elf.c

/*
# _____     ___ ____     ___ ____
#  ____|   |    ____|   |        | |____|
# |     ___|   |____ ___|    ____| |    \    PS2DEV Open Source Project.
#-----------------------------------------------------------------------
# Copyright ps2dev - http://www.ps2dev.org
# Licenced under Academic Free License version 2.0
# Review ps2sdk README & LICENSE files for further details.
*/
 
#include "elf_loader_common.h"
 
#include <kernel.h>
#include <string.h>
 
// Loader ELF variables
extern u8 ldrsrc[];
extern int size_ldrsrc;
 
int elf_loader_is_elf_ehdr_valid(const elf_loader_elf32_ehdr_t *ehdr)
{
    int ret;
 
    ret = 0;
 
    if ( memcmp(
                 ehdr->e_ident,
                 "\x7F"
                 "ELF",
                 4) )
    {
        ret = -9;
    }
    else if ( ehdr->e_entry < 0x80000 || ehdr->e_entry > (32 * 1024 * 1024) )
    {
        ret = -10;
    }
    else if ( ehdr->e_ident[4] != 1 )
    {
        ret = -1;
    }
    else if ( ehdr->e_ident[5] != 1 )
    {
        ret = -2;
    }
    else if ( ehdr->e_type != 2 )
    {
        ret = -3;
    }
    else if ( ehdr->e_machine != 8 )
    {
        ret = -4;
    }
    else if ( ehdr->e_ehsize != sizeof(elf_loader_elf32_ehdr_t) )
    {
        ret = -5;
    }
    else if ( ehdr->e_phentsize != sizeof(elf_loader_elf32_phdr_t) )
    {
        ret = -6;
    }
    else if ( ehdr->e_phnum > ELF_LOADER_MAX_PROGRAM_HEADERS )
    {
        ret = -7;
    }
    else if ( ehdr->e_shnum && ehdr->e_shentsize != 40 )
    {
        ret = -8;
    }
    return ret;
}
 
int elf_loader_is_elf_valid_for_loading(const void *buf, size_t buf_size)
{
    int i;
    int ret;
    int ph_count;
    int entrypoint_in_ph;
    u32 highest_vaddr;
    u32 highest_offset;
    const elf_loader_elf32_ehdr_t *ehdr;
    const elf_loader_elf32_phdr_t *phdr;
 
    if ( buf_size < sizeof(elf_loader_elf32_ehdr_t) )
        return -30;
    ehdr = (const elf_loader_elf32_ehdr_t *)buf;
    ret = elf_loader_is_elf_ehdr_valid(ehdr);
    if ( ret )
        return ret;
    if ( buf_size < (ehdr->e_phoff + sizeof(elf_loader_elf32_ehdr_t)) )
        return -31;
    phdr = (const elf_loader_elf32_phdr_t *)(((const u8 *)buf) + ehdr->e_phoff);
    ph_count = 0;
    entrypoint_in_ph = 0;
    highest_vaddr = 0x80000;
    highest_offset = 0;
    for ( i = 0; i < ehdr->e_phnum; i += 1 )
    {
        if ( phdr[i].p_type == 1 && phdr[i].p_filesz != 0 )
        {
            // Program headers need to be pre-sorted
            if ( phdr[i].p_vaddr < highest_vaddr || phdr[i].p_offset < highest_offset )
            {
                return -20;
            }
            highest_vaddr = phdr[i].p_vaddr;
            highest_offset = phdr[i].p_offset;
            if ( ehdr->e_entry >= phdr[i].p_vaddr && (phdr[i].p_vaddr + phdr[i].p_filesz) > ehdr->e_entry )
            {
                entrypoint_in_ph = 1;
            }
            ph_count += 1;
        }
    }
    if ( !ph_count || ph_count > ELF_LOADER_MAX_PROGRAM_HEADERS )
    {
        return -21;
    }
    if ( !entrypoint_in_ph )
    {
        return -22;
    }
    if ( buf_size < highest_offset )
        return -32;
    return 0;
}
 
int elf_loader_exec_elf_prepare_loadinfo(elf_loader_execinfo_t *execinfo, const void *buf, size_t buf_size)
{
    int ret;
    const elf_loader_elf32_ehdr_t *ehdr;
    const elf_loader_elf32_phdr_t *phdr;
    int i;
    u32 min_load_addr;
    u32 max_load_addr;
    u32 info_count;
    u32 memsize;
 
