Merge tag 'io_uring-5.7-2020-05-22' of git://git.kernel.dk/linux-block

[thirdparty/linux.git] / arch / x86 / kernel / ftrace.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Dynamic function tracing support.
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 *
 * Thanks goes to Ingo Molnar, for suggesting the idea.
 * Mathieu Desnoyers, for suggesting postponing the modifications.
 * Arjan van de Ven, for keeping me straight, and explaining to me
 * the dangers of modifying code on the run.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/memory.h>
#include <linux/vmalloc.h>

#include <trace/syscall.h>

#include <asm/set_memory.h>
#include <asm/kprobes.h>
#include <asm/ftrace.h>
#include <asm/nops.h>
#include <asm/text-patching.h>

#ifdef CONFIG_DYNAMIC_FTRACE

static int ftrace_poke_late = 0;

int ftrace_arch_code_modify_prepare(void)
    __acquires(&text_mutex)
{
        /*
         * Need to grab text_mutex to prevent a race from module loading
         * and live kernel patching from changing the text permissions while
         * ftrace has it set to "read/write".
         */
        mutex_lock(&text_mutex);
        ftrace_poke_late = 1;
        return 0;
}

int ftrace_arch_code_modify_post_process(void)
    __releases(&text_mutex)
{
        /*
         * ftrace_make_{call,nop}() may be called during
         * module load, and we need to finish the text_poke_queue()
         * that they do, here.
         */
        text_poke_finish();
        ftrace_poke_late = 0;
        mutex_unlock(&text_mutex);
        return 0;
}

static const char *ftrace_nop_replace(void)
{
        return ideal_nops[NOP_ATOMIC5];
}

static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
        return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
}

static int ftrace_verify_code(unsigned long ip, const char *old_code)
{
        char cur_code[MCOUNT_INSN_SIZE];

        /*
         * Note:
         * We are paranoid about modifying text, as if a bug was to happen, it
         * could cause us to read or write to someplace that could cause harm.
         * Carefully read and modify the code with probe_kernel_*(), and make
         * sure what we read is what we expected it to be before modifying it.
         */
        /* read the text we want to modify */
        if (probe_kernel_read(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) {
                WARN_ON(1);
                return -EFAULT;
        }

        /* Make sure it is what we expect it to be */
        if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) {
                WARN_ON(1);
                return -EINVAL;
        }

        return 0;
}

/*
 * Marked __ref because it calls text_poke_early() which is .init.text. That is
 * ok because that call will happen early, during boot, when .init sections are
 * still present.
 */
static int __ref
ftrace_modify_code_direct(unsigned long ip, const char *old_code,
                          const char *new_code)
{
        int ret = ftrace_verify_code(ip, old_code);
        if (ret)
                return ret;

        /* replace the text with the new text */
        if (ftrace_poke_late)
                text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
        else
                text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
        return 0;
}

int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
{
        unsigned long ip = rec->ip;
        const char *new, *old;

        old = ftrace_call_replace(ip, addr);
        new = ftrace_nop_replace();

        /*
         * On boot up, and when modules are loaded, the MCOUNT_ADDR
         * is converted to a nop, and will never become MCOUNT_ADDR
         * again. This code is either running before SMP (on boot up)
         * or before the code will ever be executed (module load).
         * We do not want to use the breakpoint version in this case,
         * just modify the code directly.
         */
        if (addr == MCOUNT_ADDR)
                return ftrace_modify_code_direct(ip, old, new);

        /*
         * x86 overrides ftrace_replace_code -- this function will never be used
         * in this case.
         */
        WARN_ONCE(1, "invalid use of ftrace_make_nop");
        return -EINVAL;
}

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
        unsigned long ip = rec->ip;
        const char *new, *old;

        old = ftrace_nop_replace();
        new = ftrace_call_replace(ip, addr);

        /* Should only be called when module is loaded */
        return ftrace_modify_code_direct(rec->ip, old, new);
}

