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Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Browse source 
Pull x86 asm changes from Ingo Molnar:
 "There were lots of changes in this development cycle:

   - over 100 separate cleanups, restructuring changes, speedups and
     fixes in the x86 system call, irq, trap and other entry code, part
     of a heroic effort to deobfuscate a decade old spaghetti asm code
     and its C code dependencies (Denys Vlasenko, Andy Lutomirski)

   - alternatives code fixes and enhancements (Borislav Petkov)

   - simplifications and cleanups to the compat code (Brian Gerst)

   - signal handling fixes and new x86 testcases (Andy Lutomirski)

   - various other fixes and cleanups

  By their nature many of these changes are risky - we tried to test
  them well on many different x86 systems (there are no known
  regressions), and they are split up finely to help bisection - but
  there's still a fair bit of residual risk left so caveat emptor"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (148 commits)
  perf/x86/64: Report regs_user->ax too in get_regs_user()
  perf/x86/64: Simplify regs_user->abi setting code in get_regs_user()
  perf/x86/64: Do report user_regs->cx while we are in syscall, in get_regs_user()
  perf/x86/64: Do not guess user_regs->cs, ss, sp in get_regs_user()
  x86/asm/entry/32: Tidy up JNZ instructions after TESTs
  x86/asm/entry/64: Reduce padding in execve stubs
  x86/asm/entry/64: Remove GET_THREAD_INFO() in ret_from_fork
  x86/asm/entry/64: Simplify jumps in ret_from_fork
  x86/asm/entry/64: Remove a redundant jump
  x86/asm/entry/64: Optimize [v]fork/clone stubs
  x86/asm/entry: Zero EXTRA_REGS for stub32_execve() too
  x86/asm/entry/64: Move stub_x32_execvecloser() to stub_execveat()
  x86/asm/entry/64: Use common code for rt_sigreturn() epilogue
  x86/asm/entry/64: Add forgotten CFI annotation
  x86/asm/entry/irq: Simplify interrupt dispatch table (IDT) layout
  x86/asm/entry/64: Move opportunistic sysret code to syscall code path
  x86, selftests: Add sigreturn selftest
  x86/alternatives: Guard NOPs optimization
  x86/asm/entry: Clear EXTRA_REGS for all executable formats
  x86/signal: Remove pax argument from restore_sigcontext
  ...
This commit is contained in:
Linus Torvalds 2015-04-13 13:16:36 -07:00
commit 60f898eeaa
121 changed files with 3084 additions and 2104 deletions
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1
tools/testing/selftests/Makefile
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@ -17,6 +17,7 @@ TARGETS += sysctl
TARGETS += timers
TARGETS += user
TARGETS += vm
TARGETS += x86
#Please keep the TARGETS list alphabetically sorted
TARGETS_HOTPLUG = cpu-hotplug

2
tools/testing/selftests/x86/.gitignore vendored Normal file
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@ -0,0 +1,2 @@
*_32
*_64

48
tools/testing/selftests/x86/Makefile Normal file
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@ -0,0 +1,48 @@
.PHONY: all all_32 all_64 check_build32 clean run_tests
TARGETS_C_BOTHBITS := sigreturn
BINARIES_32 := $(TARGETS_C_BOTHBITS:%=%_32)
BINARIES_64 := $(TARGETS_C_BOTHBITS:%=%_64)
CFLAGS := -O2 -g -std=gnu99 -pthread -Wall
UNAME_P := $(shell uname -p)
# Always build 32-bit tests
all: all_32
# If we're on a 64-bit host, build 64-bit tests as well
ifeq ($(shell uname -p),x86_64)
all: all_64
endif
all_32: check_build32 $(BINARIES_32)
all_64: $(BINARIES_64)
clean:
$(RM) $(BINARIES_32) $(BINARIES_64)
run_tests:
./run_x86_tests.sh
$(TARGETS_C_BOTHBITS:%=%_32): %_32: %.c
$(CC) -m32 -o $@ $(CFLAGS) $(EXTRA_CFLAGS) $^ -lrt -ldl
$(TARGETS_C_BOTHBITS:%=%_64): %_64: %.c
$(CC) -m64 -o $@ $(CFLAGS) $(EXTRA_CFLAGS) $^ -lrt -ldl
check_build32:
@if ! $(CC) -m32 -o /dev/null trivial_32bit_program.c; then \
echo "Warning: you seem to have a broken 32-bit build" 2>&1; \
echo "environment. If you are using a Debian-like"; \
echo " distribution, try:"; \
echo ""; \
echo " apt-get install gcc-multilib libc6-i386 libc6-dev-i386"; \
echo ""; \
echo "If you are using a Fedora-like distribution, try:"; \
echo ""; \
echo " yum install glibc-devel.*i686"; \
exit 1; \
fi

