riscv/ftrace: Add dynamic function tracer support
We now have dynamic ftrace with the following added items: * ftrace_make_call, ftrace_make_nop (in kernel/ftrace.c) The two functions turn each recorded call site of filtered functions into a call to ftrace_caller or nops * ftracce_update_ftrace_func (in kernel/ftrace.c) turns the nops at ftrace_call into a call to a generic entry for function tracers. * ftrace_caller (in kernel/mcount-dyn.S) The entry where each _mcount call sites calls to once they are filtered to be traced. Also, this patch fixes the semantic problems in mcount.S, which will be treated as only a reference implementation once we have the dynamic ftrace. Cc: Greentime Hu <greentime@andestech.com> Signed-off-by: Alan Kao <alankao@andestech.com> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
This commit is contained in:
Alan Kao
Palmer Dabbelt
parent
a1d2a6b4ce
commit
c15ac4fd60
@ -115,6 +115,7 @@ config ARCH_RV64I
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select HAVE_FUNCTION_TRACER
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select HAVE_FUNCTION_GRAPH_TRACER
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select HAVE_FTRACE_MCOUNT_RECORD
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select HAVE_DYNAMIC_FTRACE
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endchoice
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@ -8,3 +8,57 @@
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#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && defined(CONFIG_FRAME_POINTER)
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#define HAVE_FUNCTION_GRAPH_FP_TEST
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#endif
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#ifndef __ASSEMBLY__
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void _mcount(void);
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static inline unsigned long ftrace_call_adjust(unsigned long addr)
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{
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return addr;
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}
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struct dyn_arch_ftrace {
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};
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#endif
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#ifdef CONFIG_DYNAMIC_FTRACE
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/*
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* A general call in RISC-V is a pair of insts:
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* 1) auipc: setting high-20 pc-related bits to ra register
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* 2) jalr: setting low-12 offset to ra, jump to ra, and set ra to
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* return address (original pc + 4)
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*
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* Dynamic ftrace generates probes to call sites, so we must deal with
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* both auipc and jalr at the same time.
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*/
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#define MCOUNT_ADDR ((unsigned long)_mcount)
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#define JALR_SIGN_MASK (0x00000800)
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#define JALR_OFFSET_MASK (0x00000fff)
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#define AUIPC_OFFSET_MASK (0xfffff000)
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#define AUIPC_PAD (0x00001000)
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#define JALR_SHIFT 20
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#define JALR_BASIC (0x000080e7)
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#define AUIPC_BASIC (0x00000097)
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#define NOP4 (0x00000013)
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#define make_call(caller, callee, call) \
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do { \
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call[0] = to_auipc_insn((unsigned int)((unsigned long)callee - \
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(unsigned long)caller)); \
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call[1] = to_jalr_insn((unsigned int)((unsigned long)callee - \
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(unsigned long)caller)); \
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} while (0)
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#define to_jalr_insn(offset) \
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(((offset & JALR_OFFSET_MASK) << JALR_SHIFT) | JALR_BASIC)
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#define to_auipc_insn(offset) \
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((offset & JALR_SIGN_MASK) ? \
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(((offset & AUIPC_OFFSET_MASK) + AUIPC_PAD) | AUIPC_BASIC) : \
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((offset & AUIPC_OFFSET_MASK) | AUIPC_BASIC))
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/*
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* Let auipc+jalr be the basic *mcount unit*, so we make it 8 bytes here.
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*/
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#define MCOUNT_INSN_SIZE 8
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#endif
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@ -34,7 +34,8 @@ CFLAGS_setup.o := -mcmodel=medany
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obj-$(CONFIG_SMP) += smpboot.o
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obj-$(CONFIG_SMP) += smp.o
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obj-$(CONFIG_MODULES) += module.o
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obj-$(CONFIG_FUNCTION_TRACER) += mcount.o
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obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
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obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o
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obj-$(CONFIG_DYNAMIC_FTRACE) += mcount-dyn.o
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clean:
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@ -6,9 +6,109 @@
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*/
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#include <linux/ftrace.h>
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#include <linux/uaccess.h>
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#include <asm/cacheflush.h>
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#ifdef CONFIG_DYNAMIC_FTRACE
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static int ftrace_check_current_call(unsigned long hook_pos,
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unsigned int *expected)
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{
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unsigned int replaced[2];
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unsigned int nops[2] = {NOP4, NOP4};
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/* we expect nops at the hook position */
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if (!expected)
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expected = nops;
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/*
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* Read the text we want to modify;
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* return must be -EFAULT on read error
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*/
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if (probe_kernel_read(replaced, (void *)hook_pos, MCOUNT_INSN_SIZE))
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return -EFAULT;
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/*
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* Make sure it is what we expect it to be;
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* return must be -EINVAL on failed comparison
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*/
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if (memcmp(expected, replaced, sizeof(replaced))) {
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pr_err("%p: expected (%08x %08x) but get (%08x %08x)",
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(void *)hook_pos, expected[0], expected[1], replaced[0],
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replaced[1]);
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return -EINVAL;
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}
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return 0;
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}
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static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
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bool enable)
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{
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unsigned int call[2];
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unsigned int nops[2] = {NOP4, NOP4};
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int ret = 0;
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make_call(hook_pos, target, call);
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/* replace the auipc-jalr pair at once */
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ret = probe_kernel_write((void *)hook_pos, enable ? call : nops,
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MCOUNT_INSN_SIZE);
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/* return must be -EPERM on write error */
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if (ret)
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return -EPERM;
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smp_mb();
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flush_icache_range((void *)hook_pos, (void *)hook_pos + MCOUNT_INSN_SIZE);
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return 0;
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}
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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int ret = ftrace_check_current_call(rec->ip, NULL);
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if (ret)
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return ret;
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return __ftrace_modify_call(rec->ip, addr, true);
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}
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int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
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unsigned long addr)
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{
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unsigned int call[2];
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int ret;
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make_call(rec->ip, addr, call);
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ret = ftrace_check_current_call(rec->ip, call);
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if (ret)
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return ret;
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return __ftrace_modify_call(rec->ip, addr, false);
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}
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int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
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(unsigned long)func, true);
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if (!ret) {
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ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
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(unsigned long)func, true);
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}
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return ret;
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}
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int __init ftrace_dyn_arch_init(void)
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{
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return 0;
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}
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#endif
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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/*
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* Most of this file is copied from arm64.
