ptrace: PTRACE_SINGLESTEP

apps/dbg.c

@@ -403,6 +403,11 @@ static void show_commandline(pid_t pid, int status, struct regs * regs) {
 			if (signum == SIGINT) signum = 0;
 			ptrace(PTRACE_CONT, pid, NULL, (void*)(uintptr_t)signum);
 			return;
+		} else if (!strcmp(buf, "step") || !strcmp(buf,"s")) {
+			int signum = WSTOPSIG(status);
+			if (signum == SIGINT) signum = 0;
+			ptrace(PTRACE_SINGLESTEP, pid, NULL, (void*)(uintptr_t)signum);
+			return;
 		} else if (!strcmp(buf, "poke")) {
 			char * addr = arg;
 			char * data = strstr(addr, " ");
@@ -599,8 +604,19 @@ int main(int argc, char * argv[]) {
 				if (WIFSTOPPED(status)) {
 					if (WSTOPSIG(status) == SIGTRAP) {
 						/* Don't care about TRAP right now */
-						//ptrace(PTRACE_SIGNALS_ONLY_PLZ, p, NULL, NULL);
+						int event = (status >> 16) & 0xFF;
-						ptrace(PTRACE_CONT, p, NULL, NULL);
+						switch (event) {
+							case PTRACE_EVENT_SINGLESTEP: {
+									struct regs regs;
+									ptrace(PTRACE_GETREGS, res, NULL, &regs);
+									show_commandline(res, status, &regs);
+								}
+								break;
+							default:
+								//ptrace(PTRACE_SIGNALS_ONLY_PLZ, p, NULL, NULL);
+								ptrace(PTRACE_CONT, p, NULL, NULL);
+								break;
+						}
 					} else {
 						printf("Program received signal %s.\n", sig_to_str(WSTOPSIG(status)));
 

base/usr/include/sys/ptrace.h

@@ -13,12 +13,14 @@ enum __ptrace_request {
 	PTRACE_GETREGS,
 	PTRACE_PEEKDATA,
 	PTRACE_SIGNALS_ONLY_PLZ,
-	PTRACE_POKEDATA
+	PTRACE_POKEDATA,
+	PTRACE_SINGLESTEP
 };
 
 enum __ptrace_event {
 	PTRACE_EVENT_SYSCALL_ENTER,
 	PTRACE_EVENT_SYSCALL_EXIT,
+	PTRACE_EVENT_SINGLESTEP,
 };
 
 #ifndef __kernel__

kernel/arch/x86_64/idt.c

@@ -7,9 +7,12 @@
 #include <kernel/signal.h>
 #include <kernel/misc.h>
 #include <kernel/time.h>
+#include <kernel/ptrace.h>
 
 #include <sys/time.h>
 #include <sys/utsname.h>
+#include <sys/ptrace.h>
+
 #include <kernel/arch/x86_64/mmu.h>
 #include <kernel/arch/x86_64/ports.h>
 #include <kernel/arch/x86_64/pml.h>
@@ -229,11 +232,21 @@ struct regs * isr_handler(struct regs * r) {
 			/* Spurious interrupt */
 			break;
 		}
+		case 1: {
+			/* Debug interrupt */
+			r->rflags &= ~(1 << 8);
+			if (this_core->current_process->flags & PROC_FLAG_TRACE_SIGNALS) {
+				ptrace_signal(SIGTRAP, PTRACE_EVENT_SINGLESTEP);
+			}
+			return r;
+		}
 		default: {
 			if (r->int_no < 32) {
 				if (!this_core->current_process || r->cs == 0x08) {
 					arch_fatal();
 				}
+				printf("int_no %ld in process %d\n",
+					r->int_no, this_core->current_process->id);
 				send_signal(this_core->current_process->id, SIGILL, 1);
 			} else {
 				for (size_t i = 0; i < IRQ_CHAIN_DEPTH; i++) {

kernel/sys/ptrace.c

@@ -127,6 +127,22 @@ long ptrace_signals_only(pid_t pid) {
 	return 0;
 }
 
+long ptrace_singlestep(pid_t pid, int sig) {
+	process_t * tracee = process_from_pid(pid);
+	if (!tracee || (tracee->tracer != this_core->current_process->id) || !(tracee->flags & PROC_FLAG_SUSPENDED)) return -ESRCH;
+
+	struct regs * target = tracee->interrupt_registers ? tracee->interrupt_registers : tracee->syscall_registers;
+
+	/* arch_set_singlestep? */
+	target->rflags |= (1 << 8);
+
+	__sync_and_and_fetch(&tracee->flags, ~(PROC_FLAG_SUSPENDED));
+	tracee->status = (sig << 8);
+	make_process_ready(tracee);
+
+	return 0;
+}
+
 long ptrace_handle(long request, pid_t pid, void * addr, void * data) {
 	switch (request) {
 		case PTRACE_ATTACH:
@@ -143,6 +159,8 @@ long ptrace_handle(long request, pid_t pid, void * addr, void * data) {
 			return ptrace_poke(pid,addr,data);
 		case PTRACE_SIGNALS_ONLY_PLZ:
 			return ptrace_signals_only(pid);
+		case PTRACE_SINGLESTEP:
+			return ptrace_singlestep(pid,(uintptr_t)data);
 		default:
 			return -EINVAL;
 	}