11
tools/testing/selftests/x86/run_x86_tests.sh Normal file
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@ -0,0 +1,11 @@
#!/bin/bash
# This is deliberately minimal. IMO kselftests should provide a standard
# script here.
./sigreturn_32 || exit 1
if [[ "$uname -p" -eq "x86_64" ]]; then
./sigreturn_64 || exit 1
fi
exit 0

684
tools/testing/selftests/x86/sigreturn.c Normal file
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@ -0,0 +1,684 @@
/*
* sigreturn.c - tests for x86 sigreturn(2) and exit-to-userspace
* Copyright (c) 2014-2015 Andrew Lutomirski
*
* This program is free software; you can redistribute it and/or modify
* it under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* This is a series of tests that exercises the sigreturn(2) syscall and
* the IRET / SYSRET paths in the kernel.
*
* For now, this focuses on the effects of unusual CS and SS values,
* and it has a bunch of tests to make sure that ESP/RSP is restored
* properly.
*
* The basic idea behind these tests is to raise(SIGUSR1) to create a
* sigcontext frame, plug in the values to be tested, and then return,
* which implicitly invokes sigreturn(2) and programs the user context
* as desired.
*
* For tests for which we expect sigreturn and the subsequent return to
* user mode to succeed, we return to a short trampoline that generates
* SIGTRAP so that the meat of the tests can be ordinary C code in a
* SIGTRAP handler.
*
* The inner workings of each test is documented below.
*
* Do not run on outdated, unpatched kernels at risk of nasty crashes.
*/
#define _GNU_SOURCE
#include <sys/time.h>
#include <time.h>
#include <stdlib.h>
#include <sys/syscall.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <sys/mman.h>
#include <sys/signal.h>
#include <sys/ucontext.h>
#include <asm/ldt.h>
#include <err.h>
#include <setjmp.h>
#include <stddef.h>
#include <stdbool.h>
#include <sys/ptrace.h>
#include <sys/user.h>
/*
* In principle, this test can run on Linux emulation layers (e.g.
* Illumos "LX branded zones"). Solaris-based kernels reserve LDT
* entries 0-5 for their own internal purposes, so start our LDT
* allocations above that reservation. (The tests don't pass on LX
* branded zones, but at least this lets them run.)
*/
#define LDT_OFFSET 6
/* An aligned stack accessible through some of our segments. */
static unsigned char stack16[65536] __attribute__((aligned(4096)));
/*
* An aligned int3 instruction used as a trampoline. Some of the tests
* want to fish out their ss values, so this trampoline copies ss to eax
* before the int3.
*/
asm (".pushsection .text\n\t"
".type int3, @function\n\t"
".align 4096\n\t"
"int3:\n\t"
"mov %ss,%eax\n\t"
"int3\n\t"
".size int3, . - int3\n\t"
".align 4096, 0xcc\n\t"
".popsection");
extern char int3[4096];
/*
* At startup, we prepapre:
*
* - ldt_nonexistent_sel: An LDT entry that doesn't exist (all-zero
* descriptor or out of bounds).
* - code16_sel: A 16-bit LDT code segment pointing to int3.
