[Qemu-devel] [PATCH] Ignore PROT_GROWSDOWN and PROT_GROWSUP

[Qemu-devel] [PATCH] Ignore PROT_GROWSDOWN and PROT_GROWSUP

[Alexander Graf]

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In an mprotect call the flags PROT_GROWSDOWN and PROT_GROWSUP can be
defined. Currently qemu returns an EINVAL as soon as one of these is
found, which breaks some programs (especially mplayer).
As far as I can tell it is safe to ignore these flags and just go on as
if nothing happened. To be on the safe side a warning message to the
user is thrown though.

Is there anything wrong with ignoring these? Should they be implemented
properly? Comments appreciated.

Alex


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Index: qemu/linux-user/mmap.c
===================================================================
--- qemu.orig/linux-user/mmap.c
+++ qemu/linux-user/mmap.c
@@ -48,8 +48,10 @@ int target_mprotect(target_ulong start, 
     end = start + len;
     if (end < start)
         return -EINVAL;
-    if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC))
-        return -EINVAL;
+    if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC)) {
+	gemu_log("WARNING: dirty hack in mprotect: setting prot (%#x -> %#x)\n", prot, prot & (PROT_READ | PROT_WRITE | PROT_EXEC));
+        prot &= (PROT_READ | PROT_WRITE | PROT_EXEC);
+    }
     if (len == 0)
         return 0;