// SPDX-License-Identifier: GPL-2.0
#include "callchain.h"
#include "debug.h"
#include "dso.h"
#include "env.h"
#include "map.h"
#include "perf_regs.h"
#include "session.h"
#include "symbol.h"
#include "thread.h"
#include "unwind.h"
#include "libunwind-arch/libunwind-arch.h"
#include <dwarf-regs.h>
#include <elf.h>
#include <fcntl.h>
#include <gelf.h>
#include <inttypes.h>

#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 intentionally 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
 */

#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 u64 elf_base_address(int fd)
{
        Elf *elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        GElf_Phdr phdr;
        u64 retval = 0;
        size_t i, phdrnum = 0;

        if (elf == NULL)
                return 0;
        (void)elf_getphdrnum(elf, &phdrnum);
        /* PT_LOAD segments are sorted by p_vaddr, so the first has the minimum p_vaddr. */
        for (i = 0; i < phdrnum; i++) {
                if (gelf_getphdr(elf, i, &phdr) && phdr.p_type == PT_LOAD) {
                        retval = phdr.p_vaddr & -getpagesize();
                        break;
                }
        }

        elf_end(elf);
        return retval;
}

static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
                               u64 offset, u64 *table_data_offset, u64 *fde_count)
{
        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[];
        } __packed 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);
        *table_data_offset = enc - (u8 *) &hdr;
        return 0;
}

struct read_unwind_spec_eh_frame_maps_cb_args {
        struct dso *dso;
        u64 base_addr;
};

static int read_unwind_spec_eh_frame_maps_cb(struct map *map, void *data)
{

        struct read_unwind_spec_eh_frame_maps_cb_args *args = data;

        if (map__dso(map) == args->dso && map__start(map) - map__pgoff(map) < args->base_addr)
                args->base_addr = map__start(map) - map__pgoff(map);

        return 0;
}

static int elf_section_address_and_offset(int fd, const char *name, u64 *address, u64 *offset)
{
        Elf *elf;
        GElf_Ehdr ehdr;
        GElf_Shdr shdr;
        int ret = -1;

        elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        if (elf == NULL)
                return -1;

        if (gelf_getehdr(elf, &ehdr) == NULL)
                goto out_err;

        if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
                goto out_err;

        *address = shdr.sh_addr;
        *offset = shdr.sh_offset;
        ret = 0;
out_err:
        elf_end(elf);
        return ret;
}

static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
                                     u64 *table_data, u64 *segbase,
                                     u64 *fde_count)
{
        struct read_unwind_spec_eh_frame_maps_cb_args args = {
                .dso = dso,
                .base_addr = UINT64_MAX,
        };
        int ret, fd;

        if (dso__data(dso)->eh_frame_hdr_offset == 0) {
                if (!dso__data_get_fd(dso, ui->machine, &fd))
                        return -EINVAL;

                /* Check the .eh_frame section for unwinding info */
                ret = elf_section_address_and_offset(fd, ".eh_frame_hdr",
                                                     &dso__data(dso)->eh_frame_hdr_addr,
                                                     &dso__data(dso)->eh_frame_hdr_offset);
                dso__data(dso)->elf_base_addr = elf_base_address(fd);
                dso__data_put_fd(dso);
                if (ret || dso__data(dso)->eh_frame_hdr_offset == 0)
                        return -EINVAL;
        }

        maps__for_each_map(thread__maps(ui->thread), read_unwind_spec_eh_frame_maps_cb, &args);

        args.base_addr -= dso__data(dso)->elf_base_addr;
        /* Address of .eh_frame_hdr */
        *segbase = args.base_addr + dso__data(dso)->eh_frame_hdr_addr;
        ret = unwind_spec_ehframe(dso, ui->machine, dso__data(dso)->eh_frame_hdr_offset,
                                   table_data, fde_count);
        if (ret)
                return ret;
        /* binary_search_table offset plus .eh_frame_hdr address */
        *table_data += *segbase;
        return 0;
}

static u64 elf_section_offset(int fd, const char *name)
{
        u64 address, offset = 0;

        if (elf_section_address_and_offset(fd, name, &address, &offset))
                return 0;

        return offset;
}

static int read_unwind_spec_debug_frame(struct dso *dso,
                                        struct machine *machine, u64 *offset)
{
        int fd;
        u64 ofs = dso__data(dso)->debug_frame_offset;

