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Add a stack canary, setup on boot

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This commit is contained in:
Toby Jaffey 2025-12-10 01:00:36 +00:00
parent 9596838a4b
commit 9baedb42e8
21 changed files with 61 additions and 16 deletions
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30
uvm32/uvm32.c
View file

@ -10,6 +10,9 @@
// On an invalid operation, an error is set in uvm32_state_t, but a valid pointer still needs to be temporarily used
static uint32_t garbage;
// magic value for stack canary
#define STACK_CANARY_VALUE 0x42
#ifndef UVM32_MEMCPY
#define UVM32_MEMCPY uvm32_memcpy
void uvm32_memcpy(void *dst, const void *src, int len) {
@ -84,6 +87,8 @@ bool uvm32_load(uvm32_state_t *vmst, const uint8_t *rom, int len) {
}
UVM32_MEMCPY(vmst->memory, rom, len);
vmst->stack_canary = (uint8_t *)UVM32_NULL;
return true;
}
@ -135,6 +140,12 @@ void uvm32_clearError(uvm32_state_t *vmst) {
uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter) {
uint32_t num_instr = 0;
if (vmst->stack_canary != UVM32_NULL && *vmst->stack_canary != STACK_CANARY_VALUE) {
setStatusErr(vmst, UVM32_ERR_STACKOVERFLOW);
setup_err_evt(vmst, evt);
return num_instr;
}
if (vmst->status != UVM32_STATUS_PAUSED) {
setStatusErr(vmst, UVM32_ERR_NOTREADY);
setup_err_evt(vmst, evt);
@ -163,6 +174,25 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
vmst->ioevt.typ = UVM32_EVT_YIELD;
setStatus(vmst, UVM32_STATUS_PAUSED);
break;
case UVM32_SYSCALL_STACKPROTECT: {
// don't allow errant code to change it once set
if (vmst->stack_canary == (uint8_t *)UVM32_NULL) {
uint32_t param0 = vmst->core.regs[10];
uint32_t mem_offset = param0 - MINIRV32_RAM_IMAGE_OFFSET;
// check data fits in ram
if (mem_offset > UVM32_MEMORY_SIZE) {
setStatusErr(vmst, UVM32_ERR_STACKOVERFLOW);
setup_err_evt(vmst, evt);
}
// check canary is inside valid memory
if (mem_offset < UVM32_MEMORY_SIZE) {
// set canary
vmst->stack_canary = &vmst->memory[mem_offset];
*vmst->stack_canary = STACK_CANARY_VALUE;
}
}
} break;
default:
// user defined syscalls
vmst->ioevt.typ = UVM32_EVT_SYSCALL;

2
uvm32/uvm32.h
View file

@ -15,6 +15,7 @@
X(UVM32_ERR_INTERNAL_CORE) \
X(UVM32_ERR_INTERNAL_STATE) \
X(UVM32_ERR_ARGS) \
X(UVM32_ERR_STACKOVERFLOW) \
#define X(name) name,
typedef enum {
@ -69,6 +70,7 @@ typedef struct {
struct MiniRV32IMAState core;
uint8_t memory[UVM32_MEMORY_SIZE];
uvm32_evt_t ioevt; // for building up in callbacks
uint8_t *stack_canary;
} uvm32_state_t;
void uvm32_init(uvm32_state_t *vmst);