/*
 * Post mortem Dwarf CFI based unwinding on top of regs and stack dumps.
 *
 * Lots of this code have been borrowed or heavily inspired from parts of
 * the libunwind 0.99 code which are (amongst other contributors I may have
 * forgotten):
 *
 * Copyright (C) 2002-2007 Hewlett-Packard Co
 *      Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
 *
 * And the bugs have been added by:
 *
 * Copyright (C) 2010, Frederic Weisbecker <fweisbec@gmail.com>
 * Copyright (C) 2012, Jiri Olsa <jolsa@redhat.com>
 *
 */

#include <elf.h>
#include <gelf.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <linux/list.h>
#include <libunwind.h>
#include <libunwind-ptrace.h>
#include "thread.h"
#include "session.h"
#include "perf_regs.h"
#include "unwind.h"
#include "util.h"

extern int
UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
                                    unw_word_t ip,
                                    unw_dyn_info_t *di,
                                    unw_proc_info_t *pi,
                                    int need_unwind_info, void *arg);

#define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)

#define DW_EH_PE_FORMAT_MASK    0x0f    /* format of the encoded value */
#define DW_EH_PE_APPL_MASK      0x70    /* how the value is to be applied */

/* Pointer-encoding formats: */
#define DW_EH_PE_omit           0xff
#define DW_EH_PE_ptr            0x00    /* pointer-sized unsigned value */
#define DW_EH_PE_udata4         0x03    /* unsigned 32-bit value */
#define DW_EH_PE_udata8         0x04    /* unsigned 64-bit value */
#define DW_EH_PE_sdata4         0x0b    /* signed 32-bit value */
#define DW_EH_PE_sdata8         0x0c    /* signed 64-bit value */

/* Pointer-encoding application: */
#define DW_EH_PE_absptr         0x00    /* absolute value */
#define DW_EH_PE_pcrel          0x10    /* rel. to addr. of encoded value */

/*
 * The following are not documented by LSB v1.3, yet they are used by
 * GCC, presumably they aren't documented by LSB since they aren't
 * used on Linux:
 */
#define DW_EH_PE_funcrel        0x40    /* start-of-procedure-relative */
#define DW_EH_PE_aligned        0x50    /* aligned pointer */

/* Flags intentionaly not handled, since they're not needed:
 * #define DW_EH_PE_indirect      0x80
 * #define DW_EH_PE_uleb128       0x01
 * #define DW_EH_PE_udata2        0x02
 * #define DW_EH_PE_sleb128       0x09
 * #define DW_EH_PE_sdata2        0x0a
 * #define DW_EH_PE_textrel       0x20
 * #define DW_EH_PE_datarel       0x30
 */

struct unwind_info {
        struct perf_sample      *sample;
        struct machine          *machine;
        struct thread           *thread;
        u64                     sample_uregs;
};

#define dw_read(ptr, type, end) ({      \
        type *__p = (type *) ptr;       \
        type  __v;                      \
        if ((__p + 1) > (type *) end)   \
                return -EINVAL;         \
        __v = *__p++;                   \
        ptr = (typeof(ptr)) __p;        \
        __v;                            \
        })

static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
                                   u8 encoding)
{
        u8 *cur = *p;
        *val = 0;

        switch (encoding) {
        case DW_EH_PE_omit:
                *val = 0;
                goto out;
        case DW_EH_PE_ptr:
                *val = dw_read(cur, unsigned long, end);
                goto out;
        default:
                break;
        }

        switch (encoding & DW_EH_PE_APPL_MASK) {
        case DW_EH_PE_absptr:
                break;
        case DW_EH_PE_pcrel:
                *val = (unsigned long) cur;
                break;
        default:
                return -EINVAL;
        }

        if ((encoding & 0x07) == 0x00)
                encoding |= DW_EH_PE_udata4;

        switch (encoding & DW_EH_PE_FORMAT_MASK) {
        case DW_EH_PE_sdata4:
                *val += dw_read(cur, s32, end);
                break;
        case DW_EH_PE_udata4:
                *val += dw_read(cur, u32, end);
                break;
        case DW_EH_PE_sdata8:
                *val += dw_read(cur, s64, end);
                break;
        case DW_EH_PE_udata8:
                *val += dw_read(cur, u64, end);
                break;
        default:
                return -EINVAL;
        }

 out:
        *p = cur;
        return 0;
}

#define dw_read_encoded_value(ptr, end, enc) ({                 \
        u64 __v;                                                \
        if (__dw_read_encoded_value(&ptr, end, &__v, enc)) {    \
                return -EINVAL;                                 \
        }                                                       \
        __v;                                                    \
        })

static Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
                                    GElf_Shdr *shp, const char *name)
{
        Elf_Scn *sec = NULL;

        while ((sec = elf_nextscn(elf, sec)) != NULL) {
                char *str;

                gelf_getshdr(sec, shp);
                str = elf_strptr(elf, ep->e_shstrndx, shp->sh_name);
                if (!strcmp(name, str))
                        break;
        }

        return sec;
}

static u64 elf_section_offset(int fd, const char *name)
{
        Elf *elf;
        GElf_Ehdr ehdr;
        GElf_Shdr shdr;
        u64 offset = 0;

        elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        if (elf == NULL)
                return 0;

        do {
                if (gelf_getehdr(elf, &ehdr) == NULL)
                        break;

                if (!elf_section_by_name(elf, &ehdr, &shdr, name))
                        break;

                offset = shdr.sh_offset;
        } while (0);

        elf_end(elf);
        return offset;
}

struct table_entry {
        u32 start_ip_offset;
        u32 fde_offset;
};

struct eh_frame_hdr {
        unsigned char version;
        unsigned char eh_frame_ptr_enc;
        unsigned char fde_count_enc;
        unsigned char table_enc;

