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Disable stack canary by default

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This commit is contained in:
Toby Jaffey 2025-12-12 21:01:40 +00:00
parent 3ecd16c8bf
commit 789cd74516
4 changed files with 13 additions and 3 deletions
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12
uvm32/uvm32.c
View file

@ -16,8 +16,9 @@
// 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
#ifdef UVM32_STACK_PROTECTION
#define STACK_CANARY_VALUE 0x42 // magic value for stack canary
#endif
#ifndef UVM32_MEMCPY
#define UVM32_MEMCPY uvm32_memcpy
@ -101,8 +102,9 @@ bool uvm32_load(uvm32_state_t *vmst, const uint8_t *rom, int len) {
}
UVM32_MEMCPY(vmst->_memory, rom, len);
#ifdef UVM32_STACK_PROTECTION
vmst->_stack_canary = (uint8_t *)NULL;
#endif
return true;
}
@ -207,11 +209,13 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
orig_instr_meter = min_instrs;
}
#ifdef UVM32_STACK_PROTECTION
if (vmst->_stack_canary != NULL && *vmst->_stack_canary != STACK_CANARY_VALUE) {
setStatusErr(vmst, UVM32_ERR_INTERNAL_CORE);
setup_err_evt(vmst, evt);
return orig_instr_meter - instr_meter;
}
#endif
if (vmst->_status != UVM32_STATUS_PAUSED) {
setStatusErr(vmst, UVM32_ERR_NOTREADY);
@ -243,6 +247,7 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
setStatus(vmst, UVM32_STATUS_ENDED);
break;
case UVM32_SYSCALL_STACKPROTECT: {
#ifdef UVM32_STACK_PROTECTION
// don't allow errant code to change it once set
if (vmst->_stack_canary == (uint8_t *)NULL) {
uint32_t param0 = vmst->_core.regs[10]; // a0
@ -263,6 +268,7 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
*vmst->_stack_canary = STACK_CANARY_VALUE;
}
}
#endif
} break;
default:
// user defined syscalls

2
uvm32/uvm32.h
View file

@ -118,7 +118,9 @@ typedef struct {
struct MiniRV32IMAState _core; /*! CPU registers */
uint8_t _memory[UVM32_MEMORY_SIZE]; /*! Memory */
uvm32_evt_t _ioevt; /*! Event to be returned on next pause */
#ifdef UVM32_STACK_PROTECTION
uint8_t *_stack_canary; /*! Location of stack canary */
#endif
uint8_t *_extram; /*! External RAM pointer, or NULL */
uint32_t _extramLen; /*! Length of external RAM */
bool _extramDirty; /*! Flag to indicate VM code has modified extram since last run */