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From: Luis Machado via Gdb-patches <gdb-patches@sourceware.org>
To: gdb-patches@sourceware.org
Cc: mark@klomp.org, tdevries@suse.de
Subject: [PING][PATCH,v2] [Arm] Fix endianness handling for arm record self tests
Date: Thu, 1 Sep 2022 10:29:16 +0100	[thread overview]
Message-ID: <14ce7cf2-82be-4b93-b875-d7cc7a323f2d@arm.com> (raw)
In-Reply-To: <20220823203210.1561735-1-luis.machado@arm.com>

On 8/23/22 21:32, Luis Machado via Gdb-patches wrote:
> 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>
> ---
>   gdb/arm-tdep.c | 150 ++++++++++++++++++++++---------------------------
>   1 file changed, 68 insertions(+), 82 deletions(-)
> 
> diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
> index 0091d14708f..ead9bbf46c5 100644
> --- 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.  */
>   


  reply	other threads:[~2022-09-01  9:29 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-08 10:12 [PATCH] " Luis Machado via Gdb-patches
2022-08-08 12:30 ` Andrew Burgess via Gdb-patches
2022-08-10  8:47   ` Andrew Burgess via Gdb-patches
2022-08-09  9:43 ` Tom de Vries via Gdb-patches
2022-08-09  9:57   ` Tom de Vries via Gdb-patches
2022-08-15 12:13     ` Luis Machado via Gdb-patches
2022-08-09 11:31   ` Luis Machado via Gdb-patches
2022-08-09 11:48     ` Tom de Vries via Gdb-patches
2022-08-09 12:08       ` Tom de Vries via Gdb-patches
2022-08-09 12:09         ` Luis Machado via Gdb-patches
2022-08-09 12:13           ` Tom de Vries via Gdb-patches
2022-08-09 15:24             ` Mark Wielaard
2022-08-15 12:10   ` Luis Machado via Gdb-patches
2022-08-23 20:32 ` [PATCH,v2] " Luis Machado via Gdb-patches
2022-09-01  9:29   ` Luis Machado via Gdb-patches [this message]
2022-09-06 10:39     ` [PING][PATCH,v2] " Tom de Vries via Gdb-patches
2022-09-07  8:19       ` Luis Machado via Gdb-patches

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