From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Wed, 16 Aug 2017 19:31:56 +0200
Subject: [PATCH] x86/paravirt/xen: Remove xen_patch()
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CVE-2017-5754

Xen's paravirt patch function xen_patch() does some special casing for
irq_ops functions to apply relocations when those functions can be
patched inline instead of calls.

Unfortunately none of the special case function replacements is small
enough to be patched inline, so the special case never applies.

As xen_patch() will call paravirt_patch_default() in all cases it can
be just dropped. xen-asm.h doesn't seem necessary without xen_patch()
as the only thing left in it would be the definition of XEN_EFLAGS_NMI
used only once. So move that definition and remove xen-asm.h.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boris.ostrovsky@oracle.com
Cc: lguest@lists.ozlabs.org
Cc: rusty@rustcorp.com.au
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/20170816173157.8633-2-jgross@suse.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit edcb5cf84f05e5d2e2af25422a72ccde359fcca9)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
(cherry picked from commit c96c9c712136a9e24a7aaf0aac4c149eee01bd8e)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
 arch/x86/xen/xen-asm.h      | 12 ---------
 arch/x86/xen/xen-ops.h      | 15 +++---------
 arch/x86/xen/enlighten_pv.c | 59 +--------------------------------------------
 arch/x86/xen/xen-asm.S      | 26 +++++---------------
 arch/x86/xen/xen-asm_32.S   | 27 ++++-----------------
 arch/x86/xen/xen-asm_64.S   | 20 ++++-----------
 6 files changed, 21 insertions(+), 138 deletions(-)
 delete mode 100644 arch/x86/xen/xen-asm.h

diff --git a/arch/x86/xen/xen-asm.h b/arch/x86/xen/xen-asm.h
deleted file mode 100644
index 465276467a47..000000000000
--- a/arch/x86/xen/xen-asm.h
+++ /dev/null
@@ -1,12 +0,0 @@
-#ifndef _XEN_XEN_ASM_H
-#define _XEN_XEN_ASM_H
-
-#include <linux/linkage.h>
-
-#define RELOC(x, v)	.globl x##_reloc; x##_reloc=v
-#define ENDPATCH(x)	.globl x##_end; x##_end=.
-
-/* Pseudo-flag used for virtual NMI, which we don't implement yet */
-#define XEN_EFLAGS_NMI	0x80000000
-
-#endif
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 0d5004477db6..70301ac0d414 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -129,17 +129,10 @@ static inline void __init xen_efi_init(void)
 }
 #endif
 
-/* Declare an asm function, along with symbols needed to make it
-   inlineable */
-#define DECL_ASM(ret, name, ...)		\
-	__visible ret name(__VA_ARGS__);	\
-	extern char name##_end[] __visible;	\
-	extern char name##_reloc[] __visible
-
-DECL_ASM(void, xen_irq_enable_direct, void);
-DECL_ASM(void, xen_irq_disable_direct, void);
-DECL_ASM(unsigned long, xen_save_fl_direct, void);
-DECL_ASM(void, xen_restore_fl_direct, unsigned long);
+__visible void xen_irq_enable_direct(void);
+__visible void xen_irq_disable_direct(void);
+__visible unsigned long xen_save_fl_direct(void);
+__visible void xen_restore_fl_direct(unsigned long);
 
 /* These are not functions, and cannot be called normally */
 __visible void xen_iret(void);
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index df1921751aa5..6c279c8f0a0e 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -988,59 +988,6 @@ void __ref xen_setup_vcpu_info_placement(void)
 	}
 }
 
