linux/arch/x86
Pavel Tatashin 6fffacb303 x86/alternatives, jumplabel: Use text_poke_early() before mm_init()
It supposed to be safe to modify static branches after jump_label_init().
But, because static key modifying code eventually calls text_poke() it can
end up accessing a struct page which has not been initialized yet.

Here is how to quickly reproduce the problem. Insert code like this
into init/main.c:

| +static DEFINE_STATIC_KEY_FALSE(__test);
| asmlinkage __visible void __init start_kernel(void)
| {
|        char *command_line;
|@@ -587,6 +609,10 @@ asmlinkage __visible void __init start_kernel(void)
|        vfs_caches_init_early();
|        sort_main_extable();
|        trap_init();
|+       {
|+       static_branch_enable(&__test);
|+       WARN_ON(!static_branch_likely(&__test));
|+       }
|        mm_init();

The following warnings show-up:
WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:701 text_poke+0x20d/0x230
RIP: 0010:text_poke+0x20d/0x230
Call Trace:
 ? text_poke_bp+0x50/0xda
 ? arch_jump_label_transform+0x89/0xe0
 ? __jump_label_update+0x78/0xb0
 ? static_key_enable_cpuslocked+0x4d/0x80
 ? static_key_enable+0x11/0x20
 ? start_kernel+0x23e/0x4c8
 ? secondary_startup_64+0xa5/0xb0

---[ end trace abdc99c031b8a90a ]---

If the code above is moved after mm_init(), no warning is shown, as struct
pages are initialized during handover from memblock.

Use text_poke_early() in static branching until early boot IRQs are enabled
and from there switch to text_poke. Also, ensure text_poke() is never
invoked when unitialized memory access may happen by using adding a
!after_bootmem assertion.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: douly.fnst@cn.fujitsu.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-9-pasha.tatashin@oracle.com
2018-07-20 00:02:38 +02:00
..
boot efi/x86: Fix mixed mode reboot loop by removing pointless call to PciIo->Attributes() 2018-07-11 13:15:21 +02:00
configs x86/unwind: Rename unwinder config options to 'CONFIG_UNWINDER_*' 2017-10-14 10:12:12 +02:00
crypto crypto: x86 - Add missing RETs 2018-07-01 23:33:20 +08:00
entry x86/entry/64/compat: Fix "x86/entry/64/compat: Preserve r8-r11 in int $0x80" 2018-06-27 09:35:40 +02:00
events treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
hyperv x86/hyper-v: Fix the circular dependency in IPI enlightenment 2018-07-06 12:32:59 +02:00
ia32 syscalls/x86: auto-create compat_sys_*() prototypes 2018-04-02 20:16:18 +02:00
include x86/alternatives, jumplabel: Use text_poke_early() before mm_init() 2018-07-20 00:02:38 +02:00
kernel x86/alternatives, jumplabel: Use text_poke_early() before mm_init() 2018-07-20 00:02:38 +02:00
kvm Miscellaneous bugfixes, plus a small patchlet related to Spectre v2. 2018-07-18 11:08:44 -07:00
lib libnvdimm for 4.18 2018-06-08 17:21:52 -07:00
math-emu License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mm x86/mm: Clean up the printk()s in show_fault_oops() 2018-06-27 14:08:11 +02:00
net treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
oprofile x86/oprofile: Fix bogus GCC-8 warning in nmi_setup() 2018-02-21 09:54:17 +01:00
pci treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
platform x86/platform/intel-mid: Remove per platform code 2018-07-03 13:08:21 +02:00
power x86/mm: Stop pretending pgtable_l5_enabled is a variable 2018-05-19 11:56:57 +02:00
purgatory x86/purgatory: add missing FORCE to Makefile target 2018-07-14 11:11:09 -07:00
ras License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
realmode x86-64/realmode: Add instruction suffix 2018-02-20 09:33:41 +01:00
tools x86: Treat R_X86_64_PLT32 as R_X86_64_PC32 2018-02-22 09:01:10 -08:00
um Kconfig updates for v4.18 2018-06-06 11:31:45 -07:00
video
xen xen: fixes for 4.18-rc5 2018-07-14 12:30:13 -07:00
.gitignore x86/build: Add arch/x86/tools/insn_decoder_test to .gitignore 2018-02-13 14:10:29 +01:00
Kbuild Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-07 09:25:15 -07:00
Kconfig Kbuild: rename HAVE_CC_STACKPROTECTOR config variable 2018-06-15 07:15:28 +09:00
Kconfig.cpu Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-03-25 07:36:02 -10:00
Kconfig.debug x86, nfit_test: Add unit test for memcpy_mcsafe() 2018-05-22 23:18:31 -07:00
Makefile Merge branch 'linus' into x86/urgent 2018-06-22 21:20:35 +02:00
Makefile_32.cpu License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Makefile.um License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00