vmmon: fix version check for <linux/frame.h> include

Both the version check for include of <linux/frame.h> in common/crosspage.c
and the comment explaining it are wrong for multiple reasons:

  1. <linux/frame.h> was introduced in v4.6-rc1, not v4.5-rc5
  2. ANNOTATE_INTRA_FUNCTION_CALL was introduced in v5.8-rc1, not v5.7
  3. Even if it were, the check should use ">=", not ">"
  4. Most important, the code in fact needs STACK_FRAME_NON_STANDARD

Without the definition of STACK_FRAME_NON_STANDARD, build against vanilla
5.7 kernel fails on objtool error (but succeeds against 5.7.1, because of
the mistake from point 3).

Change the check from "> 5.7" to ">= 4.6" to get STACK_FRAME_NON_STANDARD
whenever available and update the explaining comment.

vmmon-only/common/crosspage.c

@@ -51,9 +51,7 @@
  * linux/frame.h dates back to 4.6-rc1, we need the STACK_FRAME_NON_STANDARD
  * definition from it which is there from the start.
  */
-#   if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 10, 0)
-#      include <linux/objtool.h>
-#   elif LINUX_VERSION_CODE >= KERNEL_VERSION(4, 6, 0)
+#   if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 6, 0)
 #      include <linux/frame.h>
 #   endif
 #endif

vmmon-only/linux/hostif.c

@@ -55,7 +55,6 @@
 #include <linux/hrtimer.h>
 #include <linux/signal.h>
 #include <linux/taskstats_kern.h> // For linux/sched/signal.h without version check
-#include <linux/eventfd.h>
 
 #include "vmware.h"
 #include "x86apic.h"
@@ -2331,27 +2330,6 @@ HostIF_VMLockIsHeld(VMDriver *vm) // IN
 
 #if defined(CONFIG_SMP) || defined(CONFIG_X86_UP_IOAPIC) || \
     defined(CONFIG_X86_UP_APIC) || defined(CONFIG_X86_LOCAL_APIC)
-
-#if COMPAT_LINUX_VERSION_CHECK_LT(5, 8, 0)
-static long compat_copy_from_kernel_nofault(void *dst, VA src, size_t size)
-{
-   mm_segment_t old_fs;
-   long ret;
-
-   old_fs = get_fs();
-   set_fs(KERNEL_DS);
-   ret = HostIF_CopyFromUser(dst, src, size);
-   set_fs(old_fs);
-
-   return ret;
-}
-#else
-static long compat_copy_from_kernel_nofault(void *dst, VA src, size_t size)
-{
-   return copy_from_kernel_nofault(dst, (const void *)src, size);
-}
-#endif
-
 /*
  *----------------------------------------------------------------------
  *
@@ -2371,11 +2349,15 @@ static long compat_copy_from_kernel_nofault(void *dst, VA src, size_t size)
 static Bool
 isVAReadable(VA r)  // IN:
 {
+   mm_segment_t old_fs;
    uint32 dummy;
-   long ret;
+   int ret;
 
+   old_fs = get_fs();
+   set_fs(KERNEL_DS);
    r = APICR_TO_ADDR(r, APICR_VERSION);
-   ret = compat_copy_from_kernel_nofault(&dummy, r, sizeof(dummy));
+   ret = HostIF_CopyFromUser(&dummy, r, sizeof dummy);
+   set_fs(old_fs);
 
    return ret == 0;
 }
@@ -2688,7 +2670,6 @@ HostIF_SemaphoreForceWakeup(VMDriver *vm,       // IN:
 int
 HostIF_SemaphoreSignal(uint64 *args)  // IN:
 {
-   struct eventfd_ctx *eventfd;
    struct file *file;
    int res;
    int signalFD = args[1];
@@ -2699,17 +2680,6 @@ HostIF_SemaphoreSignal(uint64 *args)  // IN:
       return MX_WAITERROR;
    }
 
-   /*
-    * If it's eventfd, use specific eventfd interface as kernel writes
-    * to eventfd may not be allowed in kernel 5.10 and later.
-    */
-   eventfd = eventfd_ctx_fileget(file);
-   if (!IS_ERR(eventfd)) {
-      eventfd_signal(eventfd, 1);
-      fput(file);
-      return MX_WAITNORMAL;
-   }
-
    /*
     * Always write sizeof(uint64) bytes. This works fine for eventfd and
     * pipes. The data written is formatted to make an eventfd happy should
@@ -3273,9 +3243,12 @@ static int
 HostIFFastClockThread(void *unused)  // IN:
 {
    int res;
+   mm_segment_t oldFS;
    unsigned int rate = 0;
    unsigned int prevRate = 0;
 
+   oldFS = get_fs();
+   set_fs(KERNEL_DS);
    allow_signal(SIGKILL);
 
    while ((rate = linuxState.fastClockRate) > MIN_RATE) {
@@ -3298,6 +3271,8 @@ HostIFFastClockThread(void *unused)  // IN:
    }
 
  out:
+   set_fs(oldFS);
+
    /*
     * Do not exit thread until we are told to do so.
     */

vmnet-only/userif.c

@@ -87,24 +87,6 @@ extern unsigned int  vnet_max_qlen;
 #   define skb_frag_off(frag) (frag)->page_offset
 #endif
 
-#if COMPAT_LINUX_VERSION_CHECK_LT(5, 10, 0)
-static inline
-__wsum compat_csum_and_copy_to_user(const void *src, void __user *dst, int len)
-{
-	int err;
-	__wsum ret;
-
-	ret = csum_and_copy_to_user(src, dst, len, 0, &err);
-	return err ? 0 : ret;
-}
-#else
-static inline
-__wsum compat_csum_and_copy_to_user(const void *src, void __user *dst, int len)
-{
-	return csum_and_copy_to_user(src, dst, len);
-}
-#endif
-
 /*
  *-----------------------------------------------------------------------------
  *
@@ -566,6 +548,7 @@ VNetCsumCopyDatagram(const struct sk_buff *skb,	// IN: skb to copy
 		     char *buf)			// OUT: where to copy data
 {
    unsigned int csum;
+   int err = 0;
    int len = skb_headlen(skb) - offset;
    char *curr = buf;
    const skb_frag_t *frag;
@@ -578,9 +561,10 @@ VNetCsumCopyDatagram(const struct sk_buff *skb,	// IN: skb to copy
       return -EINVAL;
    }
 
-   csum = compat_csum_and_copy_to_user(skb->data + offset, curr, len);
-   if (!csum)
-	   return -EFAULT;
+   csum = csum_and_copy_to_user(skb->data + offset, curr, len, 0, &err);
+   if (err) {
+      return err;
+   }
    curr += len;
 
    for (frag = skb_shinfo(skb)->frags;
@@ -591,12 +575,13 @@ VNetCsumCopyDatagram(const struct sk_buff *skb,	// IN: skb to copy
 	 const void *vaddr;
 
 	 vaddr = kmap(skb_frag_page(frag));
-	 tmpCsum = compat_csum_and_copy_to_user(vaddr + skb_frag_off(frag),
-						curr, skb_frag_size(frag));
+	 tmpCsum = csum_and_copy_to_user(vaddr + skb_frag_off(frag),
+					 curr, skb_frag_size(frag), 0, &err);
 	 kunmap(skb_frag_page(frag));
 
-	 if (!tmpCsum)
-		 return -EFAULT;
+	 if (err) {
+	    return err;
+	 }
 	 csum = csum_block_add(csum, tmpCsum, curr - buf);
 	 curr += skb_frag_size(frag);
       }