gdb: move the type cast into gdbarch_tdep

I built GDB for all targets on a x86-64/GNU-Linux system, and
then (accidentally) passed GDB a RISC-V binary, and asked GDB to "run"
the binary on the native target.  I got this error:

  (gdb) show architecture
  The target architecture is set to "auto" (currently "i386").
  (gdb) file /tmp/hello.rv32.exe
  Reading symbols from /tmp/hello.rv32.exe...
  (gdb) show architecture
  The target architecture is set to "auto" (currently "riscv:rv32").
  (gdb) run
  Starting program: /tmp/hello.rv32.exe
  ../../src/gdb/i387-tdep.c:596: internal-error: i387_supply_fxsave: Assertion `tdep->st0_regnum >= I386_ST0_REGNUM' failed.

What's going on here is this; initially the architecture is i386, this
is based on the default architecture, which is set based on the native
target.  After loading the RISC-V executable the architecture of the
current inferior is updated based on the architecture of the
executable.

When we "run", GDB does a fork & exec, with the inferior being
controlled through ptrace.  GDB sees an initial stop from the inferior
as soon as the inferior comes to life.  In response to this stop GDB
ends up calling save_stop_reason (linux-nat.c), which ends up trying
to read register from the inferior, to do this we end up calling
target_ops::fetch_registers, which, for the x86-64 native target,
calls amd64_linux_nat_target::fetch_registers.

After this I eventually end up in i387_supply_fxsave, different x86
based targets will end in different functions to fetch registers, but
it doesn't really matter which function we end up in, the problem is
this line, which is repeated in many places:

  i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);

The problem here is that the ARCH in this line comes from the current
inferior, which, as we discussed above, will be a RISC-V gdbarch, the
tdep field will actually be of type riscv_gdbarch_tdep, not
i386_gdbarch_tdep.  After this cast we are relying on undefined
behaviour, in my case I happen to trigger an assert, but this might
not always be the case.

The thing I tried that exposed this problem was of course, trying to
start an executable of the wrong architecture on a native target.  I
don't think that the correct solution for this problem is to detect,
at the point of cast, that the gdbarch_tdep object is of the wrong
type, but, I did wonder, is there a way that we could protect
ourselves from incorrectly casting the gdbarch_tdep object?

I think that there is something we can do here, and this commit is the
first step in that direction, though no actual check is added by this
commit.

This commit can be split into two parts:

 (1) In gdbarch.h and arch-utils.c.  In these files I have modified
 gdbarch_tdep (the function) so that it now takes a template argument,
 like this:

    template<typename TDepType>
    static inline TDepType *
    gdbarch_tdep (struct gdbarch *gdbarch)
    {
      struct gdbarch_tdep *tdep = gdbarch_tdep_1 (gdbarch);
      return static_cast<TDepType *> (tdep);
    }

  After this change we are no better protected, but the cast is now
  done within the gdbarch_tdep function rather than at the call sites,
  this leads to the second, much larger change in this commit,

  (2) Everywhere gdbarch_tdep is called, we make changes like this:

    -  i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);
    +  i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (arch);

There should be no functional change after this commit.

In the next commit I will build on this change to add an assertion in
gdbarch_tdep that checks we are casting to the correct type.

1 files changed, 24 insertions, 24 deletions

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 15b577c..8670197 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -502,7 +502,7 @@ aarch64_analyze_prologue (struct gdbarch *gdbarch,
       else if (inst.opcode->iclass == ic_system)
 	{
 	  aarch64_gdbarch_tdep *tdep
-	    = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+	    = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 	  int ra_state_val = 0;
 
 	  if (insn == 0xd503233f /* paciasp.  */
@@ -640,7 +640,7 @@ aarch64_analyze_prologue_test (void)
   struct aarch64_prologue_cache cache;
   cache.saved_regs = trad_frame_alloc_saved_regs (gdbarch);
 
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   /* Test the simple prologue in which frame pointer is used.  */
   {
@@ -1076,7 +1076,7 @@ aarch64_prologue_frame_unwind_stop_reason (struct frame_info *this_frame,
 
   /* Halt the backtrace at "_start".  */
   gdbarch *arch = get_frame_arch (this_frame);
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (arch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (arch);
   if (cache->prev_pc <= tdep->lowest_pc)
     return UNWIND_OUTERMOST;
 
@@ -1120,7 +1120,7 @@ aarch64_prologue_prev_register (struct frame_info *this_frame,
       CORE_ADDR lr;
       struct gdbarch *gdbarch = get_frame_arch (this_frame);
       aarch64_gdbarch_tdep *tdep
-	= (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+	= gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
       lr = frame_unwind_register_unsigned (this_frame, AARCH64_LR_REGNUM);
 
