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Add exception handler

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Степанов Платон
2026-02-09 11:48:24 +04:00
parent fde896f371
commit 6043cc0d5c
3 changed files with 137 additions and 3 deletions
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86
src/kernel.c
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@@ -21,9 +21,95 @@ struct sbiret sbi_call(long arg0, long arg1, long arg2, long arg3, long arg4,
void putchar(char ch) { sbi_call(ch, 0, 0, 0, 0, 0, 0, 1); }
__attribute__((naked)) __attribute__((aligned(4))) void kernel_entry(void) {
__asm__ __volatile__("csrw sscratch, sp\n"
"addi sp, sp, -4 * 31\n"
"sw ra, 4 * 0(sp)\n"
"sw gp, 4 * 1(sp)\n"
"sw tp, 4 * 2(sp)\n"
"sw t0, 4 * 3(sp)\n"
"sw t1, 4 * 4(sp)\n"
"sw t2, 4 * 5(sp)\n"
"sw t3, 4 * 6(sp)\n"
"sw t4, 4 * 7(sp)\n"
"sw t5, 4 * 8(sp)\n"
"sw t6, 4 * 9(sp)\n"
"sw a0, 4 * 10(sp)\n"
"sw a1, 4 * 11(sp)\n"
"sw a2, 4 * 12(sp)\n"
"sw a3, 4 * 13(sp)\n"
"sw a4, 4 * 14(sp)\n"
"sw a5, 4 * 15(sp)\n"
"sw a6, 4 * 16(sp)\n"
"sw a7, 4 * 17(sp)\n"
"sw s0, 4 * 18(sp)\n"
"sw s1, 4 * 19(sp)\n"
"sw s2, 4 * 20(sp)\n"
"sw s3, 4 * 21(sp)\n"
"sw s4, 4 * 22(sp)\n"
"sw s5, 4 * 23(sp)\n"
"sw s6, 4 * 24(sp)\n"
"sw s7, 4 * 25(sp)\n"
"sw s8, 4 * 26(sp)\n"
"sw s9, 4 * 27(sp)\n"
"sw s10, 4 * 28(sp)\n"
"sw s11, 4 * 29(sp)\n"
"csrr a0, sscratch\n"
"sw a0, 4 * 30(sp)\n"
"mv a0, sp\n"
"call handle_trap\n"
"lw ra, 4 * 0(sp)\n"
"lw gp, 4 * 1(sp)\n"
"lw tp, 4 * 2(sp)\n"
"lw t0, 4 * 3(sp)\n"
"lw t1, 4 * 4(sp)\n"
"lw t2, 4 * 5(sp)\n"
"lw t3, 4 * 6(sp)\n"
"lw t4, 4 * 7(sp)\n"
"lw t5, 4 * 8(sp)\n"
"lw t6, 4 * 9(sp)\n"
"lw a0, 4 * 10(sp)\n"
"lw a1, 4 * 11(sp)\n"
"lw a2, 4 * 12(sp)\n"
"lw a3, 4 * 13(sp)\n"
"lw a4, 4 * 14(sp)\n"
"lw a5, 4 * 15(sp)\n"
"lw a6, 4 * 16(sp)\n"
"lw a7, 4 * 17(sp)\n"
"lw s0, 4 * 18(sp)\n"
"lw s1, 4 * 19(sp)\n"
"lw s2, 4 * 20(sp)\n"
"lw s3, 4 * 21(sp)\n"
"lw s4, 4 * 22(sp)\n"
"lw s5, 4 * 23(sp)\n"
"lw s6, 4 * 24(sp)\n"
"lw s7, 4 * 25(sp)\n"
"lw s8, 4 * 26(sp)\n"
"lw s9, 4 * 27(sp)\n"
"lw s10, 4 * 28(sp)\n"
"lw s11, 4 * 29(sp)\n"
"lw sp, 4 * 30(sp)\n"
"sret\n");
}
void handle_trap(struct trap_frame *f) {
uint32_t scause = READ_CSR(scause);
uint32_t stval = READ_CSR(stval);
uint32_t user_pc = READ_CSR(sepc);
PANIC("unexpected trap scause=%x, stval=%x, sepc=%x\n", scause, stval,
user_pc);
}
void kernel_main(void) {
memset(__bss, 0, (size_t)__bss_end - (size_t)__bss);
WRITE_CSR(stvec, (uint32_t)kernel_entry);
__asm__ __volatile__("unimp");
PANIC("booted!");
printf("unreachable here!\n");
}

47
src/kernel.h
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@@ -15,3 +15,50 @@ struct sbiret {
while (1) { \
} \
} while (0)
struct trap_frame {
uint32_t ra;
uint32_t gp;
uint32_t tp;
uint32_t t0;
uint32_t t1;
uint32_t t2;
uint32_t t3;
uint32_t t4;
uint32_t t5;
uint32_t t6;
uint32_t a0;
uint32_t a1;
uint32_t a2;
uint32_t a3;
uint32_t a4;
uint32_t a5;
uint32_t a6;
uint32_t a7;
uint32_t s0;
uint32_t s1;
uint32_t s2;
uint32_t s3;
uint32_t s4;
uint32_t s5;
uint32_t s6;
uint32_t s7;
uint32_t s8;
uint32_t s9;
uint32_t s10;
uint32_t s11;
uint32_t sp;
} __attribute__((packed));
#define READ_CSR(reg) \
({ \
unsigned long __tmp; \
__asm__ __volatile__("csrr %0, " #reg : "=r"(__tmp)); \
__tmp; \
})
#define WRITE_CSR(reg, value) \
do { \
uint32_t __tmp = (value); \
__asm__ __volatile__("csrw " #reg ", %0" ::"r"(__tmp)); \
} while (0)

1
src/run.sh Normal file → Executable file
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@@ -1,4 +1,5 @@
#!/bin/bash
set -xue
make kernel
qemu-system-riscv32 -machine virt -bios default -nographic -serial mon:stdio --no-reboot -kernel kernel.elf