[binutils-gdb] gdb: aarch64: Remove MTE address checking from get_memtag

[binutils-gdb] gdb: aarch64: Remove MTE address checking from get_memtag

[Luis Machado]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=75606e5e8de136a1ad217e53ce5943a91d5ea424

commit 75606e5e8de136a1ad217e53ce5943a91d5ea424
Author: Gustavo Romero <gustavo.romero@linaro.org>
Date:   Thu Apr 18 20:10:32 2024 +0000

    gdb: aarch64: Remove MTE address checking from get_memtag
    
    This commit removes aarch64_linux_tagged_address_p from
    aarch64_linux_get_memtag. aarch64_linux_tagged_address_p checks if an
    address is tagged (MTE) or not.
    
    The check is redundant because aarch64_linux_get_memtag is always called
    from the upper layers (i.e. from printcmd.c via gdbarch hook
    gdbarch_get_memtag) after either gdbarch_tagged_address_p (that already
    points to aarch64_linux_tagged_address_p) has been called or
    after should_validate_memtags (that calls gdbarch_tagged_address_p at
    the end) has been called, so the address is already checked. Hence:
    
    a) in print_command_1, aarch64_linux_get_memtag (via gdbarch_get_memtag
    hook) is called but only after should_validate_memtags, which calls
    gdbarch_tagged_address_p;
    
    b) in do_examine, aarch64_linux_get_memtag is also called only after
    gdbarch_tagged_address_p is directly called;
    
    c) in memory_tag_check_command, gdbarch_get_memtag is called -- tags
    matching or not -- after the initial check via direct call to
    gdbarch_tagged_address_p;
    
    d) in memory_tag_print_tag_command, address is checked directly via
    gdbarch_tagged_address_p before gdbarch_get_memtag is called.
    
    Also, because after this change the address checking only happens at the
    upper layer it now allows the address checking to be specialized easily
    per target, via a target hook.
    
    Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
    Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
    Approved-By: Luis Machado <luis.machado@arm.com>
    Tested-By: Luis Machado <luis.machado@arm.com>

Diff:
---
 gdb/aarch64-linux-tdep.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
index 0b9784f38e4..50055ac3f48 100644
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -2575,10 +2575,6 @@ aarch64_linux_get_memtag (struct gdbarch *gdbarch, struct value *address,
     tag = aarch64_mte_get_ltag (addr);
   else
     {
-      /* Make sure we are dealing with a tagged address to begin with.  */
-      if (!aarch64_linux_tagged_address_p (gdbarch, address))
-	return nullptr;
-
       /* Remove the top byte.  */
       addr = gdbarch_remove_non_address_bits (gdbarch, addr);
       std::optional<CORE_ADDR> atag = aarch64_mte_get_atag (addr);