tools: bpftool: use "/proc/self/" i.o. crafting links with getpid()

The getpid() function is called in a couple of places in bpftool to
craft links of the shape "/proc/<pid>/...". Instead, it is possible to
use the "/proc/self/" shortcut, which makes things a bit easier, in
particular in jit_disasm.c.

Do the replacement, and remove the includes of <sys/types.h> from the
relevant files, now we do not use getpid() anymore.
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/bpf/bpftool/common.c

@@ -48,7 +48,6 @@
 #include <sys/mount.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
-#include <sys/types.h>
 #include <sys/vfs.h>
 
 #include <bpf.h>
@@ -276,7 +275,7 @@ int get_fd_type(int fd)
 	char buf[512];
 	ssize_t n;
 
-	snprintf(path, sizeof(path), "/proc/%d/fd/%d", getpid(), fd);
+	snprintf(path, sizeof(path), "/proc/self/fd/%d", fd);
 
 	n = readlink(path, buf, sizeof(buf));
 	if (n < 0) {
@@ -304,7 +303,7 @@ char *get_fdinfo(int fd, const char *key)
 	ssize_t n;
 	FILE *fdi;
 
-	snprintf(path, sizeof(path), "/proc/%d/fdinfo/%d", getpid(), fd);
+	snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", fd);
 
 	fdi = fopen(path, "r");
 	if (!fdi) {

tools/bpf/bpftool/jit_disasm.c

@@ -19,7 +19,6 @@
 #include <string.h>
 #include <bfd.h>
 #include <dis-asm.h>
-#include <sys/types.h>
 #include <sys/stat.h>
 #include <limits.h>
 
@@ -28,20 +27,12 @@
 
 static void get_exec_path(char *tpath, size_t size)
 {
+	const char *path = "/proc/self/exe";
 	ssize_t len;
-	char *path;
-
-	snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
-	tpath[size - 1] = 0;
-
-	path = strdup(tpath);
-	assert(path);
 
 	len = readlink(path, tpath, size - 1);
 	assert(len > 0);
 	tpath[len] = 0;
-
-	free(path);
 }
 
 static int oper_count;