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arc-v/kpatch/main.c
AuxXxilium 2085e367e8 arc: init reloaded 
Signed-off-by: AuxXxilium <info@auxxxilium.tech>
2023-11-02 20:15:04 +01:00

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/*
* Copyright (c) 2022 Fabio Belavenuto <belavenuto@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/
/**
* Converted from php code by Fabio Belavenuto <belavenuto@gmail.com>
*
* A quick tool for patching the boot_params check in the DSM kernel image
* This lets you tinker with the initial ramdisk contents without disabling mount() features and modules loading
*
* The overall pattern we need to find is:
* - an CDECL function
* - does "LOCK OR [const-ptr],n" 4x
* - values of ORs are 1/2/4/8 respectively
* - [const-ptr] is always the same
*
* Added patch for CMOS_WRITE by Fabio Belavenuto
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <getopt.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdarg.h>
#include <gelf.h>
const int DIR_FWD = 1;
const int DIR_RWD = -1;
/* Variables */
int fd, verbose = 1, read_only = 0;
Elf *elfHandle;
GElf_Ehdr elfExecHeader;
uint64_t orPos[4], fileSize, rodataAddr, rodataOffs, initTextOffs;
unsigned char *fileData;
/*****************************************************************************/
void errorMsg(char *fmt, ...)
{
va_list args;
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
fprintf(stderr, "\n");
exit(1);
}
/*****************************************************************************/
void errorNum()
{
char str[100] = {0};
perror(str);
exit(2);
}
/*****************************************************************************/
void elfErrno()
{
int err;
if ((err = elf_errno()) != 0)
{
fprintf(stderr, "%s\n", elf_errmsg(err));
exit(3);
}
}
/*****************************************************************************/
// Finding a function boundary is non-trivial really as patters can vary, we can have multiple exit points, and in CISC
// there are many things which may match e.g. "PUSH EBP". Implementing even a rough disassembler is pointless.
// However, we can certainly cheat here as we know with CDECL a non-empty function will always contain one or more
// PUSH (0x41) R12-R15 (0x54-57) sequences. Then we can search like a 1K forward for these characteristic LOCK OR.
uint64_t findPUSH_R12_R15_SEQ(uint64_t start)
{
uint64_t i;
for (i = start; i < fileSize; i++)
{
if (fileData[i] == 0x41 && (fileData[i + 1] >= 0x54 && fileData[i + 1] <= 0x57))
{
return i;
}
}
return -1;
}
/*****************************************************************************/
//[0xF0, 0x80, null, null, null, null, null, 0xXX],
uint64_t findORs(uint64_t start, uint32_t maxCheck)
{
uint64_t i;
int c = 0;
uint8_t lb = 0x01;
for (i = start; i < fileSize; i++)
{
if (fileData[i] == 0xF0 && fileData[i + 1] == 0x80 && fileData[i + 7] == lb)
{
orPos[c++] = i;
i += 7;
lb <<= 1;
}
if (c == 4)
{
break;
}
if (--maxCheck == 0)
{
break;
}
}
return c;
}
/*****************************************************************************/
void patchBootParams()
{
uint64_t addr, pos;
uint64_t newPtrOffset, ptrOffset;
