Fix endianness handling for arm record self tests

v2:

- Add 32-bit Arm instruction selftest
- Refactored abstract memory reader into abstract instruction reader
- Adjusted code to use templated type and to use host endianness as
  opposed to target endianness.

The arm record tests handle 16-bit and 32-bit thumb instructions, but the
code is laid out in a way that handles the 32-bit thumb instructions as
two 16-bit parts.

This is fine, but it is prone to host-endianness issues given how the two
16-bit parts are stored and how they are accessed later on. Arm is
little-endian by default, so running this test with a GDB built with
--enable-targets=all and on a big endian host will run into the following:

Running selftest arm-record.
Process record and replay target doesn't support syscall number -2036195
Process record does not support instruction 0x7f70ee1d at address 0x0.
Self test failed: self-test failed at ../../binutils-gdb/gdb/arm-tdep.c:14482

It turns out the abstract memory reader class is more generic than it needs to
be, and we can simplify the code a bit by assuming we have a simple instruction
reader that only reads up to 4 bytes, which is the length of a 32-bit
instruction.

Instead of returning a bool, we return instead the instruction that has been
read. This way we avoid having to deal with the endianness conversion, and use
the host endianness instead. The Arm selftests can be executed on non-Arm
hosts.

While at it, Tom suggested adding a 32-bit Arm instruction selftest to increase
the coverage of the selftests.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29432

Co-authored-by: Tom de Vries <tdevries@suse.de>

diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 0091d14708fec23f78240ecbb7cdc435b1d62970..ead9bbf46c5c28662ea7e748dfd85a21b320d9cc 100644 (file)
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -14252,59 +14252,39 @@ thumb2_record_decode_insn_handler (arm_insn_decode_record *thumb2_insn_r)
 }
 
 namespace {
-/* Abstract memory reader.  */
+/* Abstract instruction reader.  */
 
-class abstract_memory_reader
+class abstract_instruction_reader
 {
 public:
-  /* Read LEN bytes of target memory at address MEMADDR, placing the
-     results in GDB's memory at BUF.  Return true on success.  */
+  /* Read one instruction of size LEN from address MEMADDR and using
+     BYTE_ORDER endianness.  */
 
-  virtual bool read (CORE_ADDR memaddr, gdb_byte *buf, const size_t len) = 0;
+  virtual ULONGEST read (CORE_ADDR memaddr, const size_t len,
+                        enum bfd_endian byte_order) = 0;
 };
 
 /* Instruction reader from real target.  */
 
-class instruction_reader : public abstract_memory_reader
+class instruction_reader : public abstract_instruction_reader
 {
  public:
-  bool read (CORE_ADDR memaddr, gdb_byte *buf, const size_t len) override
+  ULONGEST read (CORE_ADDR memaddr, const size_t len,
+                enum bfd_endian byte_order) override
   {
-    if (target_read_memory (memaddr, buf, len))
-      return false;
-    else
-      return true;
+    return read_code_unsigned_integer (memaddr, len, byte_order);
   }
 };
 
 } // namespace
 
-/* Extracts arm/thumb/thumb2 insn depending on the size, and returns 0 on success 
-and positive val on failure.  */
-
-static int
-extract_arm_insn (abstract_memory_reader& reader,
-                 arm_insn_decode_record *insn_record, uint32_t insn_size)
-{
-  gdb_byte buf[insn_size];
-
-  memset (&buf[0], 0, insn_size);
-  
-  if (!reader.read (insn_record->this_addr, buf, insn_size))
-    return 1;
-  insn_record->arm_insn = (uint32_t) extract_unsigned_integer (&buf[0],
-                          insn_size, 
-                          gdbarch_byte_order_for_code (insn_record->gdbarch));
-  return 0;
-}
-
 typedef int (*sti_arm_hdl_fp_t) (arm_insn_decode_record*);
 
 /* Decode arm/thumb insn depending on condition cods and opcodes; and
    dispatch it.  */
 
 static int
-decode_insn (abstract_memory_reader &reader,
+decode_insn (abstract_instruction_reader &reader,
             arm_insn_decode_record *arm_record,
             record_type_t record_type, uint32_t insn_size)
 {
@@ -14339,20 +14319,12 @@ decode_insn (abstract_memory_reader &reader,
 
   uint32_t ret = 0;    /* return value: negative:failure   0:success.  */
   uint32_t insn_id = 0;
+  enum bfd_endian code_endian
+    = gdbarch_byte_order_for_code (arm_record->gdbarch);
+  arm_record->arm_insn
+    = reader.read (arm_record->this_addr, insn_size, code_endian);
 
-  if (extract_arm_insn (reader, arm_record, insn_size))
-    {
-      if (record_debug)
-       {
-         gdb_printf (gdb_stdlog,
-                     _("Process record: error reading memory at "
-                       "addr %s len = %d.\n"),
-                     paddress (arm_record->gdbarch,
-                               arm_record->this_addr), insn_size);
-       }
-      return -1;
-    }
-  else if (ARM_RECORD == record_type)
+  if (ARM_RECORD == record_type)
     {
       arm_record->cond = bits (arm_record->arm_insn, 28, 31);
       insn_id = bits (arm_record->arm_insn, 25, 27);
@@ -14412,36 +14384,35 @@ decode_insn (abstract_memory_reader &reader,
 #if GDB_SELF_TEST
 namespace selftests {
 
-/* Provide both 16-bit and 32-bit thumb instructions.  */
+/* Instruction reader class for selftests.
+
+   For 16-bit Thumb instructions, an array of uint16_t should be used.
 
