From: Mark Kettenis <mark.kettenis@xs4all.nl>
Subject: Re: glxgears BTI SIGILL, arm64
To: Jonathan Gray <jsg@jsg.id.au>
Cc: tech@openbsd.org
Date: Sun, 17 Mar 2024 21:09:08 +0100

> Date: Sun, 17 Mar 2024 17:08:14 +1100
> From: Jonathan Gray <jsg@jsg.id.au>
> Content-Type: text/plain; charset=us-ascii
> Content-Disposition: inline
> 
> On Sat, Mar 16, 2024 at 12:10:19PM +0000, Stuart Henderson wrote:
> >  10913 glxgears PSIG  SIGILL SIG_DFL code=ILL_BTCFI addr=0x21ca5a3000 trapno=905969666
> > 
> > Anyone have suggestions as to how to track this down any further?
> 
> This is on an apple machine?  If so it will be using llvmpipe.
> To avoid the jit you can use:
> 
> LIBGL_ALWAYS_SOFTWARE=1 GALLIUM_DRIVER=softpipe glxgears
> 
> Do you still see it with that?

Diff below seems to fix llvmpipe.  At least I can run glxgears now.

As far as I can tell there isn't an option that can be passed to the
core llvm code that turns it on.  What clang does is pass a function
attribute or module flag that turns it on.  So I made Mesa do the
same.

Not sure if this is the correct way to do things, but there is a
precedent in overriding module parameters.

ok?


Index: lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_init.c
===================================================================
RCS file: /cvs/xenocara/lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_init.c,v
retrieving revision 1.15
diff -u -p -r1.15 lp_bld_init.c
--- lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_init.c	2 Nov 2023 04:53:36 -0000	1.15
+++ lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_init.c	17 Mar 2024 19:39:06 -0000
@@ -360,6 +360,10 @@ init_gallivm_state(struct gallivm_state 
    lp_set_module_stack_alignment_override(gallivm->module, 4);
 #endif
 
+#if DETECT_ARCH_AARCH64
+   lp_set_module_branch_target_enforcement(gallivm->module);
+#endif
+
    gallivm->builder = LLVMCreateBuilderInContext(gallivm->context);
    if (!gallivm->builder)
       goto fail;
Index: lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp
===================================================================
RCS file: /cvs/xenocara/lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp,v
retrieving revision 1.17
diff -u -p -r1.17 lp_bld_misc.cpp
--- lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp	2 Nov 2023 04:53:36 -0000	1.17
+++ lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp	17 Mar 2024 19:39:06 -0000
@@ -619,3 +619,10 @@ lp_set_module_stack_alignment_override(L
    M->setOverrideStackAlignment(align);
 #endif
 }
+
+extern "C" void
+lp_set_module_branch_target_enforcement(LLVMModuleRef MRef)
+{
+   llvm::Module *M = llvm::unwrap(MRef);
+   M->addModuleFlag(llvm::Module::Override, "branch-target-enforcement", 1);
+}
Index: lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_misc.h
===================================================================
RCS file: /cvs/xenocara/lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_misc.h,v
retrieving revision 1.10
diff -u -p -r1.10 lp_bld_misc.h
--- lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_misc.h	9 Dec 2021 00:21:07 -0000	1.10
+++ lib/mesa/src/gallium/auxiliary/gallivm/lp_bld_misc.h	17 Mar 2024 19:39:06 -0000
@@ -94,6 +94,10 @@ lp_free_objcache(void *objcache);
 
 void
 lp_set_module_stack_alignment_override(LLVMModuleRef M, unsigned align);
+
+void
+lp_set_module_branch_target_enforcement(LLVMModuleRef M);
+
 #ifdef __cplusplus
 }
 #endif