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[sw/lib] fixed bug in goto_user_mode function (that might have caused stack corruption)

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stnolting 2020-10-22 16:43:26 +02:00
parent 38fcd8d197
commit ea03d97148
1 changed files with 6 additions and 6 deletions
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12
sw/lib/source/neorv32_cpu.c
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@ -246,11 +246,11 @@ void neorv32_cpu_delay_ms(uint32_t time_ms) {
**************************************************************************/
void __attribute__((naked)) neorv32_cpu_goto_user_mode(void) {
register uint32_t mask = (1<<CPU_MSTATUS_MPP_H) | (1<<CPU_MSTATUS_MPP_L);
asm volatile ("csrrc zero, mstatus, %[input_j]" : : [input_j] "r" (mask));
// make sure to use NO registers in here! -> naked
// return switching to user mode
asm volatile ("csrw mepc, ra");
asm volatile ("mret");
asm volatile ("csrw mepc, ra \n\t" // move return address to mepc so we can return using "mret". also, we can use ra as general purpose register in here
"li ra, %[input_imm] \n\t" // bit mask to clear the two MPP bits
"csrrc zero, mstatus, ra \n\t" // clear MPP bits -> MPP=u-mode
"mret \n\t" // return and switch to user mode
: : [input_imm] "i" ((1<<CPU_MSTATUS_MPP_H) | (1<<CPU_MSTATUS_MPP_L)));
}