From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DF1EE8F6E; Sun, 27 Jul 2025 00:32:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753576379; cv=none; b=pWFfELk6u+AHhtraUEYvnen5FWmTy8RSkLnX+MK6ufxTFqyt2qBgeEIyM1kYz1PFtZ8PX5TiZZh64xAeRhb+2W2zRKcI8szDfglE+pwRU/fpZbMkpjy1+1eHS6G08S4cqRFkSQ7IU6uFUBQF1NUhrjOQTQ/+dEJ1UCB40lRvIeI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753576379; c=relaxed/simple; bh=D3mfNsWwLzNw4RKH7gD+3bEZhoGiXBvaoS6jwOI8/h8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KBKzHmqX5HxGgnT0JvGW/T78v6PtF1GbmZa74cWiQwJiceq/MlKP6n70sJIG2XVXc0HmGub/RvfIEZxPSEbcrUYat/jErnSdc9OFNjkPoNWNFKpuVioQOPM+dNTIoWp8NbQ3bzKpPtW4F04jg55Paqd5LPl8jXKfp9inDshEngc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AS1EWWYv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AS1EWWYv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCC8CC4CEED; Sun, 27 Jul 2025 00:32:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753576378; bh=D3mfNsWwLzNw4RKH7gD+3bEZhoGiXBvaoS6jwOI8/h8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=AS1EWWYvy6yRud7e4XewHlVqWbqPAsE5VjS7uPvcnmlK0AthKeFwF7Ohpm2RFQGsN UZ7/EiKxW5kNRjBhxZhqRzZ83S7q1GWXJJibwwRpl80e3E/Emh9/g2vdHv5+fzd2a3 yHaGO6DL41iHffT5xDnDC7HbIqheJAOEtg7iYHf8iBVUeS4Wu97YWmgay17/3nMkIw Eu9AbJZqFEqLjZfhQFrxVhhYeUr662I8hB0I7mSnoyUkZqpGsB69cIM6aj4jSibB+2 c8lFky6HMHeQV6aO+QjDoSAbS7kQyC6HOURLtDu9WO9aOlIHfVdBVJm2J6Nol6CFt+ uLxlHB0rc/BpQ== Date: Sat, 26 Jul 2025 17:32:56 -0700 From: Namhyung Kim To: Zecheng Li Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , Masami Hiramatsu , Zecheng Li , Xu Liu , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 6/6] perf annotate: Track arithmetic instructions on pointers Message-ID: References: <20250725202809.1230085-1-zecheng@google.com> <20250725202809.1230085-7-zecheng@google.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250725202809.1230085-7-zecheng@google.com> On Fri, Jul 25, 2025 at 08:28:09PM +0000, Zecheng Li wrote: > Track the arithmetic operations on registers with pointer types. We > handle only add and lea instructions. The original pointer information I'm afraid of possible inaccuracy due to incompleteness. While I think 'add' is the common case, but it may have 'sub', 'mul', 'div' or other arith operations too. In general, I think it's better not to report rather then incorrect result. Maybe we can invalidate the state once it's used by any unsupported arith instruction? Thanks, Namhyung > needs to be preserved for getting outermost struct types. For example, > reg0 points to a struct cfs_rq, when we add 0x10 to reg0, it should > preserve the information of struct cfs_rq + 0x10 in the register instead > of a pointer type to the child field at 0x10. > > Details: > > 1. struct type_state_reg now includes an offset, indicating if the > register points to the start or an internal part of its associated > type. This offset is used in mem to reg and reg to stack mem > transfers, and also applied to the final type offset. > > 2. lea offset(%sp/%fp), reg is now treated as taking the address of a > stack variable. It worked fine in most cases, but an issue with this > approach is the pointer type may not exist. > > 3. lea offset(%base), reg is handled by moving the type from %base and > adding an offset, similar to an add operation followed by a mov reg > to reg. > > 4. Non-stack variables from DWARF with non-zero offsets in their > location expressions are now accepted with register offset tracking. > > Limitation: Offset tracking for register moved to the stack