linux-kernel - [PATCH 30/62] x86/head/64: Move early exception dispatch to C code

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Date:   Tue, 11 Feb 2020 14:52:24 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>
Subject: [PATCH 30/62] x86/head/64: Move early exception dispatch to C code

From: Joerg Roedel <jroedel@...e.de>

Move the assembly coded dispatch between page-faults and all other
exceptions to C code to make it easier to maintain and extend.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/kernel/head64.c  | 20 ++++++++++++++++++++
 arch/x86/kernel/head_64.S | 11 +----------
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 7cdfb7113811..d83c62ebaa85 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -36,6 +36,8 @@
 #include <asm/microcode.h>
 #include <asm/kasan.h>
 #include <asm/fixmap.h>
+#include <asm/extable.h>
+#include <asm/trap_defs.h>
 
 /*
  * Manage page tables very early on.
@@ -377,6 +379,24 @@ int __init early_make_pgtable(unsigned long address)
 	return __early_make_pgtable(address, pmd);
 }
 
+void __init early_exception(struct pt_regs *regs, int trapnr)
+{
+	unsigned long cr2;
+	int r;
+
+	switch (trapnr) {
+	case X86_TRAP_PF:
+		cr2 = native_read_cr2();
+		r = early_make_pgtable(cr2);
+		break;
+	default:
+		r = 1;
+	}
+
+	if (r)
+		early_fixup_exception(regs, trapnr);
+}
+
 /* Don't add a printk in there. printk relies on the PDA which is not initialized 
    yet. */
 static void __init clear_bss(void)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 0af79f783659..81cf6c5763ef 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -357,18 +357,9 @@ SYM_CODE_START_LOCAL(early_idt_handler_common)
 	pushq %r15				/* pt_regs->r15 */
 	UNWIND_HINT_REGS
 
-	cmpq $14,%rsi		/* Page fault? */
-	jnz 10f
-	GET_CR2_INTO(%rdi)	/* can clobber %rax if pv */
-	call early_make_pgtable
-	andl %eax,%eax
-	jz 20f			/* All good */
-
-10:
 	movq %rsp,%rdi		/* RDI = pt_regs; RSI is already trapnr */
-	call early_fixup_exception
+	call early_exception
 
-20:
 	decl early_recursion_flag(%rip)
 	jmp restore_regs_and_return_to_kernel
 SYM_CODE_END(early_idt_handler_common)
-- 
2.17.1