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fix(kexec-fiwix): NOT TESTED, JUST A TRY compute entry point from PT_LOAD mapping instead of first-phdr heuristic

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vxtls 2026-03-01 09:20:52 -05:00
parent 9db40954d2
commit d588f4d83f
1 changed files with 30 additions and 6 deletions
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36
steps/kexec-fiwix-1.0/src/kexec-fiwix.c
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@ -6,6 +6,7 @@
#include "multiboot1.h"
#define MULTIBOOT_MAGIC 0x2BADB002
#define ELF_PT_LOAD 1
multiboot_uint32_t get_memmap(char *filename, void *memmap_addr) {
@ -99,24 +100,43 @@ int main(int argc, char **argv) {
unsigned int e_phentsize = *((unsigned int *) (&fiwix_mem[0x2A]));
e_phentsize &= 0xFFFF;
printf("ELF size of program headers : %d\n", e_phentsize);
if ((unsigned long) e_phoff + ((unsigned long) e_phnum * (unsigned long) e_phentsize) > (unsigned long) fiwix_len) {
printf("kexec-fiwix: invalid ELF header table (offset=0x%x num=%u entsize=%u)\n",
e_phoff, e_phnum, e_phentsize);
return EXIT_FAILURE;
}
/* Load the kernel */
puts("kexec-fiwix: Placing kernel in memory...");
int header_num;
int found_entry = 0;
unsigned int e_entry_phys = 0;
for (header_num = 0; header_num < e_phnum; header_num++) {
char * fiwix_prog_header = &fiwix_mem[e_phoff + header_num * e_phentsize];
unsigned int p_type = *((unsigned int *) (&fiwix_prog_header[0x00]));
unsigned int p_offset = *((unsigned int *) (&fiwix_prog_header[0x04]));
unsigned int p_vaddr = *((unsigned int *) (&fiwix_prog_header[0x08]));
unsigned int p_paddr = *((unsigned int *) (&fiwix_prog_header[0x0C]));
unsigned int p_filesz = *((unsigned int *) (&fiwix_prog_header[0x10]));
unsigned int p_memsz = *((unsigned int *) (&fiwix_prog_header[0x14]));
if (header_num == 0) {
e_entry -= (p_vaddr - p_paddr);
printf("ELF physical entry point : 0x%x\n", e_entry);
if (p_type != ELF_PT_LOAD) {
continue;
}
if (p_filesz > p_memsz) {
printf("kexec-fiwix: invalid segment %d, p_filesz > p_memsz\n", header_num);
return EXIT_FAILURE;
}
if ((unsigned long) p_offset + (unsigned long) p_filesz > (unsigned long) fiwix_len) {
printf("kexec-fiwix: invalid segment %d, out-of-bounds file range\n", header_num);
return EXIT_FAILURE;
}
if (!found_entry && e_entry >= p_vaddr && (e_entry - p_vaddr) < p_memsz) {
e_entry_phys = p_paddr + (e_entry - p_vaddr);
found_entry = 1;
}
printf("header %d:\n", header_num);
@ -128,6 +148,11 @@ int main(int argc, char **argv) {
memset((void *)p_paddr, 0, p_memsz + 0x10000);
memcpy((void *)p_paddr, &fiwix_mem[p_offset], p_filesz);
}
if (!found_entry) {
printf("kexec-fiwix: could not map ELF entry 0x%x to a PT_LOAD segment\n", e_entry);
return EXIT_FAILURE;
}
printf("ELF physical entry point : 0x%x\n", e_entry_phys);
puts("Preparing multiboot info for kernel...");
@ -251,7 +276,6 @@ int main(int argc, char **argv) {
/* Jump to kernel entry point */
unsigned int magic = MULTIBOOT_BOOTLOADER_MAGIC;
unsigned int dummy = 0;
unsigned int multiboot_info_num = (unsigned int) pmultiboot_info;
printf("Preparing trampoline...\n");
@ -270,7 +294,7 @@ int main(int argc, char **argv) {
0xF3, 0xA4, /* rep movsb */
0xB8, 0x00, 0x00, 0x00, 0x00, /* mov eax, 0x00000000 */
0xBB, 0x00, 0x00, 0x00, 0x00, /* mov ebx, 0x00000000 */
0xFA, /* cli */
0xFB, /* sti */
0xEA, 0x00, 0x00, 0x00, 0x00, 0x08, 0x00 /* jmp far 0x0008:0x00000000 */
};
@ -280,7 +304,7 @@ int main(int argc, char **argv) {
*((unsigned int *) &trampoline[11]) = initrd_len;
*((unsigned int *) &trampoline[19]) = magic;
*((unsigned int *) &trampoline[24]) = multiboot_info_num;
*((unsigned int *) &trampoline[30]) = e_entry;
*((unsigned int *) &trampoline[30]) = e_entry_phys;
memcpy((void *)0x4000, trampoline, sizeof(trampoline));