* - data16_sel: A 16-bit LDT data segment pointing to stack16.
* - npcode32_sel: A 32-bit not-present LDT code segment pointing to int3.
* - npdata32_sel: A 32-bit not-present LDT data segment pointing to stack16.
* - gdt_data16_idx: A 16-bit GDT data segment pointing to stack16.
* - gdt_npdata32_idx: A 32-bit not-present GDT data segment pointing to
* stack16.
*
* For no particularly good reason, xyz_sel is a selector value with the
* RPL and LDT bits filled in, whereas xyz_idx is just an index into the
* descriptor table. These variables will be zero if their respective
* segments could not be allocated.
*/
static unsigned short ldt_nonexistent_sel;
static unsigned short code16_sel, data16_sel, npcode32_sel, npdata32_sel;
static unsigned short gdt_data16_idx, gdt_npdata32_idx;
static unsigned short GDT3(int idx)
{
return (idx << 3) | 3;
}
static unsigned short LDT3(int idx)
{
return (idx << 3) | 7;
}
/* Our sigaltstack scratch space. */
static char altstack_data[SIGSTKSZ];
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
int flags)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = handler;
sa.sa_flags = SA_SIGINFO | flags;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
static void clearhandler(int sig)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = SIG_DFL;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
static void add_ldt(const struct user_desc *desc, unsigned short *var,
const char *name)
{
if (syscall(SYS_modify_ldt, 1, desc, sizeof(*desc)) == 0) {
*var = LDT3(desc->entry_number);
} else {
printf("[NOTE]\tFailed to create %s segment\n", name);
*var = 0;
}
}
static void setup_ldt(void)
{
if ((unsigned long)stack16 > (1ULL << 32) - sizeof(stack16))
errx(1, "stack16 is too high\n");
if ((unsigned long)int3 > (1ULL << 32) - sizeof(int3))
errx(1, "int3 is too high\n");
ldt_nonexistent_sel = LDT3(LDT_OFFSET + 2);
const struct user_desc code16_desc = {
.entry_number = LDT_OFFSET + 0,
.base_addr = (unsigned long)int3,
.limit = 4095,
.seg_32bit = 0,
.contents = 2, /* Code, not conforming */
.read_exec_only = 0,
.limit_in_pages = 0,
.seg_not_present = 0,
.useable = 0
};
add_ldt(&code16_desc, &code16_sel, "code16");
const struct user_desc data16_desc = {
.entry_number = LDT_OFFSET + 1,
.base_addr = (unsigned long)stack16,
.limit = 0xffff,
.seg_32bit = 0,
.contents = 0, /* Data, grow-up */
.read_exec_only = 0,
.limit_in_pages = 0,
.seg_not_present = 0,
.useable = 0
};
add_ldt(&data16_desc, &data16_sel, "data16");
const struct user_desc npcode32_desc = {
.entry_number = LDT_OFFSET + 3,
.base_addr = (unsigned long)int3,
.limit = 4095,
.seg_32bit = 1,
.contents = 2, /* Code, not conforming */
.read_exec_only = 0,
.limit_in_pages = 0,
.seg_not_present = 1,
.useable = 0
};
add_ldt(&npcode32_desc, &npcode32_sel, "npcode32");
const struct user_desc npdata32_desc = {
.entry_number = LDT_OFFSET + 4,
.base_addr = (unsigned long)stack16,
.limit = 0xffff,
.seg_32bit = 1,
.contents = 0, /* Data, grow-up */
.read_exec_only = 0,
.limit_in_pages = 0,
.seg_not_present = 1,
.useable = 0
};
add_ldt(&npdata32_desc, &npdata32_sel, "npdata32");
struct user_desc gdt_data16_desc = {
.entry_number = -1,
.base_addr = (unsigned long)stack16,
.limit = 0xffff,
.seg_32bit = 0,
.contents = 0, /* Data, grow-up */
.read_exec_only = 0,
.limit_in_pages = 0,
.seg_not_present = 0,
.useable = 0
};
if (syscall(SYS_set_thread_area, &gdt_data16_desc) == 0) {
/*
* This probably indicates vulnerability to CVE-2014-8133.