is not yet > implemented. Currently, moving an register with offset to the stack > resolves to the member type, which worked in some of the cases. Strictly > it should be a pointer to the immediate child member. Multi-register > addressing modes in LEA are not supported. > > Signed-off-by: Zecheng Li > --- > tools/perf/arch/x86/annotate/instructions.c | 109 +++++++++++++++++++- > tools/perf/util/annotate-data.c | 14 ++- > tools/perf/util/annotate-data.h | 6 ++ > 3 files changed, 120 insertions(+), 9 deletions(-) > > diff --git a/tools/perf/arch/x86/annotate/instructions.c b/tools/perf/arch/x86/annotate/instructions.c > index c6d403eae744..82fc0106a4de 100644 > --- a/tools/perf/arch/x86/annotate/instructions.c > +++ b/tools/perf/arch/x86/annotate/instructions.c > @@ -248,6 +248,7 @@ static void update_insn_state_x86(struct type_state *state, > tsr = &state->regs[state->ret_reg]; > tsr->type = type_die; > tsr->kind = TSR_KIND_TYPE; > + tsr->offset = 0; > tsr->ok = true; > > pr_debug_dtp("call [%x] return -> reg%d", > @@ -284,6 +285,7 @@ static void update_insn_state_x86(struct type_state *state, > !strcmp(var_name, "this_cpu_off") && > tsr->kind == TSR_KIND_CONST) { > tsr->kind = TSR_KIND_PERCPU_BASE; > + tsr->offset = 0; > tsr->ok = true; > imm_value = tsr->imm_value; > } > @@ -291,6 +293,15 @@ static void update_insn_state_x86(struct type_state *state, > else > return; > > + /* Ignore add to non-pointer types like int */ > + if (dwarf_tag(&tsr->type) == DW_TAG_pointer_type && > + src->reg1 != DWARF_REG_PC && tsr->kind == TSR_KIND_TYPE && !dst->mem_ref) { > + tsr->offset += imm_value; > + pr_debug_dtp("add [%x] offset %#"PRIx64" to reg%d", > + insn_offset, imm_value, dst->reg1); > + pr_debug_type_name(&tsr->type, tsr->kind); > + } > + > if (tsr->kind != TSR_KIND_PERCPU_BASE) > return; > > @@ -302,6 +313,7 @@ static void update_insn_state_x86(struct type_state *state, > */ > tsr->type = type_die; > tsr->kind = TSR_KIND_POINTER; > + tsr->offset = 0; > tsr->ok = true; > > pr_debug_dtp("add [%x] percpu %#"PRIx64" -> reg%d", > @@ -311,6 +323,68 @@ static void update_insn_state_x86(struct type_state *state, > return; > } > > + if (!strncmp(dl->ins.name, "lea", 3)) { > + struct type_state_reg *src_tsr; > + int sreg = src->reg1; > + > + if (!has_reg_type(state, sreg) || > + !has_reg_type(state, dst->reg1) || > + !src->mem_ref) > + return; > + > + src_tsr = &state->regs[sreg]; > + tsr = &state->regs[dst->reg1]; > + > + tsr->copied_from = -1; > + tsr->ok = false; > + > + /* Case 1: Based on stack pointer or frame pointer */ > + if (sreg == fbreg || sreg == state->stack_reg) { > + struct type_state_stack *stack; > + int offset = src->offset - fboff; > + > + stack = find_stack_state(state, offset); > + if (!stack) > + return; > + > + /* TODO: the pointer type may not exist */ > + /* Now the register becomes a pointer to the stack variable */ > + if (!die_find_pointer_to_type(cu_die, &stack->type, &type_die)) > + return; > + > + tsr->type = type_die; > + tsr->kind = TSR_KIND_TYPE; > + tsr->offset = 0; > + tsr->ok = true; > + > + pr_debug_dtp("lea [%x] -> reg%d points to %s + %#x on stack\n", > + insn_offset, dst->reg1, > + (sreg == fbreg) ? "fbreg" : "sp", offset); > + pr_debug_type_name(&tsr->type, tsr->kind); > + } > + /* Case 2: Based on a register holding a typed pointer */ > + else if (has_reg_type(state, sreg) && > + state->regs[sreg].ok && > + state->regs[sreg].kind == TSR_KIND_TYPE) { > + > + /* Check if the target type has a member at the new offset */ > + if (__die_get_real_type(&state->regs[sreg].type, &type_die) == NULL || > + !die_get_member_type(&type_die, > + src->offset + src_tsr->offset, &type_die)) > + return; > + > + tsr->type = src_tsr->type; > + tsr->kind = TSR_KIND_TYPE; > + tsr->offset = src->offset + src_tsr->offset; > + tsr->ok = true; > + > + pr_debug_dtp("lea [%x] -> reg%d points to reg%d + %#x\n", > + insn_offset, dst->reg1, sreg, src->offset); > + pr_debug_type_name(&tsr->type, tsr->kind); > + } > + return; > + } > + > if (strncmp(dl->ins.name, "mov", 3)) > return; > > @@ -345,6 +419,7 @@ static void update_insn_state_x86(struct type_state *state, > > if (var_addr == 40) { > tsr->kind = TSR_KIND_CANARY; > + tsr->offset = 0; > tsr->ok = true; > > pr_debug_dtp("mov [%x] stack canary -> reg%d\n", > @@ -361,6 +436,7 @@ static void update_insn_state_x86(struct type_state *state, > > tsr->type = type_die; > tsr->kind = TSR_KIND_TYPE; > + tsr->offset = 0; > tsr->ok = true; > > pr_debug_dtp("mov [%x] this-cpu addr=%#"PRIx64" -> reg%d", > @@ -372,6 +448,7 @@ static void update_insn_state_x86(struct type_state *state, > if (src->imm) { > tsr->kind = TSR_KIND_CONST; > tsr->imm_value = src->offset; > + tsr->offset = 0; > tsr->ok = true; > > pr_debug_dtp("mov [%x] imm=%#x -> reg%d\n", > @@ -388,6 +465,7 @@ static void update_insn_state_x86(struct type_state *state, > tsr->type = state->regs[src->reg1].type; > tsr->kind = state->regs[src->reg1].kind; > tsr->imm_value = state->regs[src->reg1].imm_value; > + tsr->offset = 0; > tsr->ok = true; > > /* To copy back the variable type later (hopefully) */ > @@ -421,12 +499,14 @@ static void update_insn_state_x86(struct type_state *state, > } else if (!stack->compound) { > tsr->type = stack->type; > tsr->kind = stack->kind; > + tsr->offset = 0; > tsr->ok = true; > } else if (die_get_member_type(&stack->type, > offset - stack->offset, > &type_die)) { > tsr->type = type_die; > tsr->kind = TSR_KIND_TYPE; > + tsr->offset = 0; > tsr->ok = true; > } else { > tsr->ok = false; > @@ -446,9 +526,10 @@ static void update_insn_state_x86(struct type_state *state, > else if (has_reg_type(state, sreg) && state->regs[sreg].ok && > state->regs[sreg].kind == TSR_KIND_TYPE && > die_deref_ptr_type(&state->regs[sreg].type, > - src->offset, &type_die)) { > + src->offset + state->regs[sreg].offset, &type_die)) { > tsr->type = type_die; > tsr->kind = TSR_KIND_TYPE; > + tsr->offset = 0; > tsr->ok = true; > > pr_debug_dtp("mov [%x] %#x(reg%d) -> reg%d", > @@ -473,6 +554,7 @@ static void update_insn_state_x86(struct type_state *state, > > tsr->type = type_die; > tsr->kind = TSR_KIND_TYPE; > + tsr->offset = 0; > tsr->ok = true; > > pr_debug_dtp("mov [%x] global addr=%"PRIx64" -> reg%d", > @@ -504,6 +586,7 @@ static void update_insn_state_x86(struct type_state *state, > die_get_member_type(&type_die, offset, &type_die)) { > tsr->type = type_die; > tsr->kind = TSR_KIND_TYPE; > + tsr->offset = 0; > tsr->ok = true; > > if (src->multi_regs) { > @@ -526,6 +609,7 @@ static void update_insn_state_x86(struct type_state *state, > src->offset, &type_die)) { > tsr->type = type_die; > tsr->kind = TSR_KIND_TYPE; > + tsr->offset = 0; > tsr->ok = true; > > pr_debug_dtp("mov [%x] pointer %#x(reg%d) -> reg%d", > @@ -548,6 +632,7 @@ static void update_insn_state_x86(struct type_state *state, > &var_name, &offset) && > !strcmp(var_name, "__per_cpu_offset")) { > tsr->kind = TSR_KIND_PERCPU_BASE; > + tsr->offset = 0; > tsr->ok = true; > > pr_debug_dtp("mov [%x] percpu base reg%d\n", > @@ -571,6 +656,22 @@ static void update_insn_state_x86(struct