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[committed,1/6] arm: Fix general issues with patterns for VLLDM and VLSTM

Message ID 20210824105928.3869183-2-rearnsha@arm.com
State New
Headers show
Series arm: mitigation for CVE-2021-35465 | expand

Commit Message

Richard Earnshaw Aug. 24, 2021, 10:59 a.m. UTC 
Both lazy_store_multiple_insn and lazy_load_multiple_insn contain
invalid RTL (eg they contain a post_inc statement outside of a mem).
What's more, the instructions concerned do not modify their input
address register.  We probably got away with this because they are
generated so late in the compilation that no subsequent pass needed to
understand them.  Nevertheless, this could cause problems someday, so
fixed to use a simple legal unspec.

gcc:
	* config/arm/vfp.md (lazy_store_multiple_insn): Rewrite as valid RTL.
	(lazy_load_multiple_insn): Likewise.
---
 gcc/config/arm/vfp.md | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)
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Patch

diff --git a/gcc/config/arm/vfp.md b/gcc/config/arm/vfp.md
index 93e963696da..9961f9389fe 100644
--- a/gcc/config/arm/vfp.md
+++ b/gcc/config/arm/vfp.md
@@ -1703,12 +1703,15 @@  (define_insn "*clear_vfp_multiple"
    (set_attr "type" "mov_reg")]
 )
 
+;; Both this and the next instruction are treated by GCC in the same
+;; way as a blockage pattern.  That's perhaps stronger than it needs
+;; to be, but we do not want accesses to the VFP register bank to be
+;; moved across either instruction.
+
 (define_insn "lazy_store_multiple_insn"
-  [(set (match_operand:SI 0 "s_register_operand" "+&rk")
-	(post_dec:SI (match_dup 0)))
-   (unspec_volatile [(const_int 0)
-		     (mem:SI (post_dec:SI (match_dup 0)))]
-		    VUNSPEC_VLSTM)]
+  [(unspec_volatile
+    [(mem:BLK (match_operand:SI 0 "s_register_operand" "rk"))]
+    VUNSPEC_VLSTM)]
   "use_cmse && reload_completed"
   "vlstm%?\\t%0"
   [(set_attr "predicable" "yes")
@@ -1716,11 +1719,9 @@  (define_insn "lazy_store_multiple_insn"
 )
 
 (define_insn "lazy_load_multiple_insn"
-  [(set (match_operand:SI 0 "s_register_operand" "+&rk")
-	(post_inc:SI (match_dup 0)))
-   (unspec_volatile:SI [(const_int 0)
-			(mem:SI (match_dup 0))]
-		       VUNSPEC_VLLDM)]
+  [(unspec_volatile
+    [(mem:BLK (match_operand:SI 0 "s_register_operand" "rk"))]
+    VUNSPEC_VLLDM)]
   "use_cmse && reload_completed"
   "vlldm%?\\t%0"
   [(set_attr "predicable" "yes")