* Merely getting here isn't definitive, though, and we'll
* diagnose the problem for real later on.
*/
printf("[WARN]\tset_thread_area allocated data16 at index %d\n",
gdt_data16_desc.entry_number);
gdt_data16_idx = gdt_data16_desc.entry_number;
} else {
printf("[OK]\tset_thread_area refused 16-bit data\n");
}
struct user_desc gdt_npdata32_desc = {
.entry_number = -1,
.base_addr = (unsigned long)stack16,
.limit = 0xffff,
.seg_32bit = 1,
.contents = 0, /* Data, grow-up */
.read_exec_only = 0,
.limit_in_pages = 0,
.seg_not_present = 1,
.useable = 0
};
if (syscall(SYS_set_thread_area, &gdt_npdata32_desc) == 0) {
/*
* As a hardening measure, newer kernels don't allow this.
*/
printf("[WARN]\tset_thread_area allocated npdata32 at index %d\n",
gdt_npdata32_desc.entry_number);
gdt_npdata32_idx = gdt_npdata32_desc.entry_number;
} else {
printf("[OK]\tset_thread_area refused 16-bit data\n");
}
}
/* State used by our signal handlers. */
static gregset_t initial_regs, requested_regs, resulting_regs;
/* Instructions for the SIGUSR1 handler. */
static volatile unsigned short sig_cs, sig_ss;
static volatile sig_atomic_t sig_trapped, sig_err, sig_trapno;
/* Abstractions for some 32-bit vs 64-bit differences. */
#ifdef __x86_64__
# define REG_IP REG_RIP
# define REG_SP REG_RSP
# define REG_AX REG_RAX
struct selectors {
unsigned short cs, gs, fs, ss;
};
static unsigned short *ssptr(ucontext_t *ctx)
{
struct selectors *sels = (void *)&ctx->uc_mcontext.gregs[REG_CSGSFS];
return &sels->ss;
}
static unsigned short *csptr(ucontext_t *ctx)
{
struct selectors *sels = (void *)&ctx->uc_mcontext.gregs[REG_CSGSFS];
return &sels->cs;
}
#else
# define REG_IP REG_EIP
# define REG_SP REG_ESP
# define REG_AX REG_EAX
static greg_t *ssptr(ucontext_t *ctx)
{
return &ctx->uc_mcontext.gregs[REG_SS];
}
static greg_t *csptr(ucontext_t *ctx)
{
return &ctx->uc_mcontext.gregs[REG_CS];
}
#endif
/* Number of errors in the current test case. */
static volatile sig_atomic_t nerrs;
/*
* SIGUSR1 handler. Sets CS and SS as requested and points IP to the
* int3 trampoline. Sets SP to a large known value so that we can see
* whether the value round-trips back to user mode correctly.
*/
static void sigusr1(int sig, siginfo_t *info, void *ctx_void)
{
ucontext_t *ctx = (ucontext_t*)ctx_void;
memcpy(&initial_regs, &ctx->uc_mcontext.gregs, sizeof(gregset_t));
*csptr(ctx) = sig_cs;
*ssptr(ctx) = sig_ss;
ctx->uc_mcontext.gregs[REG_IP] =
sig_cs == code16_sel ? 0 : (unsigned long)&int3;
ctx->uc_mcontext.gregs[REG_SP] = (unsigned long)0x8badf00d5aadc0deULL;
ctx->uc_mcontext.gregs[REG_AX] = 0;
memcpy(&requested_regs, &ctx->uc_mcontext.gregs, sizeof(gregset_t));
requested_regs[REG_AX] = *ssptr(ctx); /* The asm code does this. */
return;
}
/*
* Called after a successful sigreturn. Restores our state so that
* the original raise(SIGUSR1) returns.
