linux-hardening - [PATCH] x86/paravirt: Fix tlb_remove_table function callback prototype warning

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Date:   Wed, 26 Jul 2023 16:11:43 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Juergen Gross <jgross@...e.com>
Cc:     Kees Cook <keescook@...omium.org>,
        kernel test robot <lkp@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Ajay Kaher <akaher@...are.com>,
        Alexey Makhalov <amakhalov@...are.com>,
        VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, x86@...nel.org, llvm@...ts.linux.dev,
        linux-hardening@...r.kernel.org
Subject: [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@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202307260332.pJntWR6o-lkp@intel.com/
Cc: Juergen Gross <jgross@...e.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Ajay Kaher <akaher@...are.com>
Cc: Alexey Makhalov <amakhalov@...are.com>
Cc: VMware PV-Drivers Reviewers <pv-drivers@...are.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: virtualization@...ts.linux-foundation.org
Signed-off-by: Kees Cook <keescook@...omium.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