SIZE (vq));
@@ -720,7 +722,7 @@ aarch64_sve_regs_copy_from_reg_buf (int tid,
   gdb::byte_vector new_state (SVE_PT_SIZE (32, SVE_PT_REGS_SVE), 0);
   memcpy (new_state.data (), sve_state.data (), sve_state.size ());
   header = (struct user_sve_header *) new_state.data ();
-  char *base = (char *) new_state.data ();
+  gdb_byte *base = new_state.data ();
 
   /* Sanity check the data in the header.  */
   if (!sve_vl_valid (header->vl)
@@ -805,9 +807,11 @@ aarch64_sve_regs_copy_from_reg_buf (int tid,
 	    }
 
 	  if (REG_VALID == reg_buf->get_register_status (AARCH64_FPSR_REGNUM))
-	    reg_buf->raw_collect (AARCH64_FPSR_REGNUM, &fpsimd->fpsr);
+	    reg_buf->raw_collect (AARCH64_FPSR_REGNUM,
+				  (gdb_byte *) &fpsimd->fpsr);
 	  if (REG_VALID == reg_buf->get_register_status (AARCH64_FPCR_REGNUM))
-	    reg_buf->raw_collect (AARCH64_FPCR_REGNUM, &fpsimd->fpcr);
+	    reg_buf->raw_collect (AARCH64_FPCR_REGNUM,
+				  (gdb_byte *) &fpsimd->fpcr);
 
 	  /* At this point we have collected all the data from the register
 	     cache and we are ready to update the FPSIMD register content
@@ -894,7 +898,7 @@ aarch64_za_regs_copy_to_reg_buf (int tid, struct reg_buffer_common *reg_buf,
   /* Sanity check.  */
   gdb_assert (!za_state.empty ());
 
-  char *base = (char *) za_state.data ();
+  gdb_byte *base = za_state.data ();
   struct user_za_header *header = (struct user_za_header *) base;
 
   /* If we have ZA state, read it.  Otherwise, make the contents of ZA
@@ -1027,7 +1031,7 @@ aarch64_za_regs_copy_from_reg_buf (int tid,
       /* Fetch the current ZA state from the thread.  */
       gdb::byte_vector za_state = aarch64_fetch_za_regset (tid);
 
-      char *base = (char *) za_state.data ();
+      gdb_byte *base = za_state.data ();
       struct user_za_header *za_header = (struct user_za_header *) base;
       uint64_t svq = sve_vq_from_vl (za_header->vl);