*/
static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
{
ucontext_t *ctx = (ucontext_t*)ctx_void;
sig_err = ctx->uc_mcontext.gregs[REG_ERR];
sig_trapno = ctx->uc_mcontext.gregs[REG_TRAPNO];
unsigned short ss;
asm ("mov %%ss,%0" : "=r" (ss));
greg_t asm_ss = ctx->uc_mcontext.gregs[REG_AX];
if (asm_ss != sig_ss && sig == SIGTRAP) {
/* Sanity check failure. */
printf("[FAIL]\tSIGTRAP: ss = %hx, frame ss = %hx, ax = %llx\n",
ss, *ssptr(ctx), (unsigned long long)asm_ss);
nerrs++;
}
memcpy(&resulting_regs, &ctx->uc_mcontext.gregs, sizeof(gregset_t));
memcpy(&ctx->uc_mcontext.gregs, &initial_regs, sizeof(gregset_t));
sig_trapped = sig;
}
/*
* Checks a given selector for its code bitness or returns -1 if it's not
* a usable code segment selector.
*/
int cs_bitness(unsigned short cs)
{
uint32_t valid = 0, ar;
asm ("lar %[cs], %[ar]\n\t"
"jnz 1f\n\t"
"mov $1, %[valid]\n\t"
"1:"
: [ar] "=r" (ar), [valid] "+rm" (valid)
: [cs] "r" (cs));
if (!valid)
return -1;
bool db = (ar & (1 << 22));
bool l = (ar & (1 << 21));
if (!(ar & (1<<11)))
return -1; /* Not code. */
if (l && !db)
return 64;
else if (!l && db)
return 32;
else if (!l && !db)
return 16;
else
return -1; /* Unknown bitness. */
}
/* Finds a usable code segment of the requested bitness. */
int find_cs(int bitness)
{
unsigned short my_cs;
asm ("mov %%cs,%0" : "=r" (my_cs));
if (cs_bitness(my_cs) == bitness)
return my_cs;
if (cs_bitness(my_cs + (2 << 3)) == bitness)
return my_cs + (2 << 3);
if (my_cs > (2<<3) && cs_bitness(my_cs - (2 << 3)) == bitness)
return my_cs - (2 << 3);
if (cs_bitness(code16_sel) == bitness)
return code16_sel;
printf("[WARN]\tCould not find %d-bit CS\n", bitness);
return -1;
}
static int test_valid_sigreturn(int cs_bits, bool use_16bit_ss, int force_ss)
{
int cs = find_cs(cs_bits);
if (cs == -1) {
printf("[SKIP]\tCode segment unavailable for %d-bit CS, %d-bit SS\n",
cs_bits, use_16bit_ss ? 16 : 32);
return 0;
}
if (force_ss != -1) {
sig_ss = force_ss;
} else {
if (use_16bit_ss) {
if (!data16_sel) {
printf("[SKIP]\tData segment unavailable for %d-bit CS, 16-bit SS\n",
cs_bits);
return 0;
}
sig_ss = data16_sel;
} else {
asm volatile ("mov %%ss,%0" : "=r" (sig_ss));
}
}
sig_cs = cs;
printf("[RUN]\tValid sigreturn: %d-bit CS (%hx), %d-bit SS (%hx%s)\n",
cs_bits, sig_cs, use_16bit_ss ? 16 : 32, sig_ss,
(sig_ss & 4) ? "" : ", GDT");
raise(SIGUSR1);
nerrs = 0;
/*
* Check that each register had an acceptable value when the
* int3 trampoline was invoked.
*/
for (int i = 0; i < NGREG; i++) {
greg_t req = requested_regs[i], res = resulting_regs[i];
if (i == REG_TRAPNO || i == REG_IP)
continue; /* don't care */
if (i == REG_SP) {
printf("\tSP: %llx -> %llx\n", (unsigned long long)req,
(unsigned long long)res);
/*
* In many circumstances, the high 32 bits of rsp
* are zeroed. For example, we could be a real
* 32-bit program, or we could hit any of a number
* of poorly-documented IRET or segmented ESP
* oddities. If this happens, it's okay.
