[LibOS] Implement getrandom syscall

LibOS/shim/include/shim_table.h

@@ -537,5 +537,10 @@ ssize_t shim_do_sendmmsg(int sockfd, struct mmsghdr* msg, unsigned int vlen, int
 int shim_do_eventfd2(unsigned int count, int flags);
 int shim_do_eventfd(unsigned int count);
 int shim_do_getcpu(unsigned* cpu, unsigned* node, struct getcpu_cache* unused);
+long shim_do_getrandom(char* buf, size_t count, unsigned int flags);
+
+#define GRND_NONBLOCK 0x0001
+#define GRND_RANDOM   0x0002
+#define GRND_INSECURE 0x0004
 
 #endif /* _SHIM_TABLE_H_ */

LibOS/shim/src/Makefile

@@ -93,6 +93,7 @@ objs = \
 	sys/shim_futex.o \
 	sys/shim_getcwd.o \
 	sys/shim_getpid.o \
+	sys/shim_getrandom.o \
 	sys/shim_getrlimit.o \
 	sys/shim_ioctl.o \
 	sys/shim_mmap.o \

LibOS/shim/src/shim_parser.c

@@ -52,6 +52,7 @@ static void parse_seek(va_list*);
 static void parse_at_fdcwd(va_list*);
 static void parse_wait_options(va_list*);
 static void parse_waitid_which(va_list*);
+static void parse_getrandom_flags(va_list*);
 
 struct parser_table {
     int slow;
@@ -386,7 +387,7 @@ struct parser_table {
         [__NR_sched_getattr]     = {.slow = 0, .parser = {NULL}},
         [__NR_renameat2]         = {.slow = 0, .parser = {NULL}},
         [__NR_seccomp]           = {.slow = 0, .parser = {NULL}},
-        [__NR_getrandom]         = {.slow = 0, .parser = {NULL}},
+        [__NR_getrandom]         = {.slow = 0, .parser = {NULL, NULL, parse_getrandom_flags}},
         [__NR_memfd_create]      = {.slow = 0, .parser = {NULL}},
         [__NR_kexec_file_load]   = {.slow = 0, .parser = {NULL}},
         [__NR_bpf]               = {.slow = 0, .parser = {NULL}},
@@ -1395,3 +1396,19 @@ static void parse_waitid_which(va_list* ap) {
             break;
     }
 }
+
+static void parse_getrandom_flags(va_list* ap) {
+    unsigned int flags = va_arg(*ap, unsigned int);
+
+#define FLG(n) { #n, n }
+    const struct flag_table all_flags[] = {
+        FLG(GRND_NONBLOCK),
+        FLG(GRND_RANDOM),
+        FLG(GRND_INSECURE),
+    };
+#undef FLG
+
+    flags = parse_flags(flags, all_flags, ARRAY_SIZE(all_flags));
+    if (flags)
+        PRINTF("|0x%x", flags);
+}

LibOS/shim/src/shim_syscalls.c

@@ -1060,7 +1060,8 @@ SHIM_SYSCALL_RETURN_ENOSYS(renameat2, 5, long, int, olddfd, const char*, oldname
 
 SHIM_SYSCALL_RETURN_ENOSYS(seccomp, 3, long, unsigned int, op, unsigned int, flags, void*, uargs)
 
-SHIM_SYSCALL_RETURN_ENOSYS(getrandom, 3, long, char*, buf, size_t, count, unsigned int, flags)
+DEFINE_SHIM_SYSCALL(getrandom, 3, shim_do_getrandom, long, char*, buf, size_t, count, unsigned int,
+                    flags)
 
 SHIM_SYSCALL_RETURN_ENOSYS(memfd_create, 2, long, const char*, uname, unsigned int, flags)
 

LibOS/shim/src/sys/shim_getrandom.c

@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/* Copyright (C) 2020 Intel Corporation
+ *                    Michał Kowalczyk <mkow@invisiblethingslab.com>
+ */
+
+#include <limits.h>
+#include <stdint.h>
+
+#include "shim_internal.h"
+#include "shim_table.h"
+
+long shim_do_getrandom(char* buf, size_t count, unsigned int flags) {
+    if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE))
+        return -EINVAL;
+
+    if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM))
+        return -EINVAL;
+
+    /* Weird, but that's what kernel does */
+    if (count > INT_MAX)
+        count = INT_MAX;
+
+    if (test_user_memory(buf, count, /*write=*/true))
+        return -EFAULT;
+
+    /* In theory, DkRandomBitsRead may block on some PALs (which conflicts with GRND_NONBLOCK flag),
+     * but this shouldn't be possible in practice, so we don't care.
+     */
+    int ret = DkRandomBitsRead(buf, count);
+    if (ret < 0)
+        return -EINVAL;
+
+    return count;
+}

LibOS/shim/test/ltp/ltp.cfg

@@ -180,7 +180,7 @@ must-pass =
     3
 
 [clock_nanosleep02]
-must-pass =
+skip = yes
 
 [clock_nanosleep2_01]
 skip = yes
@@ -871,18 +871,6 @@ skip = yes
 [getpriority02]
 skip = yes
 
-[getrandom01]
-skip = yes
-
-[getrandom02]
-skip = yes
-
-[getrandom03]
-skip = yes
-
-[getrandom04]
-skip = yes
-
 [getresgid01]
 skip = yes