[Bug gdb/28947] GDB does not remove AArch64 pointer signatures before doing memory accesses

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=28947

--- Comment #7 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Luis Machado <luisgpm@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d88cb738e6a7a7179dfaff8af78d69250c852af1

commit d88cb738e6a7a7179dfaff8af78d69250c852af1
Author: Luis Machado <luis.machado@arm.com>
Date:   Tue May 24 23:31:09 2022 +0100

    [aarch64] Fix removal of non-address bits for PAuth

    PR gdb/28947

    The address_significant gdbarch setting was introduced as a way to remove
    non-address bits from pointers, and it is specified by a constant.  This
    constant represents the number of address bits in a pointer.

    Right now AArch64 is the only architecture that uses it, and 56 was a
    correct option so far.

    But if we are using Pointer Authentication (PAuth), we might use up to 2
bytes
    from the address space to store the required information.  We could also
have
    cases where we're using both PAuth and MTE.

    We could adjust the constant to 48 to cover those cases, but this doesn't
    cover the case where GDB needs to sign-extend kernel addresses after
removal
    of the non-address bits.

    This has worked so far because bit 55 is used to select between
kernel-space
    and user-space addresses.  But trying to clear a range of bits crossing the
    bit 55 boundary requires the hook to be smarter.

    The following patch renames the gdbarch hook from significant_addr_bit to
    remove_non_address_bits and passes a pointer as opposed to the number of
    bits.  The hook is now responsible for removing the required non-address
bits
    and sign-extending the address if needed.

    While at it, make GDB and GDBServer share some more code for aarch64 and
add a
    new arch-specific testcase gdb.arch/aarch64-non-address-bits.exp.

    Bug-url: https://sourceware.org/bugzilla/show_bug.cgi?id=28947

    Approved-By: Simon Marchi <simon.marchi@efficios.com>

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