commit f647d7c155f069c1a068030255c300663516420e upstream.
Otherwise, if buggy user code points DS or ES into the TLS
array, they would be corrupted after a context switch.
This also significantly improves the comments and documents some
gotchas in the code.
Before this patch, the both tests below failed. With this
patch, the es test passes, although the gsbase test still fails.
----- begin es test -----
/*
* Copyright (c) 2014 Andy Lutomirski
* GPL v2
*/
static unsigned short GDT3(int idx)
{
return (idx << 3) | 3;
}
static int create_tls(int idx, unsigned int base)
{
struct user_desc desc = {
.entry_number = idx,
.base_addr = base,
.limit = 0xfffff,
.seg_32bit = 1,
.contents = 0, /* Data, grow-up */
.read_exec_only = 0,
.limit_in_pages = 1,
.seg_not_present = 0,
.useable = 0,
};
if (syscall(SYS_set_thread_area, &desc) != 0)
err(1, "set_thread_area");
return desc.entry_number;
}
int main()
{
int idx = create_tls(-1, 0);
printf("Allocated GDT index %d\n", idx);
unsigned short orig_es;
asm volatile ("mov %%es,%0" : "=rm" (orig_es));
int errors = 0;
int total = 1000;
for (int i = 0; i < total; i++) {
asm volatile ("mov %0,%%es" : : "rm" (GDT3(idx)));
usleep(100);
unsigned short es;
asm volatile ("mov %%es,%0" : "=rm" (es));
asm volatile ("mov %0,%%es" : : "rm" (orig_es));
if (es != GDT3(idx)) {
if (errors == 0)
printf("[FAIL]\tES changed from 0x%hx to 0x%hx\n",
GDT3(idx), es);
errors++;
}
}
if (errors) {
printf("[FAIL]\tES was corrupted %d/%d times\n", errors, total);
return 1;
} else {
printf("[OK]\tES was preserved\n");
return 0;
}
}
----- end es test -----
----- begin gsbase test -----
/*
* gsbase.c, a gsbase test
* Copyright (c) 2014 Andy Lutomirski
* GPL v2
*/
static unsigned char *testptr, *testptr2;
static unsigned char read_gs_testvals(void)
{
unsigned char ret;
asm volatile ("movb %%gs:%1, %0" : "=r" (ret) : "m" (*testptr));
return ret;
}
int main()
{
int errors = 0;
testptr = mmap((void *)0x200000000UL, 1, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
if (testptr == MAP_FAILED)
err(1, "mmap");
testptr2 = mmap((void *)0x300000000UL, 1, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
if (testptr2 == MAP_FAILED)
err(1, "mmap");
*testptr = 0;
*testptr2 = 1;
if (syscall(SYS_arch_prctl, ARCH_SET_GS,
(unsigned long)testptr2 - (unsigned long)testptr) != 0)
err(1, "ARCH_SET_GS");
usleep(100);
if (read_gs_testvals() == 1) {
printf("[OK]\tARCH_SET_GS worked\n");
} else {
printf("[FAIL]\tARCH_SET_GS failed\n");
errors++;
}
asm volatile ("mov %0,%%gs" : : "r" (0));
if (read_gs_testvals() == 0) {
printf("[OK]\tWriting 0 to gs worked\n");
} else {
printf("[FAIL]\tWriting 0 to gs failed\n");
errors++;
}
usleep(100);
if (read_gs_testvals() == 0) {
printf("[OK]\tgsbase is still zero\n");
} else {
printf("[FAIL]\tgsbase was corrupted\n");
errors++;
}
return errors == 0 ? 0 : 1;
}
----- end gsbase test -----
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/509d27c9fec78217691c3dad91cec87e1006b34a.1418075657.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 1adfa76a95fe4444124a502f7cc858a39d5b8e01 upstream. Bit 1 in the x86 EFLAGS is always set. Name the macro something that actually tries to explain what it is all about, rather than being a tautology. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Gleb Natapov <gleb@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Link: http://lkml.kernel.org/n/tip-f10rx5vjjm6tfnt8o1wseb3v@git.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
show_regs() is inherently arch-dependent but it does make sense to print
generic debug information and some archs already do albeit in slightly
different forms. This patch introduces a generic function to print debug
information from show_regs() so that different archs print out the same
information and it's much easier to modify what's printed.
show_regs_print_info() prints out the same debug info as dump_stack()
does plus task and thread_info pointers.
* Archs which didn't print debug info now do.
alpha, arc, blackfin, c6x, cris, frv, h8300, hexagon, ia64, m32r,
metag, microblaze, mn10300, openrisc, parisc, score, sh64, sparc,
um, xtensa
* Already prints debug info. Replaced with show_regs_print_info().
The printed information is superset of what used to be there.
arm, arm64, avr32, mips, powerpc, sh32, tile, unicore32, x86
* s390 is special in that it used to print arch-specific information
along with generic debug info. Heiko and Martin think that the
arch-specific extra isn't worth keeping s390 specfic implementation.
Converted to use the generic version.
Note that now all archs print the debug info before actual register
dumps.
