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Rework syscall ABI.

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Syscalls now accept two parameters, allowing for things like "int count = read(buf, len)"
Rather than providing safe signatures for syscalls, the user is now given helper functions to safely parse incoming values, c-strings and slices.
This commit is contained in:
Toby Jaffey 2025-12-09 21:51:35 +00:00
parent f046a590c0
commit 76fba39a21
28 changed files with 543 additions and 537 deletions
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145
uvm32/uvm32.c
View file

@ -7,6 +7,9 @@
#define UVM32_NULL (void *)0
// 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;
#ifndef UVM32_MEMCPY
#define UVM32_MEMCPY uvm32_memcpy
void uvm32_memcpy(void *dst, const void *src, int len) {
@ -52,26 +55,26 @@ static void setStatus(uvm32_state_t *vmst, uvm32_status_t newStatus) {
}
static void setStatusErr(uvm32_state_t *vmst, uvm32_err_t err) {
setStatus(vmst, UVM32_STATUS_ERROR);
vmst->err = err;
// if already in error state, stay in the first error state
if (vmst->status != UVM32_STATUS_ERROR) {
setStatus(vmst, UVM32_STATUS_ERROR);
vmst->err = err;
}
}
void uvm32_init(uvm32_state_t *vmst, const uvm32_mapping_t *mappings, uint32_t numMappings) {
void uvm32_init(uvm32_state_t *vmst) {
UVM32_MEMSET(vmst, 0x00, sizeof(uvm32_state_t));
vmst->status = UVM32_STATUS_PAUSED;
UVM32_MEMSET(vmst->memory, 0x00, UVM32_MEMORY_SIZE);
vmst->core.pc = MINIRV32_RAM_IMAGE_OFFSET;
// https://projectf.io/posts/riscv-cheat-sheet/
// setup stack pointer
// la sp, _sstack
// addi sp,sp,-16
vmst->core.regs[2] = (MINIRV32_RAM_IMAGE_OFFSET + UVM32_MEMORY_SIZE - sizeof(struct MiniRV32IMAState)) - 16;
vmst->core.regs[2] = (MINIRV32_RAM_IMAGE_OFFSET + UVM32_MEMORY_SIZE) - 16;
vmst->core.regs[10] = 0x00; //hart ID
vmst->core.regs[11] = 0;
vmst->core.extraflags |= 3; // Machine-mode.
vmst->mappings = mappings;
vmst->numMappings = numMappings;
}
bool uvm32_load(uvm32_state_t *vmst, uint8_t *rom, int len) {
@ -85,48 +88,52 @@ bool uvm32_load(uvm32_state_t *vmst, uint8_t *rom, int len) {
}
// Read C-string up to terminator and return len,ptr
static void get_safeptr_terminated(uvm32_state_t *vmst, uint32_t addr, uint8_t terminator, uvm32_evt_syscall_buf_t *buf) {
bool get_safeptr_null_terminated(uvm32_state_t *vmst, uint32_t addr, uvm32_evt_syscall_buf_t *buf) {
uint32_t ptrstart = addr - MINIRV32_RAM_IMAGE_OFFSET;
uint32_t p = ptrstart;
if (p >= UVM32_MEMORY_SIZE) {
setStatusErr(vmst, UVM32_ERR_MEM_RD);
buf->ptr = UVM32_NULL;
buf->ptr = (uint8_t *)UVM32_NULL;
buf->len = 0;
return;
return false;
}
while(vmst->memory[p] != terminator) {
while(vmst->memory[p] != '\0') {
p++;
if (p >= UVM32_MEMORY_SIZE) {
setStatusErr(vmst, UVM32_ERR_MEM_RD);
buf->ptr = UVM32_NULL;
buf->ptr = (uint8_t *)UVM32_NULL;
buf->len = 0;
return;
return false;
}
}
buf->ptr = &vmst->memory[ptrstart];
buf->len = p - ptrstart;
return true;
}
#if 0
static void get_safeptr(uvm32_state_t *vmst, uint32_t addr, uint32_t len, uvm32_evt_syscall_buf_t *buf) {
bool get_safeptr(uvm32_state_t *vmst, uint32_t addr, uint32_t len, uvm32_evt_syscall_buf_t *buf) {
uint32_t ptrstart = addr - MINIRV32_RAM_IMAGE_OFFSET;
if (ptrstart + len >= UVM32_MEMORY_SIZE) {
if ((ptrstart > UVM32_MEMORY_SIZE) || (ptrstart + len >= UVM32_MEMORY_SIZE)) {
