Bring up Linux kernel

Author: ChinYikMing

Makefile

@@ -47,6 +47,8 @@ OBJS_EXT :=
 
 ifeq ($(call has, SYSTEM), 1)
 OBJS_EXT += system.o
+OBJS_EXT += plic.o
+OBJS_EXT += uart.o
 endif
 
 # Integer Multiplication and Division instructions

build/Image

@@ -27,6 +27,21 @@
 
 #define MASK(n) (~((~0U << (n))))
 
+/*
+ * Integer log base 2
+ *
+ * The input will be ORed with 1 to prevent x = 0 since
+ * the result is undefined if x = 0
+ *
+ */
+#if defined(__GNUC__) || defined(__clang__)
+#define ilog2(x) 31 - __builtin_clz(x | 1)
+#elif defined(_MSC_VER)
+/* FIXME */
+#else /* unsupported compilers */
+#define ilog2(x)
+#endif
+
 /* Alignment macro */
 #if defined(__GNUC__) || defined(__clang__)
 #define __ALIGNED(x) __attribute__((aligned(x)))

build/minimal.dtb

@@ -922,9 +922,7 @@ static inline bool op_misc_mem(rv_insn_t *ir, const uint32_t insn)
      * FENCE   FM[3:0]   pred[3:0]  succ[3:0]  rs1   000     rd   0001111
      * FENCEI            imm[11:0]             rs1   001     rd   0001111
      */
-
     const uint32_t funct3 = decode_funct3(insn);
-
     switch (funct3) {
     case 0b000:
         ir->opcode = rv_insn_fence;

build/rootfs.cpio

@@ -90,7 +90,7 @@ enum op_field {
     )                                                  \
     /* RV32 Zicsr Standard Extension */                \
     IIF(RV32_HAS(Zicsr))(                              \
-        _(csrrw, 0, 4, 0, ENC(rs1, rd))                \
+        _(csrrw, 1, 4, 0, ENC(rs1, rd))                \
         _(csrrs, 0, 4, 0, ENC(rs1, rd))                \
         _(csrrc, 0, 4, 0, ENC(rs1, rd))                \
         _(csrrwi, 0, 4, 0, ENC(rs1, rd))               \

src/common.h

@@ -10,6 +10,10 @@
 #include <stdlib.h>
 #include <string.h>
 
+#if RV32_HAS(SYSTEM)
+#include "plic.h"
+#endif /* RV32_HAS(SYSTEM) */
+
 #ifdef __EMSCRIPTEN__
 #include <emscripten.h>
 #endif
@@ -41,6 +45,12 @@ extern struct target_ops gdbstub_ops;
 #define IF_rs2(i, r) (i->rs2 == rv_reg_##r)
 #define IF_imm(i, v) (i->imm == v)
 
+#if RV32_HAS(SYSTEM)
+static uint32_t reloc_enable_mmu_jalr_addr;
+static bool reloc_enable_mmu = false;
+bool need_retranslate = false;
+#endif
+
 static void rv_trap_default_handler(riscv_t *rv)
 {
     rv->csr_mepc += rv->compressed ? 2 : 4;
@@ -81,6 +91,13 @@ static inline void update_time(riscv_t *rv)
     rv->csr_time[1] = t >> 32;
 }
 
+#if RV32_HAS(SYSTEM)
+static inline void get_time_now(struct timeval *tv)
+{
+    rv_gettimeofday(tv);
+}
+#endif
+
 #if RV32_HAS(Zicsr)
 /* get a pointer to a CSR */
 static uint32_t *csr_get_ptr(riscv_t *rv, uint32_t csr)
@@ -177,6 +194,13 @@ static uint32_t csr_csrrw(riscv_t *rv, uint32_t csr, uint32_t val)
 
     *c = val;
 
+    /*
+     * guestOS's process might have same VA,
+     * so block_map cannot be reused
+     */
+    if (c == &rv->csr_satp)
+        block_map_clear(rv);
+
     return out;
 }
 
@@ -349,6 +373,11 @@ static set_t pc_set;
 static bool has_loops = false;
 #endif
 
