Re: [PATCH] Patch 2 of 2 for aarch64 ILP32 support in gdb

[Steve Ellcey <sellcey at caviumnetworks dot com>]

On Sun, 2017-01-29 at 22:40 +0000, Yao Qi wrote:

> This changes the word size and address size, which is used to determine
> the inferior is arm or aarch64 by checking "bits_per_word == 32" in
> multi-arch debugging.  You can find some instances of such check in
> aarch64-linux-nat.c.  If the bits_per_word is 32 in ILP32, GDB thinks
> the inferior is an ARM one, rather than an AArch64 ILP32 one. which is
> wrong.  We need to tweak the condition above to correctly identify the
> ARM inferior.
> 
> Do you compare the ILP32 gdb test result with normal aarch64 one?

OK, I fixed up arch64-linux-nat.c and didn't find any other places were
the bits_per_word was being checked and I fixed the TRUE/true
FALSE/false constants.  If I run gdb without any changes or with this
patch but debugging 64 bit code I get around 500 failures.  The number
doesn't seem to be constant, I have gotten anywhere from 488 to 503
failures testing the same code.  My last run had:

# of expected passes            30428
# of unexpected failures        503
# of expected failures          53
# of unknown successes          2
# of known failures             64
# of untested testcases         66
# of unresolved testcases       6
# of unsupported tests          293

Many of the failures seem to be thread related and I see a lot of
messages about timeouts and 'program is no longer running'.  When
I run gdb on 32 bit programs with:

	RUNTESTFLAGS="--target_board=unix/-mabi=ilp32"

I get 700+ failures.  My last run had:

# of expected passes            29482
# of unexpected failures        740
# of expected failures          30
# of unknown successes          2
# of known failures             65
# of untested testcases         79
# of unresolved testcases       4
# of unsupported tests          288

So there are more failures in ILP32 mode but there seem to be enough
passes that I think it still makes sense to check in the patch to get
some gdb functionality working.

Here is the latest patch.

Steve Ellcey
sellcey@cavium.com


gdb ChangeLog:

2017-01-31  Andrew Pinski  <apinski@cavium.com>
	    Steve Ellcey  <sellcey@cavium.com>
	    Yao Qi  <yao.qi@linaro.org>

	* aarch64-linux-nat.c (IS_ARM32): New macro.
	(fetch_gregs_from_thread): Use IS_ARM32 macro.
	(store_gregs_to_thread): Ditto.
	(fetch_fpregs_from_thread): Ditto.
	(store_fpregs_to_thread): Ditto.
	(ps_get_thread_area): Ditto.
	(aarch64_linux_siginfo_fixup): Ditto.
	* aarch64-linux-tdep.c (aarch64_linux_init_abi): Set link
	map offsets to 32 or 64 bits.
	* aarch64-tdep.c (aarch64_ilp32_register_type): New function.
	(aarch64_gdbarch_init): Setup ILP32 support.
	Make sure the gdbarches have compatible ilp32 flags.
	Set long and ptr sizes correctly for ilp32.
	* aarch64-tdep.h (gdbarch_tdep) <ilp32>: New field.

gdbserver ChangeLog:

2017-01-31  Andrew Pinski  <apinski@cavium.com>
	    Steve Ellcey  <sellcey@cavium.com>

	* linux-aarch64-low.c (aarch64_linux_read_description): Use
	machine instead of is_elf64 to determine architecture.  Give an
	error when using 32 bit gdbserver on 64 bit program.

diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index 0d472e2..f6fd19a 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -49,6 +49,9 @@
 #define TRAP_HWBKPT 0x0004
 #endif
 
+/* Check if we are on arm (as opposed to aarch64).  */
+#define IS_ARM32(arch) (gdbarch_bfd_arch_info(arch)->mach == bfd_mach_arm)
+
 /* Per-process data.  We don't bind this to a per-inferior registry
    because of targets like x86 GNU/Linux that need to keep track of
    processes that aren't bound to any inferior (e.g., fork children,
@@ -166,7 +169,7 @@ fetch_gregs_from_thread (struct regcache *regcache)
   tid = ptid_get_lwp (inferior_ptid);
 
   iovec.iov_base = &regs;
-  if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
+  if (IS_ARM32 (gdbarch))
     iovec.iov_len = 18 * 4;
   else
     iovec.iov_len = sizeof (regs);
@@ -175,7 +178,7 @@ fetch_gregs_from_thread (struct regcache *regcache)
   if (ret < 0)
     perror_with_name (_("Unable to fetch general registers."));
 