        /* debug_frame can reside in:
         *  - dso
         *  - debug pointed by symsrc_filename
         *  - gnu_debuglink, which doesn't necessary
         *    has to be pointed by symsrc_filename
         */
        if (ofs == 0) {
                if (dso__data_get_fd(dso, machine, &fd)) {
                        ofs = elf_section_offset(fd, ".debug_frame");
                        dso__data_put_fd(dso);
                }

                if (ofs <= 0) {
                        fd = open(dso__symsrc_filename(dso), O_RDONLY);
                        if (fd >= 0) {
                                ofs = elf_section_offset(fd, ".debug_frame");
                                close(fd);
                        }
                }

                if (ofs <= 0) {
                        char *debuglink = malloc(PATH_MAX);
                        int ret = 0;

                        if (debuglink == NULL) {
                                pr_err("unwind: Can't read unwind spec debug frame.\n");
                                return -ENOMEM;
                        }

                        ret = dso__read_binary_type_filename(
                                dso, DSO_BINARY_TYPE__DEBUGLINK,
                                machine->root_dir, debuglink, PATH_MAX);
                        if (!ret) {
                                fd = open(debuglink, O_RDONLY);
                                if (fd >= 0) {
                                        ofs = elf_section_offset(fd,
                                                        ".debug_frame");
                                        close(fd);
                                }
                        }
                        if (ofs > 0) {
                                if (dso__symsrc_filename(dso) != NULL) {
                                        pr_warning(
                                                "%s: overwrite symsrc(%s,%s)\n",
                                                        __func__,
                                                        dso__symsrc_filename(dso),
                                                        debuglink);
                                        dso__free_symsrc_filename(dso);
                                }
                                dso__set_symsrc_filename(dso, debuglink);
                        } else {
                                free(debuglink);
                        }
                }

                dso__data(dso)->debug_frame_offset = ofs;
        }

        *offset = ofs;
        if (*offset)
                return 0;

        return -EINVAL;
}

static struct map *find_map(uint64_t ip, struct unwind_info *ui)
{
        struct addr_location al;
        struct map *ret;

        addr_location__init(&al);
        thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
        ret = map__get(al.map);
        addr_location__exit(&al);
        return ret;
}

static int elf_is_exec(int fd, const char *name)
{
        Elf *elf;
        GElf_Ehdr ehdr;
        int retval = 0;

        elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        if (elf == NULL)
                return 0;
        if (gelf_getehdr(elf, &ehdr) == NULL)
                goto out;

        retval = (ehdr.e_type == ET_EXEC);

out:
        elf_end(elf);
        pr_debug3("unwind: elf_is_exec(%s): %d\n", name, retval);
        return retval;
}

int __libunwind__find_proc_info(void *as, uint64_t ip, void *pi, int need_unwind_info, void *arg)
{
        struct unwind_info *ui = arg;
        struct map *map;
        struct dso *dso;
        u64 table_data, segbase, fde_count;
        int ret = -EINVAL;

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

        dso = map__dso(map);
        if (!dso) {
                map__put(map);
                return -EINVAL;
        }

        pr_debug3("unwind: find_proc_info dso %s\n", dso__name(dso));

        /* Check the .eh_frame section for unwinding info */
        if (!read_unwind_spec_eh_frame(dso, ui, &table_data, &segbase, &fde_count)) {
                struct table_entry {
                        u32 start_ip_offset;
                        u32 fde_offset;
                };
                struct libarch_unwind__dyn_info di = {
                        .start_ip = map__start(map),
                        .end_ip   = map__end(map),
                        .segbase    = segbase,
                        .table_data = table_data,
                        .table_len  = fde_count * sizeof(struct table_entry) / ui->unw_word_t_size,
                };

                ret = libunwind_arch__dwarf_search_unwind_table(ui->e_machine, as, ip, &di, pi,
                                                                need_unwind_info, arg);
        }