*/
if (res == (req & 0xFFFFFFFF))
continue; /* OK; not expected to work */
}
bool ignore_reg = false;
#if __i386__
if (i == REG_UESP)
ignore_reg = true;
#else
if (i == REG_CSGSFS) {
struct selectors *req_sels =
(void *)&requested_regs[REG_CSGSFS];
struct selectors *res_sels =
(void *)&resulting_regs[REG_CSGSFS];
if (req_sels->cs != res_sels->cs) {
printf("[FAIL]\tCS mismatch: requested 0x%hx; got 0x%hx\n",
req_sels->cs, res_sels->cs);
nerrs++;
}
if (req_sels->ss != res_sels->ss) {
printf("[FAIL]\tSS mismatch: requested 0x%hx; got 0x%hx\n",
req_sels->ss, res_sels->ss);
nerrs++;
}
continue;
}
#endif
/* Sanity check on the kernel */
if (i == REG_AX && requested_regs[i] != resulting_regs[i]) {
printf("[FAIL]\tAX (saved SP) mismatch: requested 0x%llx; got 0x%llx\n",
(unsigned long long)requested_regs[i],
(unsigned long long)resulting_regs[i]);
nerrs++;
continue;
}
if (requested_regs[i] != resulting_regs[i] && !ignore_reg) {
/*
* SP is particularly interesting here. The
* usual cause of failures is that we hit the
* nasty IRET case of returning to a 16-bit SS,
* in which case bits 16:31 of the *kernel*
* stack pointer persist in ESP.
*/
printf("[FAIL]\tReg %d mismatch: requested 0x%llx; got 0x%llx\n",
i, (unsigned long long)requested_regs[i],
(unsigned long long)resulting_regs[i]);
nerrs++;
}
}
if (nerrs == 0)
printf("[OK]\tall registers okay\n");
return nerrs;
}
static int test_bad_iret(int cs_bits, unsigned short ss, int force_cs)
{
int cs = force_cs == -1 ? find_cs(cs_bits) : force_cs;
if (cs == -1)
return 0;
sig_cs = cs;
sig_ss = ss;
printf("[RUN]\t%d-bit CS (%hx), bogus SS (%hx)\n",
cs_bits, sig_cs, sig_ss);
sig_trapped = 0;
raise(SIGUSR1);
if (sig_trapped) {
char errdesc[32] = "";
if (sig_err) {
const char *src = (sig_err & 1) ? " EXT" : "";
const char *table;
if ((sig_err & 0x6) == 0x0)
table = "GDT";
else if ((sig_err & 0x6) == 0x4)
table = "LDT";
else if ((sig_err & 0x6) == 0x2)
table = "IDT";
else
table = "???";
sprintf(errdesc, "%s%s index %d, ",
table, src, sig_err >> 3);
}
char trapname[32];
if (sig_trapno == 13)
strcpy(trapname, "GP");
else if (sig_trapno == 11)
strcpy(trapname, "NP");
else if (sig_trapno == 12)
strcpy(trapname, "SS");
else if (sig_trapno == 32)
strcpy(trapname, "IRET"); /* X86_TRAP_IRET */
else
sprintf(trapname, "%d", sig_trapno);
printf("[OK]\tGot #%s(0x%lx) (i.e. %s%s)\n",
trapname, (unsigned long)sig_err,
errdesc, strsignal(sig_trapped));
return 0;
} else {
printf("[FAIL]\tDid not get SIGSEGV\n");
return 1;
}
}
int main()
{
int total_nerrs = 0;
unsigned short my_cs, my_ss;
asm volatile ("mov %%cs,%0" : "=r" (my_cs));
asm volatile ("mov %%ss,%0" : "=r" (my_ss));
setup_ldt();
stack_t stack = {
.ss_sp = altstack_data,
.ss_size = SIGSTKSZ,
};
if (sigaltstack(&stack, NULL) != 0)
err(1, "sigaltstack");
sethandler(SIGUSR1, sigusr1, 0);
sethandler(SIGTRAP, sigtrap, SA_ONSTACK);
/* Easy cases: return to a 32-bit SS in each possible CS bitness. */
total_nerrs += test_valid_sigreturn(64, false, -1);
total_nerrs += test_valid_sigreturn(32, false, -1);
total_nerrs += test_valid_sigreturn(16, false, -1);
/*
* Test easy espfix cases: return to a 16-bit LDT SS in each possible
* CS bitness. NB: with a long mode CS, the SS bitness is irrelevant.
