/*
 * Dynamic function tracing support.
 *
 * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
 * Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
 *
 * For licencing details, see COPYING.
 *
 * Defines low-level handling of mcount calls when the kernel
 * is compiled with the -pg flag. When using dynamic ftrace, the
 * mcount call-sites get patched with NOP till they are enabled.
 * All code mutation routines here are called under stop_machine().
 */

#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/stop_machine.h>

#include <asm/cacheflush.h>
#include <asm/opcodes.h>
#include <asm/ftrace.h>
#include <asm/insn.h>
#include <asm/set_memory.h>
#include <asm/stacktrace.h>
#include <asm/text-patching.h>

/*
 * The compiler emitted profiling hook consists of
 *
 *   PUSH    {LR}
 *   BL      __gnu_mcount_nc
 *
 * To turn this combined sequence into a NOP, we need to restore the value of
 * SP before the PUSH. Let's use an ADD rather than a POP into LR, as LR is not
 * modified anyway, and reloading LR from memory is highly likely to be less
 * efficient.
 */
#ifdef CONFIG_THUMB2_KERNEL
#define NOP             0xf10d0d04      /* add.w sp, sp, #4 */
#else
#define NOP             0xe28dd004      /* add   sp, sp, #4 */
#endif

#ifdef CONFIG_DYNAMIC_FTRACE

static int __ftrace_modify_code(void *data)
{
        int *command = data;

        ftrace_modify_all_code(*command);

        return 0;
}

void arch_ftrace_update_code(int command)
{
        stop_machine(__ftrace_modify_code, &command, NULL);
}

static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
{
        return NOP;
}

void ftrace_caller_from_init(void);
void ftrace_regs_caller_from_init(void);

static unsigned long __ref adjust_address(struct dyn_ftrace *rec,
                                          unsigned long addr)
{
        if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE) ||
            system_state >= SYSTEM_FREEING_INITMEM ||
            likely(!is_kernel_inittext(rec->ip)))
                return addr;
        if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) ||
            addr == (unsigned long)&ftrace_caller)
                return (unsigned long)&ftrace_caller_from_init;
        return (unsigned long)&ftrace_regs_caller_from_init;
}

void ftrace_arch_code_modify_prepare(void)
{
}

void ftrace_arch_code_modify_post_process(void)
{
        /* Make sure any TLB misses during machine stop are cleared. */
        flush_tlb_all();
}

static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
                                         bool warn)
{
        return arm_gen_branch_link(pc, addr, warn);
}

static int ftrace_modify_code(unsigned long pc, unsigned long old,
                              unsigned long new, bool validate)
{
        unsigned long replaced;

        if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
                old = __opcode_to_mem_thumb32(old);
        else
                old = __opcode_to_mem_arm(old);

        if (validate) {
                if (copy_from_kernel_nofault(&replaced, (void *)pc,
                                MCOUNT_INSN_SIZE))
                        return -EFAULT;

                if (replaced != old)
                        return -EINVAL;
        }

        __patch_text((void *)pc, new);

        return 0;
}

int ftrace_update_ftrace_func(ftrace_func_t func)
{
        unsigned long pc;
        unsigned long new;
        int ret;

        pc = (unsigned long)&ftrace_call;
        new = ftrace_call_replace(pc, (unsigned long)func, true);

        ret = ftrace_modify_code(pc, 0, new, false);

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
        if (!ret) {
                pc = (unsigned long)&ftrace_regs_call;
                new = ftrace_call_replace(pc, (unsigned long)func, true);

                ret = ftrace_modify_code(pc, 0, new, false);
        }
#endif

        return ret;
}

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
        unsigned long new, old;
        unsigned long ip = rec->ip;
        unsigned long aaddr = adjust_address(rec, addr);
        struct module *mod = NULL;

