blob: bff058317062e367941604f97f758b11986002cf [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Based on arch/arm64/kernel/ftrace.c
*
* Copyright (C) 2022 Loongson Technology Corporation Limited
*/
#include <linux/ftrace.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <asm/inst.h>
#include <asm/module.h>
static int ftrace_modify_code(unsigned long pc, u32 old, u32 new, bool validate)
{
u32 replaced;
if (validate) {
if (larch_insn_read((void *)pc, &replaced))
return -EFAULT;
if (replaced != old)
return -EINVAL;
}
if (larch_insn_patch_text((void *)pc, new))
return -EPERM;
return 0;
}
#ifdef CONFIG_MODULES
static bool reachable_by_bl(unsigned long addr, unsigned long pc)
{
long offset = (long)addr - (long)pc;
return offset >= -SZ_128M && offset < SZ_128M;
}
static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr)
{
struct plt_entry *plt = mod->arch.ftrace_trampolines;
if (addr == FTRACE_ADDR)
return &plt[FTRACE_PLT_IDX];
if (addr == FTRACE_REGS_ADDR &&
IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
return &plt[FTRACE_REGS_PLT_IDX];
return NULL;
}
/*
* Find the address the callsite must branch to in order to reach '*addr'.
*
* Due to the limited range of 'bl' instruction, modules may be placed too far
* away to branch directly and we must use a PLT.
*
* Returns true when '*addr' contains a reachable target address, or has been
* modified to contain a PLT address. Returns false otherwise.
*/
static bool ftrace_find_callable_addr(struct dyn_ftrace *rec, struct module *mod, unsigned long *addr)
{
unsigned long pc = rec->ip + LOONGARCH_INSN_SIZE;
struct plt_entry *plt;
/*
* If a custom trampoline is unreachable, rely on the ftrace_regs_caller
* trampoline which knows how to indirectly reach that trampoline through
* ops->direct_call.
*/
if (*addr != FTRACE_ADDR && *addr != FTRACE_REGS_ADDR && !reachable_by_bl(*addr, pc))
*addr = FTRACE_REGS_ADDR;
/*
* When the target is within range of the 'bl' instruction, use 'addr'
* as-is and branch to that directly.
*/
if (reachable_by_bl(*addr, pc))
return true;
/*
* '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.
*
* 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.
*/
if (!mod) {
preempt_disable();
mod = __module_text_address(pc);
preempt_enable();
}
if (WARN_ON(!mod))
return false;
plt = get_ftrace_plt(mod, *addr);
if (!plt) {
pr_err("ftrace: no module PLT for %ps\n", (void *)*addr);
return false;
}
*addr = (unsigned long)plt;
return true;
}
#else /* !CONFIG_MODULES */
static bool ftrace_find_callable_addr(struct dyn_ftrace *rec, struct module *mod, unsigned long *addr)
{
return true;
}
#endif
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)
{
u32 old, new;
unsigned long pc;
pc = rec->ip + LOONGARCH_INSN_SIZE;
if (!ftrace_find_callable_addr(rec, NULL, &addr))
return -EINVAL;
if (!ftrace_find_callable_addr(rec, NULL, &old_addr))
return -EINVAL;
new = larch_insn_gen_bl(pc, addr);
old = larch_insn_gen_bl(pc, old_addr);
return ftrace_modify_code(pc, old, new, true);
}
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
int ftrace_update_ftrace_func(ftrace_func_t func)
{
u32 new;
unsigned long pc;
pc = (unsigned long)&ftrace_call;
new = larch_insn_gen_bl(pc, (unsigned long)func);
return ftrace_modify_code(pc, 0, new, false);
}
/*
* The compiler has inserted 2 NOPs before the regular function prologue.
* T series registers are available and safe because of LoongArch's psABI.
*
* At runtime, we can replace nop with bl to enable ftrace call and replace bl
* with nop to disable ftrace call. The bl requires us to save the original RA
* value, so it saves RA at t0 here.
