[PATCH v6 14/26] perf annotate-data: Add arch_get_reg_offset helper
From: Tengda Wu
Date: Tue Sep 15 2026 - 21:33:34 EST
Add a helper to compute the effective offset from a base register
for instruction operands. Currently handles arm64 addressing modes
including post-indexed, single-register, SIB-style indexed with
shift/extension, and constant-offset register pairs.
Fallback to instruction's raw offset for other architectures.
Signed-off-by: Tengda Wu <wutengda@xxxxxxxxxxxxxxx>
---
tools/perf/util/annotate-data.c | 115 ++++++++++++++++++++++++++------
tools/perf/util/annotate-data.h | 4 +-
2 files changed, 98 insertions(+), 21 deletions(-)
diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index 9196f54b7297..d9f0bfd3f0a7 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -1122,6 +1122,74 @@ static void setup_stack_canary(struct data_loc_info *dloc)
}
}
+int arch_get_reg_offset(const struct arch *arch, struct annotated_op_loc *op_loc,
+ int breg, struct type_state *state, bool apply_index,
+ int *offset)
+{
+ if (arch__is_arm64(arch)) {
+ int reg2;
+
+ /* Post-indexed addressing: offset is 0 when not applying index */
+ if (op_loc->addr_mode == PERF_AAM_POST_INDEX && !apply_index) {
+ *offset = 0;
+ return 0;
+ }
+
+ /* Single-register addressing: return the stored offset directly */
+ if (!op_loc->multi_regs) {
+ *offset = op_loc->offset;
+ return 0;
+ }
+
+ /*
+ * SIB (Scale-Index-Base) style indexed addressing, e.g.:
+ * Array element load: ldr dst, [base, index, lsl #3]
+ * Array element load: ldr dst, [base, index, uxtw #3]
+ * Array address calc: add dst, base, index lsl #3
+ *
+ * The index reg only computes element offset without modifying
+ * the underlying data type; the dst type is inherited from base.
+ * Therefore, the base reg offset can be treated as 0.
+ */
+ if (op_loc->extend_type || op_loc->shift_type) {
+ /* Memory references use the breg as the address base. */
+ if (op_loc->mem_ref) {
+ *offset = 0;
+ return 0;
+ }
+ /*
+ * Otherwise, require breg to be a known pointer type to
+ * avoid treating integer operations as address calculations.
+ */
+ if (has_reg_type(state, breg) && state->regs[breg].ok &&
+ (state->regs[breg].kind == TSR_KIND_POINTER ||
+ (state->regs[breg].kind == TSR_KIND_TYPE &&
+ dwarf_tag(&state->regs[breg].type) == DW_TAG_pointer_type))) {
+ *offset = 0;
+ return 0;
+ }
+ return -1;
+ }
+
+ /*
+ * For register-based addressing without shift/extension,
+ * reg2 may be a constant offset. Use its value as the offset
+ * from the base register.
+ */
+ reg2 = op_loc->reg1 == breg ? op_loc->reg2 : op_loc->reg1;
+ if (has_reg_type(state, reg2) && state->regs[reg2].ok &&
+ state->regs[reg2].kind == TSR_KIND_CONST) {
+ *offset = (s64)state->regs[reg2].imm_value;
+ return 0;
+ }
+
+ return -1;
+ }
+
+ *offset = op_loc->offset;
+ return 0;
+}
+
/*
* It's at the target address, check if it has a matching type.
* It returns PERF_TMR_BAIL_OUT when it looks up per-cpu variables which
@@ -1136,18 +1204,25 @@ static enum type_match_result check_matching_type(struct type_state *state,
Dwarf_Word size;
u32 insn_offset = dl->al.offset;
int reg = dloc->op->reg1;
- int offset = dloc->op->offset;
- const char *offset_sign = "";
+ int offset;
+ const char *offset_sign;
bool retry = true;
- if (offset < 0) {
- offset = -offset;
- offset_sign = "-";
+again:
+ if (arch_get_reg_offset(dloc->arch, dloc->op, reg, state, false, &offset)) {
+ /*
+ * Fall back to the instruction's offset. This prevents the
+ * register type of the instruction from being completely lost.
+ * Compared to dropping this type inference entirely, providing
+ * a rough type hint is likely more useful.