-class instruction_reader_thumb : public abstract_memory_reader
+   For 32-bit Thumb instructions and regular 32-bit Arm instructions, an array
+   of uint32_t should be used.  */
+
+template<typename T>
+class instruction_reader_selftest : public abstract_instruction_reader
 {
 public:
   template<size_t SIZE>
-  instruction_reader_thumb (enum bfd_endian endian,
-                           const uint16_t (&insns)[SIZE])
-    : m_endian (endian), m_insns (insns), m_insns_size (SIZE)
+  instruction_reader_selftest (const T (&insns)[SIZE])
+    : m_insns (insns), m_insns_size (SIZE)
   {}
 
-  bool read (CORE_ADDR memaddr, gdb_byte *buf, const size_t len) override
+  ULONGEST read (CORE_ADDR memaddr, const size_t length,
+                enum bfd_endian byte_order) override
   {
-    SELF_CHECK (len == 4 || len == 2);
-    SELF_CHECK (memaddr % 2 == 0);
-    SELF_CHECK ((memaddr / 2) < m_insns_size);
+    SELF_CHECK (length == sizeof (T));
+    SELF_CHECK (memaddr % sizeof (T) == 0);
+    SELF_CHECK ((memaddr / sizeof (T)) < m_insns_size);
 
-    store_unsigned_integer (buf, 2, m_endian, m_insns[memaddr / 2]);
-    if (len == 4)
-      {
-       store_unsigned_integer (&buf[2], 2, m_endian,
-                               m_insns[memaddr / 2 + 1]);
-      }
-    return true;
+    return m_insns[memaddr / sizeof (T)];
   }
 
 private:
-  enum bfd_endian m_endian;
-  const uint16_t *m_insns;
-  size_t m_insns_size;
+  const T *m_insns;
+  const size_t m_insns_size;
 };
 
 static void
@@ -14461,6 +14432,8 @@ arm_record_test (void)
     memset (&arm_record, 0, sizeof (arm_insn_decode_record));
     arm_record.gdbarch = gdbarch;
 
+    /* Use the endian-free representation of the instructions here.  The test
+       will handle endianness conversions.  */
     static const uint16_t insns[] = {
       /* db b2 uxtb    r3, r3 */
       0xb2db,
@@ -14468,8 +14441,7 @@ arm_record_test (void)
       0x58cd,
     };
 
-    enum bfd_endian endian = gdbarch_byte_order_for_code (arm_record.gdbarch);
-    instruction_reader_thumb reader (endian, insns);
+    instruction_reader_selftest<uint16_t> reader (insns);
     int ret = decode_insn (reader, &arm_record, THUMB_RECORD,
                           THUMB_INSN_SIZE_BYTES);
 
@@ -14495,13 +14467,14 @@ arm_record_test (void)
     memset (&arm_record, 0, sizeof (arm_insn_decode_record));
     arm_record.gdbarch = gdbarch;
 
-    static const uint16_t insns[] = {
-      /* 1d ee 70 7f    mrc    15, 0, r7, cr13, cr0, {3} */
-      0xee1d, 0x7f70,
+    /* Use the endian-free representation of the instruction here.  The test
+       will handle endianness conversions.  */
+    static const uint32_t insns[] = {
+      /* mrc   15, 0, r7, cr13, cr0, {3} */
+      0x7f70ee1d,
     };
 
-    enum bfd_endian endian = gdbarch_byte_order_for_code (arm_record.gdbarch);
-    instruction_reader_thumb reader (endian, insns);
+    instruction_reader_selftest<uint32_t> reader (insns);
     int ret = decode_insn (reader, &arm_record, THUMB2_RECORD,
                           THUMB2_INSN_SIZE_BYTES);
 
@@ -14510,6 +14483,27 @@ arm_record_test (void)
     SELF_CHECK (arm_record.reg_rec_count == 1);
     SELF_CHECK (arm_record.arm_regs[0] == 7);
   }
+
+  /* 32-bit instructions.  */
+  {
+    arm_insn_decode_record arm_record;
+
+    memset (&arm_record, 0, sizeof (arm_insn_decode_record));
+    arm_record.gdbarch = gdbarch;
+
+    /* Use the endian-free representation of the instruction here.  The test
+       will handle endianness conversions.  */
+    static const uint32_t insns[] = {
+      /* mov     r5, r0 */
+      0xe1a05000,
+    };
+
+    instruction_reader_selftest<uint32_t> reader (insns);
+    int ret = decode_insn (reader, &arm_record, ARM_RECORD,
+                          ARM_INSN_SIZE_BYTES);
+
+    SELF_CHECK (ret == 0);
+  }
 }
 
 /* Instruction reader from manually cooked instruction sequences.  */
@@ -14609,18 +14603,10 @@ arm_process_record (struct gdbarch *gdbarch, struct regcache *regcache,
     }
 
   instruction_reader reader;
-  if (extract_arm_insn (reader, &arm_record, 2))
-    {
-      if (record_debug)
-       {
-         gdb_printf (gdb_stdlog,
-                     _("Process record: error reading memory at "
-                       "addr %s len = %d.\n"),
-                     paddress (arm_record.gdbarch,
-                               arm_record.this_addr), 2);
-       }
-      return -1;
-    }
+  enum bfd_endian code_endian
+    = gdbarch_byte_order_for_code (arm_record.gdbarch);
+  arm_record.arm_insn
+    = reader.read (arm_record.this_addr, 2, code_endian);
 
   /* Check the insn, whether it is thumb or arm one.  */