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/*
* Copyright (c) 2025 Ian Marco Moffett and L5 engineers
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the project nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Description: Subsystem to convert PIIR to instruction bytes
* Author: Ian Marco Moffett
*/
#include <sys/types.h>
#include <sys/errno.h>
#include <sys/syslog.h>
#include <machine/piir.h>
#include <np/piir.h>
#include <os/np.h>
#define pr_trace(fmt, ...) printf("piir.conv: " fmt, ##__VA_ARGS__)
#define pr_error(fmt, ...) printf("piir.conv: error: " fmt, ##__VA_ARGS__)
typedef md_byte_t inst_t[8];
/*
* Valid 32-bit register IDs
*/
typedef enum {
R32_EAX,
R32_ECX,
R32_EDX,
R32_EBX,
R32_ESP,
R32_EBP,
R32_ESI,
R32_RDI
} r32_t;
/* SYS-V ABI specific */
#define R32_RETVAL R32_EAX
/* Declare an instruction array */
#define INST_DECL(...) ((inst_t)__VA_ARGS__)
/* Near return [C2] */
#define OP_NRET INST_DECL({0xC2})
#define OP_NRET_LEN 1
/* No-operation */
#define OP_NOP INST_DECL({0x90})
#define OP_NOP_LEN 1
/* MOV R32, IMM32 (B8 + rd) */
#define OP_LOAD32_R32(IMM32, RD) INST_DECL({0xB8 + (RD), (IMM32)})
#define OP_LOAD32_R32_LEN 5
/*
* Push an instruction byte into the virtual
* machine descriptor's code buffer
*/
static ssize_t
vm_push(struct piir_vm *vm, inst_t inst, size_t len)
{
for (int i = 0; i < len; ++i) {
if (vm->code_i >= sizeof(vm->code) - 1) {
return -1;
}
vm->code[vm->code_i++] = inst[i];
}
return len;
}
ssize_t
md_piir_decode(struct np_work *work, struct piir_vm *vm, ir_byte_t input)
{
struct piir_stack *stack;
ssize_t len;
if (vm == NULL) {
return -EINVAL;
}
vm->last_ir = input;
stack = work->piir_stack;
/*
* Convert the instruction from IR to machine
* code so that it actually may be executed
*/
switch (input) {
case PIIR_RET_NUM:
if ((input = piir_pop(stack)) < 0) {
pr_error("bad input on PIIR_RET_NUM\n");
return input;
}
return vm_push(
vm, OP_LOAD32_R32(input, R32_RETVAL),
OP_LOAD32_R32_LEN
);
case PIIR_NOP:
return vm_push(vm, OP_NOP, OP_NOP_LEN);
case PIIR_RET_NIL:
return vm_push(vm, OP_NRET, OP_NRET_LEN);
}
return 0;
}
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