*
* Details are:
*
* | Compiled | Disabled | Enabled |
* +------------+------------------------+------------------------+
* | nop | move t0, ra | move t0, ra |
* | nop | nop | bl ftrace_caller |
* | func_body | func_body | func_body |
*
* The RA value will be recovered by ftrace_regs_entry, and restored into RA
* before returning to the regular function prologue. When a function is not
* being traced, the "move t0, ra" is not harmful.
*/
int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
{
u32 old, new;
unsigned long pc;
pc = rec->ip;
old = larch_insn_gen_nop();
new = larch_insn_gen_move(LOONGARCH_GPR_T0, LOONGARCH_GPR_RA);
return ftrace_modify_code(pc, old, new, true);
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
u32 old, new;
unsigned long pc;
pc = rec->ip + LOONGARCH_INSN_SIZE;
if (!ftrace_find_callable_addr(rec, NULL, &addr))
return -EINVAL;
old = larch_insn_gen_nop();
new = larch_insn_gen_bl(pc, addr);
return ftrace_modify_code(pc, old, new, true);
}
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
{
u32 old, new;
unsigned long pc;
pc = rec->ip + LOONGARCH_INSN_SIZE;
if (!ftrace_find_callable_addr(rec, NULL, &addr))
return -EINVAL;
new = larch_insn_gen_nop();
old = larch_insn_gen_bl(pc, addr);
return ftrace_modify_code(pc, old, new, true);
}
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;
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent)
{
unsigned long old;
unsigned long return_hooker = (unsigned long)&return_to_handler;
if (unlikely(atomic_read(&current->tracing_graph_pause)))
return;
old = *parent;
if (!function_graph_enter(old, self_addr, 0, parent))
*parent = return_hooker;
}
#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs)
{
struct pt_regs *regs = &fregs->regs;
unsigned long *parent = (unsigned long *)&regs->regs[1];
prepare_ftrace_return(ip, (unsigned long *)parent);
}
#else
static int ftrace_modify_graph_caller(bool enable)
{
u32 branch, nop;
unsigned long pc, func;
extern void ftrace_graph_call(void);
pc = (unsigned long)&ftrace_graph_call;
func = (unsigned long)&ftrace_graph_caller;
nop = larch_insn_gen_nop();
branch = larch_insn_gen_b(pc, func);
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_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
#ifdef CONFIG_KPROBES_ON_FTRACE
/* Ftrace callback handler for kprobes -- called under preepmt disabled */
void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
int bit;
struct pt_regs *regs;
struct kprobe *p;
struct kprobe_ctlblk *kcb;
if (unlikely(kprobe_ftrace_disabled))
return;
bit = ftrace_test_recursion_trylock(ip, parent_ip);
if (bit < 0)
return;
p = get_kprobe((kprobe_opcode_t *)ip);
if (unlikely(!p) || kprobe_disabled(p))
goto out;
regs = ftrace_get_regs(fregs);
if (!regs)
goto out;
kcb = get_kprobe_ctlblk();
if (kprobe_running()) {
kprobes_inc_nmissed_count(p);
} else {
unsigned long orig_ip = instruction_pointer(regs);
instruction_pointer_set(regs, ip);
__this_cpu_write(current_kprobe, p);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
if (!p->pre_handler || !p->pre_handler(p, regs)) {
/*
* Emulate singlestep (and also recover regs->csr_era)
* as if there is a nop
*/
instruction_pointer_set(regs, (unsigned long)p->addr + MCOUNT_INSN_SIZE);
if (unlikely(p->post_handler)) {
kcb->kprobe_status = KPROBE_HIT_SSDONE;
p->post_handler(p, regs, 0);
}
instruction_pointer_set(regs, orig_ip);
}
/*
* If pre_handler returns !0, it changes regs->csr_era. We have to
* skip emulating post_handler.
*/
__this_cpu_write(current_kprobe, NULL);
}
out:
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
int arch_prepare_kprobe_ftrace(struct kprobe *p)
{
p->ainsn.insn = NULL;
return 0;
}
#endif /* CONFIG_KPROBES_ON_FTRACE */