kernel: profiling infrastructure

tools/prof/Makefile

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

tools/prof/main.c

@@ -0,0 +1,73 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/poll.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <termios.h>
+
+static char *progname;
+
+static int open_or_die(const char *name, int flag, mode_t mode) {
+	int fd = open(name, flag, mode);
+	if (fd < 0) {
+		fprintf(stderr, "%s: open %s: %s\n", progname, name, strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+	return fd;
+}
+
+int main(int argc, char *argv[]) {
+	progname = argv[0];
+	if (argc != 2) {
+		fprintf(stderr, "%s: usage: %s FILE\n", argv[0], argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	// right now the limit for each trace is 256
+	uintptr_t buf[256];
+
+	int infd = open_or_die("/dev/prof", O_RDONLY | O_NONBLOCK, 0);
+	int outfd = open_or_die(argv[1], O_WRONLY | O_CREAT, 0644);
+
+	// enable raw mode
+	if (isatty(outfd)) {
+		struct termios termios;
+		tcgetattr(outfd, &termios);
+		cfmakeraw(&termios);
+		termios.c_oflag &= ~ONLCR;
+		tcsetattr(outfd, TCSANOW, &termios);
+	}
+
+	printf("%s: draining /dev/prof\n", argv[0]);
+	// empty it
+	if (ioctl(infd, 12345678, NULL) > 0)
+		return EXIT_FAILURE;
+
+	struct pollfd pollfd[2];
+
+	pollfd[0].fd = 0;
+	pollfd[0].events = POLLIN;
+	pollfd[0].revents = 0;
+	pollfd[1].fd = infd;
+	pollfd[1].events = POLLIN;
+	pollfd[1].revents = 0;
+
+	printf("%s: working...\n", argv[0]);
+	while (poll(pollfd, 2, -1)) {
+		if (pollfd[0].revents)
+			break;
+
+		uint8_t count;
+		read(infd, &count, 1);
+		read(infd, buf, 8 * count);
+		write(outfd, &count, 1);
+		write(outfd, buf, 8 * count);
+	}
+
+	printf("%s: done\n", argv[0]);
+
+	return EXIT_SUCCESS;
+}