// SPDX-License-Identifier: GPL-2.0-only
/*
 * genelf.c
 * Copyright (C) 2014, Google, Inc
 *
 * Contributed by:
 *      Stephane Eranian <eranian@gmail.com>
 */

#include <sys/types.h>
#include <stddef.h>
#include <libelf.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include <err.h>
#ifdef HAVE_LIBDW_SUPPORT
#include <dwarf.h>
#endif

#include "blake2s.h"
#include "genelf.h"
#include "../util/jitdump.h"
#include <linux/compiler.h>

#ifndef NT_GNU_BUILD_ID
#define NT_GNU_BUILD_ID 3
#endif

typedef struct {
  unsigned int namesz;  /* Size of entry's owner string */
  unsigned int descsz;  /* Size of the note descriptor */
  unsigned int type;    /* Interpretation of the descriptor */
  char         name[0]; /* Start of the name+desc data */
} Elf_Note;

static char shd_string_table[] = {
        0,
        '.', 't', 'e', 'x', 't', 0,                     /*  1 */
        '.', 's', 'h', 's', 't', 'r', 't', 'a', 'b', 0, /*  7 */
        '.', 's', 'y', 'm', 't', 'a', 'b', 0,           /* 17 */
        '.', 's', 't', 'r', 't', 'a', 'b', 0,           /* 25 */
        '.', 'n', 'o', 't', 'e', '.', 'g', 'n', 'u', '.', 'b', 'u', 'i', 'l', 'd', '-', 'i', 'd', 0, /* 33 */
        '.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */
        '.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */
        '.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */
        '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */
        '.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */
};

static struct buildid_note {
        Elf_Note desc;          /* descsz: size of build-id, must be multiple of 4 */
        char     name[4];       /* GNU\0 */
        u8       build_id[20];
} bnote;

static Elf_Sym symtab[]={
        /* symbol 0 MUST be the undefined symbol */
        { .st_name  = 0, /* index in sym_string table */
          .st_info  = ELF_ST_TYPE(STT_NOTYPE),
          .st_shndx = 0, /* for now */
          .st_value = 0x0,
          .st_other = ELF_ST_VIS(STV_DEFAULT),
          .st_size  = 0,
        },
        { .st_name  = 1, /* index in sym_string table */
          .st_info  = ELF_ST_BIND(STB_LOCAL) | ELF_ST_TYPE(STT_FUNC),
          .st_shndx = 1,
          .st_value = 0, /* for now */
          .st_other = ELF_ST_VIS(STV_DEFAULT),
          .st_size  = 0, /* for now */
        }
};

static int
jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size,
                      uint64_t unwinding_size, uint64_t base_offset)
{
        Elf_Data *d;
        Elf_Scn *scn;
        Elf_Shdr *shdr;
        uint64_t unwinding_table_size = unwinding_size - unwinding_header_size;

        /*
         * setup eh_frame section
         */
        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                return -1;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                return -1;
        }

        d->d_align = 8;
        d->d_off = 0LL;
        d->d_buf = unwinding;
        d->d_type = ELF_T_BYTE;
        d->d_size = unwinding_table_size;
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                return -1;
        }

        shdr->sh_name = 104;
        shdr->sh_type = SHT_PROGBITS;
        shdr->sh_addr = base_offset;
        shdr->sh_flags = SHF_ALLOC;
        shdr->sh_entsize = 0;

        /*
         * setup eh_frame_hdr section
         */
        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                return -1;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                return -1;
        }

        d->d_align = 4;
        d->d_off = 0LL;
        d->d_buf = unwinding + unwinding_table_size;
        d->d_type = ELF_T_BYTE;
        d->d_size = unwinding_header_size;
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                return -1;
        }

        shdr->sh_name = 90;
        shdr->sh_type = SHT_PROGBITS;
        shdr->sh_addr = base_offset + unwinding_table_size;
        shdr->sh_flags = SHF_ALLOC;
        shdr->sh_entsize = 0;

        return 0;
}

enum {
        TAG_CODE = 0,
        TAG_SYMTAB = 1,
        TAG_STRSYM = 2,
};

/*
 * Update the hash using the given data, also prepending a (tag, len) prefix to
 * ensure that distinct input tuples reliably result in distinct hashes.
 */
static void blake2s_update_tagged(struct blake2s_ctx *ctx, int tag,
                                  const void *data, size_t len)
{
        u64 prefix = ((u64)tag << 56) | len;

        blake2s_update(ctx, (const u8 *)&prefix, sizeof(prefix));
        blake2s_update(ctx, data, len);
}

/*
 * fd: file descriptor open for writing for the output file
 * load_addr: code load address (could be zero)
 * sym: function name (for native code - used as the symbol)
 * code: the native code
 * csize: the code size in bytes
 */
int
jit_write_elf(int fd, uint64_t load_addr __maybe_unused, const char *sym,
              const void *code, int csize,
              void *debug __maybe_unused, int nr_debug_entries __maybe_unused,
              void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size)
{
        Elf *e;
        Elf_Data *d;
        Elf_Scn *scn;
        Elf_Ehdr *ehdr;
        Elf_Phdr *phdr;
        Elf_Shdr *shdr;
        uint64_t eh_frame_base_offset;
        char *strsym = NULL;
        struct blake2s_ctx ctx;
        int symlen;
        int retval = -1;

        if (elf_version(EV_CURRENT) == EV_NONE) {
                warnx("ELF initialization failed");
                return -1;
        }

        e = elf_begin(fd, ELF_C_WRITE, NULL);
        if (!e) {
                warnx("elf_begin failed");
                goto error;
        }

