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 7C1161400E; Sat, 30 Aug 2025 07:13:35 +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=1756538015; cv=none; b=DZMbCu/MkOoENGoX9EQR2EE0s4GFeZ9foQpHN4GXaDxsbQdxlMM33Yupu/DFPiI5PXOr0MGQhYBtC0bVQTOn919M/f1juZXhoQnB1bMGnXYidHbLJAnHRGnReFIH0K+xJb+NC9iA+c60hFG+g3ELaOHCznkRmycT7cxVrtD2ldk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756538015; c=relaxed/simple; bh=pTw0tMyy59J/b3SybTuf9no95KkTnbFfcsUegOyPDYA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZfgLCWLLL61Fw8nGtMaGb4tmV+zpsRMZdmWdQz7ccf1Omi8dlOQbgKm9R1DWAhJ7T5WjgGjip9B6km3BunabnlMPOnEIq+Yw7iPQ179V8Rboe6lJE3AKLZFC4SLPtnwBngCa96eD0GfD3DVh+9/zgKY+a/fNwIYDVAmkvAYXC7g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F5uIg7iZ; 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="F5uIg7iZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9319DC4CEEB; Sat, 30 Aug 2025 07:13:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756538015; bh=pTw0tMyy59J/b3SybTuf9no95KkTnbFfcsUegOyPDYA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=F5uIg7iZugVADfnZZtDIdAmkEG2NEhexAMDPTgfXeAnazRjsIsDFfbQ5BiW24gE5v DFR/kB5b1UzwyMMST+BCnTVW9Frfe+XgXPvejmuu62CLVcIPF+hPZHt8h2wVS75Inv RuY3ETs7Fmc8ENGFIgQuLg6drCLYB746vka/R0WrFUEhiMAq+ewD72OEcKaeLmEpIU jiY7eFDwOVYgeiSCpb4rXiXzpH/4xYkUJCFKFiT6NmX+CRq5YsrM8a25dlwH4KzOxo 85lqwQTIlUK3hzHLSbbjykV7LjftY5P9Yru2GEmR8nB6UB13Ayh/50dPhLQB9rCOn6 YC4FdsKBj7vUQ== Date: Sat, 30 Aug 2025 00:13:33 -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 , Xu Liu , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 06/10] perf annotate: Track arithmetic instructions on pointers Message-ID: References: <20250825195737.225824-1-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: <20250825195737.225824-1-zecheng@google.com> On Mon, Aug 25, 2025 at 07:57:37PM +0000, Zecheng Li wrote: > Track the arithmetic operations on registers with pointer types. We > handle only add, sub and lea instructions. The original pointer > information 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 | 138 +++++++++++++++++++- > tools/perf/util/annotate-data.c | 14 +- > tools/perf/util/annotate-data.h | 6 + > 3 files changed, 149 insertions(+), 9 deletions(-) > > diff --git a/tools/perf/arch/x86/annotate/instructions.c b/tools/perf/arch/x86/annotate/instructions.c > index c6d403eae744..540b4d0a01af 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 +323,96 @@ static void update_insn_state_x86(struct type_state *state, > return; > } > > + if (!strncmp(dl->ins.name, "sub", 3)) { > + u64 imm_value = -1ULL; > + > + if (!has_reg_type(state, dst->reg1)) > + return; > + > + tsr = &state->regs[dst->reg1]; > + tsr->copied_from = -1; > + > + if (src->imm) > + imm_value = src->offset; > + else if (has_reg_type(state, src->reg1) && > + state->regs[src->reg1].kind == TSR_KIND_CONST) > + imm_value = state->regs[src->reg1].imm_value; > + > + 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("sub [%x] offset %#"PRIx64" to reg%d", > + insn_offset, imm_value, dst->reg1); > + pr_debug_type_name(&tsr->type, tsr->kind); > + } > + } > + > + if (!strncmp(dl->ins.name, "lea", 3)) { > + int sreg = src->reg1; > + struct type_state_reg src_tsr; > + > + 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; > + > + /* 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; I was thinking we can use TSR_KIND_POINTER here. Probably we need to distinguish it from the existing percpu base use case. Maybe you want to rename it. Then you don't need to find a pointer type in the DWARF. > + tsr->offset = 0; I think it can refer to a member in a struct. How about this? tsr->offset = state->offset - offset; Thanks, Namhyung > + tsr->ok = true; > + > + if (sreg == fbreg) { > + pr_debug_dtp("lea [%x] address of -%#x(stack) -> reg%d", > + insn_offset, -src->offset, dst->reg1); > + } else { > + pr_debug_dtp("lea [%x] address of %#x(reg%d) -> reg%d", > + insn_offset, src->offset, sreg, dst->reg1); > + } > + > + pr_debug_type_name(&tsr->type, tsr->kind); > + } > + /* Case 2: Based on a register holding a typed pointer */ > + else if (src_tsr.ok && src_tsr.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) == NULL) > + 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] address of %s%#x(reg%d) -> reg%d", > + insn_offset, src->offset < 0 ? "-" : "", > + abs(src->offset), sreg, dst->reg1); > + > + pr_debug_type_name(&tsr->type, tsr->kind); > + } > + return; > + } > + > if (strncmp(dl->ins.name, "mov", 3)) > return; > > @@ -345,6 +447,7 @@ 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 +464,7 @@ 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 +476,7 @@ 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 +493,7 @@ 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 +527,14 @@ 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 +554,10 @@ 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 +582,7 @@ 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 +614,7 @@ 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 +637,7 @@ 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 +660,7 @@ 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 +684,19 @@ 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) == NULL) > + return; > + } > > stack = find_stack_state(state, offset); > if (stack) { > @@ -583,10 +709,10 @@ 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 +722,11 @@ 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); > + if (tsr->offset != 0) > + pr_debug_dtp(" reg%d offset %#x ->", > + src->reg1, tsr->offset); > + > + 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 258157cc43c2..e067e91f2037 100644 > --- a/tools/perf/util/annotate-data.c > +++ b/tools/perf/util/annotate-data.c > @@ -892,7 +892,7 @@ 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; > > @@ -907,13 +907,17 @@ 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 offset %x", > + insn_offset, var->reg, var->offset); > pr_debug_type_name(&mem_die, TSR_KIND_TYPE); > > /* > @@ -1101,7 +1105,7 @@ 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..47a4c752b917 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; > -- > 2.51.0.261.g7ce5a0a67e-goog >