diff mbox

Add support for the __flash qualifier on AVR

Message ID 1404816844-1639-1-git-send-email-pierre.langlois@embecosm.com
State New
Headers show

Commit Message

Pierre Langlois July 8, 2014, 10:54 a.m. UTC
The __flash qualifier is part of the named address spaces for AVR [1]. It allows
putting read-only data in the flash memory, normally reserved for code.

When used together with a pointer, the DW_AT_address_class attribute is set to 1
and allows GDB to detect that when it will be dereferenced, the data will be
loaded from the flash memory (with the LPM instruction).

We can now properly debug the following code:

~~~
const __flash char data_in_flash = 0xab;

int
main (void)
{
  const __flash char *pointer_to_flash = &data_in_flash;
}
~~~

~~~
(gdb) print pointer_to_flash
$1 = 0x1e8 <data_in_flash> "\253"
(gdb) print/x *pointer_to_flash
$2 = 0xab
(gdb) x/x pointer_to_flash
0x1e8 <data_in_flash>: 0xXXXXXXab
~~~

Whereas previously, GDB would revert to the default address space which is RAM
and mapped in higher memory:

~~~
(gdb) print pointer_to_flash
$1 = 0x8001e8 ""
~~~

Thanks,

Pierre

[1] https://gcc.gnu.org/onlinedocs/gcc/Named-Address-Spaces.html

2014-07-08  Pierre Langlois  <pierre.langlois@embecosm.com>

gdb/
	* avr-tdep.c (AVR_TYPE_ADDRESS_CLASS_FLASH): New macro.
	(AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH): Likewise.
	(avr_address_to_pointer): Check for AVR_TYPE_ADDRESS_CLASS_FLASH.
	(avr_pointer_to_address): Likewise.
	(avr_address_class_type_flags): New function.
	(avr_address_class_type_flags_to_name): Likewise.
	(avr_address_class_name_to_type_flags): Likewise.
	(avr_gdbarch_init): Set address_class_type_flags,
	address_class_type_flags_to_name and
	address_class_name_to_type_flags.

gdb/testsuite/
	* gdb.arch/avr-flash-qualifer.c: New.
	* gdb.arch/avr-flash-qualifer.exp: New.
---
 gdb/avr-tdep.c                                 | 77 ++++++++++++++++++++++++--
 gdb/testsuite/gdb.arch/avr-flash-qualifier.c   | 32 +++++++++++
 gdb/testsuite/gdb.arch/avr-flash-qualifier.exp | 52 +++++++++++++++++
 3 files changed, 156 insertions(+), 5 deletions(-)
 create mode 100644 gdb/testsuite/gdb.arch/avr-flash-qualifier.c
 create mode 100644 gdb/testsuite/gdb.arch/avr-flash-qualifier.exp

Comments

Pierre Langlois July 15, 2014, 10:12 a.m. UTC | #1
Ping.