        /* Check the .debug_frame section for unwinding info */
        if (ret < 0 && !read_unwind_spec_debug_frame(dso, ui->machine, &segbase)) {
                int fd;
                u64 start = map__start(map);
                u64 base = start;
                const char *symfile;
                struct libarch_unwind__dyn_info di = {};

                if (dso__data_get_fd(dso, ui->machine, &fd)) {
                        if (elf_is_exec(fd, dso__name(dso)))
                                base = 0;
                        dso__data_put_fd(dso);
                }

                symfile = dso__symsrc_filename(dso) ?: dso__name(dso);

                if (libunwind_arch__dwarf_find_debug_frame(ui->e_machine, /*found=*/0, &di, ip,
                                                           base, symfile, start, map__end(map))) {
                        ret = libunwind_arch__dwarf_search_unwind_table(ui->e_machine, as, ip, &di, pi,
                                                                        need_unwind_info, arg);
                }
        }
        map__put(map);
        return ret;
}

static int access_dso_mem(struct unwind_info *ui, uint64_t addr, void *data_word)
{
        struct map *map;
        struct dso *dso;
        ssize_t size;

        map = find_map(addr, ui);
        if (!map) {
                pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
                return -1;
        }

        dso = map__dso(map);

        if (!dso) {
                map__put(map);
                return -1;
        }

        size = dso__data_read_addr(dso, map, ui->machine,
                                   addr,
                                   (u8 *) data_word,
                                   ui->unw_word_t_size);
        map__put(map);
        return !((size_t)size == ui->unw_word_t_size);
}

int __libunwind__access_mem(void *as __maybe_unused, uint64_t addr, void *valp_word,
                            int __write, void *arg)
{
        struct unwind_info *ui = arg;
        struct stack_dump *stack = &ui->sample->user_stack;
        u64 start, end;
        int offset;
        int ret;

        /* Don't support write, probably not needed. */
        if (__write || !stack || !ui->sample->user_regs || !ui->sample->user_regs->regs) {
                uint64_t zero = 0;

                memcpy(valp_word, &zero, ui->unw_word_t_size);
                return 0;
        }

        ret = perf_reg_value(&start, perf_sample__user_regs(ui->sample),
                             perf_arch_reg_sp(ui->e_machine));
        if (ret)
                return ret;

        end = start + stack->size;

        /* Check overflow. */
        if (addr + ui->unw_word_t_size < addr)
                return -EINVAL;

        if (addr < start || addr + ui->unw_word_t_size >= end) {
                ret = access_dso_mem(ui, addr, valp_word);
                if (ret) {
                        pr_debug3("unwind: access_mem %p not inside range"
                                  " 0x%" PRIx64 "-0x%" PRIx64 "\n",
                                  (void *) (uintptr_t) addr, start, end);
                        memset(valp_word, 0, ui->unw_word_t_size);
                        return ret;
                }
                return 0;
        }

        offset = addr - start;
        memcpy(valp_word, &stack->data[offset], ui->unw_word_t_size);
        pr_debug3("unwind: access_mem addr %p val %lx, offset %d\n",
                  (void *) (uintptr_t) addr, *((unsigned long *)valp_word), offset);
        return 0;
}

int __libunwind__access_reg(void *as __maybe_unused, int regnum, void *valp_word, int __write,
                            void *arg)
{
        struct unwind_info *ui = arg;
        int id, ret;
        u64 val;