-static unsigned xen_patch(u8 type, u16 clobbers, void *insnbuf,
-			  unsigned long addr, unsigned len)
-{
-	char *start, *end, *reloc;
-	unsigned ret;
-
-	start = end = reloc = NULL;
-
-#define SITE(op, x)							\
-	case PARAVIRT_PATCH(op.x):					\
-	if (xen_have_vcpu_info_placement) {				\
-		start = (char *)xen_##x##_direct;			\
-		end = xen_##x##_direct_end;				\
-		reloc = xen_##x##_direct_reloc;				\
-	}								\
-	goto patch_site
-
-	switch (type) {
-		SITE(pv_irq_ops, irq_enable);
-		SITE(pv_irq_ops, irq_disable);
-		SITE(pv_irq_ops, save_fl);
-		SITE(pv_irq_ops, restore_fl);
-#undef SITE
-
-	patch_site:
-		if (start == NULL || (end-start) > len)
-			goto default_patch;
-
-		ret = paravirt_patch_insns(insnbuf, len, start, end);
-
-		/* Note: because reloc is assigned from something that
-		   appears to be an array, gcc assumes it's non-null,
-		   but doesn't know its relationship with start and
-		   end. */
-		if (reloc > start && reloc < end) {
-			int reloc_off = reloc - start;
-			long *relocp = (long *)(insnbuf + reloc_off);
-			long delta = start - (char *)addr;
-
-			*relocp += delta;
-		}
-		break;
-
-	default_patch:
-	default:
-		ret = paravirt_patch_default(type, clobbers, insnbuf,
-					     addr, len);
-		break;
-	}
-
-	return ret;
-}
-
 static const struct pv_info xen_info __initconst = {
 	.shared_kernel_pmd = 0,
 
@@ -1050,10 +997,6 @@ static const struct pv_info xen_info __initconst = {
 	.name = "Xen",
 };
 
-static const struct pv_init_ops xen_init_ops __initconst = {
-	.patch = xen_patch,
-};
-
 static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 	.cpuid = xen_cpuid,
 
@@ -1251,7 +1194,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
 	/* Install Xen paravirt ops */
 	pv_info = xen_info;
-	pv_init_ops = xen_init_ops;
+	pv_init_ops.patch = paravirt_patch_default;
 	pv_cpu_ops = xen_cpu_ops;
 
 	x86_platform.get_nmi_reason = xen_get_nmi_reason;
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index eff224df813f..dcd31fa39b5d 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -1,14 +1,8 @@
 /*
- * Asm versions of Xen pv-ops, suitable for either direct use or
- * inlining.  The inline versions are the same as the direct-use
- * versions, with the pre- and post-amble chopped off.
- *
- * This code is encoded for size rather than absolute efficiency, with
- * a view to being able to inline as much as possible.
+ * Asm versions of Xen pv-ops, suitable for direct use.
  *
  * We only bother with direct forms (ie, vcpu in percpu data) of the
- * operations here; the indirect forms are better handled in C, since
- * they're generally too large to inline anyway.
+ * operations here; the indirect forms are better handled in C.
  */
 
 #include <asm/asm-offsets.h>
@@ -16,7 +10,7 @@
 #include <asm/processor-flags.h>
 #include <asm/frame.h>
 
-#include "xen-asm.h"
+#include <linux/linkage.h>
 
 /*
  * Enable events.  This clears the event mask and tests the pending
@@ -38,13 +32,11 @@ ENTRY(xen_irq_enable_direct)
 	testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
 	jz 1f
 
-2:	call check_events
+	call check_events
 1:
-ENDPATCH(xen_irq_enable_direct)
 	FRAME_END
 	ret
 	ENDPROC(xen_irq_enable_direct)
-	RELOC(xen_irq_enable_direct, 2b+1)
 
 
 /*
@@ -53,10 +45,8 @@ ENDPATCH(xen_irq_enable_direct)
  */
 ENTRY(xen_irq_disable_direct)
 	movb $1, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
-ENDPATCH(xen_irq_disable_direct)
 	ret
-	ENDPROC(xen_irq_disable_direct)
-	RELOC(xen_irq_disable_direct, 0)
+ENDPROC(xen_irq_disable_direct)
 
 /*
  * (xen_)save_fl is used to get the current interrupt enable status.
@@ -71,10 +61,8 @@ ENTRY(xen_save_fl_direct)
 	testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
 	setz %ah
 	addb %ah, %ah
-ENDPATCH(xen_save_fl_direct)
 	ret
 	ENDPROC(xen_save_fl_direct)
-	RELOC(xen_save_fl_direct, 0)
 