type_state *state, > int offset = dst->offset - fboff; > > tsr = &state->regs[src->reg1]; > + type_die = tsr->type; > + > + /* The register is derived from a pointer to the type */ > + if (tsr->offset != 0) { > + /* > + * deref gets the innermost field, but we actually want direct > + * child field and take a pointer to it. > + * However array type like unsigned long[] is already a pointer > + * and is the most common case for this kind of stack variable. > + */ > + if (die_deref_ptr_type(&tsr->type, tsr->offset, &type_die)) { > + pr_debug_dtp("find member: tsr->offset: %d", tsr->offset); > + pr_debug_type_name(&type_die, tsr->kind); > + } else > + return; > + } > > stack = find_stack_state(state, offset); > if (stack) { > @@ -583,10 +684,10 @@ static void update_insn_state_x86(struct type_state *state, > */ > if (!stack->compound) > set_stack_state(stack, offset, tsr->kind, > - &tsr->type); > + &type_die); > } else { > findnew_stack_state(state, offset, tsr->kind, > - &tsr->type); > + &type_die); > } > > if (dst->reg1 == fbreg) { > @@ -596,7 +697,7 @@ static void update_insn_state_x86(struct type_state *state, > pr_debug_dtp("mov [%x] reg%d -> %#x(reg%d)", > insn_offset, src->reg1, offset, dst->reg1); > } > - pr_debug_type_name(&tsr->type, tsr->kind); > + pr_debug_type_name(&type_die, tsr->kind); > } > /* > * Ignore other transfers since it'd set a value in a struct > diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c > index 1ef2edbc71d9..9cb215e499ef 100644 > --- a/tools/perf/util/annotate-data.c > +++ b/tools/perf/util/annotate-data.c > @@ -887,7 +887,7 @@ static void update_var_state(struct type_state *state, struct data_loc_info *dlo > insn_offset, -offset); > } > pr_debug_type_name(&mem_die, TSR_KIND_TYPE); > - } else if (has_reg_type(state, var->reg) && var->offset == 0) { > + } else if (has_reg_type(state, var->reg)) { > struct type_state_reg *reg; > Dwarf_Die orig_type; > > @@ -898,13 +898,17 @@ static void update_var_state(struct type_state *state, struct data_loc_info *dlo > continue; > > orig_type = reg->type; > - > + /* > + * var->offset + reg value is the beginning of the struct > + * reg->offset is the offset the reg points > + */ > + reg->offset = -var->offset; > reg->type = mem_die; > reg->kind = TSR_KIND_TYPE; > reg->ok = true; > > - pr_debug_dtp("var [%"PRIx64"] reg%d", > - insn_offset, var->reg); > + pr_debug_dtp("var [%"PRIx64"] reg%d at offset %d", > + insn_offset, var->reg, var->offset); > pr_debug_type_name(&mem_die, TSR_KIND_TYPE); > > /* > @@ -1092,7 +1096,7 @@ static enum type_match_result check_matching_type(struct type_state *state, > if (__die_get_real_type(&state->regs[reg].type, type_die) == NULL) > return PERF_TMR_NO_POINTER; > > - dloc->type_offset = dloc->op->offset; > + dloc->type_offset = dloc->op->offset + state->regs[reg].offset; > > if (dwarf_tag(type_die) == DW_TAG_typedef) > die_get_real_type(type_die, &sized_type); > diff --git a/tools/perf/util/annotate-data.h b/tools/perf/util/annotate-data.h > index 541fee1a5f0a..a6df0491eebf 100644 > --- a/tools/perf/util/annotate-data.h > +++ b/tools/perf/util/annotate-data.h > @@ -173,6 +173,12 @@ extern struct annotated_data_stat ann_data_stat; > struct type_state_reg { > Dwarf_Die type; > u32 imm_value; > + /* > + * The offset within the struct that the register points to. > + * A value of 0 means the register points to the beginning. > + * type_offset = op->offset + reg->offset > + */ > + s32 offset; > bool ok; > bool caller_saved; > u8 kind; > -- > 2.50.1.470.g6ba607880d-goog >