int n;
printf("Patching boot params.\n");
// The function will reside in init code part. We don't care we may potentially search beyond as we expect it to be found
while (initTextOffs < fileSize)
{
addr = findPUSH_R12_R15_SEQ(initTextOffs);
if (addr == -1)
break; // no more "functions" left
printf("\rAnalyzing f() candidate @ %lX, PUSH @ %lX", initTextOffs, addr);
// we found something looking like PUSH R12-R15, now find the ORs
n = findORs(initTextOffs, 1024);
if (n != 4)
{
// We can always move forward by the function token length (obvious) but if we couldn't find any LOCK-OR tokens
// we can skip the whole look ahead distance. We CANNOT do that if we found even a single token because the next one
// might have been just after the look ahead distance
initTextOffs += 2;
if (n == 0)
{
initTextOffs += 1024;
}
continue; // Continue the main search loop to find next function candidate
}
// We found LOCK(); OR ptr sequences so we can print some logs and collect ptrs (as this is quite expensive)
printf("\n[?] Found possible f() @ %lX\n", initTextOffs);
ptrOffset = 0;
int ec = 0;
for (n = 0; n < 4; n++)
{
// data will have the following bytes:
// [0-LOCK()] [1-OR()] [2-BYTE-PTR] [3-OFFS-b3] [4-OFFS-b2] [5-OFFS-b1] [6-OFFS-b1] [7-NUMBER]
pos = orPos[n];
// how far it "jumps"
newPtrOffset = pos + (fileData[pos + 6] << 24 | fileData[pos + 5] << 16 | fileData[pos + 4] << 8 | fileData[pos + 3]);
if (ptrOffset == 0)
{
ptrOffset = newPtrOffset;
++ec;
}
else if (ptrOffset == newPtrOffset)
{
++ec;
}
printf("\t[+] Found LOCK-OR#%d sequence @ %lX => %02X %02X %02X %02X %02X %02X %02X %02X [RIP+%lX]\n",
n, pos, fileData[pos], fileData[pos + 1], fileData[pos + 2], fileData[pos + 3], fileData[pos + 4],
fileData[pos + 5], fileData[pos + 6], fileData[pos + 7], newPtrOffset);
}
if (ec != 4)
{
printf("\t[-] LOCK-OR PTR offset mismatch - %d/4 matched\n", ec);
// If the pointer checking failed we can at least move beyond the last LOCK-OR found as we know there's no valid
// sequence of LOCK-ORs there
initTextOffs = orPos[3];
continue;
}
printf("\t[+] All %d LOCK-OR PTR offsets equal - match found!\n", ec);
break;
}
if (addr == -1)
{
errorMsg("\nFailed to find matching sequences\n");
}
else
{
// Patch offsets
for (n = 0; n < 4; n++)
{
// The offset will point at LOCK(), we need to change the OR (0x80 0x0d) to AND (0x80 0x25) so the two bytes after
pos = orPos[n] + 2;
printf("Patching OR to AND @ %lX\n", pos);
fileData[pos] = 0x25;
}
}
}
/*****************************************************************************/
uint32_t changeEndian(uint32_t num)
{
return ((num >> 24) & 0xff) | // move byte 3 to byte 0
((num << 8) & 0xff0000) | // move byte 1 to byte 2
((num >> 8) & 0xff00) | // move byte 2 to byte 1
((num << 24) & 0xff000000); // move byte 0 to byte 3
}
/*****************************************************************************/
uint64_t findSeq(const char *seq, int len, uint32_t pos, int dir, uint64_t max)
{
uint64_t i = pos;
do
{
if (memcmp((const char *)fileData + i, seq, len) == 0)
{
return i;
}
i += dir;
--max;
} while (i > 0 && i < fileSize && max > 0);
return -1;