+#if RV32_HAS(SYSTEM)
+extern void emu_update_uart_interrupts(riscv_t *rv);
+static uint32_t peripheral_update_ctr = 64;
+#endif
+
 /* Interpreter-based execution path */
 #define RVOP(inst, code, asm)                                         \
     static bool do_##inst(riscv_t *rv, rv_insn_t *ir, uint64_t cycle, \
@@ -539,6 +568,8 @@ FORCE_INLINE bool insn_is_unconditional_branch(uint8_t opcode)
 
 static void block_translate(riscv_t *rv, block_t *block)
 {
+retranslate:
+    memset(block, 0, sizeof(block_t));
     block->pc_start = block->pc_end = rv->PC;
 
     rv_insn_t *prev_ir = NULL;
@@ -551,7 +582,16 @@ static void block_translate(riscv_t *rv, block_t *block)
             prev_ir->next = ir;
 
         /* fetch the next instruction */
-        const uint32_t insn = rv->io.mem_ifetch(rv, block->pc_end);
+        uint32_t insn = rv->io.mem_ifetch(rv, block->pc_end);
+
+#if RV32_HAS(SYSTEM)
+        if (!insn && need_retranslate) {
+            need_retranslate = false;
+            goto retranslate;
+        }
+#endif
+
+        assert(insn);
 
         /* decode the instruction */
         if (!rv_decode(ir, insn)) {
@@ -560,8 +600,7 @@ static void block_translate(riscv_t *rv, block_t *block)
             break;
         }
         ir->impl = dispatch_table[ir->opcode];
-        ir->pc = block->pc_end;
-        /* compute the end of pc */
+        ir->pc = block->pc_end; /* compute the end of pc */
         block->pc_end += is_compressed(insn) ? 2 : 4;
         block->n_insn++;
         prev_ir = ir;
@@ -878,6 +917,14 @@ static bool runtime_profiler(riscv_t *rv, block_t *block)
 }
 #endif
 
+#if RV32_HAS(SYSTEM)
+static bool rv_has_plic_trap(riscv_t *rv)
+{
+    return ((rv->csr_sstatus & SSTATUS_SIE || !rv->priv_mode) &&
+            (rv->csr_sip & rv->csr_sie));
+}
+#endif
+
 void rv_step(void *arg)
 {
     assert(arg);
@@ -891,6 +938,48 @@ void rv_step(void *arg)
 
     /* loop until hitting the cycle target */
     while (rv->csr_cycle < cycles_target && !rv->halt) {
+#if RV32_HAS(SYSTEM)
+        /* check for any interrupt after every block emulation */
+
+        /* now time */
+        struct timeval tv;
+
+        if (peripheral_update_ctr-- == 0) {
+            peripheral_update_ctr = 64;
+
+            u8250_check_ready(PRIV(rv)->uart);
+            if (PRIV(rv)->uart->in_ready)
+                emu_update_uart_interrupts(rv);
+        }
+
+        get_time_now(&tv);
+        uint64_t t = (uint64_t) (tv.tv_sec * 1e6) + (uint32_t) tv.tv_usec;
+
+        if (t > attr->timer) {
+            rv->csr_sip |= RV_INT_STI;
+        } else {
+            rv->csr_sip &= ~RV_INT_STI;
+        }
+
+        if (rv_has_plic_trap(rv)) {
+            uint32_t intr_applicable = rv->csr_sip & rv->csr_sie;
+            uint8_t intr_idx = ilog2(intr_applicable);
+            switch (intr_idx) {
+            case 1:
+                SET_CAUSE_AND_TVAL_THEN_TRAP(rv, SUPERVISOR_SW_INTR, 0);
+                break;
+            case 5:
+                SET_CAUSE_AND_TVAL_THEN_TRAP(rv, SUPERVISOR_TIMER_INTR, 0);
+                break;
+            case 9:
+                SET_CAUSE_AND_TVAL_THEN_TRAP(rv, SUPERVISOR_EXTERNAL_INTR, 0);
+                break;
+            default:
+                break;
+            }
+        }
+#endif /* RV32_HAS(SYSTEM) */
+
         if (prev && prev->pc_start != last_pc) {
             /* update previous block */
 #if !RV32_HAS(JIT)
@@ -1018,6 +1107,8 @@ static void __trap_handler(riscv_t *rv)
         assert(insn);
 