+ */
+ offset = dloc->op->offset;
}
-again:
+ offset_sign = offset < 0 ? "-" : "";
+
pr_debug_dtp("chk [%x] reg%d offset=%s%#x ok=%d kind=%d ",
- insn_offset, reg, offset_sign, offset,
+ insn_offset, reg, offset_sign, abs(offset),
state->regs[reg].ok, state->regs[reg].kind);
if (!state->regs[reg].ok)
@@ -1170,7 +1245,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
*/
ptr_type = die_get_pointer_type(&state->regs[reg].type, &ptr_die);
if (!ptr_type) {
- if (dloc->op->offset < 0 && reg != state->stack_reg)
+ if (offset < 0 && reg != state->stack_reg)
goto check_kernel;
return PERF_TMR_NO_POINTER;
@@ -1180,7 +1255,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
if (__die_get_real_type(ptr_type, type_die) == NULL)
return PERF_TMR_NO_POINTER;
- dloc->type_offset = dloc->op->offset + state->regs[reg].offset;
+ dloc->type_offset = offset + state->regs[reg].offset;
if (dwarf_tag(type_die) == DW_TAG_typedef)
die_get_real_type(type_die, &sized_type);
@@ -1209,7 +1284,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
*/
*type_die = state->regs[reg].type;
- dloc->type_offset = dloc->op->offset + state->regs[reg].offset;
+ dloc->type_offset = offset + state->regs[reg].offset;
/* Get the size of the actual type */
if (dwarf_aggregate_size(type_die, &size) < 0 ||
@@ -1228,7 +1303,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
*/
*type_die = state->regs[reg].type;
- dloc->type_offset = dloc->op->offset;
+ dloc->type_offset = offset;
/* Get the size of the actual type */
if (dwarf_aggregate_size(type_die, &size) < 0 ||
@@ -1252,7 +1327,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
}
if (state->regs[reg].kind == TSR_KIND_PERCPU_BASE) {
- u64 var_addr = dloc->op->offset;
+ u64 var_addr = (s64) offset;
int var_offset;
pr_debug_dtp("percpu var");
@@ -1279,7 +1354,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
if (state->regs[reg].kind == TSR_KIND_CONST &&
dso__kernel(map__dso(dloc->ms->map))) {
- if (dloc->op->offset < 0 && reg != state->stack_reg && reg != dloc->fbreg)
+ if (offset < 0 && reg != state->stack_reg && reg != dloc->fbreg)
goto check_kernel;
}
check_non_register:
@@ -1288,7 +1363,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
pr_debug_dtp("%s", reg == dloc->fbreg ? "fbreg" : "stack");
- stack = find_stack_state(state, dloc->type_offset);
+ stack = find_stack_state(state, offset);
if (stack == NULL) {
if (retry) {
pr_debug_dtp(" : retry\n");
@@ -1311,7 +1386,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
*type_die = stack->type;
/* Update the type offset from the start of slot */
- dloc->type_offset -= stack->offset;
+ dloc->type_offset = offset - stack->offset;
return PERF_TMR_OK;
}
@@ -1329,7 +1404,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
if (reg != fbreg)
return PERF_TMR_NO_TYPE;
- stack = find_stack_state(state, dloc->type_offset - fboff);
+ stack = find_stack_state(state, offset - fboff);
if (stack == NULL) {
if (retry) {
pr_debug_dtp(" : retry\n");
@@ -1352,7 +1427,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
*type_die = stack->type;
/* Update the type offset from the start of slot */
- dloc->type_offset -= fboff + stack->offset;
+ dloc->type_offset = offset - fboff - stack->offset;
return PERF_TMR_OK;
}
@@ -1366,7 +1441,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
arch__is_x86(dloc->arch)) {
pr_debug_dtp("this-cpu var");
- addr = dloc->op->offset;
+ addr = (s64) offset;
if (get_global_var_type(cu_die, dloc, dloc->ip, addr,
&offset, type_die)) {
@@ -1377,8 +1452,8 @@ static enum type_match_result check_matching_type(struct type_state *state,
}
/* Access to global variable like "-0x7dcf0500(,%rdx,8)" */
- if (dloc->op->offset < 0 && reg != state->stack_reg) {
- addr = (s64) dloc->op->offset;
+ if (offset < 0 && reg != state->stack_reg) {
+ addr = (s64) offset;
if (get_global_var_type(cu_die, dloc, dloc->ip, addr,
&offset, type_die)) {
diff --git a/tools/perf/util/annotate-data.h b/tools/perf/util/annotate-data.h
index 2af70e3cf73f..68e3feda2eda 100644
--- a/tools/perf/util/annotate-data.h
+++ b/tools/perf/util/annotate-data.h
@@ -265,7 +265,9 @@ bool get_global_var_type(Dwarf_Die *cu_die, struct data_loc_info *dloc,
bool get_global_var_info(struct data_loc_info *dloc, u64 addr,
const char **var_name, int *var_offset);
void pr_debug_type_name(Dwarf_Die *die, enum type_state_kind kind);
-
+int arch_get_reg_offset(const struct arch *arch, struct annotated_op_loc *op_loc,
+ int breg, struct type_state *state, bool apply_index,
+ int *offset);
#else /* HAVE_LIBDW_SUPPORT */
static inline struct annotated_data_type *
--
2.34.1