1#include <asm.h>
2#include <atomic.h>
3#include <ndjson.h>
4#include <sync/raw_spinlock.h>
5
6#include "internal.h"
7
8#define UART_DATA 0
9#define UART_INT_ENABLE 1
10#define UART_FIFO_CTRL 2
11#define UART_LINE_CTRL 3
12#define UART_MODEM_CTRL 4
13#define UART_LINE_STATUS 5
14
15#define UART_LSR_THRE 0x20 /* transmit holding register empty */
16#define UART_LCR_DLAB 0x80
17#define UART_LCR_8N1 0x03
18#define UART_DIVISOR 0x03 /* 38400 baud */
19
20#define NDJSON_PANIC_LOCK_SPINS 1000000
21
22/* Panic transport must remain usable when normal lock validation fails. */
23static struct raw_spinlock carrier_lock = RAW_SPINLOCK_INIT;
24static uint16_t carrier_port;
25static atomic_bool carrier_up;
26static atomic_bool carrier_panicked;
27
28void ndjson_carrier_init(uint16_t port) {
29 outb(port: port + UART_INT_ENABLE, value: 0x00);
30 outb(port: port + UART_LINE_CTRL, UART_LCR_DLAB);
31 outb(port: port + UART_DATA, UART_DIVISOR);
32 outb(port: port + UART_INT_ENABLE, value: 0x00);
33 outb(port: port + UART_LINE_CTRL, UART_LCR_8N1);
34 outb(port: port + UART_FIFO_CTRL, value: 0xC7);
35 outb(port: port + UART_MODEM_CTRL, value: 0x0B);
36
37 carrier_port = port;
38 atomic_store_release(&carrier_up, true);
39}
40
41void ndjson_carrier_disable(void) {
42 atomic_store_release(&carrier_up, false);
43}
44
45bool ndjson_carrier_online(void) {
46 return atomic_load_acq(&carrier_up);
47}
48
49void ndjson_enter_panic(void) TSA_NO_ANALYSIS {
50 atomic_store_release(&carrier_panicked, true);
51 raw_spin_unlock(lock: &carrier_lock);
52}
53
54/* Raw spinlocks here, because if something IRQL related panics,
55 * it would not be able to use ndjson to log */
56bool ndjson_carrier_begin(bool *irqs_were_on) TSA_NO_ANALYSIS {
57 *irqs_were_on = false;
58
59 if (!ndjson_carrier_online())
60 return false;
61
62 *irqs_were_on = irq_disable_save();
63
64 if (atomic_load_acq(&carrier_panicked)) {
65 for (uint64_t i = 0; i < NDJSON_PANIC_LOCK_SPINS; i++) {
66 if (raw_spin_trylock(lock: &carrier_lock))
67 break;
68 cpu_pause();
69 }
70 return true;
71 }
72
73 raw_spin_lock(lock: &carrier_lock);
74 return true;
75}
76
77void ndjson_carrier_end(bool irqs_were_on) TSA_NO_ANALYSIS {
78 raw_spin_unlock(lock: &carrier_lock);
79
80 if (irqs_were_on)
81 irq_enable();
82}
83
84void ndjson_carrier_putc(char c) {
85 while (!(inb(port: carrier_port + UART_LINE_STATUS) & UART_LSR_THRE))
86 cpu_pause();
87
88 outb(port: carrier_port + UART_DATA, value: (uint8_t) c);
89}
90
91void ndjson_carrier_write(const char *s, size_t len) {
92 for (size_t i = 0; i < len; i++)
93 ndjson_carrier_putc(c: s[i]);
94}
95