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Commit a474e67c authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/vdso/compat: Wire up SYSENTER and SYSCSALL for compat userspace 



What, you didn't realize that SYSENTER and SYSCALL were actually
the same thing? :)

Unlike the old code, this actually passes the ptrace_syscall_32
test on AMD systems.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/b74615af58d785aa02d917213ec64e2022a2c796.1444091585.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 710246df

arch/x86/entry/entry_64_compat.S

+54 −36
Original line number Diff line number Diff line
@@ -52,15 +52,18 @@ ENTRY(entry_SYSENTER_compat) 
	SWAPGS_UNSAFE_STACK

	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp



	/* Zero-extending 32-bit regs, do not remove */

	movl	%ebp, %ebp

	/*

	 * User tracing code (ptrace or signal handlers) might assume that

	 * the saved RAX contains a 32-bit number when we're invoking a 32-bit

	 * syscall.  Just in case the high bits are nonzero, zero-extend

	 * the syscall number.  (This could almost certainly be deleted

	 * with no ill effects.)

	 */

	movl	%eax, %eax



	movl	ASM_THREAD_INFO(TI_sysenter_return, %rsp, 0), %r10d



	/* Construct struct pt_regs on stack */

	pushq	$__USER32_DS		/* pt_regs->ss */

	pushq	%rbp			/* pt_regs->sp */

	pushq	%rcx			/* pt_regs->sp */



	/*

	 * Push flags.  This is nasty.  First, interrupts are currently
@@ -70,17 +73,28 @@ ENTRY(entry_SYSENTER_compat) 
	 */

	pushfq				/* pt_regs->flags (except IF = 0) */

	orl	$X86_EFLAGS_IF, (%rsp)	/* Fix saved flags */

	ASM_CLAC			/* Clear AC after saving FLAGS */



	pushq	$__USER32_CS		/* pt_regs->cs */

	pushq	%r10			/* pt_regs->ip = thread_info->sysenter_return */

	xorq    %r8,%r8

	pushq	%r8			/* pt_regs->ip = 0 (placeholder) */

	pushq	%rax			/* pt_regs->orig_ax */

	pushq	%rdi			/* pt_regs->di */

	pushq	%rsi			/* pt_regs->si */

	pushq	%rdx			/* pt_regs->dx */

	pushq	%rcx			/* pt_regs->cx */

	pushq	%rcx			/* pt_regs->cx (will be overwritten) */

	pushq	$-ENOSYS		/* pt_regs->ax */

	pushq   %r8                     /* pt_regs->r8  = 0 */

	pushq   %r8                     /* pt_regs->r9  = 0 */

	pushq   %r8                     /* pt_regs->r10 = 0 */

	pushq   %r8                     /* pt_regs->r11 = 0 */

	pushq   %rbx                    /* pt_regs->rbx */

	pushq   %rbp                    /* pt_regs->rbp */

	pushq   %r8                     /* pt_regs->r12 = 0 */

	pushq   %r8                     /* pt_regs->r13 = 0 */

	pushq   %r8                     /* pt_regs->r14 = 0 */

	pushq   %r8                     /* pt_regs->r15 = 0 */

	cld

	sub	$(10*8), %rsp /* pt_regs->r8-11, bp, bx, r12-15 not saved */



	/*

	 * Sysenter doesn't filter flags, so we need to clear NT
@@ -93,16 +107,15 @@ ENTRY(entry_SYSENTER_compat) 
	jnz	sysenter_fix_flags

sysenter_flags_fixed:



	/* Temporary: SYSENTER is disabled. */

#ifdef CONFIG_CONTEXT_TRACKING

	call enter_from_user_mode

#endif

	ENABLE_INTERRUPTS(CLBR_NONE)

	movl $11, %edi

	call do_exit

	/*

	 * User mode is traced as though IRQs are on, and SYSENTER

	 * turned them off.

