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98 lines
2.1 KiB
C
98 lines
2.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Code for replacing ftrace calls with jumps.
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*
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* Author: Huacai Chen <chenhuacai@loongson.cn>
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* Copyright (C) 2020 Loongson Technology Corporation Limited
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*
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* Thanks goes to Steven Rostedt for writing the original x86 version.
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*/
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#include <linux/uaccess.h>
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#include <linux/init.h>
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#include <linux/ftrace.h>
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#include <linux/syscalls.h>
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#include <asm/asm.h>
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#include <asm/asm-offsets.h>
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#include <asm/cacheflush.h>
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#include <asm/inst.h>
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#include <asm/loongarchregs.h>
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#include <asm/syscall.h>
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#include <asm/unistd.h>
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#include <asm-generic/sections.h>
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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/*
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* As `call _mcount` follows LoongArch psABI, ra-saved operation and
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* stack operation can be found before this insn.
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*/
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static inline bool is_ra_save_ins(union loongarch_instruction *ip)
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{
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/* st.d $ra, $sp, offset */
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return ip->reg2i12_format.opcode == std_op &&
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ip->reg2i12_format.rj == 3 &&
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ip->reg2i12_format.rd == 1;
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}
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static inline bool is_stack_open_ins(union loongarch_instruction *ip)
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{
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/* addi.d $sp, $sp, -imm */
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return ip->reg2i12_format.opcode == addid_op &&
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ip->reg2i12_format.rj == 3 &&
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ip->reg2i12_format.rd == 3 &&
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ip->reg2i12_format.simmediate < 0;
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}
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static int ftrace_get_parent_ra_addr(unsigned long insn_addr, int *ra_off)
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{
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union loongarch_instruction *insn;
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int limit = 32;
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insn = (union loongarch_instruction *)insn_addr;
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do {
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insn--;
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limit--;
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if (is_ra_save_ins(insn))
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*ra_off = insn->reg2i12_format.simmediate;
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} while (!is_stack_open_ins(insn) && limit);
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if (!limit)
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return -EINVAL;
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return 0;
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}
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void prepare_ftrace_return(unsigned long self_addr,
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unsigned long callsite_sp, unsigned long old)
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{
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int ra_off;
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unsigned long return_hooker = (unsigned long)&return_to_handler;
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if (unlikely(ftrace_graph_is_dead()))
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return;
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if (unlikely(atomic_read(¤t->tracing_graph_pause)))
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return;
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if (ftrace_get_parent_ra_addr(self_addr, &ra_off))
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goto out;
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if (!function_graph_enter(old, self_addr, 0, NULL)) {
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*(unsigned long *)(callsite_sp + ra_off) = return_hooker;
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}
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return;
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out:
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ftrace_graph_stop();
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WARN_ON(1);
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return;
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}
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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