On 08/07/14 11:54, Pierre Langlois wrote:
> The __flash qualifier is part of the named address spaces for AVR [1]. It allows
> putting read-only data in the flash memory, normally reserved for code.
>
> When used together with a pointer, the DW_AT_address_class attribute is set to 1
> and allows GDB to detect that when it will be dereferenced, the data will be
> loaded from the flash memory (with the LPM instruction).
>
> We can now properly debug the following code:
>
> ~~~
> const __flash char data_in_flash = 0xab;
>
> int
> main (void)
> {
>    const __flash char *pointer_to_flash = &data_in_flash;
> }
> ~~~
>
> ~~~
> (gdb) print pointer_to_flash
> $1 = 0x1e8 <data_in_flash> "\253"
> (gdb) print/x *pointer_to_flash
> $2 = 0xab
> (gdb) x/x pointer_to_flash
> 0x1e8 <data_in_flash>: 0xXXXXXXab
> ~~~
>
> Whereas previously, GDB would revert to the default address space which is RAM
> and mapped in higher memory:
>
> ~~~
> (gdb) print pointer_to_flash
> $1 = 0x8001e8 ""
> ~~~
>
> Thanks,
>
> Pierre
>
> [1] https://gcc.gnu.org/onlinedocs/gcc/Named-Address-Spaces.html
>
> 2014-07-08  Pierre Langlois  <pierre.langlois@embecosm.com>
>
> gdb/
> 	* avr-tdep.c (AVR_TYPE_ADDRESS_CLASS_FLASH): New macro.
> 	(AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH): Likewise.
> 	(avr_address_to_pointer): Check for AVR_TYPE_ADDRESS_CLASS_FLASH.
> 	(avr_pointer_to_address): Likewise.
> 	(avr_address_class_type_flags): New function.
> 	(avr_address_class_type_flags_to_name): Likewise.
> 	(avr_address_class_name_to_type_flags): Likewise.
> 	(avr_gdbarch_init): Set address_class_type_flags,
> 	address_class_type_flags_to_name and
> 	address_class_name_to_type_flags.
>
> gdb/testsuite/
> 	* gdb.arch/avr-flash-qualifer.c: New.
> 	* gdb.arch/avr-flash-qualifer.exp: New.
> ---
>   gdb/avr-tdep.c                                 | 77 ++++++++++++++++++++++++--
>   gdb/testsuite/gdb.arch/avr-flash-qualifier.c   | 32 +++++++++++
>   gdb/testsuite/gdb.arch/avr-flash-qualifier.exp | 52 +++++++++++++++++
>   3 files changed, 156 insertions(+), 5 deletions(-)
>   create mode 100644 gdb/testsuite/gdb.arch/avr-flash-qualifier.c
>   create mode 100644 gdb/testsuite/gdb.arch/avr-flash-qualifier.exp
>
> diff --git a/gdb/avr-tdep.c b/gdb/avr-tdep.c
> index 9b0bfaf..eb99748 100644
> --- a/gdb/avr-tdep.c
> +++ b/gdb/avr-tdep.c
> @@ -71,6 +71,16 @@
>
>   /* Constants: prefixed with AVR_ to avoid name space clashes */
>
> +/* Address space flags */
> +
> +/* We are assigning the TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1 to the flash address
> +   space.  */
> +
> +#define AVR_TYPE_ADDRESS_CLASS_FLASH TYPE_ADDRESS_CLASS_1
> +#define AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH  \
> +  TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1
> +
> +
>   enum
>   {
>     AVR_REG_W = 24,
> @@ -295,10 +305,19 @@ avr_address_to_pointer (struct gdbarch *gdbarch,
>   {
>     enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
>
> +  /* Is it a data address in flash?  */
> +  if (AVR_TYPE_ADDRESS_CLASS_FLASH (type))
> +    {
> +      /* A data address in flash is always byte addressed.  */
> +      store_unsigned_integer (buf, TYPE_LENGTH (type), byte_order,
> +			      avr_convert_iaddr_to_raw (addr));
> +    }
>     /* Is it a code address?  */
> -  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
> -      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD)
> +  else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
> +	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD)
>       {
> +      /* A code address, either a function pointer or the program counter, is
> +	 word (16 bits) addressed.  */
>         store_unsigned_integer (buf, TYPE_LENGTH (type), byte_order,
>   			      avr_convert_iaddr_to_raw (addr >> 1));
>       }
> @@ -318,10 +337,13 @@ avr_pointer_to_address (struct gdbarch *gdbarch,
>     CORE_ADDR addr
>       = extract_unsigned_integer (buf, TYPE_LENGTH (type), byte_order);
>
> +  /* Is it a data address in flash?  */
> +  if (AVR_TYPE_ADDRESS_CLASS_FLASH (type))
> +    return avr_make_iaddr (addr);
>     /* Is it a code address?  */
> -  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
> -      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
> -      || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
