tools/nolibc: add support for getrlimit/setrlimit

The implementation uses the prlimit64 systemcall as that is available on
all architectures.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/lkml/20231123-nolibc-rlimit-v1-2-a428b131de2a@weissschuh.net/Acked-by: Willy Tarreau <w@1wt.eu>

tools/include/nolibc/sys.h

@@ -21,6 +21,7 @@
 #include <linux/fcntl.h> /* for O_* and AT_* */
 #include <linux/stat.h>  /* for statx() */
 #include <linux/prctl.h>
+#include <linux/resource.h>
 
 #include "arch.h"
 #include "errno.h"
@@ -898,6 +899,43 @@ int reboot(int cmd)
 }
 
 
+/*
+ * int getrlimit(int resource, struct rlimit *rlim);
+ * int setrlimit(int resource, const struct rlimit *rlim);
+ */
+
+static __attribute__((unused))
+int sys_prlimit64(pid_t pid, int resource,
+		  const struct rlimit64 *new_limit, struct rlimit64 *old_limit)
+{
+	return my_syscall4(__NR_prlimit64, pid, resource, new_limit, old_limit);
+}
+
+static __attribute__((unused))
+int getrlimit(int resource, struct rlimit *rlim)
+{
+	struct rlimit64 rlim64;
+	int ret;
+
+	ret = __sysret(sys_prlimit64(0, resource, NULL, &rlim64));
+	rlim->rlim_cur = rlim64.rlim_cur;
+	rlim->rlim_max = rlim64.rlim_max;
+
+	return ret;
+}
+
+static __attribute__((unused))
+int setrlimit(int resource, const struct rlimit *rlim)
+{
+	struct rlimit64 rlim64 = {
+		.rlim_cur = rlim->rlim_cur,
+		.rlim_max = rlim->rlim_max,
+	};
+
+	return __sysret(sys_prlimit64(0, resource, &rlim64, NULL));
+}
+
+
 /*
  * int sched_yield(void);
  */

tools/testing/selftests/nolibc/nolibc-test.c

@@ -22,6 +22,7 @@
 #include <sys/mount.h>
 #include <sys/prctl.h>
 #include <sys/reboot.h>
+#include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/sysmacros.h>
@@ -839,6 +840,33 @@ int test_pipe(void)
 	return !!memcmp(buf, msg, len);
 }
 
+int test_rlimit(void)
+{
+	struct rlimit rlim = {
+		.rlim_cur = 1 << 20,
+		.rlim_max = 1 << 21,
+	};
+	int ret;
+
+	ret = setrlimit(RLIMIT_CORE, &rlim);
+	if (ret)
+		return -1;
+
+	rlim.rlim_cur = 0;
+	rlim.rlim_max = 0;
+
+	ret = getrlimit(RLIMIT_CORE, &rlim);
+	if (ret)
+		return -1;
+
+	if (rlim.rlim_cur != 1 << 20)
+		return -1;
+	if (rlim.rlim_max != 1 << 21)
+		return -1;
+
+	return 0;
+}
+
 
 /* Run syscall tests between IDs <min> and <max>.
  * Return 0 on success, non-zero on failure.
@@ -928,6 +956,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(poll_fault);        EXPECT_SYSER(1, poll(NULL, 1, 0), -1, EFAULT); break;
 		CASE_TEST(prctl);             EXPECT_SYSER(1, prctl(PR_SET_NAME, (unsigned long)NULL, 0, 0, 0), -1, EFAULT); break;
 		CASE_TEST(read_badf);         EXPECT_SYSER(1, read(-1, &tmp, 1), -1, EBADF); break;
+		CASE_TEST(rlimit);            EXPECT_SYSZR(1, test_rlimit()); break;
 		CASE_TEST(rmdir_blah);        EXPECT_SYSER(1, rmdir("/blah"), -1, ENOENT); break;
 		CASE_TEST(sched_yield);       EXPECT_SYSZR(1, sched_yield()); break;
 		CASE_TEST(select_null);       EXPECT_SYSZR(1, ({ struct timeval tv = { 0 }; select(0, NULL, NULL, NULL, &tv); })); break;