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x86/asm/entry/32, selftests: Add a selftest for kernel entries from VM86 mode

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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: Andy 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: 394838c960 x86/asm/entry/32: Fix user_mode() misuses
Tests: 7ba554b5ac x86/asm/entry/32: Really make user_mode() work correctly for VM86 mode
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-05-29 14:58:24 -07:00 committed by Ingo Molnar
parent 927392d73a
commit c2affbf9a5
2 changed files with 118 additions and 2 deletions
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6
tools/testing/selftests/x86/Makefile
View File

@ -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

114
tools/testing/selftests/x86/entry_from_vm86.c Normal file
View File

@ -0,0 +1,114 @@
/*
* 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);
}