267 lines
7.1 KiB
C
267 lines
7.1 KiB
C
/*
|
|
* arch/arm64/kernel/ftrace.c
|
|
*
|
|
* Copyright (C) 2013 Linaro Limited
|
|
* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
|
|
#include <linux/ftrace.h>
|
|
#include <linux/module.h>
|
|
#include <linux/swab.h>
|
|
#include <linux/uaccess.h>
|
|
|
|
#include <asm/cacheflush.h>
|
|
#include <asm/debug-monitors.h>
|
|
#include <asm/ftrace.h>
|
|
#include <asm/insn.h>
|
|
|
|
#ifdef CONFIG_DYNAMIC_FTRACE
|
|
/*
|
|
* Replace a single instruction, which may be a branch or NOP.
|
|
* If @validate == true, a replaced instruction is checked against 'old'.
|
|
*/
|
|
static int ftrace_modify_code(unsigned long pc, u32 old, u32 new,
|
|
bool validate)
|
|
{
|
|
u32 replaced;
|
|
|
|
/*
|
|
* Note:
|
|
* We are paranoid about modifying text, as if a bug were to happen, it
|
|
* could cause us to read or write to someplace that could cause harm.
|
|
* Carefully read and modify the code with aarch64_insn_*() which uses
|
|
* probe_kernel_*(), and make sure what we read is what we expected it
|
|
* to be before modifying it.
|
|
*/
|
|
if (validate) {
|
|
if (aarch64_insn_read((void *)pc, &replaced))
|
|
return -EFAULT;
|
|
|
|
if (replaced != old)
|
|
return -EINVAL;
|
|
}
|
|
if (aarch64_insn_patch_text_nosync((void *)pc, new))
|
|
return -EPERM;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Replace tracer function in ftrace_caller()
|
|
*/
|
|
int ftrace_update_ftrace_func(ftrace_func_t func)
|
|
{
|
|
unsigned long pc;
|
|
u32 new;
|
|
|
|
pc = (unsigned long)&ftrace_call;
|
|
new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
|
|
AARCH64_INSN_BRANCH_LINK);
|
|
|
|
return ftrace_modify_code(pc, 0, new, false);
|
|
}
|
|
|
|
/*
|
|
* Turn on the call to ftrace_caller() in instrumented function
|
|
*/
|
|
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
|
|
{
|
|
unsigned long pc = rec->ip;
|
|
u32 old, new;
|
|
long offset = (long)pc - (long)addr;
|
|
|
|
if (offset < -SZ_128M || offset >= SZ_128M) {
|
|
#ifdef CONFIG_ARM64_MODULE_PLTS
|
|
struct plt_entry trampoline;
|
|
struct module *mod;
|
|
|
|
/*
|
|
* On kernels that support module PLTs, the offset between the
|
|
* branch instruction and its target may legally exceed the
|
|
* range of an ordinary relative 'bl' opcode. In this case, we
|
|
* need to branch via a trampoline in the module.
|
|
*
|
|
* NOTE: __module_text_address() must be called with preemption
|
|
* disabled, but we can rely on ftrace_lock to ensure that 'mod'
|
|
* retains its validity throughout the remainder of this code.
|
|
*/
|
|
preempt_disable();
|
|
mod = __module_text_address(pc);
|
|
preempt_enable();
|
|
|
|
if (WARN_ON(!mod))
|
|
return -EINVAL;
|
|
|
|
/*
|
|
* There is only one ftrace trampoline per module. For now,
|
|
* this is not a problem since on arm64, all dynamic ftrace
|
|
* invocations are routed via ftrace_caller(). This will need
|
|
* to be revisited if support for multiple ftrace entry points
|
|
* is added in the future, but for now, the pr_err() below
|
|
* deals with a theoretical issue only.
|
|
*/
|
|
trampoline = get_plt_entry(addr, mod->arch.ftrace_trampoline);
|
|
if (!plt_entries_equal(mod->arch.ftrace_trampoline,
|
|
&trampoline)) {
|
|
if (!plt_entries_equal(mod->arch.ftrace_trampoline,
|
|
&(struct plt_entry){})) {
|
|
pr_err("ftrace: far branches to multiple entry points unsupported inside a single module\n");
|
|
return -EINVAL;
|
|
}
|
|
|
|
/* point the trampoline to our ftrace entry point */
|
|
module_disable_ro(mod);
|
|
*mod->arch.ftrace_trampoline = trampoline;
|
|
module_enable_ro(mod, true);
|
|
|
|
/* update trampoline before patching in the branch */
|
|
smp_wmb();
|
|
}
|
|
addr = (unsigned long)(void *)mod->arch.ftrace_trampoline;
|
|
#else /* CONFIG_ARM64_MODULE_PLTS */
|
|
return -EINVAL;
|
|
#endif /* CONFIG_ARM64_MODULE_PLTS */
|
|
}
|
|
|
|
old = aarch64_insn_gen_nop();
|
|
new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
|
|
|
|
return ftrace_modify_code(pc, old, new, true);
|
|
}
|
|
|
|
/*
|
|
* Turn off the call to ftrace_caller() in instrumented function
|
|
*/
|
|
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
|
|
unsigned long addr)
|
|
{
|
|
unsigned long pc = rec->ip;
|
|
bool validate = true;
|
|
u32 old = 0, new;
|
|
long offset = (long)pc - (long)addr;
|
|
|
|
if (offset < -SZ_128M || offset >= SZ_128M) {
|
|
#ifdef CONFIG_ARM64_MODULE_PLTS
|
|
u32 replaced;
|
|
|
|
/*
|
|
* 'mod' is only set at module load time, but if we end up
|
|
* dealing with an out-of-range condition, we can assume it
|
|
* is due to a module being loaded far away from the kernel.