setStatusErr(vmst, UVM32_ERR_MEM_RD);
buf->ptr = (uint8_t *)UVM32_NULL;
buf->len = 0;
return false;
}
buf->ptr = &vmst->memory[ptrstart];
buf->len = len;
return true;
}
#endif
uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter) {
uint32_t num_instr = 0;
void uvm32_clearError(uvm32_state_t *vmst) {
if (vmst->status == UVM32_STATUS_ERROR) {
// vm is in an error state, but user wants to continue
// most likely after UVM32_ERR_HUNG
vmst->status = UVM32_STATUS_PAUSED;
}
}
uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter) {
uint32_t num_instr = 0;
if (vmst->status != UVM32_STATUS_PAUSED) {
setStatusErr(vmst, UVM32_ERR_NOTREADY);
@ -142,9 +149,8 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
uint32_t ret;
ret = MiniRV32IMAStep(vmst, &vmst->core, vmst->memory, 0, elapsedUs, 1);
if (3 == ret) {
// Fetch registers used by syscall
const uint32_t syscall = vmst->core.regs[17]; // a7
uint32_t value = vmst->core.regs[10]; // a0
bool syscall_valid = false;
// on exception we should jump to mtvec, but we handle directly
// and skip over the ecall instruction
vmst->core.pc += 4;
@ -152,46 +158,19 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
// inbuilt syscalls
case UVM32_SYSCALL_HALT:
setStatus(vmst, UVM32_STATUS_ENDED);
syscall_valid = true;
break;
case UVM32_SYSCALL_YIELD:
vmst->ioevt.typ = UVM32_EVT_YIELD;
setStatus(vmst, UVM32_STATUS_PAUSED);
syscall_valid = true;
break;
// user defined syscalls
default:
// search in mappings
for (int i=0;i<vmst->numMappings;i++) {
if (syscall == vmst->mappings[i].syscall) {
// setup ioevt.data according to mapping typ
switch(vmst->mappings[i].typ) {
case UVM32_SYSCALL_TYP_VOID:
break;
case UVM32_SYSCALL_TYP_U32_WR:
vmst->ioevt.data.syscall.val.u32 = value;
break;
case UVM32_SYSCALL_TYP_BUF_TERMINATED_WR:
get_safeptr_terminated(vmst, value, 0x00, &vmst->ioevt.data.syscall.val.buf);
break;
case UVM32_SYSCALL_TYP_U32_RD:
// pass link to r1 for user function to update
vmst->ioevt.data.syscall.val.u32p = &vmst->core.regs[11];
break;
}
vmst->ioevt.typ = UVM32_EVT_SYSCALL;
vmst->ioevt.data.syscall.code = vmst->mappings[i].code;
vmst->ioevt.data.syscall.typ = vmst->mappings[i].typ;
setStatus(vmst, UVM32_STATUS_PAUSED);
syscall_valid = true;
break; // stop searching
}
}
// no mapping found
if (!syscall_valid) {
setStatusErr(vmst, UVM32_ERR_BAD_SYSCALL);
}
// user defined syscalls
vmst->ioevt.typ = UVM32_EVT_SYSCALL;
vmst->ioevt.data.syscall.code = syscall;
vmst->ioevt.data.syscall.ret = &vmst->core.regs[12]; // a2
vmst->ioevt.data.syscall.params[0] = &vmst->core.regs[10]; // a0
vmst->ioevt.data.syscall.params[1] = &vmst->core.regs[11]; // a1
setStatus(vmst, UVM32_STATUS_PAUSED);
break;
}
} else if (ret != 0) {
@ -235,4 +214,54 @@ bool uvm32_hasEnded(const uvm32_state_t *vmst) {
return vmst->status == UVM32_STATUS_ENDED;
}
static uint32_t *arg_to_ptr(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t arg) {
switch(arg) {
case ARG0:
return evt->data.syscall.params[0];
break;
case ARG1:
return evt->data.syscall.params[1];
break;
case RET:
return evt->data.syscall.ret;
break;
default:
// if something invalid is passed to arg, we should never crash
// return a pointer to something readable
setStatusErr(vmst, UVM32_ERR_ARGS);
garbage = 0;
return &garbage;
break;
}
}
void uvm32_setval(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t arg, uint32_t val) {