> +  else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
> +	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
> +	   || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
>       return avr_make_iaddr (addr << 1);
>     else
>       return avr_make_saddr (addr);
> @@ -1342,6 +1364,45 @@ avr_dwarf_reg_to_regnum (struct gdbarch *gdbarch, int reg)
>     return -1;
>   }
>
> +/* Map DW_AT_address_class attributes to a type_instance_flag_value.  Note that
> +   this attribute is only valid with pointer types and therefore the flag is set
> +   to the pointer type and not its target type.  */
> +
> +static int
> +avr_address_class_type_flags (int byte_size, int dwarf2_addr_class)
> +{
> +  // __flash qualifier
> +  if (dwarf2_addr_class == 1 && byte_size == 2)
> +    return AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH;
> +  return 0;
> +}
> +
> +/* Convert a type_instance_flag_value to an address space qualifier and
> +   vice-versa.  */
> +
> +static const char*
> +avr_address_class_type_flags_to_name (struct gdbarch *gdbarch, int type_flags)
> +{
> +  if (type_flags & AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH)
> +    return "flash";
> +  else
> +    return NULL;
> +}
> +
> +static int
> +avr_address_class_name_to_type_flags (struct gdbarch *gdbarch,
> +                                      const char* name,
> +                                      int *type_flags_ptr)
> +{
> +  if (strcmp (name, "flash") == 0)
> +    {
> +      *type_flags_ptr = AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH;
> +      return 1;
> +    }
> +  else
> +    return 0;
> +}
> +
>   /* Initialize the gdbarch structure for the AVR's.  */
>
>   static struct gdbarch *
> @@ -1452,6 +1513,12 @@ avr_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
>     set_gdbarch_unwind_pc (gdbarch, avr_unwind_pc);
>     set_gdbarch_unwind_sp (gdbarch, avr_unwind_sp);
>
> +  set_gdbarch_address_class_type_flags (gdbarch, avr_address_class_type_flags);
> +  set_gdbarch_address_class_name_to_type_flags
> +    (gdbarch, avr_address_class_name_to_type_flags);
> +  set_gdbarch_address_class_type_flags_to_name
> +    (gdbarch, avr_address_class_type_flags_to_name);
> +
>     return gdbarch;
>   }
>
> diff --git a/gdb/testsuite/gdb.arch/avr-flash-qualifier.c b/gdb/testsuite/gdb.arch/avr-flash-qualifier.c
> new file mode 100644
> index 0000000..4e5b451
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/avr-flash-qualifier.c
> @@ -0,0 +1,32 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2014 Free Software Foundation, Inc.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +const __flash char data_in_flash = 0xab;
> +
> +static void
> +pass_to_function (const __flash char *p)
> +{
> +}
> +
> +int
> +main (void)
> +{
> +  const __flash char *pointer_to_flash = &data_in_flash;
> +  /* break here.  */
> +  pass_to_function (&data_in_flash);
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.arch/avr-flash-qualifier.exp b/gdb/testsuite/gdb.arch/avr-flash-qualifier.exp
> new file mode 100644
> index 0000000..e9ccb4f
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/avr-flash-qualifier.exp
> @@ -0,0 +1,52 @@
> +# Copyright 2014 Free Software Foundation, Inc.
> +
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +#
> +# This file is part of the gdb testsuite.
> +#
> +# Contributed by Pierre Langlois  <pierre.langlois@embecosm.com>
> +# Tests for the AVR __flash named address space qualifier.
> +
> +if {![istarget "avr*"]} {
> +  verbose "Skipping ${gdb_test_file_name}."
> +  return
> +}
> +
> +# The __flash qualifier was added in GCC 4.7.
> +if {[test_compiler_info {gcc-[0-4]-[0-6]}]} {
> +  verbose "Skipping ${gdb_test_file_name}."
> +  return
> +}
> +
> +standard_testfile
> +if {[prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}]} {
> +  return -1
> +}
> +
> +if ![runto [gdb_get_line_number "break here."]] {
> +  untested "could not run to \"break here.\""
> +  return -1
> +}
> +
> +gdb_test "print pointer_to_flash" \
> +  " = $hex <data_in_flash> .*"
> +
> +gdb_breakpoint "pass_to_function"
> +gdb_continue_to_breakpoint "pass_to_function"
> +
> +gdb_test "print p" \
> +  " = $hex <data_in_flash> .*"
> +
> +gdb_test "backtrace 1" \
> +  "\#0  pass_to_function \\(p=$hex <data_in_flash> .*\\).*"
>
Joel Brobecker July 15, 2014, 1:33 p.m. UTC | #2
Hello,

