[DTrace-devel] [PATCH v2 16/17] cg: support casts of pointers to integers

[Nick Alcock]

When we cast a pointer to an integer, we want to scalarize it,
i.e. ensure that it is no longer a map_value, so that the user can
compare it freely to other integers.

Signed-off-by: Nick Alcock <nick.alcock at oracle.com>
---
 libdtrace/dt_cg.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
index 1f622d365464..c940ce7b8bc6 100644
--- a/libdtrace/dt_cg.c
+++ b/libdtrace/dt_cg.c
@@ -3009,6 +3009,8 @@ out:
  * a scalar type is being narrowed or changing signed-ness.  We first shift the
  * desired bits high (losing excess bits if narrowing) and then shift them down
  * using logical shift (unsigned result) or arithmetic shift (signed result).
+ *
+ * We also need to scalarize pointers if we are casting them to an integral type.
  */
 static void
 dt_cg_typecast(const dt_node_t *src, const dt_node_t *dst,
@@ -3035,6 +3037,18 @@ dt_cg_typecast(const dt_node_t *src, const dt_node_t *dst,
 		emit(dlp, BPF_MOV_REG(dst->dn_reg, src->dn_reg));
 		emit(dlp, BPF_ALU64_IMM(BPF_LSH, dst->dn_reg, n));
 		emit(dlp, BPF_ALU64_IMM((dst->dn_flags & DT_NF_SIGNED) ? BPF_ARSH : BPF_RSH, dst->dn_reg, n));
+	} else if (dt_node_is_scalar(dst) && dt_node_is_pointer(src)) {
+		int mst;
+
+		if ((mst = dt_regset_alloc(drp)) == -1)
+			longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
+
+		emit(dlp,  BPF_LOAD(BPF_DW, mst, BPF_REG_FP, DT_STK_DCTX));
+		emit(dlp,  BPF_LOAD(BPF_DW, mst, mst, DCTX_MST));
+		emit(dlp,  BPF_STORE(BPF_DW, mst, DMST_SCALARIZER, src->dn_reg));
+		emit(dlp,  BPF_LOAD(BPF_DW, dst->dn_reg, mst, DMST_SCALARIZER));
+
+		dt_regset_free(drp, mst);
 	}
 }
 
-- 
2.35.1.261.g8402f930ba.dirty