x86/head: Pass a real pt_regs and trapnr to early_fixup_exception()

early_fixup_exception() is limited by the fact that it doesn't have a
real struct pt_regs.  Change both the 32-bit and 64-bit asm and the
C code to pass and accept a real pt_regs.

Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/e3fb680fcfd5e23e38237e8328b64a25cc121d37.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 37 insertions, 31 deletions

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 22fbf9d..9e8636d 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -20,6 +20,7 @@
 #include <asm/processor-flags.h>
 #include <asm/percpu.h>
 #include <asm/nops.h>
+#include "../entry/calling.h"
 
 #ifdef CONFIG_PARAVIRT
 #include <asm/asm-offsets.h>
@@ -357,39 +358,52 @@ early_idt_handler_common:
 	jz  1f
 	incl early_recursion_flag(%rip)
 
-	pushq %rax		# 64(%rsp)
-	pushq %rcx		# 56(%rsp)
-	pushq %rdx		# 48(%rsp)
-	pushq %rsi		# 40(%rsp)
-	pushq %rdi		# 32(%rsp)
-	pushq %r8		# 24(%rsp)
-	pushq %r9		# 16(%rsp)
-	pushq %r10		#  8(%rsp)
-	pushq %r11		#  0(%rsp)
-
-	cmpl $__KERNEL_CS,96(%rsp)
+	/* The vector number is currently in the pt_regs->di slot. */
+	pushq %rsi				/* pt_regs->si */
+	movq 8(%rsp), %rsi			/* RSI = vector number */
+	movq %rdi, 8(%rsp)			/* pt_regs->di = RDI */
+	pushq %rdx				/* pt_regs->dx */
+	pushq %rcx				/* pt_regs->cx */
+	pushq %rax				/* pt_regs->ax */
+	pushq %r8				/* pt_regs->r8 */
+	pushq %r9				/* pt_regs->r9 */
+	pushq %r10				/* pt_regs->r10 */
+	pushq %r11				/* pt_regs->r11 */
+	pushq %rbx				/* pt_regs->bx */
+	pushq %rbp				/* pt_regs->bp */
+	pushq %r12				/* pt_regs->r12 */
+	pushq %r13				/* pt_regs->r13 */
+	pushq %r14				/* pt_regs->r14 */
+	pushq %r15				/* pt_regs->r15 */
+
+	cmpl $__KERNEL_CS,CS(%rsp)
 	jne 11f
 
-	cmpl $14,72(%rsp)	# Page fault?
+	cmpq $14,%rsi		/* Page fault? */
 	jnz 10f
-	GET_CR2_INTO(%rdi)	# can clobber any volatile register if pv
+	GET_CR2_INTO(%rdi)	/* Can clobber any volatile register if pv */
 	call early_make_pgtable
 	andl %eax,%eax
-	jz 20f			# All good
+	jz 20f			/* All good */
 
 10:
-	leaq 88(%rsp),%rdi	# Pointer to %rip
+	movq %rsp,%rdi		/* RDI = pt_regs; RSI is already trapnr */
 	call early_fixup_exception
 	andl %eax,%eax
 	jnz 20f			# Found an exception entry
 
 11:
 #ifdef CONFIG_EARLY_PRINTK
-	GET_CR2_INTO(%r9)	# can clobber any volatile register if pv
-	movl 80(%rsp),%r8d	# error code
-	movl 72(%rsp),%esi	# vector number
-	movl 96(%rsp),%edx	# %cs
-	movq 88(%rsp),%rcx	# %rip
+	/*
+	 * On paravirt kernels, GET_CR2_INTO clobbers callee-clobbered regs.
+	 * We only care about RSI, so we need to save it.
+	 */
+	movq %rsi,%rbx		/* Save vector number */
+	GET_CR2_INTO(%r9)
+	movq ORIG_RAX(%rsp),%r8	/* error code */
+	movq %rbx,%rsi		/* vector number */
+	movq CS(%rsp),%rdx
+	movq RIP(%rsp),%rcx
 	xorl %eax,%eax
 	leaq early_idt_msg(%rip),%rdi
 	call early_printk
@@ -398,24 +412,16 @@ early_idt_handler_common:
 	call dump_stack
 #ifdef CONFIG_KALLSYMS	
 	leaq early_idt_ripmsg(%rip),%rdi
-	movq 40(%rsp),%rsi	# %rip again
+	movq RIP(%rsp),%rsi	# %rip again
 	call __print_symbol
 #endif
 #endif /* EARLY_PRINTK */
 1:	hlt
 	jmp 1b
 
-20:	# Exception table entry found or page table generated
-	popq %r11
-	popq %r10
-	popq %r9
-	popq %r8
-	popq %rdi
-	popq %rsi
-	popq %rdx
-	popq %rcx
-	popq %rax
+20:	/* Exception table entry found or page table generated */
 	decl early_recursion_flag(%rip)
+	jmp restore_regs_and_iret
 .Lis_nmi:
 	addq $16,%rsp		# drop vector number and error code
 	INTERRUPT_RETURN