> 2014-07-08  Pierre Langlois  <pierre.langlois@embecosm.com>
> 
> gdb/
> 	* avr-tdep.c (AVR_TYPE_ADDRESS_CLASS_FLASH): New macro.
> 	(AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH): Likewise.
> 	(avr_address_to_pointer): Check for AVR_TYPE_ADDRESS_CLASS_FLASH.
> 	(avr_pointer_to_address): Likewise.
> 	(avr_address_class_type_flags): New function.
> 	(avr_address_class_type_flags_to_name): Likewise.
> 	(avr_address_class_name_to_type_flags): Likewise.
> 	(avr_gdbarch_init): Set address_class_type_flags,
> 	address_class_type_flags_to_name and
> 	address_class_name_to_type_flags.
> 
> gdb/testsuite/
> 	* gdb.arch/avr-flash-qualifer.c: New.
> 	* gdb.arch/avr-flash-qualifer.exp: New.

Sorry about the delay in reviewing this. Some comments below.

> +/* Map DW_AT_address_class attributes to a type_instance_flag_value.  Note that
> +   this attribute is only valid with pointer types and therefore the flag is set
> +   to the pointer type and not its target type.  */

Can you start the comment by saying that this function implements the
address_class_name_to_type_flags gdbarch method?  You can then add
the comment above as a second paragraph, or perhaps as an implementation
comment inside the function body itself.

> +static int
> +avr_address_class_type_flags (int byte_size, int dwarf2_addr_class)
> +{

Please add a comment saying that this function implements the
address_class_type_flags gdbarch method. Generally speaking, all
new functions without exception should have an introductory comment.

> +  // __flash qualifier

Please do not use C++-style comments for the moment.

> +  if (dwarf2_addr_class == 1 && byte_size == 2)
> +    return AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH;
> +  return 0;
> +}
> +
> +/* Convert a type_instance_flag_value to an address space qualifier and
> +   vice-versa.  */
> +
> +static const char*
> +avr_address_class_type_flags_to_name (struct gdbarch *gdbarch, int type_flags)

Same as above regarding the function's introductory comment. And also,
I'd prefer it if we avoided two functions being documented with
the same comment, as this opens the door for a function becoming
undocumented if the two functions somehow get separated.

> +{
> +  if (type_flags & AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH)
> +    return "flash";
> +  else
> +    return NULL;
> +}
> +
> +static int
> +avr_address_class_name_to_type_flags (struct gdbarch *gdbarch,
> +                                      const char* name,
> +                                      int *type_flags_ptr)

Missing introductory comment ("Implements the ...").
Pierre Langlois July 15, 2014, 2:39 p.m. UTC | #3
Hello Joel,

>
> Sorry about the delay in reviewing this. Some comments below.
>

That's OK, thank you very much for the review!

>> +  // __flash qualifier
>
> Please do not use C++-style comments for the moment.
>

Oh dear, I'm sorry about this.

Thanks,

Pierre
Pedro Alves July 21, 2014, 3:45 p.m. UTC | #4
Hi Pierre,

On 07/08/2014 11:54 AM, Pierre Langlois wrote:
> The __flash qualifier is part of the named address spaces for AVR [1]. It allows
> putting read-only data in the flash memory, normally reserved for code.
> 
> When used together with a pointer, the DW_AT_address_class attribute is set to 1
> and allows GDB to detect that when it will be dereferenced, the data will be
> loaded from the flash memory (with the LPM instruction).
> 

Thanks.  This looks good to me, with a couple nits pointed out
below addressed.

