Pass through and record PR_SVE system calls on arm

CMakeLists.txt

@@ -1450,6 +1450,7 @@ set(BASIC_TESTS
   sysinfo
   syslog
   arm/tagged_addr_ctrl
+  arm/sve_vl
   tgkill
   thread_yield
   timer

src/kernel_supplement.h

@@ -520,6 +520,17 @@ enum {
 #define BLKGETNRZONES _IOR(0x12, 133, __u32)
 #endif
 
+// New in the 4.15 kernel
+#ifndef PR_SVE_SET_VL
+#define PR_SVE_SET_VL 50
+#endif
+#ifndef PR_SVE_GET_VL
+#define PR_SVE_GET_VL 51
+#endif
+#ifndef PR_SVE_VL_LEN_MASK
+#define PR_SVE_VL_LEN_MASK 0xffff
+#endif
+
 // New in the 5.4 kernel
 #ifndef PR_SET_TAGGED_ADDR_CTRL
 #define PR_SET_TAGGED_ADDR_CTRL 55

src/record_syscall.cc

@@ -4792,6 +4792,8 @@ static Switchable rec_prepare_syscall_arch(RecordTask* t,
         case PR_GET_SECUREBITS:
         case PR_GET_TAGGED_ADDR_CTRL:
         case PR_GET_MDWE:
+        case PR_SVE_GET_VL:
+        case PR_SVE_SET_VL:
           break;
 
         case PR_SET_TAGGED_ADDR_CTRL:

src/replay_syscall.cc

@@ -1215,11 +1215,13 @@ static void rep_process_syscall_arch(ReplayTask* t, ReplayTraceStep* step,
     case Arch::prctl: {
       auto arg1 = t->regs().arg1();
       if (sys == Arch::prctl &&
-          (Arch::arch() != aarch64 || arg1 != PR_SET_SPECULATION_CTRL) &&
+          (Arch::arch() != aarch64 || (arg1 != PR_SET_SPECULATION_CTRL &&
+                                       arg1 != PR_SVE_SET_VL)) &&
           ((unsigned long)t->regs().arg1() != PR_SET_VMA || trace_regs.syscall_result_signed() == -EINVAL)) {
         // On aarch64 PR_SET_SPECULATION_CTRL affects the pstate
-        // register during the system call, so we need to replay
-        // it, otherwise we'll get a mismatch there.
+        // register during the system call, and PR_SVE_SET_VL affects
+        // the SVE vector length, so we need to replay them, otherwise
+        // we'll get a mismatch.
         // We want to replay PR_SET_VMA as well, but not if it originally failed
         // with EINVAL because the recording kernel may not have supported it.
         return;

src/test/arm/sve_vl.c

@@ -0,0 +1,40 @@
+/* -*- Mode: C; tab-width: 8; c-basic-offset: 2; indent-tabs-mode: nil; -*- */
+
+#include "util.h"
+
+#include <sys/prctl.h>
+#include <errno.h>
+
+#ifndef PR_SVE_SET_VL
+#define PR_SVE_SET_VL 50
+#endif
+#ifndef PR_SVE_GET_VL
+#define PR_SVE_GET_VL 51
+#endif
+#ifndef PR_SVE_VL_LEN_MASK
+#define PR_SVE_VL_LEN_MASK 0xffff
+#endif
+
+int main(void) {
+  int vl = prctl(PR_SVE_GET_VL);
+  /* Skip on hardware without SVE support. */
+  if (vl == -1 && errno == EINVAL) {
+    atomic_puts("EXIT-SUCCESS");
+    return 0;
+  }
+  test_assert(vl > 0);
+  int len = vl & PR_SVE_VL_LEN_MASK;
+  test_assert(len > 0);
+
+  /* Set the same vector length we already have. */
+  int ret = prctl(PR_SVE_SET_VL, len);
+  test_assert(ret >= 0);
+  test_assert((ret & PR_SVE_VL_LEN_MASK) == len);
+
+  /* Confirm GET still returns the same value. */
+  int vl2 = prctl(PR_SVE_GET_VL);
+  test_assert((vl2 & PR_SVE_VL_LEN_MASK) == len);
+
+  atomic_puts("EXIT-SUCCESS");
+  return 0;
+}