Re: [PATCH v2] Add SVR4 psABI specific parser for AUXV entries

Simon Marchi
2020-04-09T00:04:27Z

> diff --git a/gdb/auxv.c b/gdb/auxv.c
> index c13d7a22eb9..28e8d2f704d 100644
> --- a/gdb/auxv.c
> +++ b/gdb/auxv.c
> @@ -248,34 +248,65 @@ memory_xfer_auxv (struct target_ops *ops,
> return procfs_xfer_auxv (readbuf, writebuf, offset, len, xfered_len);
> }
>
> -/* Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
> - Return 0 if *READPTR is already at the end of the buffer.
> - Return -1 if there is insufficient buffer for a whole entry.
> - Return 1 if an entry was read into *TYPEP and *VALP. */
> -int
> -default_auxv_parse (struct target_ops *ops, gdb_byte **readptr,
> - gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp)
> +/* This function compared to other auxv_parse functions: it takes the size of
> + the auxv type field as a parameter. */
> +
> +static int
> +generic_auxv_parse (struct gdbarch *gdbarch, gdb_byte **readptr,
> + gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp,
> + int sizeof_auxv_type)
> {
> - const int sizeof_auxv_field = gdbarch_ptr_bit (target_gdbarch ())
> - / TARGET_CHAR_BIT;
> - const enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
> + struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
> + const int sizeof_auxv_val = TYPE_LENGTH (ptr_type);
> + enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
> gdb_byte *ptr = *readptr;
>
> if (endptr == ptr)
> return 0;
>
> - if (endptr - ptr < sizeof_auxv_field * 2)
> + if (endptr - ptr < 2 * sizeof_auxv_val)
> return -1;
>
> - *typep = extract_unsigned_integer (ptr, sizeof_auxv_field, byte_order);
> - ptr += sizeof_auxv_field;
> - *valp = extract_unsigned_integer (ptr, sizeof_auxv_field, byte_order);
> - ptr += sizeof_auxv_field;
> + *typep = extract_unsigned_integer (ptr, sizeof_auxv_type, byte_order);
> + /* Even if the auxv type takes less space than an auxv value, there is
> + padding after the type such that the value is aligned on a multiple of
> + its size (and this is why we advance by `sizeof_auxv_val` and not
> + `sizeof_auxv_type`. */

The parenthesis in the comment is not closed.

> diff --git a/gdb/auxv.h b/gdb/auxv.h
> index a5a932ec80e..c1d11ea2c7b 100644
> --- a/gdb/auxv.h
> +++ b/gdb/auxv.h
> @@ -25,12 +25,27 @@
> /* See "include/elf/common.h" for the definition of valid AT_* values. */
>
> /* The default implementation of to_auxv_parse, used by the target
> - stack. */
> + stack.
>
> + Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
> + Return 0 if *READPTR is already at the end of the buffer.
> + Return -1 if there is insufficient buffer for a whole entry.
> + Return 1 if an entry was read into *TYPEP and *VALP. */
> extern int default_auxv_parse (struct target_ops *ops, gdb_byte **readptr,
> gdb_byte *endptr, CORE_ADDR *typep,
> CORE_ADDR *valp);
>
> +/* The SVR4 psABI implementation of to_auxv_parse, that uses an int to
> + store the type rather than long as assumed by the default parser.
> +
> + Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
> + Return 0 if *READPTR is already at the end of the buffer.
> + Return -1 if there is insufficient buffer for a whole entry.
> + Return 1 if an entry was read into *TYPEP and *VALP. */
> +extern int svr4_auxv_parse (struct gdbarch *gdbarch, gdb_byte **readptr,
> + gdb_byte *endptr, CORE_ADDR *typep,
> + CORE_ADDR *valp);

The last two lines are not properly aligned on the parenthesis.

Simon