> +/* Address space flags */
> +
> +/* We are assigning the TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1 to the flash address
> +   space.  */
>    /* Is it a code address?  */
> -  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
> -      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD)
> +  else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
> +	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD)
>      {
> +      /* A code address, either a function pointer or the program counter, is
> +	 word (16 bits) addressed.  */

FYI, the "or the program counter" reference here looks a bit
confusion-inducing to me.

  TYPE_CODE_FUNC -> function.
  TYPE_CODE_METHOD -> C++ class member functions (methods).

I think you've added that, because the $pc register is of function
pointer type?  I'd suggest just not bringing that up, as it was before.


>    /* Is it a code address?  */
> -  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
> -      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
> -      || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
> +  else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
> +	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
> +	   || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))

Particularly since this bit didn't get that comment?

BTW, interesting/curious that TYPE_CODE_SPACE is handled
here but not in avr_address_to_pointer.  Offhand, looks like a
bug, though off topic for this patch.

>      return avr_make_iaddr (addr << 1);
>    else
>      return avr_make_saddr (addr);
> @@ -1342,6 +1364,45 @@ avr_dwarf_reg_to_regnum (struct gdbarch *gdbarch, int reg)
>    return -1;
>  }
>  
> +/* Map DW_AT_address_class attributes to a type_instance_flag_value.  Note that
> +   this attribute is only valid with pointer types and therefore the flag is set
> +   to the pointer type and not its target type.  */
> +
> +static int
> +avr_address_class_type_flags (int byte_size, int dwarf2_addr_class)
> +{
> +  // __flash qualifier

Please use /**/-style comments, and write full sentences.

> +  if (dwarf2_addr_class == 1 && byte_size == 2)
> +    return AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH;
> +  return 0;
> +}
> +

Thanks,
Pierre Langlois July 23, 2014, 4:52 p.m. UTC | #5
Hi Pedro,

On 21/07/14 16:45, Pedro Alves wrote:
> Hi Pierre,
> 
> On 07/08/2014 11:54 AM, Pierre Langlois wrote:
>> The __flash qualifier is part of the named address spaces for AVR [1]. It allows
>> putting read-only data in the flash memory, normally reserved for code.
>>
>> When used together with a pointer, the DW_AT_address_class attribute is set to 1
>> and allows GDB to detect that when it will be dereferenced, the data will be
>> loaded from the flash memory (with the LPM instruction).
>>
> 
> Thanks.  This looks good to me, with a couple nits pointed out
> below addressed.
> 

Thanks for looking at this.  I have committed a better version of this patch
last week after review.  So I just submitted another patch improving the
comments as suggested.

>> +/* Address space flags */
>> +
>> +/* We are assigning the TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1 to the flash address
>> +   space.  */
>>    /* Is it a code address?  */
>> -  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
>> -      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD)
>> +  else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
>> +	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD)
>>      {
>> +      /* A code address, either a function pointer or the program counter, is
>> +	 word (16 bits) addressed.  */
> 
> FYI, the "or the program counter" reference here looks a bit
> confusion-inducing to me.
> 
>   TYPE_CODE_FUNC -> function.
>   TYPE_CODE_METHOD -> C++ class member functions (methods).
> 
> I think you've added that, because the $pc register is of function
> pointer type?  I'd suggest just not bringing that up, as it was before.
> 

Yes you're right, I mentioned the $pc register because of its type.  I
understand it's confusing now.

> 
>>    /* Is it a code address?  */
>> -  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
>> -      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
>> -      || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
>> +  else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
>> +	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
>> +	   || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
> 
> Particularly since this bit didn't get that comment?
>
> BTW, interesting/curious that TYPE_CODE_SPACE is handled
> here but not in avr_address_to_pointer.  Offhand, looks like a
> bug, though off topic for this patch.
> 

I am bit puzzled here but I suspect this was done on purpose.  I'll submit a
patch so we can discuss it.

