Virtualization - Jul 2023 - [PATCH] x86/paravirt: Fix tlb_remove_table function callback prototype warning

Under W=1, this warning is visible in Clang 16 and newer:

arch/x86/kernel/paravirt.c:337:4: warning: cast from 'void (*)(struct
mmu_gather *, struct page *)' to 'void (*)(struct mmu_gather *, void
*)' converts to incompatible function type [-Wcast-function-type-strict]
                           (void (*)(struct mmu_gather *, void
*))tlb_remove_page,
                          
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Add a direct wrapper instead, which will make this warning (and
potential KCFI failures) go away.

Reported-by: kernel test robot <lkp at intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202307260332.pJntWR6o-lkp at
intel.com/
Cc: Juergen Gross <jgross at suse.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Sami Tolvanen <samitolvanen at google.com>
Cc: Nathan Chancellor <nathan at kernel.org>
Cc: Ajay Kaher <akaher at vmware.com>
Cc: Alexey Makhalov <amakhalov at vmware.com>
Cc: VMware PV-Drivers Reviewers <pv-drivers at vmware.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Borislav Petkov <bp at alien8.de>
Cc: Dave Hansen <dave.hansen at linux.intel.com>
Cc: virtualization at lists.linux-foundation.org
Signed-off-by: Kees Cook <keescook at chromium.org>
---
 arch/x86/kernel/paravirt.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index ac10b46c5832..23d4d7114473 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -79,6 +79,11 @@ void __init native_pv_lock_init(void)
 		static_branch_disable(&virt_spin_lock_key);
 }
 
+static void native_tlb_remove_table(struct mmu_gather *tlb, void *table)
+{
+	tlb_remove_page(tlb, table);
+}
+
 unsigned int paravirt_patch(u8 type, void *insn_buff, unsigned long addr,
 			    unsigned int len)
 {
@@ -295,8 +300,7 @@ struct paravirt_patch_template pv_ops = {
 	.mmu.flush_tlb_kernel	= native_flush_tlb_global,
 	.mmu.flush_tlb_one_user	= native_flush_tlb_one_user,
 	.mmu.flush_tlb_multi	= native_flush_tlb_multi,
-	.mmu.tlb_remove_table	-			(void (*)(struct mmu_gather *, void
*))tlb_remove_page,
+	.mmu.tlb_remove_table	= native_tlb_remove_table,
 
 	.mmu.exit_mmap		= paravirt_nop,
 	.mmu.notify_page_enc_status_changed	= paravirt_nop,
-- 
2.34.1

On 27.07.23 01:11, Kees Cook wrote:
> Under W=1, this warning is visible in Clang 16 and newer:
> 
> arch/x86/kernel/paravirt.c:337:4: warning: cast from 'void (*)(struct
mmu_gather *, struct page *)' to 'void (*)(struct mmu_gather *, void
*)' converts to incompatible function type [-Wcast-function-type-strict]
>                             (void (*)(struct mmu_gather *, void
*))tlb_remove_page,
>                            
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Add a direct wrapper instead, which will make this warning (and
> potential KCFI failures) go away.
> 
> Reported-by: kernel test robot <lkp at intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202307260332.pJntWR6o-lkp at
intel.com/
> Cc: Juergen Gross <jgross at suse.com>
> Cc: Peter Zijlstra <peterz at infradead.org>
> Cc: Sami Tolvanen <samitolvanen at google.com>
> Cc: Nathan Chancellor <nathan at kernel.org>
> Cc: Ajay Kaher <akaher at vmware.com>
> Cc: Alexey Makhalov <amakhalov at vmware.com>
> Cc: VMware PV-Drivers Reviewers <pv-drivers at vmware.com>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Ingo Molnar <mingo at redhat.com>
> Cc: Borislav Petkov <bp at alien8.de>
> Cc: Dave Hansen <dave.hansen at linux.intel.com>
> Cc: virtualization at lists.linux-foundation.org
> Signed-off-by: Kees Cook <keescook at chromium.org>
Reviewed-by: Juergen Gross <jgross at suse.com>


Juergen

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On Wed, 26 Jul 2023 16:11:43 -0700, Kees Cook wrote:
> Under W=1, this warning is visible in Clang 16 and newer:
> 
> arch/x86/kernel/paravirt.c:337:4: warning: cast from 'void (*)(struct
mmu_gather *, struct page *)' to 'void (*)(struct mmu_gather *, void
*)' converts to incompatible function type [-Wcast-function-type-strict]
>                            (void (*)(struct mmu_gather *, void
*))tlb_remove_page,
>                           
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Add a direct wrapper instead, which will make this warning (and
> potential KCFI failures) go away.
> 
> [...]
Applied to for-next/hardening, thanks!

[1/1] x86/paravirt: Fix tlb_remove_table function callback prototype warning
      https://git.kernel.org/kees/c/fcce1c6cb156

Take care,

-- 
Kees Cook