        /* 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 || !ui->sample->user_regs->regs) {
                memset(valp_word, 0, ui->unw_word_t_size);
                return 0;
        }

        id = get_perf_regnum_for_unw_regnum(ui->e_machine, regnum);
        if (id < 0)
                return -EINVAL;

        ret = perf_reg_value(&val, perf_sample__user_regs(ui->sample), id);
        if (ret) {
                if (!ui->best_effort)
                        pr_err("unwind: can't read reg %d\n", regnum);
                return ret;
        }

        if (ui->unw_word_t_size == 8)
                *(uint64_t *)valp_word = val;
        else
                *(uint32_t *)valp_word = (uint32_t)val;
        pr_debug3("unwind: reg %d, val %lx\n", regnum, val);
        return 0;
}

int unwind__prepare_access(struct maps *maps, uint16_t e_machine)
{
        void *addr_space;

        if (!dwarf_callchain_users)
                return 0;

        if (maps__addr_space(maps)) {
                pr_debug3("unwind: thread map already set\n");
                return 0;
        }

        if (e_machine == EM_NONE)
                return 0;

        maps__set_e_machine(maps, e_machine);
        addr_space = libunwind_arch__create_addr_space(e_machine);

        maps__set_addr_space(maps, addr_space);
        if (!addr_space) {
                pr_err("unwind: Can't create unwind address space.\n");
                return -ENOMEM;
        }

        return 0;
}

void unwind__flush_access(struct maps *maps)
{
        libunwind_arch__flush_access(maps);
}

void unwind__finish_access(struct maps *maps)
{
        libunwind_arch__finish_access(maps);
}

static int entry(uint64_t ip, struct thread *thread, unwind_entry_cb_t cb, void *arg)
{
        struct unwind_entry e;
        struct addr_location al;
        int ret;

        addr_location__init(&al);
        e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
        e.ip     = ip;
        e.ms.map = al.map;
        e.ms.thread = thread__get(al.thread);

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

        ret = cb(&e, arg);
        addr_location__exit(&al);
        return ret;
}

int libunwind__get_entries(unwind_entry_cb_t cb, void *arg,
                         struct thread *thread,
                         struct perf_sample *sample, int max_stack,
                         bool best_effort)
{
        struct unwind_info *ui;
        uint64_t first_ip;
        int ret, i = 0, entries = 0;
        uint16_t e_machine;

        if (!sample->user_regs || !sample->user_regs->regs)
                return 0;

        if (max_stack <= 0)
                return 0;

        if (!thread) {
                pr_warning_once("WARNING: thread is NULL");
                return 0;
        }

        e_machine = thread__e_machine(thread, /*machine=*/NULL, /*e_flags=*/NULL);
        ret = perf_reg_value(&first_ip, perf_sample__user_regs(sample),
                             perf_arch_reg_ip(e_machine));
        if (ret)
                return 0;

        if (max_stack == 1) {
                /* Special case for a single entry. */
                ret = entry(first_ip, thread, cb, arg);
                return ret ? (ret == -ENOMEM ? -ENOMEM : 0) : 1;
        }

        ui = libunwind_arch_unwind_info__new(thread, sample, max_stack, best_effort, e_machine, first_ip);
        if (!ui)
                return -ENOMEM;

        do {
                ret = libunwind_arch__unwind_step(ui);
                if (ret < 0)
                        goto out;

        } while (ret);

        /*
         * Display what we got based on the order setup.
         */
        for (i = 0; i < ui->cur_ip; i++) {
                int j = callchain_param.order == ORDER_CALLEE ? i : ui->cur_ip - i - 1;

                if (ui->ips[j]) {
                        ret = entry(ui->ips[j], thread, cb, arg);
                        if (ret)
                                break;
                        entries++;
                }
        }
out:
        libunwind_arch_unwind_info__delete(ui);
        /*
         * Unwinder return contract:
         *  > 0 : unwinding succeeded (stops fallback).
         *    0 : unwinding failed without yielding frames. Ignore non-fatal errors
         *        (e.g. stepping failure) to allow fallback unwinder or kernel callchains.
         *  < 0 : fatal error (e.g. -ENOMEM). Aborts unwinding entirely.
         */
        if (ret == -ENOMEM)
                return -ENOMEM;
        return (entries > 0 || ret == 0) ? entries : 0;
}