Thanks,

Pierre
Pedro Alves July 24, 2014, 1:33 a.m. UTC | #6
On 07/23/2014 05:52 PM, Pierre Langlois wrote:
> Hi Pedro,
> 
> On 21/07/14 16:45, Pedro Alves wrote:
>> Hi Pierre,
>>
>> On 07/08/2014 11:54 AM, Pierre Langlois wrote:
>>> The __flash qualifier is part of the named address spaces for AVR [1]. It allows
>>> putting read-only data in the flash memory, normally reserved for code.
>>>
>>> When used together with a pointer, the DW_AT_address_class attribute is set to 1
>>> and allows GDB to detect that when it will be dereferenced, the data will be
>>> loaded from the flash memory (with the LPM instruction).
>>>
>>
>> Thanks.  This looks good to me, with a couple nits pointed out
>> below addressed.
>>
> 
> Thanks for looking at this.  I have committed a better version of this patch
> last week after review.  So I just submitted another patch improving the
> comments as suggested.
>

Whoops, I completely missed that.  Sorry about that.


> Yes you're right, I mentioned the $pc register because of its type.  I
> understand it's confusing now.

> 
>>
>>>    /* Is it a code address?  */
>>> -  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
>>> -      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
>>> -      || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
>>> +  else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
>>> +	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
>>> +	   || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
>>
>> Particularly since this bit didn't get that comment?
>>
>> BTW, interesting/curious that TYPE_CODE_SPACE is handled
>> here but not in avr_address_to_pointer.  Offhand, looks like a
>> bug, though off topic for this patch.
>>
> 
> I am bit puzzled here but I suspect this was done on purpose.  I'll submit a
> patch so we can discuss it.
> 

Thanks!
diff mbox

Patch

diff --git a/gdb/avr-tdep.c b/gdb/avr-tdep.c
index 9b0bfaf..eb99748 100644
--- a/gdb/avr-tdep.c
+++ b/gdb/avr-tdep.c
@@ -71,6 +71,16 @@ 
 
 /* Constants: prefixed with AVR_ to avoid name space clashes */
 
+/* Address space flags */
+
+/* We are assigning the TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1 to the flash address
+   space.  */
+
+#define AVR_TYPE_ADDRESS_CLASS_FLASH TYPE_ADDRESS_CLASS_1
+#define AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH  \
+  TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1
+
+
 enum
 {
   AVR_REG_W = 24,
@@ -295,10 +305,19 @@  avr_address_to_pointer (struct gdbarch *gdbarch,
 {
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 
+  /* Is it a data address in flash?  */
+  if (AVR_TYPE_ADDRESS_CLASS_FLASH (type))
+    {
+      /* A data address in flash is always byte addressed.  */
+      store_unsigned_integer (buf, TYPE_LENGTH (type), byte_order,
+			      avr_convert_iaddr_to_raw (addr));
+    }
   /* Is it a code address?  */
-  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
-      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD)
+  else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
+	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD)
     {
+      /* A code address, either a function pointer or the program counter, is
+	 word (16 bits) addressed.  */
       store_unsigned_integer (buf, TYPE_LENGTH (type), byte_order,
 			      avr_convert_iaddr_to_raw (addr >> 1));
     }
@@ -318,10 +337,13 @@  avr_pointer_to_address (struct gdbarch *gdbarch,
   CORE_ADDR addr
     = extract_unsigned_integer (buf, TYPE_LENGTH (type), byte_order);
 
+  /* Is it a data address in flash?  */
+  if (AVR_TYPE_ADDRESS_CLASS_FLASH (type))
+    return avr_make_iaddr (addr);
   /* Is it a code address?  */
-  if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
-      || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
-      || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
+  else if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
+	   || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
+	   || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type)))
     return avr_make_iaddr (addr << 1);
   else
     return avr_make_saddr (addr);
@@ -1342,6 +1364,45 @@  avr_dwarf_reg_to_regnum (struct gdbarch *gdbarch, int reg)
   return -1;
 }
 