        /*
         * The rest of the header is variable-length and consists of the
         * following members:
         *
         *      encoded_t eh_frame_ptr;
         *      encoded_t fde_count;
         */

        /* A single encoded pointer should not be more than 8 bytes. */
        u64 enc[2];

        /*
         * struct {
         *    encoded_t start_ip;
         *    encoded_t fde_addr;
         * } binary_search_table[fde_count];
         */
        char data[0];
} __packed;

static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
                               u64 offset, u64 *table_data, u64 *segbase,
                               u64 *fde_count)
{
        struct eh_frame_hdr hdr;
        u8 *enc = (u8 *) &hdr.enc;
        u8 *end = (u8 *) &hdr.data;
        ssize_t r;

        r = dso__data_read_offset(dso, machine, offset,
                                  (u8 *) &hdr, sizeof(hdr));
        if (r != sizeof(hdr))
                return -EINVAL;

        /* We dont need eh_frame_ptr, just skip it. */
        dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);

        *fde_count  = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
        *segbase    = offset;
        *table_data = (enc - (u8 *) &hdr) + offset;
        return 0;
}

static int read_unwind_spec(struct dso *dso, struct machine *machine,
                            u64 *table_data, u64 *segbase, u64 *fde_count)
{
        int ret = -EINVAL, fd;
        u64 offset;

        fd = dso__data_fd(dso, machine);
        if (fd < 0)
                return -EINVAL;

        offset = elf_section_offset(fd, ".eh_frame_hdr");
        close(fd);

        if (offset)
                ret = unwind_spec_ehframe(dso, machine, offset,
                                          table_data, segbase,
                                          fde_count);

        /* TODO .debug_frame check if eh_frame_hdr fails */
        return ret;
}

static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
{
        struct addr_location al;

        thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
                              MAP__FUNCTION, ip, &al);
        return al.map;
}

static int
find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
               int need_unwind_info, void *arg)
{
        struct unwind_info *ui = arg;
        struct map *map;
        unw_dyn_info_t di;
        u64 table_data, segbase, fde_count;

        map = find_map(ip, ui);
        if (!map || !map->dso)
                return -EINVAL;

        pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);

        if (read_unwind_spec(map->dso, ui->machine,
                             &table_data, &segbase, &fde_count))
                return -EINVAL;

        memset(&di, 0, sizeof(di));
        di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
        di.start_ip = map->start;
        di.end_ip   = map->end;
        di.u.rti.segbase    = map->start + segbase;
        di.u.rti.table_data = map->start + table_data;
        di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
                              / sizeof(unw_word_t);
        return dwarf_search_unwind_table(as, ip, &di, pi,
                                         need_unwind_info, arg);
}

static int access_fpreg(unw_addr_space_t __maybe_unused as,
                        unw_regnum_t __maybe_unused num,
                        unw_fpreg_t __maybe_unused *val,
                        int __maybe_unused __write,
                        void __maybe_unused *arg)
{
        pr_err("unwind: access_fpreg unsupported\n");
        return -UNW_EINVAL;
}

static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
                                  unw_word_t __maybe_unused *dil_addr,
                                  void __maybe_unused *arg)
{
        return -UNW_ENOINFO;
}

static int resume(unw_addr_space_t __maybe_unused as,
                  unw_cursor_t __maybe_unused *cu,
                  void __maybe_unused *arg)
{
        pr_err("unwind: resume unsupported\n");
        return -UNW_EINVAL;
}

static int
get_proc_name(unw_addr_space_t __maybe_unused as,
              unw_word_t __maybe_unused addr,
                char __maybe_unused *bufp, size_t __maybe_unused buf_len,
                unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
{
        pr_err("unwind: get_proc_name unsupported\n");
        return -UNW_EINVAL;
}

static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
                          unw_word_t *data)
{
        struct addr_location al;
        ssize_t size;

        thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
                              MAP__FUNCTION, addr, &al);
        if (!al.map) {
                pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
                return -1;
        }

        if (!al.map->dso)
                return -1;

        size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
                                   addr, (u8 *) data, sizeof(*data));

        return !(size == sizeof(*data));
}

static int reg_value(unw_word_t *valp, struct regs_dump *regs, int id,
                     u64 sample_regs)
{
        int i, idx = 0;

        if (!(sample_regs & (1 << id)))
                return -EINVAL;

        for (i = 0; i < id; i++) {
                if (sample_regs & (1 << i))
                        idx++;
        }