        /*
         * setup ELF header
         */
        ehdr = elf_newehdr(e);
        if (!ehdr) {
                warnx("cannot get ehdr");
                goto error;
        }

        ehdr->e_ident[EI_DATA] = GEN_ELF_ENDIAN;
        ehdr->e_ident[EI_CLASS] = GEN_ELF_CLASS;
        ehdr->e_machine = GEN_ELF_ARCH;
        ehdr->e_type = ET_DYN;
        ehdr->e_entry = GEN_ELF_TEXT_OFFSET;
        ehdr->e_version = EV_CURRENT;
        ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */

        /*
         * setup program header
         */
        phdr = elf_newphdr(e, 1);
        phdr[0].p_type = PT_LOAD;
        phdr[0].p_offset = GEN_ELF_TEXT_OFFSET;
        phdr[0].p_vaddr = GEN_ELF_TEXT_OFFSET;
        phdr[0].p_paddr = GEN_ELF_TEXT_OFFSET;
        phdr[0].p_filesz = csize;
        phdr[0].p_memsz = csize;
        phdr[0].p_flags = PF_X | PF_R;
        phdr[0].p_align = 8;

        /*
         * setup text section
         */
        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                goto error;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                goto error;
        }

        d->d_align = 16;
        d->d_off = 0LL;
        d->d_buf = (void *)code;
        d->d_type = ELF_T_BYTE;
        d->d_size = csize;
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                goto error;
        }

        shdr->sh_name = 1;
        shdr->sh_type = SHT_PROGBITS;
        shdr->sh_addr = GEN_ELF_TEXT_OFFSET;
        shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
        shdr->sh_entsize = 0;

        blake2s_init(&ctx, sizeof(bnote.build_id));
        blake2s_update_tagged(&ctx, TAG_CODE, code, csize);

        /*
         * Setup .eh_frame_hdr and .eh_frame
         */
        if (unwinding) {
                eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize);
                retval = jit_add_eh_frame_info(e, unwinding,
                                               unwinding_header_size, unwinding_size,
                                               eh_frame_base_offset);
                if (retval)
                        goto error;
                retval = -1;
        }

        /*
         * setup section headers string table
         */
        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                goto error;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                goto error;
        }

        d->d_align = 1;
        d->d_off = 0LL;
        d->d_buf = shd_string_table;
        d->d_type = ELF_T_BYTE;
        d->d_size = sizeof(shd_string_table);
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                goto error;
        }

        shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */
        shdr->sh_type = SHT_STRTAB;
        shdr->sh_flags = 0;
        shdr->sh_entsize = 0;

        /*
         * setup symtab section
         */
        symtab[1].st_size  = csize;
        symtab[1].st_value = GEN_ELF_TEXT_OFFSET;

        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                goto error;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                goto error;
        }

        d->d_align = 8;
        d->d_off = 0LL;
        d->d_buf = symtab;
        d->d_type = ELF_T_SYM;
        d->d_size = sizeof(symtab);
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                goto error;
        }

        shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */
        shdr->sh_type = SHT_SYMTAB;
        shdr->sh_flags = 0;
        shdr->sh_entsize = sizeof(Elf_Sym);
        shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */

        blake2s_update_tagged(&ctx, TAG_SYMTAB, symtab, sizeof(symtab));

        /*
         * setup symbols string table
         * 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry
         */
        symlen = 2 + strlen(sym);
        strsym = calloc(1, symlen);
        if (!strsym) {
                warnx("cannot allocate strsym");
                goto error;
        }
        strcpy(strsym + 1, sym);

        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                goto error;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                goto error;
        }

        d->d_align = 1;
        d->d_off = 0LL;
        d->d_buf = strsym;
        d->d_type = ELF_T_BYTE;
        d->d_size = symlen;
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                goto error;
        }

        shdr->sh_name = 25; /* offset in shd_string_table */
        shdr->sh_type = SHT_STRTAB;
        shdr->sh_flags = 0;
        shdr->sh_entsize = 0;

        blake2s_update_tagged(&ctx, TAG_STRSYM, strsym, symlen);

        /*
         * setup build-id section
         */
        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                goto error;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                goto error;
        }

        /*
         * build-id generation
         */
        blake2s_final(&ctx, bnote.build_id);
        bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */
        bnote.desc.descsz = sizeof(bnote.build_id);
        bnote.desc.type   = NT_GNU_BUILD_ID;
        strcpy(bnote.name, "GNU");

        d->d_align = 4;
        d->d_off = 0LL;
        d->d_buf = &bnote;
        d->d_type = ELF_T_BYTE;
        d->d_size = sizeof(bnote);
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                goto error;
        }

        shdr->sh_name = 33; /* offset in shd_string_table */
        shdr->sh_type = SHT_NOTE;
        shdr->sh_addr = 0x0;
        shdr->sh_flags = SHF_ALLOC;
        shdr->sh_size = sizeof(bnote);
        shdr->sh_entsize = 0;

#ifdef HAVE_LIBDW_SUPPORT
        if (debug && nr_debug_entries) {
                retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries);
                if (retval)
                        goto error;
        } else
#endif
        {
                if (elf_update(e, ELF_C_WRITE) < 0) {
                        warnx("elf_update 4 failed");
                        goto error;
                }
        }

        retval = 0;
error:
        (void)elf_end(e);

        free(strsym);

        return retval;
}