 
 /*
@@ -101,13 +89,11 @@ ENTRY(xen_restore_fl_direct)
 	/* check for unmasked and pending */
 	cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_pending
 	jnz 1f
-2:	call check_events
+	call check_events
 1:
-ENDPATCH(xen_restore_fl_direct)
 	FRAME_END
 	ret
 	ENDPROC(xen_restore_fl_direct)
-	RELOC(xen_restore_fl_direct, 2b+1)
 
 
 /*
diff --git a/arch/x86/xen/xen-asm_32.S b/arch/x86/xen/xen-asm_32.S
index feb6d40a0860..1200e262a116 100644
--- a/arch/x86/xen/xen-asm_32.S
+++ b/arch/x86/xen/xen-asm_32.S
@@ -1,14 +1,8 @@
 /*
- * Asm versions of Xen pv-ops, suitable for either direct use or
- * inlining.  The inline versions are the same as the direct-use
- * versions, with the pre- and post-amble chopped off.
- *
- * This code is encoded for size rather than absolute efficiency, with
- * a view to being able to inline as much as possible.
+ * Asm versions of Xen pv-ops, suitable for direct use.
  *
  * We only bother with direct forms (ie, vcpu in pda) of the
- * operations here; the indirect forms are better handled in C, since
- * they're generally too large to inline anyway.
+ * operations here; the indirect forms are better handled in C.
  */
 
 #include <asm/thread_info.h>
@@ -18,21 +12,10 @@
 
 #include <xen/interface/xen.h>
 
-#include "xen-asm.h"
+#include <linux/linkage.h>
 
-/*
- * Force an event check by making a hypercall, but preserve regs
- * before making the call.
- */
-check_events:
-	push %eax
-	push %ecx
-	push %edx
-	call xen_force_evtchn_callback
-	pop %edx
-	pop %ecx
-	pop %eax
-	ret
+/* Pseudo-flag used for virtual NMI, which we don't implement yet */
+#define XEN_EFLAGS_NMI  0x80000000
 
 /*
  * This is run where a normal iret would be run, with the same stack setup:
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
index c5fee2680abc..3a3b6a211584 100644
--- a/arch/x86/xen/xen-asm_64.S
+++ b/arch/x86/xen/xen-asm_64.S
@@ -1,14 +1,8 @@
 /*
- * Asm versions of Xen pv-ops, suitable for either direct use or
- * inlining.  The inline versions are the same as the direct-use
- * versions, with the pre- and post-amble chopped off.
- *
- * This code is encoded for size rather than absolute efficiency, with
- * a view to being able to inline as much as possible.
+ * Asm versions of Xen pv-ops, suitable for direct use.
  *
  * We only bother with direct forms (ie, vcpu in pda) of the
- * operations here; the indirect forms are better handled in C, since
- * they're generally too large to inline anyway.
+ * operations here; the indirect forms are better handled in C.
  */
 
 #include <asm/errno.h>
@@ -20,7 +14,7 @@
 
 #include <xen/interface/xen.h>
 
-#include "xen-asm.h"
+#include <linux/linkage.h>
 
 ENTRY(xen_adjust_exception_frame)
 	mov 8+0(%rsp), %rcx
@@ -46,9 +40,7 @@ hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
  */
 ENTRY(xen_iret)
 	pushq $0
-1:	jmp hypercall_iret
-ENDPATCH(xen_iret)
-RELOC(xen_iret, 1b+1)
+	jmp hypercall_iret
 
 ENTRY(xen_sysret64)
 	/*
@@ -65,9 +57,7 @@ ENTRY(xen_sysret64)
 	pushq %rcx
 
 	pushq $VGCF_in_syscall
-1:	jmp hypercall_iret
-ENDPATCH(xen_sysret64)
-RELOC(xen_sysret64, 1b+1)
+	jmp hypercall_iret
 
 /*
  * Xen handles syscall callbacks much like ordinary exceptions, which
-- 
2.14.2