*arg_to_ptr(vmst, evt, arg) = val;
}
uint32_t uvm32_getval(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t arg) {
return *arg_to_ptr(vmst, evt, arg);
}
const char *uvm32_getcstr(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t arg) {
uvm32_evt_syscall_buf_t scb;
if (get_safeptr_null_terminated(vmst, uvm32_getval(vmst, evt, arg), &scb)) {
return (const char *)scb.ptr; // we know the buffer in cpu memory is null terminated, so safe to pass back
} else {
setStatusErr(vmst, UVM32_ERR_MEM_RD);
garbage = 0;
return (const char *)&garbage;
}
}
uvm32_evt_syscall_buf_t uvm32_getbuf(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t argPtr, uvm32_arg_t argLen) {
uvm32_evt_syscall_buf_t scb;
if (!get_safeptr(vmst, uvm32_getval(vmst, evt, argPtr), uvm32_getval(vmst, evt, argLen), &scb)) {
setStatusErr(vmst, UVM32_ERR_MEM_RD);
garbage = 0;
scb.ptr = (uint8_t *)&garbage;
scb.len = 0;
}
return scb;
}

61
uvm32/uvm32.h
View file

@ -14,6 +14,7 @@
X(UVM32_ERR_HUNG) \
X(UVM32_ERR_INTERNAL_CORE) \
X(UVM32_ERR_INTERNAL_STATE) \
X(UVM32_ERR_ARGS) \
#define X(name) name,
typedef enum {
@ -28,42 +29,17 @@ typedef enum {
UVM32_EVT_END,
} uvm32_evt_typ_t;
typedef enum {
UVM32_SYSCALL_TYP_BUF_TERMINATED_WR, // data write from vm, NULL terminated string of bytes, in uvm32_evt_syscall_t.val.buf
UVM32_SYSCALL_TYP_VOID, // no data
UVM32_SYSCALL_TYP_U32_WR, // data write from vm, in uvm32_evt_syscall_t.val.u32
UVM32_SYSCALL_TYP_U32_RD, // data read from vm, expects response in uvm32_evt_syscall_t.val.u32p
} uvm32_syscall_typ_t;
typedef uint32_t uvm32_user_syscall_code_t;
// user supplied mapping from syscall to typed syscall
typedef struct {
uint32_t syscall;
uvm32_user_syscall_code_t code;
uvm32_syscall_typ_t typ;
} uvm32_mapping_t;
typedef struct {
uint8_t *ptr;
uint32_t len;
} uvm32_evt_syscall_buf_t;
typedef struct {
uvm32_syscall_typ_t typ;
uvm32_user_syscall_code_t code;
union {
uvm32_evt_syscall_buf_t buf;
uint32_t u32;
uint32_t *u32p;
} val;
} uvm32_evt_syscall_t;
typedef struct {
uvm32_err_t errcode;
const char *errstr;
} uvm32_evt_err_t;
typedef struct {
uint32_t code; // syscall number
uint32_t *ret;
uint32_t *params[2];
} uvm32_evt_syscall_t;
typedef struct {
uvm32_evt_typ_t typ;
union {
@ -93,13 +69,30 @@ typedef struct {
struct MiniRV32IMAState core;
uint8_t memory[UVM32_MEMORY_SIZE];
uvm32_evt_t ioevt; // for building up in callbacks
const uvm32_mapping_t *mappings;
uint32_t numMappings;
} uvm32_state_t;
void uvm32_init(uvm32_state_t *vmst, const uvm32_mapping_t *mappings, uint32_t numMappings);
void uvm32_init(uvm32_state_t *vmst);
bool uvm32_load(uvm32_state_t *vmst, uint8_t *rom, int len);
bool uvm32_hasEnded(const uvm32_state_t *vmst);
uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter);
// convenience for getptr
typedef struct {
uint8_t *ptr;
uint32_t len;
} uvm32_evt_syscall_buf_t;
typedef enum {
ARG0,
ARG1,
RET
} uvm32_arg_t;
uint32_t uvm32_getval(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t);
const char *uvm32_getcstr(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t);
void uvm32_setval(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t, uint32_t val);
uvm32_evt_syscall_buf_t uvm32_getbuf(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t argPtr, uvm32_arg_t argLen);
void uvm32_clearError(uvm32_state_t *vmst);
#endif