[v5,34/43] tcg/riscv: Fix branch range checks

Commit Message

Richard Henderson Jan. 5, 2021, 5:19 p.m. UTC

The offset even checks were folded into the range check incorrectly.
By offsetting by 1, and not decrementing the width, we silently
allowed out of range branches.

Assert that the offset is always even instead.  Move tcg_out_goto
down into the CONFIG_SOFTMMU block so that it is not unused.

Reviewed-by: Alistair Francis <[e-mail]>
Signed-off-by: Richard Henderson <[e-mail]>
---
 tcg/riscv/tcg-target.c.inc | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

Patch

diff --git a/tcg/riscv/tcg-target.c.inc b/tcg/riscv/tcg-target.c.inc
index 0518595742..5b4c500a4b 100644
--- a/tcg/riscv/tcg-target.c.inc
+++ b/tcg/riscv/tcg-target.c.inc
@@ -429,7 +429,8 @@  static bool reloc_sbimm12(tcg_insn_unit *code_ptr, tcg_insn_unit *target)
 {
     intptr_t offset = (intptr_t)target - (intptr_t)code_ptr;
 
-    if (offset == sextreg(offset, 1, 12) << 1) {
+    tcg_debug_assert((offset & 1) == 0);
+    if (offset == sextreg(offset, 0, 12)) {
         code_ptr[0] |= encode_sbimm12(offset);
         return true;
     }
@@ -441,7 +442,8 @@  static bool reloc_jimm20(tcg_insn_unit *code_ptr, tcg_insn_unit *target)
 {
     intptr_t offset = (intptr_t)target - (intptr_t)code_ptr;
 
-    if (offset == sextreg(offset, 1, 20) << 1) {
+    tcg_debug_assert((offset & 1) == 0);
+    if (offset == sextreg(offset, 0, 20)) {
         code_ptr[0] |= encode_ujimm20(offset);
         return true;
     }
@@ -854,28 +856,21 @@  static void tcg_out_setcond2(TCGContext *s, TCGCond cond, TCGReg ret,
     g_assert_not_reached();
 }
 
-static inline void tcg_out_goto(TCGContext *s, tcg_insn_unit *target)
-{
-    ptrdiff_t offset = tcg_pcrel_diff(s, target);
-    tcg_debug_assert(offset == sextreg(offset, 1, 20) << 1);
-    tcg_out_opc_jump(s, OPC_JAL, TCG_REG_ZERO, offset);
-}
-
 static void tcg_out_call_int(TCGContext *s, const tcg_insn_unit *arg, bool tail)
 {
     TCGReg link = tail ? TCG_REG_ZERO : TCG_REG_RA;
     ptrdiff_t offset = tcg_pcrel_diff(s, arg);
     int ret;
 
-    if (offset == sextreg(offset, 1, 20) << 1) {
+    tcg_debug_assert((offset & 1) == 0);
+    if (offset == sextreg(offset, 0, 20)) {
         /* short jump: -2097150 to 2097152 */
         tcg_out_opc_jump(s, OPC_JAL, link, offset);
-    } else if (TCG_TARGET_REG_BITS == 32 ||
-        offset == sextreg(offset, 1, 31) << 1) {
+    } else if (TCG_TARGET_REG_BITS == 32 || offset == (int32_t)offset) {
         /* long jump: -2147483646 to 2147483648 */
         tcg_out_opc_upper(s, OPC_AUIPC, TCG_REG_TMP0, 0);
         tcg_out_opc_imm(s, OPC_JALR, link, TCG_REG_TMP0, 0);
-        ret = reloc_call(s->code_ptr - 2, arg);\
+        ret = reloc_call(s->code_ptr - 2, arg);
         tcg_debug_assert(ret == true);
     } else if (TCG_TARGET_REG_BITS == 64) {
         /* far jump: 64-bit */
@@ -962,6 +957,13 @@  QEMU_BUILD_BUG_ON(TCG_TARGET_REG_BITS < TARGET_LONG_BITS);
 QEMU_BUILD_BUG_ON(TLB_MASK_TABLE_OFS(0) > 0);
 QEMU_BUILD_BUG_ON(TLB_MASK_TABLE_OFS(0) < -(1 << 11));
 
+static void tcg_out_goto(TCGContext *s, tcg_insn_unit *target)
+{
+    tcg_out_opc_jump(s, OPC_JAL, TCG_REG_ZERO, 0);
+    bool ok = reloc_jimm20(s->code_ptr - 1, target);
+    tcg_debug_assert(ok);
+}
+
 static void tcg_out_tlb_load(TCGContext *s, TCGReg addrl,
                              TCGReg addrh, TCGMemOpIdx oi,
                              tcg_insn_unit **label_ptr, bool is_load)