}
/*****************************************************************************/
void patchRamdiskCheck()
{
uint64_t pos, errPrintAddr;
uint64_t printkPos, testPos, jzPos;
const char str[] = "3ramdisk corrupt";
printf("Patching ramdisk check.\n");
for (pos = rodataOffs; pos < fileSize; pos++)
{
if (memcmp(str, (const char *)(fileData + pos), 16) == 0)
{
pos -= rodataOffs;
break;
}
}
errPrintAddr = rodataAddr + pos - 1;
printf("LE arg addr: %08lX\n", errPrintAddr);
printkPos = findSeq((const char *)&errPrintAddr, 4, 0, DIR_FWD, -1);
if (printkPos == -1)
{
errorMsg("printk pos not found!\n");
}
// double check if it's a MOV reg,VAL (where reg is EAX/ECX/EDX/EBX/ESP/EBP/ESI/EDI)
printkPos -= 3;
if (memcmp((const char *)fileData + printkPos, "\x48\xc7", 2) != 0)
{
errorMsg("Expected MOV=>reg before printk error, got %02X %02X\n", fileData[printkPos], fileData[printkPos + 1]);
}
if (fileData[printkPos + 2] < 0xC0 || fileData[printkPos + 2] > 0xC7)
{
errorMsg("Expected MOV w/reg operand [C0-C7], got %02X\n", fileData[printkPos + 2]);
}
printf("Found printk MOV @ %08lX\n", printkPos);
// now we should seek a reasonable amount (say, up to 32 bytes) for a sequence of CALL x => TEST EAX,EAX => JZ
testPos = findSeq("\x85\xc0", 2, printkPos, DIR_RWD, 32);
if (testPos == -1)
{
errorMsg("Failed to find TEST eax,eax\n");
}
printf("Found TEST eax,eax @ %08lX\n", testPos);
jzPos = testPos + 2;
if (fileData[jzPos] != 0x74)
{
errorMsg("Failed to find JZ\n");
}
printf("OK - patching %02X%02X (JZ) to %02X%02X (JMP) @ %08lX\n",
fileData[jzPos], fileData[jzPos + 1], 0xEB, fileData[jzPos + 1], jzPos);
fileData[jzPos] = 0xEB;
}
/*****************************************************************************/
void patchCmosWrite()
{
uint64_t pos, errPrintAddr;
uint64_t pr_errPos, testPos, callPos;
const char str[] = "3smpboot: %s: this boot have memory training";
printf("Patching call to rtc_cmos_write.\n");
for (pos = rodataOffs; pos < fileSize; pos++)
{
if (memcmp(str, (const char *)(fileData + pos), 16) == 0)
{
pos -= rodataOffs;
break;
}
}
errPrintAddr = rodataAddr + pos - 1;
printf("LE arg addr: %08lX\n", errPrintAddr);
pr_errPos = findSeq((const char *)&errPrintAddr, 4, 0, DIR_FWD, -1);
if (pr_errPos == -1)
{
printf("pr_err pos not found - ignoring.\n"); // Some kernels do not have the call, exit without error
return;
}
// double check if it's a MOV reg,VAL (where reg is EAX/ECX/EDX/EBX/ESP/EBP/ESI/EDI)
pr_errPos -= 3;
if (memcmp((const char *)fileData + pr_errPos, "\x48\xc7", 2) != 0)
{
errorMsg("Expected MOV=>reg before pr_err error, got %02X %02X\n", fileData[pr_errPos], fileData[pr_errPos + 1]);
}
if (fileData[pr_errPos + 2] < 0xC0 || fileData[pr_errPos + 2] > 0xC7)
{
errorMsg("Expected MOV w/reg operand [C0-C7], got %02X\n", fileData[pr_errPos + 2]);
}
printf("Found pr_err MOV @ %08lX\n", pr_errPos);
// now we should seek a reasonable amount (say, up to 64 bytes) for a sequence of
// MOV ESI, 0x48 => MOV EDI, 0xFF => MOV EBX, EAX
testPos = findSeq("\xBE\x48\x00\x00\x00\xBF\xFF\x00\x00\x00\x89\xC3", 12, pr_errPos, DIR_RWD, 64);
if (testPos == -1)
{