    ret = elf_loader_is_elf_valid_for_loading(buf, buf_size);
    if ( ret )
        return ret;
    ehdr = (const elf_loader_elf32_ehdr_t *)buf;
    phdr = (const elf_loader_elf32_phdr_t *)(((const u8 *)buf) + ehdr->e_phoff);
    memsize = GetMemorySize();
 
    min_load_addr = 0xFFFFFFFF;
    max_load_addr = 0x00100000;
 
    info_count = 0;
    for ( i = 0; i < ehdr->e_phnum; i += 1 )
    {
        if ( phdr[i].p_type == 1 && phdr[i].p_filesz != 0 )
        {
            // Item: move memory down
            execinfo->loaderinfo.items[info_count].dest_addr = (void *)(phdr[i].p_vaddr);
            execinfo->loaderinfo.items[info_count].src_addr = (void *)(((u8 *)buf) + phdr[i].p_offset);
            execinfo->loaderinfo.items[info_count].size = phdr[i].p_filesz;
            {
                u32 load_address;
                u32 end_load_address;
                load_address = phdr[i].p_vaddr;
                end_load_address = load_address + phdr[i].p_filesz;
                if ( load_address < min_load_addr )
                {
                    min_load_addr = load_address;
                }
                if ( end_load_address > max_load_addr )
                {
                    max_load_addr = end_load_address;
                }
            }
            if (
                (u8 *)(execinfo->loaderinfo.items[info_count].dest_addr)
                >= ((u8 *)execinfo->loaderinfo.items[info_count].src_addr) )
                break;
            info_count += 1;
        }
    }
    for ( i = ehdr->e_phnum - 1; i >= 0; i -= 1 )
    {
        if ( phdr[i].p_type == 1 && phdr[i].p_filesz != 0 )
        {
            // Item: move memory up
            execinfo->loaderinfo.items[info_count].dest_addr = (void *)(phdr[i].p_vaddr);
            execinfo->loaderinfo.items[info_count].src_addr = (void *)(((u8 *)buf) + phdr[i].p_offset);
            execinfo->loaderinfo.items[info_count].size = phdr[i].p_filesz;
            {
                u32 load_address;
                u32 end_load_address;
                load_address = phdr[i].p_vaddr;
                end_load_address = load_address + phdr[i].p_filesz;
                if ( load_address < min_load_addr )
                {
                    min_load_addr = load_address;
                }
                if ( end_load_address > max_load_addr )
                {
                    max_load_addr = end_load_address;
                }
            }
            if (
                (u8 *)(execinfo->loaderinfo.items[info_count].dest_addr)
                <= ((u8 *)execinfo->loaderinfo.items[info_count].src_addr) )
                break;
            info_count += 1;
        }
    }
    if ( min_load_addr != 0xFFFFFFFF )
    {
        u32 wanted_size;
        wanted_size = min_load_addr - 0x00100000;
        if ( wanted_size != 0 )
        {
            // Item: clear memory
            execinfo->loaderinfo.items[info_count].dest_addr = (void *)0x00100000;
            execinfo->loaderinfo.items[info_count].src_addr = (void *)NULL;
            execinfo->loaderinfo.items[info_count].size = wanted_size;
            info_count += 1;
        }
    }
    if ( max_load_addr != 0x00100000 )
    {
        u32 wanted_size;
        wanted_size = memsize - (uiptr)max_load_addr;
        // Item: clear memory
        if ( wanted_size != 0 )
        {
            execinfo->loaderinfo.items[info_count].dest_addr = (void *)max_load_addr;
            execinfo->loaderinfo.items[info_count].src_addr = (void *)NULL;
            execinfo->loaderinfo.items[info_count].size = wanted_size;
            info_count += 1;
        }
    }
    // Item: execute entry point
    execinfo->loaderinfo.items[info_count].dest_addr = (void *)(ehdr->e_entry);
    execinfo->loaderinfo.items[info_count].src_addr = (void *)NULL;  // GP returned is always NULL
    execinfo->loaderinfo.items[info_count].size = 0;
 
    return 0;
}
 
int elf_loader_exec_elf_prepare_arginfo(
    elf_loader_execinfo_t *execinfo, const char *filename, const char *partition, int argc, char *argv[])
{
    char *ptr;
    int len, i;
 
