linux-kernel - [PATCH 03/11] x86/fault/32: Move is_f00f_bug() do do_kern_addr

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Date:   Sun, 31 Jan 2021 09:24:34 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Yonghong Song <yhs@...com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 03/11] x86/fault/32: Move is_f00f_bug() do do_kern_addr_fault()

bad_area() and its relatives are called from many places in fault.c, and
exactly one of them wants the F00F workaround.

__bad_area_nosemaphore() no longer contains any kernel fault code, which
prepares for further cleanups.

Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/mm/fault.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index aff35c9ba018..87d30daa5e0a 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -445,10 +445,12 @@ static int is_errata100(struct pt_regs *regs, unsigned long address)
 }
 
 /* Pentium F0 0F C7 C8 bug workaround: */
-static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
+static int is_f00f_bug(struct pt_regs *regs, unsigned long error_code,
+		       unsigned long address)
 {
 #ifdef CONFIG_X86_F00F_BUG
-	if (boot_cpu_has_bug(X86_BUG_F00F) && idt_is_f00f_address(address)) {
+	if (boot_cpu_has_bug(X86_BUG_F00F) && !(error_code & X86_PF_USER) &&
+	    idt_is_f00f_address(address)) {
 		handle_invalid_op(regs);
 		return 1;
 	}
@@ -816,9 +818,6 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
 		return;
 	}
 
-	if (is_f00f_bug(regs, address))
-		return;
-
 	no_context(regs, error_code, address, SIGSEGV, si_code);
 }
 
@@ -1158,6 +1157,9 @@ do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
 	}
 #endif
 
+	if (is_f00f_bug(regs, hw_error_code, address))
+		return;
+
 	/* Was the fault spurious, caused by lazy TLB invalidation? */
 	if (spurious_kernel_fault(hw_error_code, address))
 		return;
-- 
2.29.2