Please add support for ms_hook_prologue function attribute

[llvmbot]

Bugzilla Link	10212
Version	trunk
OS	Linux
Blocks	#7187 llvm/llvm-bugzilla-archive#10638
Reporter	LLVM Bugzilla Contributor
CC	@AaronBallman,@jeremyhu,@tritao,@nlewycky,@zygoloid,@rnk

[llvmbot]

Sorry, hit tab one to many times before hitting Submit :)

gcc added support for this a couple years ago (Sep 2009), and has been in since gcc 4.5. It's used by Wine to allow programs to hook certain APIs. Without this, Steam, xfire, and several copy protections/DRM schemes fail to function.

[llvmbot]

Still present, as of
git-svn-id: http://llvm.org/svn/llvm-project/llvm/trunk@150433 91177308-0d34-0410-b5e6-96231b3b80d8

[tritao]

I just noticed Clang already abstracts this on the CGCXXABI object (EmitInstanceFunctionProlog), so it should be pretty to hook it up on the compiler once the LLVM part is done.

[AaronBallman]

I just noticed Clang already abstracts this on the CGCXXABI object
(EmitInstanceFunctionProlog), so it should be pretty to hook it up on the
compiler once the LLVM part is done.

Instance functions aren't the only ones which would want this prologue. This is most commonly used on non-instance methods and corresponds to the /hotpatch MSVC option: http://msdn.microsoft.com/en-us/library/ms173507.aspx

What's more, it's not x86-specific (we should support it for x64 and Itanium targets as well, where it can require more than just the five-byte prologue).

For MSVC compatibility, we should consider adding a flag letting you turn this feature on or off for an entire file instead of requiring an attribute. Not saying that we shouldn't also support the function attribute.

[AaronBallman]

*** Bug llvm/llvm-bugzilla-archive#20888 has been marked as a duplicate of this bug. ***

[llvmbot]

Any progress?

[nlewycky]

This feature was temporarily added in August 2016, then reverted almost immediately thereafter:

• add ms-hotpatch r278048: https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160808/380298.html
• add ms_hook_prologue r278050: https://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20160808/167275.html
• revert ms_hook_prologue r278052: https://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20160808/167282.html
• revert ms-hotpatch r278053: https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160808/380301.html
  and I don't think was ever revisited.

[llvmbot]

mentioned in issue llvm/llvm-bugzilla-archive#10638

[AaronBallman]

mentioned in issue llvm/llvm-bugzilla-archive#20888

[llvmbot]

mentioned in issue #7187

[ThisNekoGuy]

Hope this gets fixed soon so that it can be utilized when compiling Wine :/
This is a decade-old issue

[AaronBallman]

This seems far more likely now that Clang supports -fms-hotpatch as a command line argument: 5af2433. I think it may be a matter of exposing the attribute and checking for it in CodeGenFunction::StartFunction(), though there would probably be some fit and finish work as well.