[PATCH v4 2/9] perf annotate: Track address registers via TSR_KIND_POINTER

[Zecheng Li <zecheng@google.com>]

Introduce TSR_KIND_POINTER to improve the data type profiler's ability
to track pointer-based memory accesses and address register variables.

TSR_KIND_POINTER represents that the location holds a pointer type to
the type in the type state. The semantics match the `breg` registers
that describe a memory location.

This change implements handling for this new kind in mov instructions
and in the check_matching_type() function. When a TSR_KIND_POINTER is
moved to the stack, the stack state size is set to the architecture's
pointer size.

Signed-off-by: Zecheng Li <zecheng@google.com>
---
 tools/perf/arch/x86/annotate/instructions.c | 15 ++++-
 tools/perf/util/annotate-data.c             | 63 ++++++++++++++++++---
 tools/perf/util/annotate-data.h             |  1 +
 3 files changed, 71 insertions(+), 8 deletions(-)

diff --git a/tools/perf/arch/x86/annotate/instructions.c b/tools/perf/arch/x86/annotate/instructions.c
index da98a4e3c52c..746443e04089 100644
--- a/tools/perf/arch/x86/annotate/instructions.c
+++ b/tools/perf/arch/x86/annotate/instructions.c
@@ -391,7 +391,7 @@ static void update_insn_state_x86(struct type_state *state,
 		tsr->ok = true;
 
 		/* To copy back the variable type later (hopefully) */
-		if (tsr->kind == TSR_KIND_TYPE)
+		if (tsr->kind == TSR_KIND_TYPE || tsr->kind == TSR_KIND_POINTER)
 			tsr->copied_from = src->reg1;
 
 		pr_debug_dtp("mov [%x] reg%d -> reg%d",
@@ -455,6 +455,19 @@ static void update_insn_state_x86(struct type_state *state,
 				     insn_offset, src->offset, sreg, dst->reg1);
 			pr_debug_type_name(&tsr->type, tsr->kind);
 		}
+		/* Handle dereference of TSR_KIND_POINTER registers */
+		else if (has_reg_type(state, sreg) && state->regs[sreg].ok &&
+			 state->regs[sreg].kind == TSR_KIND_POINTER &&
+			 die_get_member_type(&state->regs[sreg].type,
+					     src->offset, &type_die)) {
+			tsr->type = state->regs[sreg].type;
+			tsr->kind = TSR_KIND_TYPE;
+			tsr->ok = true;
+
+			pr_debug_dtp("mov [%x] addr %#x(reg%d) -> reg%d",
+				     insn_offset, src->offset, sreg, dst->reg1);
+			pr_debug_type_name(&tsr->type, tsr->kind);
+		}
 		/* Or check if it's a global variable */
 		else if (sreg == DWARF_REG_PC) {
 			struct map_symbol *ms = dloc->ms;
diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index 903027a6fb7d..48f3bf20070f 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -59,6 +59,10 @@ void pr_debug_type_name(Dwarf_Die *die, enum type_state_kind kind)
 		pr_info(" constant\n");
 		return;
 	case TSR_KIND_PERCPU_POINTER:
+		pr_info(" percpu pointer");
+		/* it also prints the type info */
+		break;
+	case TSR_KIND_POINTER:
 		pr_info(" pointer");
 		/* it also prints the type info */
 		break;
@@ -578,16 +582,25 @@ void set_stack_state(struct type_state_stack *stack, int offset, u8 kind,
 	int tag;
 	Dwarf_Word size;
 
-	if (dwarf_aggregate_size(type_die, &size) < 0)
+	if (kind == TSR_KIND_POINTER) {
+		/* TODO: arch-dependent pointer size */
+		size = sizeof(void *);
+	}
+	else if (dwarf_aggregate_size(type_die, &size) < 0)
 		size = 0;
 
-	tag = dwarf_tag(type_die);
-
 	stack->type = *type_die;
 	stack->size = size;
 	stack->offset = offset;
 	stack->kind = kind;
 
+	if (kind == TSR_KIND_POINTER) {
+		stack->compound = false;
+		return;
+	}
+
+	tag = dwarf_tag(type_die);
+
 	switch (tag) {
 	case DW_TAG_structure_type:
 	case DW_TAG_union_type:
@@ -898,13 +911,25 @@ static void update_var_state(struct type_state *state, struct data_loc_info *dlo
 
 			reg = &state->regs[var->reg];
 
-			/* For gp registers, skip the address registers for now */
-			if (var->is_reg_var_addr)
+			if (reg->ok && reg->kind == TSR_KIND_TYPE &&
+			   (!is_better_type(&reg->type, &mem_die) || var->is_reg_var_addr))
 				continue;
 
-			if (reg->ok && reg->kind == TSR_KIND_TYPE &&
-			    !is_better_type(&reg->type, &mem_die))
+			/* Handle address registers with TSR_KIND_POINTER */
+			if (var->is_reg_var_addr) {
+				if (reg->ok && reg->kind == TSR_KIND_POINTER &&
+				    !is_better_type(&reg->type, &mem_die))
+					continue;
+
+				reg->type = mem_die;
+				reg->kind = TSR_KIND_POINTER;
+				reg->ok = true;
+
+				pr_debug_dtp("var [%"PRIx64"] reg%d addr offset %x",
+					     insn_offset, var->reg, var->offset);
+				pr_debug_type_name(&mem_die, TSR_KIND_POINTER);
 				continue;
+			}
 
 			orig_type = reg->type;
 
@@ -1116,6 +1141,30 @@ static enum type_match_result check_matching_type(struct type_state *state,
 		return PERF_TMR_OK;
 	}
 
+	if (state->regs[reg].kind == TSR_KIND_POINTER) {
+		struct strbuf sb;
+
+		strbuf_init(&sb, 32);
+		die_get_typename_from_type(&state->regs[reg].type, &sb);
+		pr_debug_dtp("(ptr->%s)", sb.buf);
+		strbuf_release(&sb);
+
+		/*
+		 * Register holds a pointer (address) to the target variable.
+		 * The type is the type of the variable it points to.
+		 */
+		*type_die = state->regs[reg].type;
+
+		dloc->type_offset = dloc->op->offset;
+
+		/* Get the size of the actual type */
+		if (dwarf_aggregate_size(type_die, &size) < 0 ||
+		    (unsigned)dloc->type_offset >= size)
+			return PERF_TMR_BAD_OFFSET;
+
+		return PERF_TMR_OK;
+	}
+
 	if (state->regs[reg].kind == TSR_KIND_PERCPU_POINTER) {
 		pr_debug_dtp("percpu ptr");
 
diff --git a/tools/perf/util/annotate-data.h b/tools/perf/util/annotate-data.h
index df52a0a1f496..026783442056 100644
--- a/tools/perf/util/annotate-data.h
+++ b/tools/perf/util/annotate-data.h
@@ -35,6 +35,7 @@ enum type_state_kind {
 	TSR_KIND_PERCPU_BASE,
 	TSR_KIND_CONST,
 	TSR_KIND_PERCPU_POINTER,
+	TSR_KIND_POINTER,
 	TSR_KIND_CANARY,
 };
 
-- 
2.51.0.788.g6d19910ace-goog