Messages in this thread | | | Subject | Re: [PATCH 2/3] LoongArch: Add prologue unwinder support | From | Youling Tang <> | Date | Fri, 29 Jul 2022 10:03:03 +0800 |
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On 07/28/2022 10:05 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 <zhangqing@loongson.cn> > > 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/<pid>/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..bd684cff4008 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 +131,29 @@ enum loongarch_gpr { > LOONGARCH_GPR_MAX > }; > > +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 && > + ip->reg2i12_format.immediate & (1 << 11); > +} > + > +static inline bool is_ra_save_ins(union loongarch_instruction *ip) > +{ > + /* st.d $ra, $sp, offset */ > + return ip->reg2i12_format.opcode == std_op && > + ip->reg2i12_format.rj == LOONGARCH_GPR_SP && > + ip->reg2i12_format.rd == LOONGARCH_GPR_RA; > +} > + > +static inline bool is_branch_insn(union loongarch_instruction insn) > +{ > + return insn.reg1i21_format.opcode >= beqz_op && > + insn.reg1i21_format.opcode <= bgeu_op; > +} > + > u32 larch_insn_gen_lu32id(enum loongarch_gpr rd, int imm); > u32 larch_insn_gen_lu52id(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm); > u32 larch_insn_gen_jirl(enum loongarch_gpr rd, enum loongarch_gpr rj, unsigned long pc, unsigned long dest); > diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h > index 243330b39d0d..09394e536ea9 100644 > --- a/arch/loongarch/include/asm/unwind.h > +++ b/arch/loongarch/include/asm/unwind.h > @@ -14,6 +14,10 @@ > struct unwind_state { > struct stack_info stack_info; > struct task_struct *task; > +#if defined(CONFIG_UNWINDER_PROLOGUE) > + unsigned long ra; > + bool enable; > +#endif > unsigned long sp, pc; > bool first; > bool error; > diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile > index c5fa4adb23b6..918600e7b30f 100644 > --- a/arch/loongarch/kernel/Makefile > +++ b/arch/loongarch/kernel/Makefile > @@ -23,5 +23,6 @@ obj-$(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..6539c9e98364 > --- /dev/null > +++ b/arch/loongarch/kernel/unwind_prologue.c > @@ -0,0 +1,174 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) 2022 Loongson Technology Corporation Limited > + */ > +#include <linux/kallsyms.h> > + > +#include <asm/inst.h> > +#include <asm/ptrace.h> > +#include <asm/unwind.h> > + > +unsigned long unwind_get_return_address(struct unwind_state *state) > +{ > + > + if (unwind_done(state)) > + return 0; This judgment can be removed, because unwind_done() has been judged before entering this function, and unwind_get_return_address will not be called if it is true.
> + > + 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; Because the immediate member in struct reg2i12_format is defined as an unsigned type, the value obtained by frame_ra here can only be a positive number.
> + break; > + } > + if (is_branch_insn(*ip)) > + break; > + ip++; > + } > + > + if (frame_ra < 0) { In addition to judging whether the initial value of frame_ra is negative, we also want to judge whether the previously assigned frame_ra is negative.
Save the ra value to the stack in the prologue, offset must be a positive number, so we can add another judgment to is_ra_save_ins, the code is as follows: +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 && + !(ip->reg2i12_format.immediate & (1 << 11)); +} > + 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; Can be removed as above.
Thanks, Youling > + > + 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; > + > + 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); >
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