Release 4.14 arch/mips/kernel/ftrace.c
// SPDX-License-Identifier: GPL-2.0
/*
* Code for replacing ftrace calls with jumps.
*
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
* Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
* Author: Wu Zhangjin <wuzhangjin@gmail.com>
*
* Thanks goes to Steven Rostedt for writing the original x86 version.
*/
#include <linux/uaccess.h>
#include <linux/init.h>
#include <linux/ftrace.h>
#include <linux/syscalls.h>
#include <asm/asm.h>
#include <asm/asm-offsets.h>
#include <asm/cacheflush.h>
#include <asm/syscall.h>
#include <asm/uasm.h>
#include <asm/unistd.h>
#include <asm-generic/sections.h>
#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
#define MCOUNT_OFFSET_INSNS 5
#else
#define MCOUNT_OFFSET_INSNS 4
#endif
#ifdef CONFIG_DYNAMIC_FTRACE
/* Arch override because MIPS doesn't need to run this from stop_machine() */
void arch_ftrace_update_code(int command)
{
ftrace_modify_all_code(command);
}
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#endif
#ifdef CONFIG_DYNAMIC_FTRACE
#define JAL 0x0c000000
/* jump & link: ip --> ra, jump to target */
#define ADDR_MASK 0x03ffffff
/* op_code|addr : 31...26|25 ....0 */
#define JUMP_RANGE_MASK ((1UL << 28) - 1)
#define INSN_NOP 0x00000000
/* nop */
#define INSN_JAL(addr) \
((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
static unsigned int insn_jal_ftrace_caller __read_mostly;
static unsigned int insn_la_mcount[2] __read_mostly;
static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
static inline void ftrace_dyn_arch_init_insns(void)
{
u32 *buf;
unsigned int v1;
/* la v1, _mcount */
v1 = 3;
buf = (u32 *)&insn_la_mcount[0];
UASM_i_LA(&buf, v1, MCOUNT_ADDR);
/* jal (ftrace_caller + 8), jump over the first two instruction */
buf = (u32 *)&insn_jal_ftrace_caller;
uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/* j ftrace_graph_caller */
buf = (u32 *)&insn_j_ftrace_graph_caller;
uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
#endif
}
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static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
{
int faulted;
mm_segment_t old_fs;
/* *(unsigned int *)ip = new_code; */
safe_store_code(new_code, ip, faulted);
if (unlikely(faulted))
return -EFAULT;
old_fs = get_fs();
set_fs(get_ds());
flush_icache_range(ip, ip + 8);
set_fs(old_fs);
return 0;
}
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#ifndef CONFIG_64BIT
static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
unsigned int new_code2)
{
int faulted;
mm_segment_t old_fs;
safe_store_code(new_code1, ip, faulted);
if (unlikely(faulted))
return -EFAULT;
ip += 4;
safe_store_code(new_code2, ip, faulted);
if (unlikely(faulted))
return -EFAULT;
ip -= 4;
old_fs = get_fs();
set_fs(get_ds());
flush_icache_range(ip, ip + 8);
set_fs(old_fs);
return 0;
}
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static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
unsigned int new_code2)
{
int faulted;
mm_segment_t old_fs;
ip += 4;
safe_store_code(new_code2, ip, faulted);
if (unlikely(faulted))
return -EFAULT;
ip -= 4;
safe_store_code(new_code1, ip, faulted);
if (unlikely(faulted))
return -EFAULT;
old_fs = get_fs();
set_fs(get_ds());
flush_icache_range(ip, ip + 8);
set_fs(old_fs);
return 0;
}
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#endif
/*
* The details about the calling site of mcount on MIPS
*
* 1. For kernel:
*
* move at, ra
* jal _mcount --> nop
* sub sp, sp, 8 --> nop (CONFIG_32BIT)
*
* 2. For modules:
*
* 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
*
* lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
* addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT)
* move at, ra
* move $12, ra_address
* jalr v1
* sub sp, sp, 8
* 1: offset = 5 instructions
* 2.2 For the Other situations
*
* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
* addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT)
* move at, ra
* jalr v1
* nop | move $12, ra_address | sub sp, sp, 8
* 1: offset = 4 instructions
*/
#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int new;
unsigned long ip = rec->ip;
/*
* If ip is in kernel space, no long call, otherwise, long call is
* needed.
*/
new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F;
#ifdef CONFIG_64BIT
return ftrace_modify_code(ip, new);
#else
/*
* On 32 bit MIPS platforms, gcc adds a stack adjust
* instruction in the delay slot after the branch to
* mcount and expects mcount to restore the sp on return.
* This is based on a legacy API and does nothing but
* waste instructions so it's being removed at runtime.
*/
return ftrace_modify_code_2(ip, new, INSN_NOP);
#endif
}
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int new;
unsigned long ip = rec->ip;
new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];
#ifdef CONFIG_64BIT
return ftrace_modify_code(ip, new);
#else
return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ?
