[binutils-gdb] aarch64: Fix incorrect sysreg notes operand notes

[Alice Carlotti]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f9e512968b489276d5c950084e26fa2a49a9b983

commit f9e512968b489276d5c950084e26fa2a49a9b983
Author: Alice Carlotti <alice.carlotti@arm.com>
Date:   Tue Nov 4 12:28:56 2025 +0000

    aarch64: Fix incorrect sysreg notes operand notes
    
    When support for Armv8-R was added in 2020, aarch64_print_operand was
    modified to check architecture features when searching for a system
    register name.  However, this mismatch is then conflated with
    read-only/write-only mismatches, leading to incorrect note emission when
    reading a read-only or writing a write-only system register that is not
    available in whichever of Armv8-A or Armv8-R we are using.
    
    The original code also segfaults when parsing `msr mpuir_el1, w1'.  This
    segfault arises while suggesting alternative assembler input with
    corrected qualifiers, due to a missing NULL check when attempting to
    emit notes.  The segfault is unreachable after this change, but a
    subsequent patch will incorporate NULL checking anyway.
    
    Once notes are enabled by default, an existing `mrs x0, mpuir_el1' test
    will verify that the incorrect notes are no longer generated.

Diff:
---
 opcodes/aarch64-opc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/opcodes/aarch64-opc.c b/opcodes/aarch64-opc.c
index b074765920e..d7e697e7247 100644
--- a/opcodes/aarch64-opc.c
+++ b/opcodes/aarch64-opc.c
@@ -5024,9 +5024,11 @@ aarch64_print_operand (char *buf, size_t size, bfd_vma pc,
 		 indicates what we didn't want for this instruction.  e.g. If
 		 F_REG_READ is there, that means we were looking for a write
 		 register.  See aarch64_ext_sysreg.  */
-	      if (aarch64_sys_regs[i].flags & F_REG_WRITE)
+	      if (aarch64_sys_regs[i].flags & F_REG_WRITE
+		  && !(opnd->sysreg.flags & F_REG_WRITE))
 		*notes = _("reading from a write-only register");
-	      else if (aarch64_sys_regs[i].flags & F_REG_READ)
+	      else if (aarch64_sys_regs[i].flags & F_REG_READ
+		       && !(opnd->sysreg.flags & F_REG_READ))
 		*notes = _("writing to a read-only register");
 	    }
 	}