/*
 * Should never be called:
 *  As it is only called by __ftrace_replace_code() which is called by
 *  ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
 *  which is called to turn mcount into nops or nops into function calls
 *  but not to convert a function from not using regs to one that uses
 *  regs, which ftrace_modify_call() is for.
 */
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
                                 unsigned long addr)
{
        WARN_ON(1);
        return -EINVAL;
}

int ftrace_update_ftrace_func(ftrace_func_t func)
{
        unsigned long ip;
        const char *new;

        ip = (unsigned long)(&ftrace_call);
        new = ftrace_call_replace(ip, (unsigned long)func);
        text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

        ip = (unsigned long)(&ftrace_regs_call);
        new = ftrace_call_replace(ip, (unsigned long)func);
        text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);

        return 0;
}

void ftrace_replace_code(int enable)
{
        struct ftrace_rec_iter *iter;
        struct dyn_ftrace *rec;
        const char *new, *old;
        int ret;

        for_ftrace_rec_iter(iter) {
                rec = ftrace_rec_iter_record(iter);

                switch (ftrace_test_record(rec, enable)) {
                case FTRACE_UPDATE_IGNORE:
                default:
                        continue;

                case FTRACE_UPDATE_MAKE_CALL:
                        old = ftrace_nop_replace();
                        break;

                case FTRACE_UPDATE_MODIFY_CALL:
                case FTRACE_UPDATE_MAKE_NOP:
                        old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec));
                        break;
                }

                ret = ftrace_verify_code(rec->ip, old);
                if (ret) {
                        ftrace_bug(ret, rec);
                        return;
                }
        }

        for_ftrace_rec_iter(iter) {
                rec = ftrace_rec_iter_record(iter);

                switch (ftrace_test_record(rec, enable)) {
                case FTRACE_UPDATE_IGNORE:
                default:
                        continue;

                case FTRACE_UPDATE_MAKE_CALL:
                case FTRACE_UPDATE_MODIFY_CALL:
                        new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec));
                        break;

                case FTRACE_UPDATE_MAKE_NOP:
                        new = ftrace_nop_replace();
                        break;
                }

                text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL);
                ftrace_update_record(rec, enable);
        }
        text_poke_finish();
}

void arch_ftrace_update_code(int command)
{
        ftrace_modify_all_code(command);
}

int __init ftrace_dyn_arch_init(void)
{
        return 0;
}

/* Currently only x86_64 supports dynamic trampolines */
#ifdef CONFIG_X86_64

#ifdef CONFIG_MODULES
#include <linux/moduleloader.h>
/* Module allocation simplifies allocating memory for code */
static inline void *alloc_tramp(unsigned long size)
{
        return module_alloc(size);
}
static inline void tramp_free(void *tramp)
{
        module_memfree(tramp);
}
#else
/* Trampolines can only be created if modules are supported */
static inline void *alloc_tramp(unsigned long size)
{
        return NULL;
}
static inline void tramp_free(void *tramp) { }
#endif

/* Defined as markers to the end of the ftrace default trampolines */
extern void ftrace_regs_caller_end(void);
extern void ftrace_epilogue(void);
extern void ftrace_caller_op_ptr(void);
extern void ftrace_regs_caller_op_ptr(void);

/* movq function_trace_op(%rip), %rdx */
/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
#define OP_REF_SIZE     7

/*
 * The ftrace_ops is passed to the function callback. Since the
 * trampoline only services a single ftrace_ops, we can pass in
 * that ops directly.
 *
 * The ftrace_op_code_union is used to create a pointer to the
 * ftrace_ops that will be passed to the callback function.
 */
union ftrace_op_code_union {
        char code[OP_REF_SIZE];
        struct {
                char op[3];
                int offset;
        } __attribute__((packed));
};

#define RET_SIZE                1

static unsigned long
create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
{
        unsigned long start_offset;
        unsigned long end_offset;
        unsigned long op_offset;
        unsigned long call_offset;
        unsigned long offset;
        unsigned long npages;
        unsigned long size;
        unsigned long retq;
        unsigned long *ptr;
        void *trampoline;
        void *ip;
        /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
        unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
        union ftrace_op_code_union op_ptr;
        int ret;

        if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
                start_offset = (unsigned long)ftrace_regs_caller;
                end_offset = (unsigned long)ftrace_regs_caller_end;
                op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
                call_offset = (unsigned long)ftrace_regs_call;
        } else {
                start_offset = (unsigned long)ftrace_caller;
                end_offset = (unsigned long)ftrace_epilogue;
                op_offset = (unsigned long)ftrace_caller_op_ptr;
                call_offset = (unsigned long)ftrace_call;
        }

        size = end_offset - start_offset;

