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perf annotate: Track address registers via TSR_KIND_POINTER

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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>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Zecheng Li 2025-10-13 18:15:59 +00:00 committed by Namhyung Kim
parent 068b6a4524
commit 24a30ce9b1
3 changed files with 71 additions and 8 deletions
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15
tools/perf/arch/x86/annotate/instructions.c
View File

@ -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;

63
tools/perf/util/annotate-data.c
View File

@ -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");

1
tools/perf/util/annotate-data.h
View File

@ -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,
};