INSN_NOP : insn_la_mcount[1]);
#endif
}
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#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned int new;
new = INSN_JAL((unsigned long)func);
return ftrace_modify_code(FTRACE_CALL_IP, new);
}
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int __init ftrace_dyn_arch_init(void)
{
/* Encode the instructions when booting */
ftrace_dyn_arch_init_insns();
/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
return 0;
}
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#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);
#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
int ftrace_enable_ftrace_graph_caller(void)
{
return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
insn_j_ftrace_graph_caller);
}
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int ftrace_disable_ftrace_graph_caller(void)
{
return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
}
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#endif /* CONFIG_DYNAMIC_FTRACE */
#ifndef KBUILD_MCOUNT_RA_ADDRESS
#define S_RA_SP (0xafbf << 16)
/* s{d,w} ra, offset(sp) */
#define S_R_SP (0xafb0 << 16)
/* s{d,w} R, offset(sp) */
#define OFFSET_MASK 0xffff
/* stack offset range: 0 ~ PT_SIZE */
unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
{
unsigned long sp, ip, tmp;
unsigned int code;
int faulted;
/*
* For module, move the ip from the return address after the
* instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
* kernel, move after the instruction "move ra, at"(offset is 16)
*/
ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24);
/*
* search the text until finding the non-store instruction or "s{d,w}
* ra, offset(sp)" instruction
*/
do {
/* get the code at "ip": code = *(unsigned int *)ip; */
safe_load_code(code, ip, faulted);
if (unlikely(faulted))
return 0;
/*
* If we hit the non-store instruction before finding where the
* ra is stored, then this is a leaf function and it does not
* store the ra on the stack
*/
if ((code & S_R_SP) != S_R_SP)
return parent_ra_addr;
/* Move to the next instruction */
ip -= 4;
} while ((code & S_RA_SP) != S_RA_SP);
sp = fp + (code & OFFSET_MASK);
/* tmp = *(unsigned long *)sp; */
safe_load_stack(tmp, sp, faulted);
if (unlikely(faulted))
return 0;
if (tmp == old_parent_ra)
return sp;
return 0;
}
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#endif /* !KBUILD_MCOUNT_RA_ADDRESS */
/*
* Hook the return address and push it in the stack of return addrs
* in current thread info.
*/
void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
unsigned long fp)
{
unsigned long old_parent_ra;
struct ftrace_graph_ent trace;
unsigned long return_hooker = (unsigned long)
&return_to_handler;
int faulted, insns;
if (unlikely(ftrace_graph_is_dead()))
return;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
/*
* "parent_ra_addr" is the stack address saved the return address of
* the caller of _mcount.
*
* if the gcc < 4.5, a leaf function does not save the return address
* in the stack address, so, we "emulate" one in _mcount's stack space,
* and hijack it directly, but for a non-leaf function, it save the
* return address to the its own stack space, we can not hijack it
* directly, but need to find the real stack address,
* ftrace_get_parent_addr() does it!
*
* if gcc>= 4.5, with the new -mmcount-ra-address option, for a
* non-leaf function, the location of the return address will be saved
* to $12 for us, and for a leaf function, only put a zero into $12. we
* do it in ftrace_graph_caller of mcount.S.
*/
/* old_parent_ra = *parent_ra_addr; */
safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
if (unlikely(faulted))
goto out;
#ifndef KBUILD_MCOUNT_RA_ADDRESS
parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
old_parent_ra, (unsigned long)parent_ra_addr, fp);
/*
* If fails when getting the stack address of the non-leaf function's
* ra, stop function graph tracer and return
*/
if (parent_ra_addr == 0)
goto out;
#endif
/* *parent_ra_addr = return_hooker; */
safe_store_stack(return_hooker, parent_ra_addr, faulted);
if (unlikely(faulted))
goto out;
if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp,
NULL) == -EBUSY) {
*parent_ra_addr = old_parent_ra;
return;
}
/*
* Get the recorded ip of the current mcount calling site in the
* __mcount_loc section, which will be used to filter the function
* entries configured through the tracing/set_graph_function interface.
*/
insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
current->curr_ret_stack--;
*parent_ra_addr = old_parent_ra;
}
return;
out:
ftrace_graph_stop();
WARN_ON(1);
}
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
#ifdef CONFIG_FTRACE_SYSCALLS
#ifdef CONFIG_32BIT
unsigned long __init arch_syscall_addr(int nr)
{
return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
}
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#endif
#ifdef CONFIG_64BIT
unsigned long __init arch_syscall_addr(int nr)
{
#ifdef CONFIG_MIPS32_N32
if (nr >= __NR_N32_Linux && nr <= __NR_N32_Linux + __NR_N32_Linux_syscalls)
return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
#endif
if (nr >= __NR_64_Linux && nr <= __NR_64_Linux + __NR_64_Linux_syscalls)
return (unsigned long)sys_call_table[nr - __NR_64_Linux];
#ifdef CONFIG_MIPS32_O32
if (nr >= __NR_O32_Linux && nr <= __NR_O32_Linux + __NR_O32_Linux_syscalls)
return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
#endif
return (unsigned long) &sys_ni_syscall;
}
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#endif
#endif /* CONFIG_FTRACE_SYSCALLS */
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