    ptr = execinfo->arginfo.payload;
    argc = (argc > 15) ? 15 : argc;
    execinfo->arginfo.argc = argc + 1;
    // Make pointer relative to payload, so that it can be relocated later
    execinfo->arginfo.argv[0] = (char *)((uiptr)ptr - (uiptr)(execinfo->arginfo.payload));
    if ( partition != NULL )
    {
        len = strlen(partition);  // Not including NULL terminator
        if ( ((ptr - execinfo->arginfo.payload) + len) > sizeof(execinfo->arginfo.payload) )
            return -40;
        memcpy(ptr, partition, len);
        ptr += len;
    }
    len = strlen(filename) + 1;
    if ( ((ptr - execinfo->arginfo.payload) + len) > sizeof(execinfo->arginfo.payload) )
        return -40;
    memcpy(ptr, filename, len);
    ptr += len;
    for ( i = 0; i < argc; i += 1 )
    {
        execinfo->arginfo.argv[i + 1] = (char *)((uiptr)ptr - (uiptr)(execinfo->arginfo.payload));
        len = strlen(argv[i]) + 1;
        if ( ((ptr - execinfo->arginfo.payload) + len) > sizeof(execinfo->arginfo.payload) )
            return -40;
        memcpy(ptr, argv[i], len);
        ptr += len;
    }
    return 0;
}
 
static void elf_loader_ldr_entrypoint_stack();
 
static char args_storage[1024];
static elf_loader_loaderinfo_t sg_loaderinfo;
 
// Modified crt0
// bss zero is skipped, and argument handling removed
static void elf_loader_ldr_entrypoint(void)
{
    // clang-format off
    __asm__ __volatile__(
        // SetupThread
        // Arg0: gp value (NULL since not using small data)
        "move $4, $0" "\n"
        // Arg1: Stack address (at EE scratchpad)
        "move $5, $0" "\n"
        "lui $5, 0x7000" "\n"
        // Arg2: Stack size (16 KB)
        "move $6, $0" "\n"
        "ori $6, $6, 0x4000" "\n"
        // Arg3: args buffer (needs to not be NULL since kernel unconditionally writes argc to it)
        "la     $7, %0          \n"
        // Arg4: root function
        "la     $8, ExitThread  \n"
        "move   $gp, $4         \n"
        "addiu  $3, $0, 60      \n"
        "syscall                \n"
        "move   $sp, $2         \n"
        // Jump to entrypoint that can use stack
        "j      %1           \n"
        : // No output registers
        : "R"(args_storage), "Csy"(elf_loader_ldr_entrypoint_stack));
    // clang-format on
}
 
typedef void *(*ldr_getinternalinfo_callback)(void);
#define LDR_ENTRYPOINT_ADDR 0x00084000
 
static void elf_loader_ldr_entrypoint_stack()
{
    ldr_getinternalinfo_callback cb;
 
    // Use VU1 data memory as heap
    SetupHeap((void *)0x1100C000, 0x4000);
 
    FlushCache(0);
 
    memcpy((void *)LDR_ENTRYPOINT_ADDR, ldrsrc, size_ldrsrc);
    // Use VU0 data memory as storage for loader information
    memcpy((void *)0x11004000, &sg_loaderinfo, sizeof(elf_loader_loaderinfo_t));
 
    FlushCache(0);
    FlushCache(2);
 
    cb = (void *)LDR_ENTRYPOINT_ADDR;
    cb();
    // Should be unreachable here
    __builtin_trap();
}
 
int elf_loader_exec_elf(elf_loader_execinfo_t *execinfo)
{
    elf_loader_arginfo_t *low_arginfo;
    int i;
 
    if ( execinfo->arginfo.argc == 0 )
        return -1;
    memcpy(&sg_loaderinfo, &(execinfo->loaderinfo), sizeof(elf_loader_loaderinfo_t));
    // Copy argument info to low EE memory (because EE wipes VU0, VU1, or SPR memory before reading it)
    low_arginfo = (void *)0x00088000;
    memcpy((void *)low_arginfo, &(execinfo->arginfo), sizeof(elf_loader_execinfo_t));
    // Relocate the arguments to the new address
    for ( i = 0; i < low_arginfo->argc; i += 1 )
    {
        low_arginfo->argv[i] = (char *)((uiptr)(low_arginfo->argv[i]) + (uiptr)(low_arginfo->payload));
    }
    ExecPS2(&elf_loader_ldr_entrypoint, NULL, 0, NULL);
    return -1;
}