|
|
*/
|
|
if (!mod) {
|
|
preempt_disable();
|
|
mod = __module_text_address(pc);
|
|
preempt_enable();
|
|
|
|
if (WARN_ON(!mod))
|
|
return -EINVAL;
|
|
}
|
|
|
|
/*
|
|
* The instruction we are about to patch may be a branch and
|
|
* link instruction that was redirected via a PLT entry. In
|
|
* this case, the normal validation will fail, but we can at
|
|
* least check that we are dealing with a branch and link
|
|
* instruction that points into the right module.
|
|
*/
|
|
if (aarch64_insn_read((void *)pc, &replaced))
|
|
return -EFAULT;
|
|
|
|
if (!aarch64_insn_is_bl(replaced) ||
|
|
!within_module(pc + aarch64_get_branch_offset(replaced),
|
|
mod))
|
|
return -EINVAL;
|
|
|
|
validate = false;
|
|
#else /* CONFIG_ARM64_MODULE_PLTS */
|
|
return -EINVAL;
|
|
#endif /* CONFIG_ARM64_MODULE_PLTS */
|
|
} else {
|
|
old = aarch64_insn_gen_branch_imm(pc, addr,
|
|
AARCH64_INSN_BRANCH_LINK);
|
|
}
|
|
|
|
new = aarch64_insn_gen_nop();
|
|
|
|
return ftrace_modify_code(pc, old, new, validate);
|
|
}
|
|
|
|
void arch_ftrace_update_code(int command)
|
|
{
|
|
command |= FTRACE_MAY_SLEEP;
|
|
ftrace_modify_all_code(command);
|
|
}
|
|
|
|
int __init ftrace_dyn_arch_init(void)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_DYNAMIC_FTRACE */
|
|
|
|
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
|
|
/*
|
|
* function_graph tracer expects ftrace_return_to_handler() to be called
|
|
* on the way back to parent. For this purpose, this function is called
|
|
* in _mcount() or ftrace_caller() to replace return address (*parent) on
|
|
* the call stack to return_to_handler.
|
|
*
|
|
* Note that @frame_pointer is used only for sanity check later.
|
|
*/
|
|
void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
|
|
unsigned long frame_pointer)
|
|
{
|
|
unsigned long return_hooker = (unsigned long)&return_to_handler;
|
|
unsigned long old;
|
|
|
|
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
|
|
return;
|
|
|
|
/*
|
|
* Note:
|
|
* No protection against faulting at *parent, which may be seen
|
|
* on other archs. It's unlikely on AArch64.
|
|
*/
|
|
old = *parent;
|
|
|
|
if (!function_graph_enter(old, self_addr, frame_pointer, NULL))
|
|
*parent = return_hooker;
|
|
}
|
|
|
|
#ifdef CONFIG_DYNAMIC_FTRACE
|
|
/*
|
|
* Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
|
|
* depending on @enable.
|
|
*/
|
|
static int ftrace_modify_graph_caller(bool enable)
|
|
{
|
|
unsigned long pc = (unsigned long)&ftrace_graph_call;
|
|
u32 branch, nop;
|
|
|
|
branch = aarch64_insn_gen_branch_imm(pc,
|
|
(unsigned long)ftrace_graph_caller,
|
|
AARCH64_INSN_BRANCH_NOLINK);
|
|
nop = aarch64_insn_gen_nop();
|
|
|
|
if (enable)
|
|
return ftrace_modify_code(pc, nop, branch, true);
|
|
else
|
|
return ftrace_modify_code(pc, branch, nop, true);
|
|
}
|
|
|
|
int ftrace_enable_ftrace_graph_caller(void)
|
|
{
|
|
return ftrace_modify_graph_caller(true);
|
|
}
|
|
|
|
int ftrace_disable_ftrace_graph_caller(void)
|
|
{
|
|
return ftrace_modify_graph_caller(false);
|
|
}
|
|
#endif /* CONFIG_DYNAMIC_FTRACE */
|
|
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|