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Added write validation to MCAUSE

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This commit is contained in:
Eric Matthews 2020-08-14 11:37:34 -07:00
parent 27cc812806
commit b150f3a627
1 changed files with 41 additions and 3 deletions
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44
core/csr_regs.sv
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@ -386,11 +386,49 @@ generate if (ENABLE_M_MODE) begin
////////////////////////////////////////////////////
//MCAUSE
logic[XLEN-1:0] mcause_mask;
//As the exception and interrupts codes are sparsely populated,
//to ensure that only legal values are written, a ROM lookup
//is used to validate the CSR write operation
logic MCAUSE_EXCEPTION_MASKING_ROM [2**ECODE_W];
logic MCAUSE_INTERRUPT_MASKING_ROM [2**ECODE_W];
always_comb begin
MCAUSE_EXCEPTION_MASKING_ROM = '{default: 0};
MCAUSE_EXCEPTION_MASKING_ROM[INST_ADDR_MISSALIGNED] = 1;
MCAUSE_EXCEPTION_MASKING_ROM[INST_ACCESS_FAULT] = ENABLE_S_MODE;
MCAUSE_EXCEPTION_MASKING_ROM[ILLEGAL_INST] = 1;
MCAUSE_EXCEPTION_MASKING_ROM[BREAK] = 1;
MCAUSE_EXCEPTION_MASKING_ROM[LOAD_ADDR_MISSALIGNED] = 1;
MCAUSE_EXCEPTION_MASKING_ROM[LOAD_FAULT] = ENABLE_S_MODE;
MCAUSE_EXCEPTION_MASKING_ROM[STORE_AMO_ADDR_MISSALIGNED] = 1;
MCAUSE_EXCEPTION_MASKING_ROM[STORE_AMO_FAULT] = ENABLE_S_MODE;
MCAUSE_EXCEPTION_MASKING_ROM[ECALL_U] = ENABLE_S_MODE;
MCAUSE_EXCEPTION_MASKING_ROM[ECALL_S] = ENABLE_S_MODE;
MCAUSE_EXCEPTION_MASKING_ROM[ECALL_M] = 1;
MCAUSE_EXCEPTION_MASKING_ROM[INST_PAGE_FAULT] = ENABLE_S_MODE;
MCAUSE_EXCEPTION_MASKING_ROM[LOAD_PAGE_FAULT] = ENABLE_S_MODE;
MCAUSE_EXCEPTION_MASKING_ROM[STORE_OR_AMO_PAGE_FAULT] = ENABLE_S_MODE;
MCAUSE_INTERRUPT_MASKING_ROM = '{default: 0};
MCAUSE_INTERRUPT_MASKING_ROM[S_SOFTWARE_INTERRUPT] = ENABLE_S_MODE;
MCAUSE_INTERRUPT_MASKING_ROM[M_SOFTWARE_INTERRUPT] = 1;
MCAUSE_INTERRUPT_MASKING_ROM[S_TIMER_INTERRUPT] = ENABLE_S_MODE;
MCAUSE_INTERRUPT_MASKING_ROM[M_TIMER_INTERRUPT] = 1;
MCAUSE_INTERRUPT_MASKING_ROM[S_EXTERNAL_INTERRUPT] = ENABLE_S_MODE;
MCAUSE_INTERRUPT_MASKING_ROM[M_EXTERNAL_INTERRUPT] = 1;
end
logic mcause_write_valid;
always_comb begin
if (updated_csr[XLEN-1]) //interrupt
mcause_write_valid = MCAUSE_INTERRUPT_MASKING_ROM[updated_csr[ECODE_W-1:0]];
else
mcause_write_valid = MCAUSE_EXCEPTION_MASKING_ROM[updated_csr[ECODE_W-1:0]];
end
always_ff @(posedge clk) begin
mcause.zeroes <= '0;
if (mwrite_decoder[MCAUSE[7:0]] | gc_exception.valid) begin
mcause.interrupt <= gc_exception.valid ? 1'b0 :updated_csr[XLEN-1];
if ((mcause_write_valid & mwrite_decoder[MCAUSE[7:0]]) | gc_exception.valid) begin
mcause.interrupt <= gc_exception.valid ? 1'b0 : updated_csr[XLEN-1];
mcause.code <= gc_exception.valid ? gc_exception.code : updated_csr[ECODE_W-1:0];
end
end