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added a timerhalt() function #176

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added a timerhalt() function #176

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3 changes: 3 additions & 0 deletions kernel/defs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,9 @@ struct sleeplock;
struct stat;
struct superblock;

// start.c
void timerhalt(void);

// bio.c
void binit(void);
struct buf* bread(uint, uint);
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16 changes: 16 additions & 0 deletions kernel/kernelvec.S
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Expand Up @@ -97,12 +97,17 @@ timervec:
# scratch[0,8,16] : register save area.
# scratch[24] : address of CLINT's MTIMECMP register.
# scratch[32] : desired interval between interrupts.
# scratch[40] : halt flag set by timerhalt.

csrrw a0, mscratch, a0
sd a1, 0(a0)
sd a2, 8(a0)
sd a3, 16(a0)

# halt if timerhalt has set halt flag to 1
ld a1, 40(a0)
bne a1, zero, halt

# schedule the next timer interrupt
# by adding interval to mtimecmp.
ld a1, 24(a0) # CLINT_MTIMECMP(hart)
Expand All @@ -122,3 +127,14 @@ timervec:
csrrw a0, mscratch, a0

mret

halt:
# based on qemu's hw/riscv/virt.c:
# qemu halts if FINISHER_PASS(=0x5555) is
# written at address *VIRT_TEST(=0x100000L)
lui a1, 0x100
lui a2, 0x5
addi a2, a2, 0x555
sw a2, 0(a1)
spin:
j spin
1 change: 1 addition & 0 deletions kernel/printf.c
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Expand Up @@ -123,6 +123,7 @@ panic(char *s)
printf(s);
printf("\n");
panicked = 1; // freeze uart output from other CPUs
timerhalt();
for(;;)
;
}
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12 changes: 11 additions & 1 deletion kernel/start.c
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Expand Up @@ -11,7 +11,7 @@ void timerinit();
__attribute__ ((aligned (16))) char stack0[4096 * NCPU];

// a scratch area per CPU for machine-mode timer interrupts.
uint64 timer_scratch[NCPU][5];
uint64 timer_scratch[NCPU][6];

// assembly code in kernelvec.S for machine-mode timer interrupt.
extern void timervec();
Expand Down Expand Up @@ -73,9 +73,11 @@ timerinit()
// scratch[0..2] : space for timervec to save registers.
// scratch[3] : address of CLINT MTIMECMP register.
// scratch[4] : desired interval (in cycles) between timer interrupts.
// scratch[5] : halt flag to signal halt to timervec.
uint64 *scratch = &timer_scratch[id][0];
scratch[3] = CLINT_MTIMECMP(id);
scratch[4] = interval;
scratch[5] = 0;
w_mscratch((uint64)scratch);

// set the machine-mode trap handler.
Expand All @@ -87,3 +89,11 @@ timerinit()
// enable machine-mode timer interrupts.
w_mie(r_mie() | MIE_MTIE);
}

// signal halt to timervec.
void
timerhalt()
{
// set halt flag in scratch area for hartid[0] to 1.
timer_scratch[0][5] = 1;
}