On 07/14/2015 05:38 PM, Leon Alrae wrote:
There seems to be an issue when trying to keep a pointer in bottom 32-bits of a 64-bit floating point register. Load and store instructions accessing this address for some reason use the whole 64-bit content of floating point register rather than truncated 32-bit value. The following load uses incorrect address which leads to a crash if upper 32 bits of $f0 isn't 0:0x00400c60: mfc1 t8,$f0 0x00400c64: lw t9,0(t8) It can be reproduced with the following linux userland program when running on a MIPS32 with CP0.Status.FR=1 (by default mips32r5-generic and mips32r6-generic CPUs have this bit set in linux-user). int main(int argc, char *argv[]) { int tmp = 0x11111111; /* Set f0 */ __asm__ ("mtc1 %0, $f0\n" "mthc1 %1, $f0\n" : : "r" (&tmp), "r" (tmp)); /* At this point $f0: w:76fff040 d:1111111176fff040 */ __asm__ ("mfc1 $t8, $f0\n" "lw $t9, 0($t8)\n"); /* <--- crash! */ return 0; }
What compilation options, exactly? I'm having trouble reproducing. Alternately, perhaps you can send me a binary. r~
