[PATCH 4/5] RISC-V/GAS: Improve handling of invalid relocs

[Palmer Dabbelt]

From: Andrew Waterman <andrew@sifive.com>

TLS relocs against constants previously segfaulted, and illegal
symbol subtractions were silently ignored.

The previous behavior was to segfault.

gas/ChangeLog

2016-12-21  Andrew Waterman <andrew@sifive.com>

	* config/tc-riscv.c (md_apply_fix): Report TLS relocations against
	constants.  Report disallowed symbol subtractions.
---
 gas/config/tc-riscv.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c
index 03db275..03c84e8 100644
--- a/gas/config/tc-riscv.c
+++ b/gas/config/tc-riscv.c
@@ -1889,7 +1889,11 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
     case BFD_RELOC_RISCV_TLS_GD_HI20:
     case BFD_RELOC_RISCV_TLS_DTPREL32:
     case BFD_RELOC_RISCV_TLS_DTPREL64:
-      S_SET_THREAD_LOCAL (fixP->fx_addsy);
+      if (fixP->fx_addsy != NULL)
+	S_SET_THREAD_LOCAL (fixP->fx_addsy);
+      else
+	as_bad_where (fixP->fx_file, fixP->fx_line,
+		      _("TLS relocation against a constant"));
       break;
 
     case BFD_RELOC_64:
@@ -2045,6 +2049,10 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
 	as_fatal (_("internal error: bad relocation #%d"), fixP->fx_r_type);
     }
 
+  if (fixP->fx_subsy != NULL)
+    as_bad_where (fixP->fx_file, fixP->fx_line,
+		  _("unsupported symbol subtraction"));
+
   /* Add an R_RISCV_RELAX reloc if the reloc is relaxable.  */
   if (relaxable && fixP->fx_tcbit && fixP->fx_addsy != NULL)
     {
-- 
2.10.2