set the wrong value into "mtvec" in freedom-metal/src/trap.S

[gxflying]

hi，I find there somthing wrong in freedom-metal/src/trap.S:
see source code below, this will set the mtvec zero in MSB, except LSB two bits
and "jr t0" will go somewhere wrong!

[nategraff-sifive]

You're right, I need to invert the mask. Thanks for the catch!

[gxflying]

one more thing, the codes in line 20/21, actually also don't make sense in my test. it'ok when I changed those to "csrw mepc, ra".
when the trap returns by calling mret, the mepc will set into pc, and the pc=mepc=ra, where ra contains the address next to instruction like "call _metal_trap".
So I don't think the original code blow works well. how do you think? Or could you please explain why it should be like this? what "ra-1" means?
Thanks
/* Store the instruction which called _metal_trap in mepc */
addi t0, ra, -1 //line 20
csrw mepc, t0 //line 21
besides, the address of the instruction called the _metal_trap may be "ra-4" or "ra-2"