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gdb: prevent TLB misses during arbitrary memory RW operations

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redoste 2023-05-30 00:53:56 +02:00
parent 02a97719ac
commit 9c22ecea8d
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1 changed files with 54 additions and 8 deletions
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62
src/gdb/gdb.c
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@ -1,4 +1,5 @@
#include <gint/cpu.h>
#include <gint/exc.h>
#include <gint/gdb.h>
#include <gint/ubc.h>
#include <gint/usb-ff-bulk.h>
@ -306,10 +307,13 @@ static void gdb_handle_write_register(gdb_cpu_state_t* cpu_state, const char* pa
}
}
static volatile bool gdb_tlbh_enable = false;
static volatile bool gdb_tlbh_caught = false;
static void gdb_handle_read_memory(const char* packet)
{
char address_hex[16] = {0}, size_hex[16] = {0};
void* read_address;
uint8_t* read_address;
size_t read_size;
packet++; // consume 'm'
@ -323,13 +327,24 @@ static void gdb_handle_read_memory(const char* packet)
if (*packet == '\0') break;
}
read_address = (void*) gdb_unhexlify(address_hex);
read_address = (uint8_t*) gdb_unhexlify(address_hex);
read_size = (size_t) gdb_unhexlify(size_hex);
// TODO : Detect invalid reads and prevent TLB misses
char *reply_buffer = malloc(read_size * 2);
gdb_hexlify(reply_buffer, read_address, read_size);
gdb_send_packet(reply_buffer, read_size * 2);
gdb_tlbh_enable = true;
gdb_tlbh_caught = false;
for (size_t i = 0; i < read_size && !gdb_tlbh_caught; i++) {
gdb_hexlify(&reply_buffer[i * 2], &read_address[i], 1);
}
gdb_tlbh_enable = false;
if (gdb_tlbh_caught) {
gdb_send_packet("E22", 3); // EINVAL
gdb_tlbh_caught = false;
} else {
gdb_send_packet(reply_buffer, read_size * 2);
}
free(reply_buffer);
}
@ -354,11 +369,19 @@ static void gdb_handle_write_memory(const char* packet)
read_address = (uint8_t*) gdb_unhexlify(address_hex);
read_size = (size_t) gdb_unhexlify(size_hex);
// TODO : Detect invalid writes and prevent TLB misses
for (size_t i = 0; i < read_size; i++) {
gdb_tlbh_enable = true;
gdb_tlbh_caught = false;
for (size_t i = 0; i < read_size && !gdb_tlbh_caught; i++) {
read_address[i] = (uint8_t)gdb_unhexlify_sized(&packet[i * 2], 2);
}
gdb_send_packet("OK", 2);
gdb_tlbh_enable = false;
if (gdb_tlbh_caught) {
gdb_send_packet("E22", 3); // EINVAL
gdb_tlbh_caught = false;
} else {
gdb_send_packet("OK", 2);
}
}
static bool gdb_parse_hardware_breakpoint_packet(const char* packet, void** read_address)
@ -561,6 +584,26 @@ static void gdb_notifier_function(void)
gdb_handle_single_step(&fake_state);
}
/* TODO : break and let the debugger attempt to fix the issue before panicking
* in user code
*/
static int gdb_panic_handler(uint32_t code)
{
// We make sure we currently want to handle TLB misses
if (!gdb_tlbh_enable)
return 1;
// We only handle TLB miss reads (0x040) and writes (0x060)
if (code != 0x040 && code != 0x060)
return 1;
gdb_tlbh_caught = true;
// We skip the offending instruction and continue
gint_exc_skip(1);
return 0;
}
int gdb_start(void)
{
if (gdb_state != GDB_STATE_STOPPED) {
@ -578,6 +621,9 @@ int gdb_start(void)
usb_open_wait();
usb_fxlink_set_notifier(gdb_notifier_function);
// TODO : Should we detect if other panic or debug handlers are setup ?
gint_exc_catch(gdb_panic_handler);
ubc_set_debug_handler(gdb_main);
gdb_state = GDB_STATE_FIRST_BREAK;