*
* This catches the original missing-espfix-on-64-bit-kernels issue
* as well as CVE-2014-8134.
*/
total_nerrs += test_valid_sigreturn(64, true, -1);
total_nerrs += test_valid_sigreturn(32, true, -1);
total_nerrs += test_valid_sigreturn(16, true, -1);
if (gdt_data16_idx) {
/*
* For performance reasons, Linux skips espfix if SS points
* to the GDT. If we were able to allocate a 16-bit SS in
* the GDT, see if it leaks parts of the kernel stack pointer.
*
* This tests for CVE-2014-8133.
*/
total_nerrs += test_valid_sigreturn(64, true,
GDT3(gdt_data16_idx));
total_nerrs += test_valid_sigreturn(32, true,
GDT3(gdt_data16_idx));
total_nerrs += test_valid_sigreturn(16, true,
GDT3(gdt_data16_idx));
}
/*
* We're done testing valid sigreturn cases. Now we test states
* for which sigreturn itself will succeed but the subsequent
* entry to user mode will fail.
*
* Depending on the failure mode and the kernel bitness, these
* entry failures can generate SIGSEGV, SIGBUS, or SIGILL.
*/
clearhandler(SIGTRAP);
sethandler(SIGSEGV, sigtrap, SA_ONSTACK);
sethandler(SIGBUS, sigtrap, SA_ONSTACK);
sethandler(SIGILL, sigtrap, SA_ONSTACK); /* 32-bit kernels do this */
/* Easy failures: invalid SS, resulting in #GP(0) */
test_bad_iret(64, ldt_nonexistent_sel, -1);
test_bad_iret(32, ldt_nonexistent_sel, -1);
test_bad_iret(16, ldt_nonexistent_sel, -1);
/* These fail because SS isn't a data segment, resulting in #GP(SS) */
test_bad_iret(64, my_cs, -1);
test_bad_iret(32, my_cs, -1);
test_bad_iret(16, my_cs, -1);
/* Try to return to a not-present code segment, triggering #NP(SS). */
test_bad_iret(32, my_ss, npcode32_sel);
/*
* Try to return to a not-present but otherwise valid data segment.
* This will cause IRET to fail with #SS on the espfix stack. This
* exercises CVE-2014-9322.
*
* Note that, if espfix is enabled, 64-bit Linux will lose track
* of the actual cause of failure and report #GP(0) instead.
* This would be very difficult for Linux to avoid, because
* espfix64 causes IRET failures to be promoted to #DF, so the
* original exception frame is never pushed onto the stack.
*/
test_bad_iret(32, npdata32_sel, -1);
/*
* Try to return to a not-present but otherwise valid data
* segment without invoking espfix. Newer kernels don't allow
* this to happen in the first place. On older kernels, though,
* this can trigger CVE-2014-9322.
*/
if (gdt_npdata32_idx)
test_bad_iret(32, GDT3(gdt_npdata32_idx), -1);
return total_nerrs ? 1 : 0;
}

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tools/testing/selftests/x86/trivial_32bit_program.c Normal file
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/*
* Trivial program to check that we have a valid 32-bit build environment.
* Copyright (c) 2015 Andy Lutomirski
* GPL v2
*/
#include <stdio.h>
int main()
{
printf("\n");
return 0;
}