        /*
         * Allocate enough size to store the ftrace_caller code,
         * the iret , as well as the address of the ftrace_ops this
         * trampoline is used for.
         */
        trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
        if (!trampoline)
                return 0;

        *tramp_size = size + RET_SIZE + sizeof(void *);
        npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);

        /* Copy ftrace_caller onto the trampoline memory */
        ret = probe_kernel_read(trampoline, (void *)start_offset, size);
        if (WARN_ON(ret < 0))
                goto fail;

        ip = trampoline + size;

        /* The trampoline ends with ret(q) */
        retq = (unsigned long)ftrace_stub;
        ret = probe_kernel_read(ip, (void *)retq, RET_SIZE);
        if (WARN_ON(ret < 0))
                goto fail;

        /*
         * The address of the ftrace_ops that is used for this trampoline
         * is stored at the end of the trampoline. This will be used to
         * load the third parameter for the callback. Basically, that
         * location at the end of the trampoline takes the place of
         * the global function_trace_op variable.
         */

        ptr = (unsigned long *)(trampoline + size + RET_SIZE);
        *ptr = (unsigned long)ops;

        op_offset -= start_offset;
        memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);

        /* Are we pointing to the reference? */
        if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
                goto fail;

        /* Load the contents of ptr into the callback parameter */
        offset = (unsigned long)ptr;
        offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;

        op_ptr.offset = offset;

        /* put in the new offset to the ftrace_ops */
        memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);

        /* put in the call to the function */
        mutex_lock(&text_mutex);
        call_offset -= start_offset;
        memcpy(trampoline + call_offset,
               text_gen_insn(CALL_INSN_OPCODE,
                             trampoline + call_offset,
                             ftrace_ops_get_func(ops)), CALL_INSN_SIZE);
        mutex_unlock(&text_mutex);

        /* ALLOC_TRAMP flags lets us know we created it */
        ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;

        set_vm_flush_reset_perms(trampoline);

        if (likely(system_state != SYSTEM_BOOTING))
                set_memory_ro((unsigned long)trampoline, npages);
        set_memory_x((unsigned long)trampoline, npages);
        return (unsigned long)trampoline;
fail:
        tramp_free(trampoline);
        return 0;
}

void set_ftrace_ops_ro(void)
{
        struct ftrace_ops *ops;
        unsigned long start_offset;
        unsigned long end_offset;
        unsigned long npages;
        unsigned long size;

        do_for_each_ftrace_op(ops, ftrace_ops_list) {
                if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
                        continue;

                if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
                        start_offset = (unsigned long)ftrace_regs_caller;
                        end_offset = (unsigned long)ftrace_regs_caller_end;
                } else {
                        start_offset = (unsigned long)ftrace_caller;
                        end_offset = (unsigned long)ftrace_epilogue;
                }
                size = end_offset - start_offset;
                size = size + RET_SIZE + sizeof(void *);
                npages = DIV_ROUND_UP(size, PAGE_SIZE);
                set_memory_ro((unsigned long)ops->trampoline, npages);
        } while_for_each_ftrace_op(ops);
}

static unsigned long calc_trampoline_call_offset(bool save_regs)
{
        unsigned long start_offset;
        unsigned long call_offset;

        if (save_regs) {
                start_offset = (unsigned long)ftrace_regs_caller;
                call_offset = (unsigned long)ftrace_regs_call;
        } else {
                start_offset = (unsigned long)ftrace_caller;
                call_offset = (unsigned long)ftrace_call;
        }

        return call_offset - start_offset;
}

void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
{
        ftrace_func_t func;
        unsigned long offset;
        unsigned long ip;
        unsigned int size;
        const char *new;

        if (!ops->trampoline) {
                ops->trampoline = create_trampoline(ops, &size);
                if (!ops->trampoline)
                        return;
                ops->trampoline_size = size;
                return;
        }

        /*
         * The ftrace_ops caller may set up its own trampoline.
         * In such a case, this code must not modify it.
         */
        if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
                return;

        offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
        ip = ops->trampoline + offset;
        func = ftrace_ops_get_func(ops);

        mutex_lock(&text_mutex);
        /* Do a safe modify in case the trampoline is executing */
        new = ftrace_call_replace(ip, (unsigned long)func);
        text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
        mutex_unlock(&text_mutex);
}

