[binutils-gdb] ubsan: bfin: shift exponent is too large

[Alan Modra]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2fd2b153a3819d3ab6b9c4cf06943d498187714c

commit 2fd2b153a3819d3ab6b9c4cf06943d498187714c
Author: Alan Modra <amodra@gmail.com>
Date:   Tue Dec 10 22:32:06 2019 +1030

    ubsan: bfin: shift exponent is too large
    
    This was the following in fmtconst_val, x is unsigned int.
        x = SIGNEXTEND (x, constant_formats[cf].nbits);
    Problem is, the SIGNEXTEND macro assumed its arg was a long and sign
    extended by shifting left then shifting right, and didn't cast the
    arg.  So don't do the silly shift thing.  It's not guaranteed to work
    anyway according to the C standard.  ">>" might do a logical shift
    even if its args are signed.
    
    	* bfin-dis.c (HOST_LONG_WORD_SIZE, XFIELD): Delete.
    	(SIGNBIT): New.
    	(MASKBITS, SIGNEXTEND): Rewrite.
    	(fmtconst): Don't use ? expression now that SIGNEXTEND uses
    	unsigned arithmetic, instead assign result of SIGNEXTEND back
    	to x.
    	(fmtconst_val): Use 1u in shift expression.

Diff:
---
 opcodes/ChangeLog  | 10 ++++++++++
 opcodes/bfin-dis.c | 29 ++++++++++++++++-------------
 2 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index d3f1e69..faa160a 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,5 +1,15 @@
 2019-12-11  Alan Modra  <amodra@gmail.com>
 
+	* bfin-dis.c (HOST_LONG_WORD_SIZE, XFIELD): Delete.
+	(SIGNBIT): New.
+	(MASKBITS, SIGNEXTEND): Rewrite.
+	(fmtconst): Don't use ? expression now that SIGNEXTEND uses
+	unsigned arithmetic, instead assign result of SIGNEXTEND back
+	to x.
+	(fmtconst_val): Use 1u in shift expression.
+
+2019-12-11  Alan Modra  <amodra@gmail.com>
+
 	* arc-dis.c (find_format_from_table): Use ull constant when
 	shifting by up to 32.
 
diff --git a/opcodes/bfin-dis.c b/opcodes/bfin-dis.c
index 811509f..711f7e1 100644
--- a/opcodes/bfin-dis.c
+++ b/opcodes/bfin-dis.c
@@ -33,10 +33,9 @@
 
 typedef long TIword;
 
-#define HOST_LONG_WORD_SIZE (sizeof (long) * 8)
-#define XFIELD(w,p,s)       (((w) & ((1 << (s)) - 1) << (p)) >> (p))
-#define SIGNEXTEND(v, n)    ((v << (HOST_LONG_WORD_SIZE - (n))) >> (HOST_LONG_WORD_SIZE - (n)))
-#define MASKBITS(val, bits) (val & ((1 << bits) - 1))
+#define SIGNBIT(bits)       (1ul << ((bits) - 1))
+#define MASKBITS(val, bits) ((val) & ((1ul << (bits)) - 1))
+#define SIGNEXTEND(v, n)    ((MASKBITS (v, n) ^ SIGNBIT (n)) - SIGNBIT (n))
 
 #include "disassemble.h"
 
@@ -125,8 +124,11 @@ fmtconst (const_forms_t cf, TIword x, bfd_vma pc, disassemble_info *outf)
 
   if (constant_formats[cf].reloc)
     {
-      bfd_vma ea = (((constant_formats[cf].pcrel ? SIGNEXTEND (x, constant_formats[cf].nbits)
-		      : x) + constant_formats[cf].offset) << constant_formats[cf].scale);
+      bfd_vma ea;
+
+      if (constant_formats[cf].pcrel)
+	x = SIGNEXTEND (x, constant_formats[cf].nbits);
+      ea = (x + constant_formats[cf].offset) << constant_formats[cf].scale;
       if (constant_formats[cf].pcrel)
 	ea += pc;
 
@@ -153,8 +155,8 @@ fmtconst (const_forms_t cf, TIword x, bfd_vma pc, disassemble_info *outf)
       x = x | (1 << constant_formats[cf].nbits);
       x = SIGNEXTEND (x, nb);
     }
-  else
-    x = constant_formats[cf].issigned ? SIGNEXTEND (x, constant_formats[cf].nbits) : x;
+  else if (constant_formats[cf].issigned)
+    x = SIGNEXTEND (x, constant_formats[cf].nbits);
 
   if (constant_formats[cf].offset)
     x += constant_formats[cf].offset;
@@ -180,10 +182,11 @@ fmtconst_val (const_forms_t cf, unsigned int x, unsigned int pc)
 {
   if (0 && constant_formats[cf].reloc)
     {
-      bu32 ea = (((constant_formats[cf].pcrel
-		   ? SIGNEXTEND (x, constant_formats[cf].nbits)
-		   : x) + constant_formats[cf].offset)
-		 << constant_formats[cf].scale);
+      bu32 ea;
+
+      if (constant_formats[cf].pcrel)
+	x = SIGNEXTEND (x, constant_formats[cf].nbits);
+      ea = (x + constant_formats[cf].offset) << constant_formats[cf].scale;
       if (constant_formats[cf].pcrel)
 	ea += pc;
 
@@ -194,7 +197,7 @@ fmtconst_val (const_forms_t cf, unsigned int x, unsigned int pc)
   if (constant_formats[cf].negative)
     {
       int nb = constant_formats[cf].nbits + 1;
-      x = x | (1 << constant_formats[cf].nbits);
+      x = x | (1u << constant_formats[cf].nbits);
       x = SIGNEXTEND (x, nb);
     }
   else if (constant_formats[cf].issigned)