An example BUG() dump follows.
kernel BUG at /work/os/work/kernel/workqueue.c:4841!
invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.9.0-rc1-work+ #7
Hardware name: empty empty/S3992, BIOS 080011 10/26/2007
task: ffff88007c85e040 ti: ffff88007c860000 task.ti: ffff88007c860000
RIP: 0010:[<ffffffff8234a07e>] [<ffffffff8234a07e>] init_workqueues+0x4/0x6
RSP: 0000:ffff88007c861ec8 EFLAGS: 00010246
RAX: ffff88007c861fd8 RBX: ffffffff824466a8 RCX: 0000000000000001
RDX: 0000000000000046 RSI: 0000000000000001 RDI: ffffffff8234a07a
RBP: ffff88007c861ec8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff8234a07a
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88007dc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: ffff88015f7ff000 CR3: 00000000021f1000 CR4: 00000000000007f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Stack:
ffff88007c861ef8 ffffffff81000312 ffffffff824466a8 ffff88007c85e650
0000000000000003 0000000000000000 ffff88007c861f38 ffffffff82335e5d
ffff88007c862080 ffffffff8223d8c0 ffff88007c862080 ffffffff81c47760
Call Trace:
[<ffffffff81000312>] do_one_initcall+0x122/0x170
[<ffffffff82335e5d>] kernel_init_freeable+0x9b/0x1c8
[<ffffffff81c47760>] ? rest_init+0x140/0x140
[<ffffffff81c4776e>] kernel_init+0xe/0xf0
[<ffffffff81c6be9c>] ret_from_fork+0x7c/0xb0
[<ffffffff81c47760>] ? rest_init+0x140/0x140
...
v2: Typo fix in x86-32.
v3: CPU number dropped from show_regs_print_info() as
dump_stack_print_info() has been updated to print it. s390
specific implementation dropped as requested by s390 maintainers.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Chris Metcalf <cmetcalf@tilera.com> [tile bits]
Acked-by: Richard Kuo <rkuo@codeaurora.org> [hexagon bits]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
the length of dead_task->comm[] is 16 (TASK_COMM_LEN)
on pr_warn(), it is not meaningful to use %8s for task->comm[].
So change it to %s, since the line is not solid anyway.
Additional information:
%8s limit the width, not for the original string output length
if name length is more than 8, it still can be fully displayed.
if name length is less than 8, the ' ' will be filled before name.
%.8s truly limit the original string output length (precision)
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Link: http://lkml.kernel.org/n/tip-nridm1zvreai1tgfLjuexDmd@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull generic execve() changes from Al Viro: "This introduces the generic kernel_thread() and kernel_execve() functions, and switches x86, arm, alpha, um and s390 over to them." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal: (26 commits) s390: convert to generic kernel_execve() s390: switch to generic kernel_thread() s390: fold kernel_thread_helper() into ret_from_fork() s390: fold execve_tail() into start_thread(), convert to generic sys_execve() um: switch to generic kernel_thread() x86, um/x86: switch to generic sys_execve and kernel_execve x86: split ret_from_fork alpha: introduce ret_from_kernel_execve(), switch to generic kernel_execve() alpha: switch to generic kernel_thread() alpha: switch to generic sys_execve() arm: get rid of execve wrapper, switch to generic execve() implementation arm: optimized current_pt_regs() arm: introduce ret_from_kernel_execve(), switch to generic kernel_execve() arm: split ret_from_fork, simplify kernel_thread() [based on patch by rmk] generic sys_execve() generic kernel_execve() new helper: current_pt_regs() preparation for generic kernel_thread() um: kill thread->forking um: let signal_delivered() do SIGTRAP on singlestepping into handler ...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Fundamental model of the current Linux kernel is to lazily init and restore FPU instead of restoring the task state during context switch. This changes that fundamental lazy model to the non-lazy model for the processors supporting xsave feature. Reasons driving this model change are: i. Newer processors support optimized state save/restore using xsaveopt and xrstor by tracking the INIT state and MODIFIED state during context-switch. This is faster than modifying the cr0.TS bit which has serializing semantics. ii. Newer glibc versions use SSE for some of the optimized copy/clear routines. With certain workloads (like boot, kernel-compilation etc), application completes its work with in the first 5 task switches, thus taking upto 5 #DNA traps with the kernel not getting a chance to apply the above mentioned pre-load heuristic. iii. Some xstate features (like AMD's LWP feature) don't honor the cr0.TS bit and thus will not work correctly in the presence of lazy restore. Non-lazy state restore is needed for enabling such features. Some data on a two socket SNB system: * Saved 20K DNA exceptions during boot on a two socket SNB system. * Saved 50K DNA exceptions during kernel-compilation workload. * Improved throughput of the AVX based checksumming function inside the kernel by ~15% as xsave/xrstor is faster than the serializing clts/stts pair. Also now kernel_fpu_begin/end() relies on the patched alternative instructions. So move check_fpu() which uses the kernel_fpu_begin/end() after alternative_instructions(). Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Link: http://lkml.kernel.org/r/1345842782-24175-7-git-send-email-suresh.b.siddha@intel.com Merge 32-bit boot fix from, Link: http://lkml.kernel.org/r/1347300665-6209-4-git-send-email-suresh.b.siddha@intel.com Cc: Jim Kukunas <james.t.kukunas@linux.intel.com> Cc: NeilBrown <neilb@suse.de> Cc: Avi Kivity <avi@redhat.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Pull debug-for-linus git tree from Ingo Molnar. Fix up trivial conflict in arch/x86/kernel/cpu/perf_event_intel.c due to a printk() having changed to a pr_info() differently in the two branches. * 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86: Move call to print_modules() out of show_regs() x86/mm: Mark free_initrd_mem() as __init x86/microcode: Mark microcode_id[] as __initconst x86/nmi: Clean up register_nmi_handler() usage x86: Save cr2 in NMI in case NMIs take a page fault (for i386) x86: Remove cmpxchg from i386 NMI nesting code x86: Save cr2 in NMI in case NMIs take a page fault x86/debug: Add KERN_<LEVEL> to bare printks, convert printks to pr_<level>