syscall log: support for selective syscall tracing

tools/systrace/Makefile

@@ -0,0 +1,14 @@
+.phony: all install
+CC=x86_64-astral-gcc
+LD=x86_64-astral-gcc
+all: systrace
+
+install:
+	mkdir -p "$(DESTDIR)/$(PREFIX)/sbin/"
+	cp systrace "$(DESTDIR)/$(PREFIX)/sbin/systrace"
+
+systrace: main.o
+	$(LD) $(LDFLAGS) -g -o $@ $^
+
+main.o: main.c
+	$(CC) -c $(CFLAGS) -g -o $@ $<

tools/systrace/main.c

@@ -0,0 +1,62 @@
+#include <astral/archctl.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static int arch_ctl_systrace(uint64_t mode) {
+	return arch_ctl(ARCH_CTL_SET_SYSTRACE, (void *)mode);
+}
+
+int main(int argc, char *argv[]) {
+	// make sure syscall tracing is supported
+	if (arch_ctl_systrace(ARCH_CTL_SYSTRACE_OFF) != 0) {
+		if (errno == ENOTSUP) {
+			fprintf(stderr, "%s: compile the kernel with syscall tracing enabled\n", argv[0]);
+		} else {
+			perror("arch_ctl failed");
+		}
+		return 1;
+	}
+
+	uint64_t mode = ARCH_CTL_SYSTRACE_SELF;
+
+	// check for -ff flag
+	if (argc > 1 && strcmp(argv[1], "-ff") == 0) {
+		mode = ARCH_CTL_SYSTRACE_ALL;
+		argv++;
+		argc--;
+	}
+
+	if (argc < 2) {
+		fprintf(stderr, "usage: %s [-ff] <command> [args...]\n", argv[0]);
+		fprintf(stderr, "example: %s ls -l /\n", argv[0]);
+		return 1;
+	}
+
+	int pid = fork();
+	if (pid < 0) {
+		perror("fork failed");
+		return 1;
+	}
+
+	if (pid == 0) {
+		// enable syscall tracing for the child process
+		if (arch_ctl_systrace(mode) != 0) {
+			perror("failed to enable syscall tracing");
+			return 1;
+		}
+		fprintf(stderr, "%s: tracee is pid %d\n", argv[0], getpid());
+		if (execvp(argv[1], &argv[1]) != 0) {
+			arch_ctl_systrace(ARCH_CTL_SYSTRACE_OFF);
+			perror("execvp failed");
+			return 1;
+		}
+		// not reached
+	} else {
+		int status;
+		waitpid(pid, &status, 0);
+		return WIFEXITED(status) ? WEXITSTATUS(status) : 1;
+	}
+}