	 */

	TRACE_IRQS_OFF



	/* Unreachable. */

	ud2

	movq	%rsp, %rdi

	call	do_fast_syscall_32

	jmp	.Lsyscall_32_done



sysenter_fix_flags:

	pushq	$X86_EFLAGS_FIXED
@@ -135,26 +148,14 @@ ENDPROC(entry_SYSENTER_compat) 
 * edi  arg5

 * esp  user stack

 * 0(%esp) arg6

 *

 * This is purely a fast path. For anything complicated we use the int 0x80

 * path below. We set up a complete hardware stack frame to share code

 * with the int 0x80 path.

 */

ENTRY(entry_SYSCALL_compat)

	/*

	 * Interrupts are off on entry.

	 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,

	 * it is too small to ever cause noticeable irq latency.

	 */

	/* Interrupts are off on entry. */

	SWAPGS_UNSAFE_STACK



	/* Temporary: SYSCALL32 is disabled. */

	movl	$-ENOSYS, %eax

	USERGS_SYSRET32



	/* Stash user ESP and switch to the kernel stack. */

	movl	%esp, %r8d

	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp

	ENABLE_INTERRUPTS(CLBR_NONE)



	/* Zero-extending 32-bit regs, do not remove */

	movl	%eax, %eax
@@ -169,13 +170,29 @@ ENTRY(entry_SYSCALL_compat) 
	pushq	%rdi			/* pt_regs->di */

	pushq	%rsi			/* pt_regs->si */

	pushq	%rdx			/* pt_regs->dx */

	pushq	%rbp			/* pt_regs->cx */

	movl	%ebp, %ecx

	pushq	%rcx			/* pt_regs->cx (will be overwritten) */

	pushq	$-ENOSYS		/* pt_regs->ax */

	sub	$(10*8), %rsp		/* pt_regs->r8-11, bp, bx, r12-15 not saved */

	xorq    %r8,%r8

	pushq   %r8                     /* pt_regs->r8  = 0 */

	pushq   %r8                     /* pt_regs->r9  = 0 */

	pushq   %r8                     /* pt_regs->r10 = 0 */

	pushq   %r8                     /* pt_regs->r11 = 0 */

	pushq   %rbx                    /* pt_regs->rbx */

	pushq   %rbp                    /* pt_regs->rbp */

	pushq   %r8                     /* pt_regs->r12 = 0 */

	pushq   %r8                     /* pt_regs->r13 = 0 */

	pushq   %r8                     /* pt_regs->r14 = 0 */

	pushq   %r8                     /* pt_regs->r15 = 0 */



	/* Unreachable. */

	ud2

	/*

	 * User mode is traced as though IRQs are on, and SYSENTER

	 * turned them off.

	 */

	TRACE_IRQS_OFF



	movq	%rsp, %rdi

	call	do_fast_syscall_32

	jmp	.Lsyscall_32_done

END(entry_SYSCALL_compat)



/*
@@ -243,6 +260,7 @@ ENTRY(entry_INT80_compat) 


	movq	%rsp, %rdi

	call	do_int80_syscall_32

.Lsyscall_32_done:



	/* Go back to user mode. */

	TRACE_IRQS_ON

arch/x86/entry/vdso/vdso32/system_call.S

+8 −0
Original line number Diff line number Diff line
@@ -3,6 +3,8 @@ 
*/



#include <asm/dwarf2.h>

#include <asm/cpufeature.h>

#include <asm/alternative-asm.h>



/*

 * First get the common code for the sigreturn entry points.
@@ -28,6 +30,12 @@ __kernel_vsyscall: 
	CFI_REL_OFFSET		ecx, 0

	movl	%esp, %ecx



#ifdef CONFIG_X86_64

	/* If SYSENTER (Intel) or SYSCALL32 (AMD) is available, use it. */

	ALTERNATIVE_2 "", "sysenter", X86_FEATURE_SYSENTER32, \

	                  "syscall",  X86_FEATURE_SYSCALL32

#endif



	/* Enter using int $0x80 */

	movl	(%esp), %ecx

	int	$0x80