From: Tom de Vries via Gdb-patches <gdb-patches@sourceware.org>
To: Luis Machado <luis.machado@arm.com>, gdb-patches@sourceware.org
Cc: mark@klomp.org
Subject: Re: [PING][PATCH,v2] [Arm] Fix endianness handling for arm record self tests
Date: Tue, 6 Sep 2022 12:39:55 +0200 [thread overview]
Message-ID: <2f9230ad-b4f7-9f4b-c60c-7c6adfa9cb01@suse.de> (raw)
In-Reply-To: <14ce7cf2-82be-4b93-b875-d7cc7a323f2d@arm.com>
On 9/1/22 11:29, Luis Machado wrote:
> 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.
>>
LGTM.
Thanks,
- Tom
>> 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. */
>
next prev parent reply other threads:[~2022-09-06 10:40 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 ` [PING][PATCH,v2] " Luis Machado via Gdb-patches
2022-09-06 10:39 ` Tom de Vries via Gdb-patches [this message]
2022-09-07 8:19 ` Luis Machado via Gdb-patches
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