        *valp = regs->regs[idx];
        return 0;
}

static int access_mem(unw_addr_space_t __maybe_unused as,
                      unw_word_t addr, unw_word_t *valp,
                      int __write, void *arg)
{
        struct unwind_info *ui = arg;
        struct stack_dump *stack = &ui->sample->user_stack;
        unw_word_t start, end;
        int offset;
        int ret;

        /* Don't support write, probably not needed. */
        if (__write || !stack || !ui->sample->user_regs.regs) {
                *valp = 0;
                return 0;
        }

        ret = reg_value(&start, &ui->sample->user_regs, PERF_REG_SP,
                        ui->sample_uregs);
        if (ret)
                return ret;

        end = start + stack->size;

        /* Check overflow. */
        if (addr + sizeof(unw_word_t) < addr)
                return -EINVAL;

        if (addr < start || addr + sizeof(unw_word_t) >= end) {
                ret = access_dso_mem(ui, addr, valp);
                if (ret) {
                        pr_debug("unwind: access_mem %p not inside range %p-%p\n",
                                (void *)addr, (void *)start, (void *)end);
                        *valp = 0;
                        return ret;
                }
                return 0;
        }

        offset = addr - start;
        *valp  = *(unw_word_t *)&stack->data[offset];
        pr_debug("unwind: access_mem addr %p, val %lx, offset %d\n",
                 (void *)addr, (unsigned long)*valp, offset);
        return 0;
}

static int access_reg(unw_addr_space_t __maybe_unused as,
                      unw_regnum_t regnum, unw_word_t *valp,
                      int __write, void *arg)
{
        struct unwind_info *ui = arg;
        int id, ret;

        /* Don't support write, I suspect we don't need it. */
        if (__write) {
                pr_err("unwind: access_reg w %d\n", regnum);
                return 0;
        }

        if (!ui->sample->user_regs.regs) {
                *valp = 0;
                return 0;
        }

        id = unwind__arch_reg_id(regnum);
        if (id < 0)
                return -EINVAL;

        ret = reg_value(valp, &ui->sample->user_regs, id, ui->sample_uregs);
        if (ret) {
                pr_err("unwind: can't read reg %d\n", regnum);
                return ret;
        }

        pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
        return 0;
}

static void put_unwind_info(unw_addr_space_t __maybe_unused as,
                            unw_proc_info_t *pi __maybe_unused,
                            void *arg __maybe_unused)
{
        pr_debug("unwind: put_unwind_info called\n");
}

static int entry(u64 ip, struct thread *thread, struct machine *machine,
                 unwind_entry_cb_t cb, void *arg)
{
        struct unwind_entry e;
        struct addr_location al;

        thread__find_addr_location(thread, machine,
                                   PERF_RECORD_MISC_USER,
                                   MAP__FUNCTION, ip, &al, NULL);

        e.ip = ip;
        e.map = al.map;
        e.sym = al.sym;

        pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
                 al.sym ? al.sym->name : "''",
                 ip,
                 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);

        return cb(&e, arg);
}

static void display_error(int err)
{
        switch (err) {
        case UNW_EINVAL:
                pr_err("unwind: Only supports local.\n");
                break;
        case UNW_EUNSPEC:
                pr_err("unwind: Unspecified error.\n");
                break;
        case UNW_EBADREG:
                pr_err("unwind: Register unavailable.\n");
                break;
        default:
                break;
        }
}

static unw_accessors_t accessors = {
        .find_proc_info         = find_proc_info,
        .put_unwind_info        = put_unwind_info,
        .get_dyn_info_list_addr = get_dyn_info_list_addr,
        .access_mem             = access_mem,
        .access_reg             = access_reg,
        .access_fpreg           = access_fpreg,
        .resume                 = resume,
        .get_proc_name          = get_proc_name,
};

static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
                       void *arg)
{
        unw_addr_space_t addr_space;
        unw_cursor_t c;
        int ret;

        addr_space = unw_create_addr_space(&accessors, 0);
        if (!addr_space) {
                pr_err("unwind: Can't create unwind address space.\n");
                return -ENOMEM;
        }

        ret = unw_init_remote(&c, addr_space, ui);
        if (ret)
                display_error(ret);

        while (!ret && (unw_step(&c) > 0)) {
                unw_word_t ip;

                unw_get_reg(&c, UNW_REG_IP, &ip);
                ret = entry(ip, ui->thread, ui->machine, cb, arg);
        }

        unw_destroy_addr_space(addr_space);
        return ret;
}

int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
                        struct machine *machine, struct thread *thread,
                        u64 sample_uregs, struct perf_sample *data)
{
        unw_word_t ip;
        struct unwind_info ui = {
                .sample       = data,
                .sample_uregs = sample_uregs,
                .thread       = thread,
                .machine      = machine,
        };
        int ret;

        if (!data->user_regs.regs)
                return -EINVAL;

        ret = reg_value(&ip, &data->user_regs, PERF_REG_IP, sample_uregs);
        if (ret)
                return ret;

        ret = entry(ip, thread, machine, cb, arg);
        if (ret)
                return -ENOMEM;

        return get_entries(&ui, cb, arg);
}