@@ -1289,7 +1289,7 @@ aarch64_dwarf2_prev_register (struct frame_info *this_frame,
 			      void **this_cache, int regnum)
 {
   gdbarch *arch = get_frame_arch (this_frame);
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (arch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (arch);
   CORE_ADDR lr;
 
   switch (regnum)
@@ -1315,7 +1315,7 @@ aarch64_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
 			       struct dwarf2_frame_state_reg *reg,
 			       struct frame_info *this_frame)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   switch (regnum)
     {
@@ -1355,7 +1355,7 @@ static bool
 aarch64_execute_dwarf_cfa_vendor_op (struct gdbarch *gdbarch, gdb_byte op,
 				     struct dwarf2_frame_state *fs)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
   struct dwarf2_frame_state_reg *ra_state;
 
   if (op == DW_CFA_AARCH64_negate_ra_state)
@@ -1996,7 +1996,7 @@ aarch64_frame_align (struct gdbarch *gdbarch, CORE_ADDR sp)
 static struct type *
 aarch64_vnq_type (struct gdbarch *gdbarch)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   if (tdep->vnq_type == NULL)
     {
@@ -2023,7 +2023,7 @@ aarch64_vnq_type (struct gdbarch *gdbarch)
 static struct type *
 aarch64_vnd_type (struct gdbarch *gdbarch)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   if (tdep->vnd_type == NULL)
     {
@@ -2053,7 +2053,7 @@ aarch64_vnd_type (struct gdbarch *gdbarch)
 static struct type *
 aarch64_vns_type (struct gdbarch *gdbarch)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   if (tdep->vns_type == NULL)
     {
@@ -2083,7 +2083,7 @@ aarch64_vns_type (struct gdbarch *gdbarch)
 static struct type *
 aarch64_vnh_type (struct gdbarch *gdbarch)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   if (tdep->vnh_type == NULL)
     {
@@ -2116,7 +2116,7 @@ aarch64_vnh_type (struct gdbarch *gdbarch)
 static struct type *
 aarch64_vnb_type (struct gdbarch *gdbarch)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   if (tdep->vnb_type == NULL)
     {
@@ -2143,7 +2143,7 @@ aarch64_vnb_type (struct gdbarch *gdbarch)
 static struct type *
 aarch64_vnv_type (struct gdbarch *gdbarch)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   if (tdep->vnv_type == NULL)
     {
@@ -2214,7 +2214,7 @@ aarch64_vnv_type (struct gdbarch *gdbarch)
 static int
 aarch64_dwarf_reg_to_regnum (struct gdbarch *gdbarch, int reg)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   if (reg >= AARCH64_DWARF_X0 && reg <= AARCH64_DWARF_X0 + 30)
     return AARCH64_X0_REGNUM + reg - AARCH64_DWARF_X0;
@@ -2518,7 +2518,7 @@ aarch64_get_longjmp_target (struct frame_info *frame, CORE_ADDR *pc)
   CORE_ADDR jb_addr;
   gdb_byte buf[X_REGISTER_SIZE];
   struct gdbarch *gdbarch = get_frame_arch (frame);
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 
   jb_addr = get_frame_register_unsigned (frame, AARCH64_X0_REGNUM);
@@ -2549,7 +2549,7 @@ aarch64_gen_return_address (struct gdbarch *gdbarch,
 static const char *
 aarch64_pseudo_register_name (struct gdbarch *gdbarch, int regnum)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   static const char *const q_name[] =
     {
@@ -2663,7 +2663,7 @@ aarch64_pseudo_register_name (struct gdbarch *gdbarch, int regnum)
 static struct type *
 aarch64_pseudo_register_type (struct gdbarch *gdbarch, int regnum)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   int p_regnum = regnum - gdbarch_num_regs (gdbarch);
 
@@ -2700,7 +2700,7 @@ static int
 aarch64_pseudo_register_reggroup_p (struct gdbarch *gdbarch, int regnum,
 				    const struct reggroup *group)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   int p_regnum = regnum - gdbarch_num_regs (gdbarch);
 
@@ -2754,7 +2754,7 @@ static struct value *
 aarch64_pseudo_read_value (struct gdbarch *gdbarch, readable_regcache *regcache,
 			   int regnum)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
   struct value *result_value = allocate_value (register_type (gdbarch, regnum));
 
   VALUE_LVAL (result_value) = lval_register;
@@ -2824,7 +2824,7 @@ static void
 aarch64_pseudo_write (struct gdbarch *gdbarch, struct regcache *regcache,
 		      int regnum, const gdb_byte *buf)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
   regnum -= gdbarch_num_regs (gdbarch);
 
   if (regnum >= AARCH64_Q0_REGNUM && regnum < AARCH64_Q0_REGNUM + 32)
@@ -3377,7 +3377,7 @@ aarch64_get_tdesc_vq (const struct target_desc *tdesc)
 static int
 aarch64_cannot_store_register (struct gdbarch *gdbarch, int regnum)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   if (!tdep->has_pauth ())
     return 0;
@@ -3444,7 +3444,7 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
        best_arch = gdbarch_list_lookup_by_info (best_arch->next, &info))
     {
       aarch64_gdbarch_tdep *tdep
-	= (aarch64_gdbarch_tdep *) gdbarch_tdep (best_arch->gdbarch);
+	= gdbarch_tdep<aarch64_gdbarch_tdep> (best_arch->gdbarch);
       if (tdep && tdep->vq == vq)
 	return best_arch->gdbarch;
     }
@@ -3693,7 +3693,7 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 static void
 aarch64_dump_tdep (struct gdbarch *gdbarch, struct ui_file *file)
 {
-  aarch64_gdbarch_tdep *tdep = (aarch64_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
 
   if (tdep == NULL)
     return;
@@ -3915,7 +3915,7 @@ aarch64_record_branch_except_sys (aarch64_insn_decode_record *aarch64_insn_r)
 {
 
   aarch64_gdbarch_tdep *tdep
-    = (aarch64_gdbarch_tdep *) gdbarch_tdep (aarch64_insn_r->gdbarch);
+    = gdbarch_tdep<aarch64_gdbarch_tdep> (aarch64_insn_r->gdbarch);
   uint8_t insn_bits24_27, insn_bits28_31, insn_bits22_23;
   uint32_t record_buf[4];