[PATCH v4] tcg: Sanitize shift constants on ppc64le so that shift operations with large constants don't generate invalid instructions.

[agrecascino123@gmail.com]

From: "Catherine A. Frederick" <chocola@animebitch.es>

Signed-off-by: Catherine A. Frederick <chocola@animebitch.es>
---
This should finally do it, sorry for the style issues on v3.

 tcg/ppc/tcg-target.inc.c | 41 ++++++++++++++++++++++++++++++++++------
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/tcg/ppc/tcg-target.inc.c b/tcg/ppc/tcg-target.inc.c
index 7da67086c6..5ed4e4c011 100644
--- a/tcg/ppc/tcg-target.inc.c
+++ b/tcg/ppc/tcg-target.inc.c
@@ -790,21 +790,25 @@ static inline void tcg_out_ext32u(TCGContext *s, TCGReg dst, TCGReg src)
 
 static inline void tcg_out_shli32(TCGContext *s, TCGReg dst, TCGReg src, int c)
 {
+    tcg_debug_assert((c < 32) && (c >= 0));
     tcg_out_rlw(s, RLWINM, dst, src, c, 0, 31 - c);
 }
 
 static inline void tcg_out_shli64(TCGContext *s, TCGReg dst, TCGReg src, int c)
 {
+    tcg_debug_assert((c < 64) && (c >= 0));
     tcg_out_rld(s, RLDICR, dst, src, c, 63 - c);
 }
 
 static inline void tcg_out_shri32(TCGContext *s, TCGReg dst, TCGReg src, int c)
 {
+    tcg_debug_assert((c < 32) && (c >= 0));
     tcg_out_rlw(s, RLWINM, dst, src, 32 - c, c, 31);
 }
 
 static inline void tcg_out_shri64(TCGContext *s, TCGReg dst, TCGReg src, int c)
 {
+    tcg_debug_assert((c < 64) && (c >= 0));
     tcg_out_rld(s, RLDICL, dst, src, 64 - c, c);
 }
 
@@ -2610,21 +2614,33 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, const TCGArg *args,
 
     case INDEX_op_shl_i32:
         if (const_args[2]) {
-            tcg_out_shli32(s, args[0], args[1], args[2]);
+            /*
+             * Limit shift immediate to prevent illegal instruction
+             * from bitmask corruption
+             */
+            tcg_out_shli32(s, args[0], args[1], args[2] & 31);
         } else {
             tcg_out32(s, SLW | SAB(args[1], args[0], args[2]));
         }
         break;
     case INDEX_op_shr_i32:
         if (const_args[2]) {
-            tcg_out_shri32(s, args[0], args[1], args[2]);
+            /*
+             * Both use RLWINM, which has a 5 bit field for the
+             * shift mask.
+             */
+            tcg_out_shri32(s, args[0], args[1], args[2] & 31);
         } else {
             tcg_out32(s, SRW | SAB(args[1], args[0], args[2]));
         }
         break;
     case INDEX_op_sar_i32:
         if (const_args[2]) {
-            tcg_out32(s, SRAWI | RS(args[1]) | RA(args[0]) | SH(args[2]));
+            /*
+             * SRAWI has a 5 bit sized field for the shift mask
+             * as well.
+             */
+            tcg_out32(s, SRAWI | RS(args[1]) | RA(args[0]) | SH(args[2] & 31));
         } else {
             tcg_out32(s, SRAW | SAB(args[1], args[0], args[2]));
         }
@@ -2696,21 +2712,34 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, const TCGArg *args,
 
     case INDEX_op_shl_i64:
         if (const_args[2]) {
-            tcg_out_shli64(s, args[0], args[1], args[2]);
+            /*
+             * Limit shift immediate to prevent illegal instruction from
+             * from bitmask corruption
+             */
+            tcg_out_shli64(s, args[0], args[1], args[2] & 63);
         } else {
             tcg_out32(s, SLD | SAB(args[1], args[0], args[2]));
         }
         break;
     case INDEX_op_shr_i64:
         if (const_args[2]) {
-            tcg_out_shri64(s, args[0], args[1], args[2]);
+            /*
+             * Same applies here, as both RLDICL, and RLDICR have a
+             * 6 bit large mask for the shift value
+             */
+            tcg_out_shri64(s, args[0], args[1], args[2] & 63);
         } else {
             tcg_out32(s, SRD | SAB(args[1], args[0], args[2]));
         }
         break;
     case INDEX_op_sar_i64:
         if (const_args[2]) {
-            int sh = SH(args[2] & 0x1f) | (((args[2] >> 5) & 1) << 1);
+            /*
+             * Same for SRADI, except there's no function
+             * to call into.
+             */
+            int sh = SH(((args[2] & 63) & 0x1f)
+                        | ((((args[2] & 63) >> 5) & 1) << 1));
             tcg_out32(s, SRADI | RA(args[0]) | RS(args[1]) | sh);
         } else {
             tcg_out32(s, SRAD | SAB(args[1], args[0], args[2]));
-- 
2.26.2