         rv_decode(ir, insn);
+        reloc_enable_mmu_jalr_addr = rv->PC;
+
         ir->impl = dispatch_table[ir->opcode];
         rv->compressed = is_compressed(insn);
         ir->impl(rv, ir, rv->csr_cycle, rv->PC);
@@ -1117,8 +1208,13 @@ void ecall_handler(riscv_t *rv)
 {
     assert(rv);
 #if RV32_HAS(SYSTEM)
-    syscall_handler(rv);
-    rv->PC += 4;
+    if (rv->priv_mode == RV_PRIV_U_MODE) {
+        SET_CAUSE_AND_TVAL_THEN_TRAP(rv, ECALL_U, 0);
+    } else if (rv->priv_mode ==
+               RV_PRIV_S_MODE) { /* trap to SBI syscall handler */
+        rv->PC += 4;
+        syscall_handler(rv);
+    }
 #else
     SET_CAUSE_AND_TVAL_THEN_TRAP(rv, ECALL_M, 0);
     syscall_handler(rv);

src/decode.c

@@ -15,6 +15,22 @@
 
 #include "io.h"
 
+u8250_state_t *u8250_new()
+{
+    u8250_state_t *uart = calloc(1, sizeof(u8250_state_t));
+    assert(uart);
+
+    return uart;
+}
+
+plic_t *plic_new()
+{
+    plic_t *plic = calloc(1, sizeof(plic_t));
+    assert(plic);
+
+    return plic;
+}
+
 static uint8_t *data_memory_base;
 
 memory_t *memory_new(uint32_t size)

src/decode.h

@@ -5,9 +5,47 @@
 
 #pragma once
 
+#include <stdbool.h>
 #include <stdint.h>
 #include <string.h>
 
+/* UART */
+
+#define IRQ_UART 1
+#define IRQ_UART_BIT (1 << IRQ_UART)
+
+typedef struct {
+    uint8_t dll, dlh;                  /**< divisor (ignored) */
+    uint8_t lcr;                       /**< UART config */
+    uint8_t ier;                       /**< interrupt config */
+    uint8_t current_int, pending_ints; /**< interrupt status */
+    /* other output signals, loopback mode (ignored) */
+    uint8_t mcr;
+    /* I/O handling */
+    int in_fd, out_fd;
+    bool in_ready;
+} u8250_state_t;
+void u8250_update_interrupts(u8250_state_t *uart);
+void u8250_check_ready(u8250_state_t *uart);
+
+uint32_t u8250_read(u8250_state_t *uart, uint32_t addr);
+
+void u8250_write(u8250_state_t *uart, uint32_t addr, uint32_t value);
+
+/* create a UART controller */
+u8250_state_t *u8250_new();
+
+typedef struct {
+    uint32_t masked;
+    uint32_t ip;
+    uint32_t ie;
+    /* state of input interrupt lines (level-triggered), set by environment */
+    uint32_t active;
+} plic_t;
+
+/* create a PLIC core */
+plic_t *plic_new();
+
 typedef struct {
     uint8_t *mem_base;
     uint64_t mem_size;

src/emulate.c

@@ -209,7 +209,7 @@ int main(int argc, char **args)
     run_flag |= opt_prof_data << 2;
 
     vm_attr_t attr = {
-        .mem_size = MEM_SIZE,
+        .mem_size = 512 * 1024 * 1024, /* FIXME: variadic size */
         .stack_size = STACK_SIZE,
         .args_offset_size = ARGS_OFFSET_SIZE,
         .argc = prog_argc,
@@ -227,7 +227,9 @@ int main(int argc, char **args)
     };
 #if RV32_HAS(SYSTEM)
     assert(attr.data.system);
-    attr.data.system->elf_program = opt_prog_name;
+    attr.data.system->kernel = "build/Image";       /* FIXME: hardcoded */
+    attr.data.system->initrd = "build/rootfs.cpio"; /* FIXME: hardcoded */
+    attr.data.system->dtb = "build/minimal.dtb";    /* FIXME: hardcoded */
 #else
     assert(attr.data.user);
     attr.data.user->elf_program = opt_prog_name;