printf("Failed to find MOV ESI, 0x48 => MOV EDI, 0xFF => MOV EBX, EAX\n");
return;
}
printf("Found MOV ESI, 0x48 => MOV EDI, 0xFF => MOV EBX, EAX @ %08lX\n", testPos);
callPos = testPos + 12;
if (fileData[callPos] != 0xE8)
{
errorMsg("Failed to find CALL\n");
}
printf("OK - patching %02X (CALL) to 0x90.. (NOPs) @ %08lX\n",
fileData[callPos], callPos);
for (uint64_t i = 0; i < 5; i++)
fileData[callPos + i] = 0x90;
}
/*****************************************************************************/
int main(int argc, char *argv[])
{
struct stat fileInf;
Elf_Scn *section;
GElf_Shdr sectionHeader;
char *sectionName;
char *fileIn = NULL, *fileOut = NULL;
int onlyBoot = 0, onlyRD = 0, onlyCMOS = 0, c;
if (argc < 3)
{
errorMsg("Use: kpatch (option) <vmlinux> <output>\nOptions:\n -b Only bootparams\n -r Only ramdisk\n -c Only CMOS");
}
c = 1;
while (c < argc)
{
if (strcmp(argv[c], "-b") == 0)
{
onlyBoot = 1;
}
else if (strcmp(argv[c], "-r") == 0)
{
onlyRD = 1;
}
else if (strcmp(argv[c], "-c") == 0)
{
onlyCMOS = 1;
}
else if (fileIn == NULL)
{
fileIn = argv[c];
}
else
{
fileOut = argv[c];
break;
}
++c;
}
if (NULL == fileIn)
{
errorMsg("Please give a input filename");
}
if (NULL == fileOut)
{
errorMsg("Please give a output filename");
}
if (elf_version(EV_CURRENT) == EV_NONE)
elfErrno();
if ((fd = open(fileIn, O_RDONLY)) == -1)
errorNum();
if ((elfHandle = elf_begin(fd, ELF_C_READ, NULL)) == NULL)
elfErrno();
if (gelf_getehdr(elfHandle, &elfExecHeader) == NULL)
elfErrno();
switch (elf_kind(elfHandle))
{
case ELF_K_NUM:
case ELF_K_NONE:
errorMsg("file type unknown\n");
break;
case ELF_K_COFF:
errorMsg("COFF binaries not supported\n");
break;
case ELF_K_AR:
errorMsg("AR archives not supported\n");
break;
case ELF_K_ELF:
break;
}
section = NULL;
while ((section = elf_nextscn(elfHandle, section)) != NULL)
{
if (gelf_getshdr(section, &sectionHeader) != &sectionHeader)
elfErrno();
if ((sectionName = elf_strptr(elfHandle, elfExecHeader.e_shstrndx, sectionHeader.sh_name)) == NULL)
elfErrno();
if (strcmp(sectionName, ".init.text") == 0)
{
initTextOffs = sectionHeader.sh_offset;
}
else if (strcmp(sectionName, ".rodata") == 0)
{
rodataAddr = sectionHeader.sh_addr & 0xFFFFFFFF;
rodataOffs = sectionHeader.sh_offset;
}
}
elfErrno(); /* If there isn't elf_errno set, nothing will happend. */
elf_end(elfHandle);
if (fstat(fd, &fileInf) == -1)
errorNum();
fileSize = fileInf.st_size;
fileData = malloc(fileSize);
if (fileSize != read(fd, fileData, fileSize))
{
errorNum();
}
close(fd);
printf("Found .init.text offset @ %lX\n", initTextOffs);
printf("Found .rodata address @ %lX\n", rodataAddr);
printf("Found .rodata offset @ %lX\n", rodataOffs);
if (onlyBoot == 0 && onlyCMOS == 0 && onlyRD == 0)
{
patchBootParams();
patchRamdiskCheck();
patchCmosWrite();
}
else
{
if (onlyBoot == 1)
{
patchBootParams();
}
if (onlyRD == 1)
{
patchRamdiskCheck();
}
if (onlyCMOS == 1)
{
patchCmosWrite();
}
}
if ((fd = open(fileOut, O_WRONLY | O_CREAT, 0644)) == -1)
{
errorNum();
}
if (fileSize != write(fd, fileData, fileSize))
{
errorNum();
}
close(fd);
printf("Finish!\n");
return 0;
}
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