[RFC] Use address_from_register in dwarf2-frame.c:read_addr_from_reg
Commit Message
Andrew Pinski wrote:
> I think this patch broke MIPS64 n32 big-endian support. We assert here:
> gdb_assert (!gdbarch_convert_register_p (gdbarch, regnum, type));
>
> The convert_register_p code for MIPS does:
> return (register_size (gdbarch, regnum) == 8
> && regnum % num_regs > 0 && regnum % num_regs < 32
> && TYPE_LENGTH (type) < 8);
>
>
> Since the register size is 8 byte wide (MIPS64) and the type length is
> 4 (pointer), we return true. In MIPS64, the registers are stored
> 64bits but pointers are 32bits.
>
> Here is the code that is used by mips_register_to_value:
> int len = TYPE_LENGTH (type);
> CORE_ADDR offset;
>
> offset = gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG ? 8 - len : 0;
> if (!get_frame_register_bytes (frame, regnum, offset, len, to,
> optimizedp, unavailablep))
> return 0;
>
> *optimizedp = *unavailablep = 0;
> return 1;
Huh, I wasn't aware of that conversion. Note that for the register_to_value
case, I don't actually see any difference to the default behavior; it's the
value_to_register routine that's really special (because of the sign-extension
in performs).
> Is there a way to fix this in a target neutral way? (I might need a
> way like this for AARCH64 ILP32 also).
I guess it isn't too hard to support gdbarch_convert_register_p in that
routine as well; I just didn't have any target to test on.
Can you try whether something along the following lines works for you?
Bye,
Ulrich
ChangeLog:
* findvar.c (address_from_register): Handle targets requiring
a special conversion routine even for plain pointer types.
Comments
On Wed, 27 Aug 2014, Ulrich Weigand wrote:
> Andrew Pinski wrote:
>
> > I think this patch broke MIPS64 n32 big-endian support. We assert here:
> > gdb_assert (!gdbarch_convert_register_p (gdbarch, regnum, type));
> >
> > The convert_register_p code for MIPS does:
> > return (register_size (gdbarch, regnum) == 8
> > && regnum % num_regs > 0 && regnum % num_regs < 32
> > && TYPE_LENGTH (type) < 8);
> >
> >
> > Since the register size is 8 byte wide (MIPS64) and the type length is
> > 4 (pointer), we return true. In MIPS64, the registers are stored
> > 64bits but pointers are 32bits.
> >
> > Here is the code that is used by mips_register_to_value:
> > int len = TYPE_LENGTH (type);
> > CORE_ADDR offset;
> >
> > offset = gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG ? 8 - len : 0;
> > if (!get_frame_register_bytes (frame, regnum, offset, len, to,
> > optimizedp, unavailablep))
> > return 0;
> >
> > *optimizedp = *unavailablep = 0;
> > return 1;
>
> Huh, I wasn't aware of that conversion. Note that for the register_to_value
> case, I don't actually see any difference to the default behavior; it's the
> value_to_register routine that's really special (because of the sign-extension
> in performs).
>
> > Is there a way to fix this in a target neutral way? (I might need a
> > way like this for AARCH64 ILP32 also).
>
> I guess it isn't too hard to support gdbarch_convert_register_p in that
> routine as well; I just didn't have any target to test on.
>
> Can you try whether something along the following lines works for you?
I'll see if I can push it through testing, though it may take a few days
as some of MIPS hardware I use (and especially 64-bit one) is slooow (and
I already have a test run under way).
I'd expect the issue to be consistent across all ILP32 64-bit ABIs BTW,
that is e.g. x32 x86-64 as well.
Maciej
On Wed, Aug 27, 2014 at 5:21 AM, Ulrich Weigand <uweigand@de.ibm.com> wrote:
> Andrew Pinski wrote:
>
>> I think this patch broke MIPS64 n32 big-endian support. We assert here:
>> gdb_assert (!gdbarch_convert_register_p (gdbarch, regnum, type));
>>
>> The convert_register_p code for MIPS does:
>> return (register_size (gdbarch, regnum) == 8
>> && regnum % num_regs > 0 && regnum % num_regs < 32
>> && TYPE_LENGTH (type) < 8);
>>
>>
>> Since the register size is 8 byte wide (MIPS64) and the type length is
>> 4 (pointer), we return true. In MIPS64, the registers are stored
>> 64bits but pointers are 32bits.
>>
>> Here is the code that is used by mips_register_to_value:
>> int len = TYPE_LENGTH (type);
>> CORE_ADDR offset;
>>
>> offset = gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG ? 8 - len : 0;
>> if (!get_frame_register_bytes (frame, regnum, offset, len, to,
>> optimizedp, unavailablep))
>> return 0;
>>
>> *optimizedp = *unavailablep = 0;
>> return 1;
>
> Huh, I wasn't aware of that conversion. Note that for the register_to_value
> case, I don't actually see any difference to the default behavior; it's the
> value_to_register routine that's really special (because of the sign-extension
> in performs).