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* Most of this function is copied from arm64.
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*/
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void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
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unsigned long frame_pointer)
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@ -39,3 +139,4 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
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return;
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*parent = return_hooker;
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}
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#endif
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50
arch/riscv/kernel/mcount-dyn.S
Normal file
50
arch/riscv/kernel/mcount-dyn.S
Normal file
@ -0,0 +1,50 @@
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/* SPDX-License-Identifier: GPL-2.0 */
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/* Copyright (C) 2017 Andes Technology Corporation */
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#include <linux/init.h>
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#include <linux/linkage.h>
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#include <asm/asm.h>
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#include <asm/csr.h>
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#include <asm/unistd.h>
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#include <asm/thread_info.h>
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#include <asm/asm-offsets.h>
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#include <asm-generic/export.h>
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#include <asm/ftrace.h>
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.text
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.macro SAVE_ABI_STATE
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addi sp, sp, -16
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sd s0, 0(sp)
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sd ra, 8(sp)
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addi s0, sp, 16
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.endm
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.macro RESTORE_ABI_STATE
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ld ra, 8(sp)
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ld s0, 0(sp)
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addi sp, sp, 16
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.endm
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ENTRY(ftrace_caller)
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/*
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* a0: the address in the caller when calling ftrace_caller
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* a1: the caller's return address
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*/
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ld a1, -8(s0)
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addi a0, ra, -MCOUNT_INSN_SIZE
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SAVE_ABI_STATE
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ftrace_call:
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.global ftrace_call
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/*
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* For the dynamic ftrace to work, here we should reserve at least
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* 8 bytes for a functional auipc-jalr pair. The following call
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* serves this purpose.
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*
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* Calling ftrace_update_ftrace_func would overwrite the nops below.
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* Check ftrace_modify_all_code for details.
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*/
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call ftrace_stub
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RESTORE_ABI_STATE
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ret
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ENDPROC(ftrace_caller)
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@ -32,13 +32,13 @@
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addi s0, sp, 32
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.endm
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.macro STORE_ABI_STATE
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.macro RESTORE_ABI_STATE
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ld ra, 8(sp)
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ld s0, 0(sp)
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addi sp, sp, 16
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.endm
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.macro STORE_RET_ABI_STATE
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.macro RESTORE_RET_ABI_STATE
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ld ra, 24(sp)
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ld s0, 16(sp)
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ld a0, 8(sp)
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@ -46,6 +46,10 @@
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.endm
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ENTRY(ftrace_stub)
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#ifdef CONFIG_DYNAMIC_FTRACE
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.global _mcount
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.set _mcount, ftrace_stub
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#endif
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ret
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ENDPROC(ftrace_stub)
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@ -66,15 +70,15 @@ ENTRY(return_to_handler)
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#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
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mv a0, t6
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#endif
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la t0, ftrace_return_to_handler
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jalr t0
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call ftrace_return_to_handler
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mv a1, a0
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STORE_RET_ABI_STATE
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RESTORE_RET_ABI_STATE
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jalr a1
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ENDPROC(return_to_handler)
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EXPORT_SYMBOL(return_to_handler)
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#endif
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#ifndef CONFIG_DYNAMIC_FTRACE
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ENTRY(_mcount)
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la t4, ftrace_stub
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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@ -104,9 +108,8 @@ do_ftrace_graph_caller:
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ld a2, -16(s0)
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#endif
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SAVE_ABI_STATE
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la t0, prepare_ftrace_return
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jalr t0
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STORE_ABI_STATE
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call prepare_ftrace_return
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RESTORE_ABI_STATE
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ret
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#endif
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@ -120,7 +123,8 @@ do_trace:
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SAVE_ABI_STATE
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jalr t5
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STORE_ABI_STATE
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RESTORE_ABI_STATE
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ret
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ENDPROC(_mcount)
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EXPORT_SYMBOL(_mcount)
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#endif
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