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Commit c2affbf9 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/asm/entry/32, selftests: Add a selftest for kernel entries from VM86 mode 



Test a couple of special cases in 32-bit kernels for entries
from vm86 mode.  This will OOPS both old kernels due to a bug
and and 4.1-rc5 due to a regression I introduced, and it should
make sure that the SYSENTER-from-vm86-mode hack in the kernel
keeps working.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/09a9916761e0a9e42d4922f147af45a0079cc1e8.1432936374.git.luto@kernel.org


Tests: 394838c9 x86/asm/entry/32: Fix user_mode() misuses
Tests: 7ba554b5 x86/asm/entry/32: Really make user_mode() work correctly for VM86 mode
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 927392d7

tools/testing/selftests/x86/Makefile

+4 −2
Original line number Diff line number Diff line
@@ -5,8 +5,10 @@ include ../lib.mk 
.PHONY: all all_32 all_64 warn_32bit_failure clean



TARGETS_C_BOTHBITS := sigreturn single_step_syscall

TARGETS_C_32BIT_ONLY := entry_from_vm86



BINARIES_32 := $(TARGETS_C_BOTHBITS:%=%_32)

TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)

BINARIES_32 := $(TARGETS_C_32BIT_ALL:%=%_32)

BINARIES_64 := $(TARGETS_C_BOTHBITS:%=%_64)



CFLAGS := -O2 -g -std=gnu99 -pthread -Wall
@@ -32,7 +34,7 @@ all_64: $(BINARIES_64) 
clean:

	$(RM) $(BINARIES_32) $(BINARIES_64)



$(TARGETS_C_BOTHBITS:%=%_32): %_32: %.c

$(TARGETS_C_32BIT_ALL:%=%_32): %_32: %.c

	$(CC) -m32 -o $@ $(CFLAGS) $(EXTRA_CFLAGS) $^ -lrt -ldl



$(TARGETS_C_BOTHBITS:%=%_64): %_64: %.c

tools/testing/selftests/x86/entry_from_vm86.c

0 → 100644
+114 −0
Original line number Diff line number Diff line 
/*

 * entry_from_vm86.c - tests kernel entries from vm86 mode

 * Copyright (c) 2014-2015 Andrew Lutomirski

 *

 * This exercises a few paths that need to special-case vm86 mode.

 *

 * GPL v2.

 */



#define _GNU_SOURCE



#include <assert.h>

#include <stdlib.h>

#include <sys/syscall.h>

#include <sys/signal.h>

#include <sys/ucontext.h>

#include <unistd.h>

#include <stdio.h>

#include <string.h>

#include <inttypes.h>

#include <sys/mman.h>

#include <err.h>

#include <stddef.h>

#include <stdbool.h>

#include <errno.h>

#include <sys/vm86.h>



static unsigned long load_addr = 0x10000;

static int nerrs = 0;



asm (

	".pushsection .rodata\n\t"

	".type vmcode_bound, @object\n\t"

	"vmcode:\n\t"

	"vmcode_bound:\n\t"

	".code16\n\t"

	"bound %ax, (2048)\n\t"

	"int3\n\t"

	"vmcode_sysenter:\n\t"

	"sysenter\n\t"

	".size vmcode, . - vmcode\n\t"

	"end_vmcode:\n\t"

	".code32\n\t"

	".popsection"

	);



extern unsigned char vmcode[], end_vmcode[];

extern unsigned char vmcode_bound[], vmcode_sysenter[];



static void do_test(struct vm86plus_struct *v86, unsigned long eip,

		    const char *text)

{

	long ret;



	printf("[RUN]\t%s from vm86 mode\n", text);

	v86->regs.eip = eip;

	ret = vm86(VM86_ENTER, v86);



	if (ret == -1 && errno == ENOSYS) {

		printf("[SKIP]\tvm86 not supported\n");

		return;

	}



	if (VM86_TYPE(ret) == VM86_INTx) {

		char trapname[32];

		int trapno = VM86_ARG(ret);

		if (trapno == 13)

			strcpy(trapname, "GP");

		else if (trapno == 5)

			strcpy(trapname, "BR");

		else if (trapno == 14)

			strcpy(trapname, "PF");

		else

			sprintf(trapname, "%d", trapno);



		printf("[OK]\tExited vm86 mode due to #%s\n", trapname);

	} else if (VM86_TYPE(ret) == VM86_UNKNOWN) {

		printf("[OK]\tExited vm86 mode due to unhandled GP fault\n");

	} else {

		printf("[OK]\tExited vm86 mode due to type %ld, arg %ld\n",

		       VM86_TYPE(ret), VM86_ARG(ret));

	}

}



int main(void)

{

	struct vm86plus_struct v86;

	unsigned char *addr = mmap((void *)load_addr, 4096,

				   PROT_READ | PROT_WRITE | PROT_EXEC,

				   MAP_ANONYMOUS | MAP_PRIVATE, -1,0);

	if (addr != (unsigned char *)load_addr)

		err(1, "mmap");



	memcpy(addr, vmcode, end_vmcode - vmcode);

	addr[2048] = 2;

	addr[2050] = 3;



	memset(&v86, 0, sizeof(v86));



	v86.regs.cs = load_addr / 16;

	v86.regs.ss = load_addr / 16;

	v86.regs.ds = load_addr / 16;

	v86.regs.es = load_addr / 16;



	assert((v86.regs.cs & 3) == 0);	/* Looks like RPL = 0 */



	/* #BR -- should deliver SIG??? */

	do_test(&v86, vmcode_bound - vmcode, "#BR");



	/* SYSENTER -- should cause #GP or #UD depending on CPU */

	do_test(&v86, vmcode_sysenter - vmcode, "SYSENTER");



	return (nerrs == 0 ? 0 : 1);

}