+/* Map DW_AT_address_class attributes to a type_instance_flag_value.  Note that
+   this attribute is only valid with pointer types and therefore the flag is set
+   to the pointer type and not its target type.  */
+
+static int
+avr_address_class_type_flags (int byte_size, int dwarf2_addr_class)
+{
+  // __flash qualifier
+  if (dwarf2_addr_class == 1 && byte_size == 2)
+    return AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH;
+  return 0;
+}
+
+/* Convert a type_instance_flag_value to an address space qualifier and
+   vice-versa.  */
+
+static const char*
+avr_address_class_type_flags_to_name (struct gdbarch *gdbarch, int type_flags)
+{
+  if (type_flags & AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH)
+    return "flash";
+  else
+    return NULL;
+}
+
+static int
+avr_address_class_name_to_type_flags (struct gdbarch *gdbarch,
+                                      const char* name,
+                                      int *type_flags_ptr)
+{
+  if (strcmp (name, "flash") == 0)
+    {
+      *type_flags_ptr = AVR_TYPE_INSTANCE_FLAG_ADDRESS_CLASS_FLASH;
+      return 1;
+    }
+  else
+    return 0;
+}
+
 /* Initialize the gdbarch structure for the AVR's.  */
 
 static struct gdbarch *
@@ -1452,6 +1513,12 @@  avr_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   set_gdbarch_unwind_pc (gdbarch, avr_unwind_pc);
   set_gdbarch_unwind_sp (gdbarch, avr_unwind_sp);
 
+  set_gdbarch_address_class_type_flags (gdbarch, avr_address_class_type_flags);
+  set_gdbarch_address_class_name_to_type_flags
+    (gdbarch, avr_address_class_name_to_type_flags);
+  set_gdbarch_address_class_type_flags_to_name
+    (gdbarch, avr_address_class_type_flags_to_name);
+
   return gdbarch;
 }
 
diff --git a/gdb/testsuite/gdb.arch/avr-flash-qualifier.c b/gdb/testsuite/gdb.arch/avr-flash-qualifier.c
new file mode 100644
index 0000000..4e5b451
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/avr-flash-qualifier.c
@@ -0,0 +1,32 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2014 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+const __flash char data_in_flash = 0xab;
+
+static void
+pass_to_function (const __flash char *p)
+{
+}
+
+int
+main (void)
+{
+  const __flash char *pointer_to_flash = &data_in_flash;
+  /* break here.  */
+  pass_to_function (&data_in_flash);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.arch/avr-flash-qualifier.exp b/gdb/testsuite/gdb.arch/avr-flash-qualifier.exp
new file mode 100644
index 0000000..e9ccb4f
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/avr-flash-qualifier.exp
@@ -0,0 +1,52 @@ 
+# Copyright 2014 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file is part of the gdb testsuite.
+#
+# Contributed by Pierre Langlois  <pierre.langlois@embecosm.com>
+# Tests for the AVR __flash named address space qualifier.
+
+if {![istarget "avr*"]} {
+  verbose "Skipping ${gdb_test_file_name}."
+  return
+}
+
+# The __flash qualifier was added in GCC 4.7.
+if {[test_compiler_info {gcc-[0-4]-[0-6]}]} {
+  verbose "Skipping ${gdb_test_file_name}."
+  return
+}
+
+standard_testfile
+if {[prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}]} {
+  return -1
+}
+
+if ![runto [gdb_get_line_number "break here."]] {
+  untested "could not run to \"break here.\""
+  return -1
+}
+
+gdb_test "print pointer_to_flash" \
+  " = $hex <data_in_flash> .*"
+
+gdb_breakpoint "pass_to_function"
+gdb_continue_to_breakpoint "pass_to_function"
+
+gdb_test "print p" \
+  " = $hex <data_in_flash> .*"
+
+gdb_test "backtrace 1" \
+  "\#0  pass_to_function \\(p=$hex <data_in_flash> .*\\).*"