From e806d16b065c5db27206d69f76a724ce593659bc Mon Sep 17 00:00:00 2001 From: Pierre Schweitzer Date: Fri, 31 Aug 2018 19:43:04 +0200 Subject: [PATCH] [NTOSKRNL] Warn about unimplemented feature in CcMapData() (in all callers) Currently, our CcMapData() behavior (same goes for CcPinRead()) is broken and is the total opposite of what Windows kernel does. By default, the later will let you map a view in memory without even attempting to bring its data in memory. On first access, there will be a fault and memory will be read from the hardware and brought to memory. If you want to force read on mapping/pinning, you have to set the MAP_NO_READ (or PIN_NO_READ) flag where kernel will fault on your behalf (hence the need for MAP_WAIT/PIN_WAIT). On ReactOS, by default, on mapping (and thus pinning), we will force a view read so that data is in memory. The way our cache memory is managed at the moment seems not to allow to fault on invalid access and if we don't force read, the memory content will just be zeroed. So trying to match Windows behavior, by default, now CcMapData() will enforce the MAP_NO_READ flag and warn once about this behavior change. --- ntoskrnl/cc/pin.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/ntoskrnl/cc/pin.c b/ntoskrnl/cc/pin.c index 65525eed83d..73739811199 100644 --- a/ntoskrnl/cc/pin.c +++ b/ntoskrnl/cc/pin.c @@ -86,6 +86,18 @@ CcMapData ( return FALSE; } + if (!BooleanFlagOn(Flags, MAP_NO_READ)) + { + static int Warned = 0; + + SetFlag(Flags, MAP_NO_READ); + if (!Warned) + { + DPRINT1("Mapping/pinning with no read not implemented. Forcing read, might fail if wait not allowed\n"); + Warned++; + } + } + ROffset = ROUND_DOWN(ReadOffset, VACB_MAPPING_GRANULARITY); Status = CcRosRequestVacb(SharedCacheMap, ROffset, @@ -100,9 +112,9 @@ CcMapData ( return FALSE; } - if (!Valid) + if (!Valid && BooleanFlagOn(Flags, MAP_NO_READ)) { - if (!(Flags & MAP_WAIT)) + if (!BooleanFlagOn(Flags, MAP_WAIT)) { CcRosReleaseVacb(SharedCacheMap, Vacb, FALSE, FALSE, FALSE); CCTRACE(CC_API_DEBUG, "FileObject=%p FileOffset=%p Length=%lu Flags=0x%lx -> FALSE\n",