// SPDX-License-Identifier: GPL-2.0-only
/*
 *      stacktrace.c : stacktracing APIs needed by rest of kernel
 *                      (wrappers over ARC dwarf based unwinder)
 *
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 *  vineetg: aug 2009
 *  -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
 *   for displaying task's kernel mode call stack in /proc/<pid>/stack
 *  -Iterator based approach to have single copy of unwinding core and APIs
 *   needing unwinding, implement the logic in iterator regarding:
 *      = which frame onwards to start capture
 *      = which frame to stop capturing (wchan)
 *      = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
 *
 *  vineetg: March 2009
 *  -Implemented correct versions of thread_saved_pc() and get_wchan()
 *
 *  rajeshwarr: 2008
 *  -Initial implementation
 */

#include <linux/ptrace.h>
#include <linux/export.h>
#include <linux/stacktrace.h>
#include <linux/kallsyms.h>
#include <linux/sched/debug.h>

#include <asm/arcregs.h>
#include <asm/unwind.h>
#include <asm/switch_to.h>

/*-------------------------------------------------------------------------
 *              Unwinder Iterator
 *-------------------------------------------------------------------------
 */

#ifdef CONFIG_ARC_DW2_UNWIND

static int
seed_unwind_frame_info(struct task_struct *tsk, struct pt_regs *regs,
                       struct unwind_frame_info *frame_info)
{
        if (regs) {
                /*
                 * Asynchronous unwinding of intr/exception
                 *  - Just uses the pt_regs passed
                 */
                frame_info->task = tsk;

                frame_info->regs.r27 = regs->fp;
                frame_info->regs.r28 = regs->sp;
                frame_info->regs.r31 = regs->blink;
                frame_info->regs.r63 = regs->ret;
                frame_info->call_frame = 0;
        } else if (tsk == NULL || tsk == current) {
                /*
                 * synchronous unwinding (e.g. dump_stack)
                 *  - uses current values of SP and friends
                 */
                unsigned long fp, sp, blink, ret;
                frame_info->task = current;

                __asm__ __volatile__(
                        "mov %0,r27\n\t"
                        "mov %1,r28\n\t"
                        "mov %2,r31\n\t"
                        "mov %3,r63\n\t"
                        : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
                );

                frame_info->regs.r27 = fp;
                frame_info->regs.r28 = sp;
                frame_info->regs.r31 = blink;
                frame_info->regs.r63 = ret;
                frame_info->call_frame = 0;
        } else {
                /*
                 * Asynchronous unwinding of a likely sleeping task
                 *  - first ensure it is actually sleeping
                 *  - if so, it will be in __switch_to, kernel mode SP of task
                 *    is safe-kept and BLINK at a well known location in there
                 */

                if (task_is_running(tsk))
                        return -1;

                frame_info->task = tsk;

                frame_info->regs.r27 = TSK_K_FP(tsk);
                frame_info->regs.r28 = TSK_K_ESP(tsk);
                frame_info->regs.r31 = TSK_K_BLINK(tsk);
                frame_info->regs.r63 = (unsigned int)__switch_to;

                /* In the prologue of __switch_to, first FP is saved on stack
                 * and then SP is copied to FP. Dwarf assumes cfa as FP based
                 * but we didn't save FP. The value retrieved above is FP's
                 * state in previous frame.
                 * As a work around for this, we unwind from __switch_to start
                 * and adjust SP accordingly. The other limitation is that
                 * __switch_to macro is dwarf rules are not generated for inline
                 * assembly code
                 */
                frame_info->regs.r27 = 0;
                frame_info->regs.r28 += 60;
                frame_info->call_frame = 0;

        }
        return 0;
}

#endif

notrace noinline unsigned int
arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
                int (*consumer_fn) (unsigned int, void *), void *arg)
{
#ifdef CONFIG_ARC_DW2_UNWIND
        int ret = 0, cnt = 0;
        unsigned int address;
        struct unwind_frame_info frame_info;

        if (seed_unwind_frame_info(tsk, regs, &frame_info))
                return 0;

        while (1) {
                address = UNW_PC(&frame_info);

                if (!address || !__kernel_text_address(address))
                        break;

                if (consumer_fn(address, arg) == -1)
                        break;

                ret = arc_unwind(&frame_info);
                if (ret)
                        break;

                frame_info.regs.r63 = frame_info.regs.r31;

                if (cnt++ > 128) {
                        printk("unwinder looping too long, aborting !\n");
                        return 0;
                }
        }

        return address;         /* return the last address it saw */
#else
        /* On ARC, only Dward based unwinder works. fp based backtracing is
         * not possible (-fno-omit-frame-pointer) because of the way function
         * prologue is setup (callee regs saved and then fp set and not other
         * way around
         */
        pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
        return 0;

#endif
}

/*-------------------------------------------------------------------------
 * callbacks called by unwinder iterator to implement kernel APIs
 *
 * The callback can return -1 to force the iterator to stop, which by default
 * keeps going till the bottom-most frame.
 *-------------------------------------------------------------------------
 */

/* Call-back which plugs into unwinding core to dump the stack in
 * case of panic/OOPs/BUG etc
 */
static int __print_sym(unsigned int address, void *arg)
{
        const char *loglvl = arg;

        printk("%s  %pS\n", loglvl, (void *)address);
        return 0;
}

#ifdef CONFIG_STACKTRACE

/* Call-back which plugs into unwinding core to capture the
 * traces needed by kernel on /proc/<pid>/stack
 */
static int __collect_all(unsigned int address, void *arg)
{
        struct stack_trace *trace = arg;

        if (trace->skip > 0)
                trace->skip--;
        else
                trace->entries[trace->nr_entries++] = address;

        if (trace->nr_entries >= trace->max_entries)
                return -1;

        return 0;
}

static int __collect_all_but_sched(unsigned int address, void *arg)
{
        struct stack_trace *trace = arg;

        if (in_sched_functions(address))
                return 0;

        if (trace->skip > 0)
                trace->skip--;
        else
                trace->entries[trace->nr_entries++] = address;

        if (trace->nr_entries >= trace->max_entries)
                return -1;

        return 0;
}

#endif

static int __get_first_nonsched(unsigned int address, void *unused)
{
        if (in_sched_functions(address))
                return 0;

        return -1;
}

/*-------------------------------------------------------------------------
 *              APIs expected by various kernel sub-systems
 *-------------------------------------------------------------------------
 */

noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs,
                              const char *loglvl)
{
        printk("%s\nStack Trace:\n", loglvl);
        arc_unwind_core(tsk, regs, __print_sym, (void *)loglvl);
}
EXPORT_SYMBOL(show_stacktrace);

/* Expected by sched Code */
void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl)
{
        show_stacktrace(tsk, NULL, loglvl);
}

/* Another API expected by schedular, shows up in "ps" as Wait Channel
 * Of course just returning schedule( ) would be pointless so unwind until
 * the function is not in schedular code
 */
unsigned int get_wchan(struct task_struct *tsk)
{
        return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
}

#ifdef CONFIG_STACKTRACE

/*
 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
 * A typical use is when /proc/<pid>/stack is queried by userland
 */
void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
        /* Assumes @tsk is sleeping so unwinds from __switch_to */
        arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
}

void save_stack_trace(struct stack_trace *trace)
{
        /* Pass NULL for task so it unwinds the current call frame */
        arc_unwind_core(NULL, NULL, __collect_all, trace);
}
EXPORT_SYMBOL_GPL(save_stack_trace);
#endif