#ifdef CONFIG_ARM_MODULE_PLTS
        mod = rec->arch.mod;
#endif

        old = ftrace_nop_replace(rec);

        new = ftrace_call_replace(ip, aaddr, !mod);
#ifdef CONFIG_ARM_MODULE_PLTS
        if (!new && mod) {
                aaddr = get_module_plt(mod, ip, aaddr);
                new = ftrace_call_replace(ip, aaddr, true);
        }
#endif

        return ftrace_modify_code(rec->ip, old, new, true);
}

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
                                unsigned long addr)
{
        unsigned long new, old;
        unsigned long ip = rec->ip;

        old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true);

        new = ftrace_call_replace(ip, adjust_address(rec, addr), true);

        return ftrace_modify_code(rec->ip, old, new, true);
}

#endif

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

#ifdef CONFIG_ARM_MODULE_PLTS
        /* mod is only supplied during module loading */
        if (!mod)
                mod = rec->arch.mod;
        else
                rec->arch.mod = mod;
#endif

        old = ftrace_call_replace(ip, aaddr,
                                  !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
#ifdef CONFIG_ARM_MODULE_PLTS
        if (!old && mod) {
                aaddr = get_module_plt(mod, ip, aaddr);
                old = ftrace_call_replace(ip, aaddr, true);
        }
#endif

        new = ftrace_nop_replace(rec);
        /*
         * Locations in .init.text may call __gnu_mcount_mc via a linker
         * emitted veneer if they are too far away from its implementation, and
         * so validation may fail spuriously in such cases. Let's work around
         * this by omitting those from validation.
         */
        ret = ftrace_modify_code(ip, old, new, !is_kernel_inittext(ip));

        return ret;
}
#endif /* CONFIG_DYNAMIC_FTRACE */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
asmlinkage
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
                           unsigned long frame_pointer,
                           unsigned long stack_pointer)
{
        unsigned long return_hooker = (unsigned long) &return_to_handler;
        unsigned long old;

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

        if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER)) {
                /*
                 * Usually, the stack frames are contiguous in memory but cases
                 * have been observed where the next stack frame does not live
                 * at 'frame_pointer + 4' as this code used to assume.
                 *
                 * Instead, dereference the field in the stack frame that
                 * stores the SP of the calling frame: to avoid unbounded
                 * recursion, this cannot involve any ftrace instrumented
                 * functions, so use the __get_kernel_nofault() primitive
                 * directly.
                 */
                __get_kernel_nofault(&frame_pointer,
                                     (unsigned long *)(frame_pointer - 8),
                                     unsigned long, err_out);
        } else {
                struct stackframe frame = {
                        .fp = frame_pointer,
                        .sp = stack_pointer,
                        .lr = self_addr,
                        .pc = self_addr,
                };
                if (unwind_frame(&frame) < 0)
                        return;
                if (frame.lr != self_addr)
                        parent = frame.lr_addr;
                frame_pointer = frame.sp;
        }

        old = *parent;
        *parent = return_hooker;

        if (function_graph_enter(old, self_addr, frame_pointer, NULL))
                *parent = old;
}

#ifdef CONFIG_DYNAMIC_FTRACE
extern unsigned long ftrace_graph_call;
extern unsigned long ftrace_graph_call_old;
extern void ftrace_graph_caller_old(void);
extern unsigned long ftrace_graph_regs_call;
extern void ftrace_graph_regs_caller(void);

static int __ftrace_modify_caller(unsigned long *callsite,
                                  void (*func) (void), bool enable)
{
        unsigned long caller_fn = (unsigned long) func;
        unsigned long pc = (unsigned long) callsite;
        unsigned long branch = arm_gen_branch(pc, caller_fn);
        unsigned long nop = arm_gen_nop();
        unsigned long old = enable ? nop : branch;
        unsigned long new = enable ? branch : nop;

        return ftrace_modify_code(pc, old, new, true);
}

static int ftrace_modify_graph_caller(bool enable)
{
        int ret;

        ret = __ftrace_modify_caller(&ftrace_graph_call,
                                     ftrace_graph_caller,
                                     enable);

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
        if (!ret)
                ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
                                     ftrace_graph_regs_caller,
                                     enable);
#endif


        return ret;
}

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 */