/* Return the address of the function the trampoline calls */
static void *addr_from_call(void *ptr)
{
        union text_poke_insn call;
        int ret;

        ret = probe_kernel_read(&call, ptr, CALL_INSN_SIZE);
        if (WARN_ON_ONCE(ret < 0))
                return NULL;

        /* Make sure this is a call */
        if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) {
                pr_warn("Expected E8, got %x\n", call.opcode);
                return NULL;
        }

        return ptr + CALL_INSN_SIZE + call.disp;
}

void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
                           unsigned long frame_pointer);

/*
 * If the ops->trampoline was not allocated, then it probably
 * has a static trampoline func, or is the ftrace caller itself.
 */
static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
{
        unsigned long offset;
        bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
        void *ptr;

        if (ops && ops->trampoline) {
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
                /*
                 * We only know about function graph tracer setting as static
                 * trampoline.
                 */
                if (ops->trampoline == FTRACE_GRAPH_ADDR)
                        return (void *)prepare_ftrace_return;
#endif
                return NULL;
        }

        offset = calc_trampoline_call_offset(save_regs);

        if (save_regs)
                ptr = (void *)FTRACE_REGS_ADDR + offset;
        else
                ptr = (void *)FTRACE_ADDR + offset;

        return addr_from_call(ptr);
}

void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
{
        unsigned long offset;

        /* If we didn't allocate this trampoline, consider it static */
        if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
                return static_tramp_func(ops, rec);

        offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
        return addr_from_call((void *)ops->trampoline + offset);
}

void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
{
        if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
                return;

        tramp_free((void *)ops->trampoline);
        ops->trampoline = 0;
}

#endif /* CONFIG_X86_64 */
#endif /* CONFIG_DYNAMIC_FTRACE */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);

static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
{
        return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr);
}

static int ftrace_mod_jmp(unsigned long ip, void *func)
{
        const char *new;

        new = ftrace_jmp_replace(ip, (unsigned long)func);
        text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
        return 0;
}

int ftrace_enable_ftrace_graph_caller(void)
{
        unsigned long ip = (unsigned long)(&ftrace_graph_call);

        return ftrace_mod_jmp(ip, &ftrace_graph_caller);
}

int ftrace_disable_ftrace_graph_caller(void)
{
        unsigned long ip = (unsigned long)(&ftrace_graph_call);

        return ftrace_mod_jmp(ip, &ftrace_stub);
}

#endif /* !CONFIG_DYNAMIC_FTRACE */

/*
 * Hook the return address and push it in the stack of return addrs
 * in current thread info.
 */
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;
        int faulted;

        /*
         * When resuming from suspend-to-ram, this function can be indirectly
         * called from early CPU startup code while the CPU is in real mode,
         * which would fail miserably.  Make sure the stack pointer is a
         * virtual address.
         *
         * This check isn't as accurate as virt_addr_valid(), but it should be
         * good enough for this purpose, and it's fast.
         */
        if (unlikely((long)__builtin_frame_address(0) >= 0))
                return;

        if (unlikely(ftrace_graph_is_dead()))
                return;

        if (unlikely(atomic_read(&current->tracing_graph_pause)))
                return;

        /*
         * Protect against fault, even if it shouldn't
         * happen. This tool is too much intrusive to
         * ignore such a protection.
         */
        asm volatile(
                "1: " _ASM_MOV " (%[parent]), %[old]\n"
                "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
                "   movl $0, %[faulted]\n"
                "3:\n"

                ".section .fixup, \"ax\"\n"
                "4: movl $1, %[faulted]\n"
                "   jmp 3b\n"
                ".previous\n"

                _ASM_EXTABLE(1b, 4b)
                _ASM_EXTABLE(2b, 4b)

                : [old] "=&r" (old), [faulted] "=r" (faulted)
                : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
                : "memory"
        );

        if (unlikely(faulted)) {
                ftrace_graph_stop();
                WARN_ON(1);
                return;
        }

        if (function_graph_enter(old, self_addr, frame_pointer, parent))
                *parent = old;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */