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 43B787F for ; Mon, 1 Aug 2022 15:26:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBB49C43140 for ; Mon, 1 Aug 2022 15:26:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1659367594; bh=i8d0cLuEiZPD1LgL6qi1TtC9pXQQ3GBsTnxaZNuRmpE=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=hwTcJuIEWe8YEU8nWQ5I9muExZQsPs2skoJMbQhlVPlOAjD8KJCVspGCewKkcGHB1 u4SFNJQv8Hr6IG3OqffGCxDDyVT5tQ9EP+e6c1ynO8sY/SJn392Op6a74rdBqxU+T8 9cLYk9mGEh0v0li2NMENwqluixqpf8nzFSHu1OZNQfHaEscarAvR6C4I5r/asTERur DLCHcK1lmixFfJvXTwILCAtDQL/5CkaI4YnOlVHsffaXxFCvJWtX/dZ6/ib2Bh2+y6 Y2Kdijj2qP3gajfY7UscAdk+nssV90lk4R1NqOhTNo4sS7q6ZV2CAULFhvFcFhuuPr HnpTsTt+e8rrg== Received: by mail-vs1-f53.google.com with SMTP id l68so11639211vsc.0 for ; Mon, 01 Aug 2022 08:26:33 -0700 (PDT) X-Gm-Message-State: ACgBeo2wQdEjkf0t9snrEjZwIuZDsY12jU39hob5s5xB8eXI0Q3OvURc dWFFHJompR8sFwe0FBo70GF08d2VDCaVD7UP4Vc= X-Google-Smtp-Source: AA6agR5LK8hmJvnG86lpB9eL+JiW99/ERVz2wrNc3SpzzioCMvJbOuR7XYI3VJnOjIHM0Zew0MR6jfNo7bHS/iL6s4k= X-Received: by 2002:a05:6102:390d:b0:387:78b9:bf9c with SMTP id e13-20020a056102390d00b0038778b9bf9cmr334986vsu.43.1659367592849; Mon, 01 Aug 2022 08:26:32 -0700 (PDT) Precedence: bulk X-Mailing-List: loongarch@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20220801121726.9681-1-zhangqing@loongson.cn> <20220801121726.9681-3-zhangqing@loongson.cn> In-Reply-To: <20220801121726.9681-3-zhangqing@loongson.cn> From: Huacai Chen Date: Mon, 1 Aug 2022 23:26:03 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/4] LoongArch: Add prologue unwinder support To: Qing Zhang Cc: WANG Xuerui , loongarch@lists.linux.dev, LKML , Jiaxun Yang , Jinyang He Content-Type: text/plain; charset="UTF-8" Hi, Qing, On Mon, Aug 1, 2022 at 8:17 PM Qing Zhang wrote: > > It unwind the stack frame based on prologue code analyze. > CONFIG_KALLSYMS is needed, at least the address and length > of each function. > > Three stages when we do unwind, > (1)unwind_start(), the prapare of unwinding, fill unwind_state. > (2)unwind_done(), judge whether the unwind process is finished or not. > (3)unwind_next_frame(), unwind the next frame. > > Dividing unwinder helps to add new unwinders in the future, eg: > unwind_frame, unwind_orc .etc > > Signed-off-by: Qing Zhang > --- > arch/loongarch/Kconfig.debug | 19 +++ > arch/loongarch/include/asm/inst.h | 52 +++++++ > arch/loongarch/include/asm/unwind.h | 8 ++ > arch/loongarch/kernel/Makefile | 1 + > arch/loongarch/kernel/traps.c | 5 + > arch/loongarch/kernel/unwind_prologue.c | 172 ++++++++++++++++++++++++ > 6 files changed, 257 insertions(+) > create mode 100644 arch/loongarch/kernel/unwind_prologue.c > > diff --git a/arch/loongarch/Kconfig.debug b/arch/loongarch/Kconfig.debug > index 68634d4fa27b..57cdbe0cfd98 100644 > --- a/arch/loongarch/Kconfig.debug > +++ b/arch/loongarch/Kconfig.debug > @@ -1,3 +1,11 @@ > +choice > + prompt "Choose kernel unwinder" > + default UNWINDER_PROLOGUE if KALLSYMS > + help > + This determines which method will be used for unwinding kernel stack > + traces for panics, oopses, bugs, warnings, perf, /proc//stack, > + lockdep, and more. > + > config UNWINDER_GUESS > bool "Guess unwinder" > help > @@ -7,3 +15,14 @@ config UNWINDER_GUESS > > While this option often produces false positives, it can still be > useful in many cases. > + > +config UNWINDER_PROLOGUE > + bool "Prologue unwinder" > + depends on KALLSYMS > + help > + This option enables the "prologue" unwinder for unwinding kernel stack > + traces. It unwind the stack frame based on prologue code analyze. Symbol > + information is needed, at least the address and length of each function. > + Some of the addresses it reports may be incorrect. > + > +endchoice > diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h > index 575d1bb66ffb..b876907ca65a 100644 > --- a/arch/loongarch/include/asm/inst.h > +++ b/arch/loongarch/include/asm/inst.h > @@ -23,12 +23,33 @@ enum reg1i20_op { > lu32id_op = 0x0b, > }; > > +enum reg1i21_op { > + beqz_op = 0x10, > + bnez_op = 0x11, > +}; > + > enum reg2i12_op { > + addiw_op = 0x0a, > + addid_op = 0x0b, > lu52id_op = 0x0c, > + ldb_op = 0xa0, > + ldh_op = 0xa1, > + ldw_op = 0xa2, > + ldd_op = 0xa3, > + stb_op = 0xa4, > + sth_op = 0xa5, > + stw_op = 0xa6, > + std_op = 0xa7, > }; > > enum reg2i16_op { > jirl_op = 0x13, > + beq_op = 0x16, > + bne_op = 0x17, > + blt_op = 0x18, > + bge_op = 0x19, > + bltu_op = 0x1a, > + bgeu_op = 0x1b, > }; > > struct reg0i26_format { > @@ -110,6 +131,37 @@ enum loongarch_gpr { > LOONGARCH_GPR_MAX > }; > > +#define is_imm12_negative(val) is_imm_negative(val, 12) > + > +static inline bool is_imm_negative(unsigned long val, unsigned int bit) > +{ > + return val & (1UL << (bit - 1)); > +} > + > +static inline bool is_stack_alloc_ins(union loongarch_instruction *ip) > +{ > + /* addi.d $sp, $sp, -imm */ > + return ip->reg2i12_format.opcode == addid_op && > + ip->reg2i12_format.rj == LOONGARCH_GPR_SP && > + ip->reg2i12_format.rd == LOONGARCH_GPR_SP && > + is_imm12_negative(ip->reg2i12_format.immediate); > +} > + > +static inline bool is_ra_save_ins(union loongarch_instruction *ip) > +{ > + /* st.d $ra, $sp, offset */ > + return ip->reg2i12_format.opcode == std_op && > + ip->reg2i12_format.rj == LOONGARCH_GPR_SP && > + ip->reg2i12_format.rd == LOONGARCH_GPR_RA && > + !is_imm12_negative(ip->reg2i12_format.immediate); > +} > + > +static inline bool is_branch_insn(union loongarch_instruction insn) > +{ > + return insn.reg1i21_format.opcode >= beqz_op && > + insn.reg1i21_format.opcode <= bgeu_op; > +} > + > u32 larch_insn_gen_lu32id(enum loongarch_gpr rd, int imm); > u32 larch_insn_gen_lu52id(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm); > u32 larch_insn_gen_jirl(enum loongarch_gpr rd, enum loongarch_gpr rj, unsigned long pc, unsigned long dest); > diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h > index 243330b39d0d..f9f73a26504e 100644 > --- a/arch/loongarch/include/asm/unwind.h > +++ b/arch/loongarch/include/asm/unwind.h > @@ -14,6 +14,14 @@ > struct unwind_state { > struct stack_info stack_info; > struct task_struct *task; > +#if defined(CONFIG_UNWINDER_PROLOGUE) > + unsigned long ra; > + bool enable; > + /* > + * Enable is the prologue analysis method > + * otherwise is the way to guess. > + */ > +#endif > unsigned long sp, pc; > bool first; > bool error; This data struct makes me very uncomfortable, especially "enable" and the #ifdef, maybe we can rework it like this? #define UNWINDER_GUESS 0 #define UNWINDER_PROLOGURE 1 struct unwind_state { char type; /* UNWINDER_xxx */ bool first, error; unsigned long sp, pc, ra; struct task_struct *task; struct stack_info stack_info; }; Huacai > diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile > index c5fa4adb23b6..918600e7b30f 100644 > --- a/arch/loongarch/kernel/Makefile > +++ b/arch/loongarch/kernel/Makefile > @@ -23,5 +23,6 @@ obj-$(CONFIG_SMP) += smp.o > obj-$(CONFIG_NUMA) += numa.o > > obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o > +obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o > > CPPFLAGS_vmlinux.lds := $(KBUILD_CFLAGS) > diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c > index ef2c3aeb1dab..3e904fa12d48 100644 > --- a/arch/loongarch/kernel/traps.c > +++ b/arch/loongarch/kernel/traps.c > @@ -73,6 +73,11 @@ static void show_backtrace(struct task_struct *task, const struct pt_regs *regs, > > unwind_start(&state, task, pregs); > > +#ifdef CONFIG_UNWINDER_PROLOGUE > + if (user_mode(regs)) > + state.enable = false; > +#endif > + > printk("%sCall Trace:", loglvl); > for (; !unwind_done(&state); unwind_next_frame(&state)) { > addr = unwind_get_return_address(&state); > diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c > new file mode 100644 > index 000000000000..072d1f7bf4ac > --- /dev/null > +++ b/arch/loongarch/kernel/unwind_prologue.c > @@ -0,0 +1,172 