-  if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
+  if (IS_ARM32 (gdbarch))
     aarch32_gp_regcache_supply (regcache, (uint32_t *) regs, 1);
   else
     {
@@ -203,7 +206,7 @@ store_gregs_to_thread (const struct regcache *regcache)
   tid = ptid_get_lwp (inferior_ptid);
 
   iovec.iov_base = &regs;
-  if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
+  if (IS_ARM32 (gdbarch))
     iovec.iov_len = 18 * 4;
   else
     iovec.iov_len = sizeof (regs);
@@ -212,7 +215,7 @@ store_gregs_to_thread (const struct regcache *regcache)
   if (ret < 0)
     perror_with_name (_("Unable to fetch general registers."));
 
-  if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
+  if (IS_ARM32 (gdbarch))
     aarch32_gp_regcache_collect (regcache, (uint32_t *) regs, 1);
   else
     {
@@ -248,7 +251,7 @@ fetch_fpregs_from_thread (struct regcache *regcache)
 
   iovec.iov_base = &regs;
 
-  if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
+  if (IS_ARM32 (gdbarch))
     {
       iovec.iov_len = VFP_REGS_SIZE;
 
@@ -295,7 +298,7 @@ store_fpregs_to_thread (const struct regcache *regcache)
 
   iovec.iov_base = &regs;
 
-  if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
+  if (IS_ARM32 (gdbarch))
     {
       iovec.iov_len = VFP_REGS_SIZE;
 
@@ -328,7 +331,7 @@ store_fpregs_to_thread (const struct regcache *regcache)
 			      (char *) &regs.fpcr);
     }
 
-  if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
+  if (IS_ARM32 (gdbarch))
     {
       ret = ptrace (PTRACE_SETREGSET, tid, NT_ARM_VFP, &iovec);
       if (ret < 0)
@@ -460,8 +463,7 @@ ps_err_e
 ps_get_thread_area (struct ps_prochandle *ph,
 		    lwpid_t lwpid, int idx, void **base)
 {
-  int is_64bit_p
-    = (gdbarch_bfd_arch_info (target_gdbarch ())->bits_per_word == 64);
+  int is_64bit_p = !IS_ARM32 (target_gdbarch ());
 
   return aarch64_ps_get_thread_area (ph, lwpid, idx, base, is_64bit_p);
 }
@@ -517,7 +519,7 @@ aarch64_linux_siginfo_fixup (siginfo_t *native, gdb_byte *inf, int direction)
 
   /* Is the inferior 32-bit?  If so, then do fixup the siginfo
      object.  */
-  if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
+  if (IS_ARM32 (gdbarch))
     {
       if (direction == 0)
 	aarch64_compat_siginfo_from_siginfo ((struct compat_siginfo *) inf,
diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
index b94ccb2..6d0c3bd 100644
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -1000,8 +1000,12 @@ aarch64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 
   linux_init_abi (info, gdbarch);
 
-  set_solib_svr4_fetch_link_map_offsets (gdbarch,
-					 svr4_lp64_fetch_link_map_offsets);
+  if (tdep->ilp32)
+    set_solib_svr4_fetch_link_map_offsets (gdbarch,
+					   svr4_ilp32_fetch_link_map_offsets);
+  else
+    set_solib_svr4_fetch_link_map_offsets (gdbarch,
+					   svr4_lp64_fetch_link_map_offsets);
 
   /* Enable TLS support.  */
   set_gdbarch_fetch_tls_load_module_address (gdbarch,
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 801c03d..67f1a2e 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -2091,6 +2091,22 @@ aarch64_gen_return_address (struct gdbarch *gdbarch,
 }
 
 
+/* Implement the "register_type" gdbarch method.
+   Adjust the register type of $PC and $SP on ILP32.  */
+
+static struct type *
+aarch64_ilp32_register_type (struct gdbarch *gdbarch, int regnum)
+{
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+
+  gdb_assert (tdep->ilp32);
+
+  if (regnum == AARCH64_SP_REGNUM || regnum == AARCH64_PC_REGNUM)
+    return builtin_type (gdbarch)->builtin_uint64;
+  else
+    return tdesc_register_type (gdbarch, regnum);
+}
+
 /* Return the pseudo register name corresponding to register regnum.  */
 
 static const char *
@@ -2851,6 +2867,10 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   const struct tdesc_feature *feature;
   int num_regs = 0;
   int num_pseudo_regs = 0;
+  bool ilp32 = false;
+
+  if (info.bfd_arch_info->mach == bfd_mach_aarch64_ilp32)
+    ilp32 = true;
 
   /* Ensure we always have a target descriptor.  */
   if (!tdesc_has_registers (tdesc))
@@ -2908,6 +2928,9 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
        best_arch != NULL;
        best_arch = gdbarch_list_lookup_by_info (best_arch->next, &info))
     {
+      /* ILP32 and LP64 are incompatible. */
+      if (gdbarch_tdep (arches->gdbarch)->ilp32 != ilp32)
+	continue;
       /* Found a match.  */
       break;
     }
@@ -2926,6 +2949,7 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   tdep->lowest_pc = 0x20;
   tdep->jb_pc = -1;		/* Longjump support not enabled by default.  */
   tdep->jb_elt_size = 8;
+  tdep->ilp32 = ilp32;
 
   set_gdbarch_push_dummy_call (gdbarch, aarch64_push_dummy_call);
   set_gdbarch_frame_align (gdbarch, aarch64_frame_align);
@@ -2968,9 +2992,9 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   set_gdbarch_float_bit (gdbarch, 32);
   set_gdbarch_double_bit (gdbarch, 64);
   set_gdbarch_long_double_bit (gdbarch, 128);
-  set_gdbarch_long_bit (gdbarch, 64);
+  set_gdbarch_long_bit (gdbarch, ilp32 ? 32 : 64);
   set_gdbarch_long_long_bit (gdbarch, 64);
-  set_gdbarch_ptr_bit (gdbarch, 64);
+  set_gdbarch_ptr_bit (gdbarch, ilp32 ? 32 : 64);
   set_gdbarch_char_signed (gdbarch, 0);
   set_gdbarch_float_format (gdbarch, floatformats_ieee_single);
   set_gdbarch_double_format (gdbarch, floatformats_ieee_double);
@@ -3012,6 +3036,13 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 
   tdesc_use_registers (gdbarch, tdesc, tdesc_data);
 
+  if (ilp32)
+    {
+      /* Override tdesc_register_type to adjust the types of $PC and
+	 $SP in ILP32.  */
+      set_gdbarch_register_type (gdbarch, aarch64_ilp32_register_type);
+    }
+
   /* Add standard register aliases.  */
   for (i = 0; i < ARRAY_SIZE (aarch64_register_aliases); i++)
     user_reg_add (gdbarch, aarch64_register_aliases[i].name,
diff --git a/gdb/aarch64-tdep.h b/gdb/aarch64-tdep.h
index 85c6a97..87d36b6 100644
--- a/gdb/aarch64-tdep.h
+++ b/gdb/aarch64-tdep.h
@@ -97,6 +97,9 @@ struct gdbarch_tdep
 
   /* syscall record.  */
   int (*aarch64_syscall_record) (struct regcache *regcache, unsigned long svc_number);
+  /* If this is ILP32 or LP64.  */
+  bool ilp32;
+
 };
 
 extern struct target_desc *tdesc_aarch64;
diff --git a/gdb/gdbserver/linux-aarch64-low.c b/gdb/gdbserver/linux-aarch64-low.c
index 334310b..e31d5c5 100644
--- a/gdb/gdbserver/linux-aarch64-low.c
+++ b/gdb/gdbserver/linux-aarch64-low.c
@@ -484,7 +484,12 @@ aarch64_linux_read_description (void)
 
   is_elf64 = linux_pid_exe_is_elf_64_file (tid, &machine);
 
-  if (is_elf64)
+  /* There are problems with ptrace when gdbserver is 32 bits and the
+     program being debugged is 64 bits.  */
+  if (sizeof (void *) == 4 && is_elf64)
+    error (_("Can't debug 64-bit process with 32-bit GDBserver"));
+
+  if (machine == EM_AARCH64)
     return tdesc_aarch64;
   else
     return tdesc_arm_with_neon;