>
>> Is there a way to fix this in a target neutral way? (I might need a
>> way like this for AARCH64 ILP32 also).
>
> I guess it isn't too hard to support gdbarch_convert_register_p in that
> routine as well; I just didn't have any target to test on.
>
> Can you try whether something along the following lines works for you?
Yes this works for me.
Thanks,
Andrew Pinski
>
> Bye,
> Ulrich
>
> ChangeLog:
>
> * findvar.c (address_from_register): Handle targets requiring
> a special conversion routine even for plain pointer types.
>
> diff --git a/gdb/findvar.c b/gdb/findvar.c
> index 41887de..ba3dd4d 100644
> --- a/gdb/findvar.c
> +++ b/gdb/findvar.c
> @@ -764,11 +764,28 @@ address_from_register (int regnum, struct frame_info *frame)
> would therefore abort in get_frame_id. However, since we only need
> a temporary value that is never used as lvalue, we actually do not
> really need to set its VALUE_FRAME_ID. Therefore, we re-implement
> - the core of value_from_register, but use the null_frame_id.
> + the core of value_from_register, but use the null_frame_id. */
>
> - This works only if we do not require a special conversion routine,
> - which is true for plain pointer types for all current targets. */
> - gdb_assert (!gdbarch_convert_register_p (gdbarch, regnum, type));
> + /* Some targets require a special conversion routine even for plain
> + pointer types. Avoid constructing a value object in those cases. */
> + if (gdbarch_convert_register_p (gdbarch, regnum, type))
> + {
> + gdb_byte *buf = alloca (TYPE_LENGTH (type));
> + int optim, unavail, ok;
> +
> + ok = gdbarch_register_to_value (gdbarch, frame, regnum, type,
> + buf, &optim, &unavail);
> + if (!ok)
> + {
> + /* This function is used while computing a location expression.
> + Complain about the value being optimized out, rather than
> + letting value_as_address complain about some random register
> + the expression depends on not being saved. */
> + error_value_optimized_out ();
> + }
> +
> + return unpack_long (type, buf);
> + }
>
> value = gdbarch_value_from_register (gdbarch, type, regnum, null_frame_id);
> read_frame_register_value (value, frame);
>
> --
> Dr. Ulrich Weigand
> GNU/Linux compilers and toolchain
> Ulrich.Weigand@de.ibm.com
>
On Wed, 27 Aug 2014, Maciej W. Rozycki wrote:
> > I guess it isn't too hard to support gdbarch_convert_register_p in that
> > routine as well; I just didn't have any target to test on.
> >
> > Can you try whether something along the following lines works for you?
>
> I'll see if I can push it through testing, though it may take a few days
> as some of MIPS hardware I use (and especially 64-bit one) is slooow (and
> I already have a test run under way).
I had results a few days ago already, but I had to find some time to
filter out intermittent failures. I have done it now and the results look
good. For the record, I tested the mips-linux-gnu target and the
following multilibs:
-EB
-EB -msoft-float
-EB -mips16
-EB -mips16 -msoft-float
-EB -mmicromips
-EB -mmicromips -msoft-float
-EB -mabi=n32
-EB -mabi=n32 -msoft-float
-EB -mabi=64
-EB -mabi=64 -msoft-float
and the -EL variants of same. My toolchain defaults to and test hardware
used implement the MIPS32r2 or MIPS64r2 ISA as applicable.
Maciej
@@ -764,11 +764,28 @@ address_from_register (int regnum, struct frame_info *frame)
would therefore abort in get_frame_id. However, since we only need
a temporary value that is never used as lvalue, we actually do not
really need to set its VALUE_FRAME_ID. Therefore, we re-implement
- the core of value_from_register, but use the null_frame_id.
+ the core of value_from_register, but use the null_frame_id. */
- This works only if we do not require a special conversion routine,
- which is true for plain pointer types for all current targets. */
- gdb_assert (!gdbarch_convert_register_p (gdbarch, regnum, type));
+ /* Some targets require a special conversion routine even for plain
+ pointer types. Avoid constructing a value object in those cases. */
+ if (gdbarch_convert_register_p (gdbarch, regnum, type))
+ {
+ gdb_byte *buf = alloca (TYPE_LENGTH (type));
+ int optim, unavail, ok;
+
+ ok = gdbarch_register_to_value (gdbarch, frame, regnum, type,
+ buf, &optim, &unavail);
+ if (!ok)
+ {
+ /* This function is used while computing a location expression.
+ Complain about the value being optimized out, rather than
+ letting value_as_address complain about some random register
+ the expression depends on not being saved. */
+ error_value_optimized_out ();
+ }
+
+ return unpack_long (type, buf);
+ }
value = gdbarch_value_from_register (gdbarch, type, regnum, null_frame_id);
read_frame_register_value (value, frame);