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) 2022 Loongson Technology Corporation Limited > + */ > +#include > + > +#include > +#include > +#include > + > +unsigned long unwind_get_return_address(struct unwind_state *state) > +{ > + > + if (unwind_done(state)) > + return 0; > + else if (state->enable) > + return state->pc; > + else if (state->first) > + return state->pc; > + > + return *(unsigned long *)(state->sp); > + > +} > +EXPORT_SYMBOL_GPL(unwind_get_return_address); > + > +static bool unwind_by_prologue(struct unwind_state *state) > +{ > + struct stack_info *info = &state->stack_info; > + union loongarch_instruction *ip, *ip_end; > + unsigned long frame_size = 0, frame_ra = -1; > + unsigned long size, offset, pc = state->pc; > + > + if (state->sp >= info->end || state->sp < info->begin) > + return false; > + > + if (!kallsyms_lookup_size_offset(pc, &size, &offset)) > + return false; > + > + ip = (union loongarch_instruction *)(pc - offset); > + ip_end = (union loongarch_instruction *)pc; > + > + while (ip < ip_end) { > + if (is_stack_alloc_ins(ip)) { > + frame_size = (1 << 12) - ip->reg2i12_format.immediate; > + ip++; > + break; > + } > + ip++; > + } > + > + if (!frame_size) { > + if (state->first) > + goto first; > + > + return false; > + } > + > + while (ip < ip_end) { > + if (is_ra_save_ins(ip)) { > + frame_ra = ip->reg2i12_format.immediate; > + break; > + } > + if (is_branch_insn(*ip)) > + break; > + ip++; > + } > + > + if (frame_ra < 0) { > + if (state->first) { > + state->sp = state->sp + frame_size; > + goto first; > + } > + return false; > + } > + > + if (state->first) > + state->first = false; > + > + state->pc = *(unsigned long *)(state->sp + frame_ra); > + state->sp = state->sp + frame_size; > + return !!__kernel_text_address(state->pc); > + > +first: > + state->first = false; > + if (state->pc == state->ra) > + return false; > + > + state->pc = state->ra; > + > + return !!__kernel_text_address(state->ra); > +} > + > +static bool unwind_by_guess(struct unwind_state *state) > +{ > + struct stack_info *info = &state->stack_info; > + unsigned long addr; > + > + for (state->sp += sizeof(unsigned long); > + state->sp < info->end; > + state->sp += sizeof(unsigned long)) { > + addr = *(unsigned long *)(state->sp); > + if (__kernel_text_address(addr)) > + return true; > + } > + > + return false; > +} > + > +bool unwind_next_frame(struct unwind_state *state) > +{ > + struct stack_info *info = &state->stack_info; > + struct pt_regs *regs; > + unsigned long pc; > + > + if (unwind_done(state)) > + return false; > + > + do { > + if (state->enable) { > + if (unwind_by_prologue(state)) > + return true; > + > + if (info->type == STACK_TYPE_IRQ && > + info->end == state->sp) { > + regs = (struct pt_regs *)info->next_sp; > + pc = regs->csr_era; > + if (user_mode(regs) || !__kernel_text_address(pc)) > + return false; > + > + state->pc = pc; > + state->sp = regs->regs[3]; > + state->ra = regs->regs[1]; > + state->first = true; > + get_stack_info(state->sp, state->task, info); > + > + return true; > + } > + } else { > + if (state->first) > + state->first = false; > + else if (unwind_by_guess(state)) > + return true; > + } > + > + state->sp = info->next_sp; > + > + } while (!get_stack_info(state->sp, state->task, info)); > + > + return false; > +} > +EXPORT_SYMBOL_GPL(unwind_next_frame); > + > +void unwind_start(struct unwind_state *state, struct task_struct *task, > + struct pt_regs *regs) > +{ > + memset(state, 0, sizeof(*state)); > + > + if (__kernel_text_address(regs->csr_era)) > + state->enable = true; > + > + state->task = task; > + state->pc = regs->csr_era; > + state->sp = regs->regs[3]; > + state->ra = regs->regs[1]; > + state->first = true; > + > + get_stack_info(state->sp, state->task, &state->stack_info); > + > + if (!unwind_done(state) && !__kernel_text_address(state->pc)) > + unwind_next_frame(state); > +} > +EXPORT_SYMBOL_GPL(unwind_start); > -- > 2.20.1 >