63 lines
2.0 KiB
C
63 lines
2.0 KiB
C
#include "tb_cxxrtl_io.h"
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#include "hazard3_csr.h"
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// Check lr/sc which generate a bus fault generate an exception, and
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// report the correct mcause and mepc.
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// Calling convention abuse to get stable register allocation without cursed register keyword
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uint32_t __attribute__((naked)) do_lr_sc(uint32_t initial_sc, uint32_t *dst, const uint32_t *src) {
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asm volatile (
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// a5 used as a dumpster
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"lr.w a5, (a2)\n"
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// a0 not written if sc.w suppressed -> return value == initial_sc
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"sc.w a0, a0, (a1)\n"
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"ret"
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);
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}
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int main() {
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uint32_t scratch_word;
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uint32_t sc_result;
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uint32_t *bad_addr = (uint32_t*)0xcdef1234u;
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uint32_t *good_addr = &scratch_word;
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// Only the lr.w should except, because failed lr.w clears the local monitor,
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// suppressing the sc.w.
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tb_puts("Failed load, suppressed store\n");
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sc_result = do_lr_sc(123, bad_addr, bad_addr);
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// Failing sc.w must write 0 to the success register.
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tb_printf("sc.w result: %u\n", sc_result);
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// This time the sc.w should fault, after the successful lr.w.
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tb_puts("Good load, failed store\n");
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sc_result = do_lr_sc(123, bad_addr, good_addr);
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// Excepted sc.w must not write the success register.
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tb_printf("sc.w result: %u\n", sc_result);
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tb_puts("Repeated failed store\n");
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// Repeat just the sc.w. This should now be suppressed, because the prior
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// faulting sc.w should clear the monitor bit.
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asm volatile (
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"sc.w %0, zero, (%1)\n"
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: "+r" (sc_result) : "r" (bad_addr)
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);
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// Failing sc.w must write 0 to result register.
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tb_printf("sc.w result: %u\n", sc_result);
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return 0;
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}
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void __attribute__((interrupt)) handle_exception() {
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tb_printf("-> exception, mcause = %u\n", read_csr(mcause));
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write_csr(mcause, 0);
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uint32_t mepc = read_csr(mepc);
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if (*(uint16_t*)mepc & 0x3 == 0x3) {
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tb_printf("exception instr: %04x%04x\n", *(uint16_t*)(mepc + 2), *(uint16_t*)mepc);
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write_csr(mepc, mepc + 4);
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}
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else {
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tb_printf("exception instr: %04x\n", *(uint16_t*)(mepc + 2), *(uint16_t*)mepc);
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write_csr(mepc, mepc + 2);
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}
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}
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