[binutils-gdb] x86/gas: replace inappropriate assertion when parsing registers

[binutils-gdb] x86/gas: replace inappropriate assertion when parsing registers

[Jan Beulich]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=0ccade1ae2c00337d2b0bba2a175a060b93728a8

commit 0ccade1ae2c00337d2b0bba2a175a060b93728a8
Author: Jan Beulich <jbeulich@suse.com>
Date:   Thu Feb 16 09:40:08 2023 +0100

    x86/gas: replace inappropriate assertion when parsing registers
    
    PR gas/30117
    Once a symbol had its expression evaluated, the "segment" of the symbol
    may be reg_section if a register is merely involved in the expression,
    not just when the expression references a "plain" register. Therefore
    the first of the assertions put in place by 4d1bb7955a8b was too strict.
    Convert it to an if() to deal with situations like this one found by
    fuzzing:
    
            x=s
            s=%eax+0
            y=s
            or $6,x
    
    In non-debug builds this also avoids potentially silently generating bad
    code.

Diff:
---
 gas/config/tc-i386.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index e421a1718db..7cd50f5e267 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -13057,17 +13057,19 @@ parse_register (char *reg_string, char **end_op)
 	{
 	  const expressionS *e = symbol_get_value_expression (symbolP);
 
-	  know (e->X_op == O_register);
-	  know (e->X_add_number >= 0
-		&& (valueT) e->X_add_number < i386_regtab_size);
-	  r = i386_regtab + e->X_add_number;
-	  if (!check_register (r))
+	  if (e->X_op == O_register)
+	    {
+	      know (e->X_add_number >= 0
+		    && (valueT) e->X_add_number < i386_regtab_size);
+	      r = i386_regtab + e->X_add_number;
+	      *end_op = input_line_pointer;
+	    }
+	  if (r && !check_register (r))
 	    {
 	      as_bad (_("register '%s%s' cannot be used here"),
 		      register_prefix, r->reg_name);
 	      r = &bad_reg;
 	    }
-	  *end_op = input_line_pointer;
 	}
       *input_line_pointer = c;
       input_line_pointer = save;