diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-08 16:59:34 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-08 16:59:34 -0700 |
commit | a1aab6f3d295f078c008893ee7fa2c011626c46f (patch) | |
tree | 1ae344c8ed1b1dc531be1ae99188c180ad0c6c7c /arch/x86/kernel/alternative.c | |
parent | dad1c12ed831a7a89cc01e5582cd0b81a4be7f19 (diff) | |
parent | 7457c0da024b181a9143988d740001f9bc98698d (diff) |
Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 asm updates from Ingo Molnar:
"Most of the changes relate to Peter Zijlstra's cleanup of ptregs
handling, in particular the i386 part is now much simplified and
standardized - no more partial ptregs stack frames via the esp/ss
oddity. This simplifies ftrace, kprobes, the unwinder, ptrace, kdump
and kgdb.
There's also a CR4 hardening enhancements by Kees Cook, to make the
generic platform functions such as native_write_cr4() less useful as
ROP gadgets that disable SMEP/SMAP. Also protect the WP bit of CR0
against similar attacks.
The rest is smaller cleanups/fixes"
* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/alternatives: Add int3_emulate_call() selftest
x86/stackframe/32: Allow int3_emulate_push()
x86/stackframe/32: Provide consistent pt_regs
x86/stackframe, x86/ftrace: Add pt_regs frame annotations
x86/stackframe, x86/kprobes: Fix frame pointer annotations
x86/stackframe: Move ENCODE_FRAME_POINTER to asm/frame.h
x86/entry/32: Clean up return from interrupt preemption path
x86/asm: Pin sensitive CR0 bits
x86/asm: Pin sensitive CR4 bits
Documentation/x86: Fix path to entry_32.S
x86/asm: Remove unused TASK_TI_flags from asm-offsets.c
Diffstat (limited to 'arch/x86/kernel/alternative.c')
-rw-r--r-- | arch/x86/kernel/alternative.c | 81 |
1 files changed, 77 insertions, 4 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index bd542f9b0953..c3468b5242fd 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -616,11 +616,83 @@ extern struct paravirt_patch_site __start_parainstructions[], __stop_parainstructions[]; #endif /* CONFIG_PARAVIRT */ +/* + * Self-test for the INT3 based CALL emulation code. + * + * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up + * properly and that there is a stack gap between the INT3 frame and the + * previous context. Without this gap doing a virtual PUSH on the interrupted + * stack would corrupt the INT3 IRET frame. + * + * See entry_{32,64}.S for more details. + */ +static void __init int3_magic(unsigned int *ptr) +{ + *ptr = 1; +} + +extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */ + +static int __init +int3_exception_notify(struct notifier_block *self, unsigned long val, void *data) +{ + struct die_args *args = data; + struct pt_regs *regs = args->regs; + + if (!regs || user_mode(regs)) + return NOTIFY_DONE; + + if (val != DIE_INT3) + return NOTIFY_DONE; + + if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip) + return NOTIFY_DONE; + + int3_emulate_call(regs, (unsigned long)&int3_magic); + return NOTIFY_STOP; +} + +static void __init int3_selftest(void) +{ + static __initdata struct notifier_block int3_exception_nb = { + .notifier_call = int3_exception_notify, + .priority = INT_MAX-1, /* last */ + }; + unsigned int val = 0; + + BUG_ON(register_die_notifier(&int3_exception_nb)); + + /* + * Basically: int3_magic(&val); but really complicated :-) + * + * Stick the address of the INT3 instruction into int3_selftest_ip, + * then trigger the INT3, padded with NOPs to match a CALL instruction + * length. + */ + asm volatile ("1: int3; nop; nop; nop; nop\n\t" + ".pushsection .init.data,\"aw\"\n\t" + ".align " __ASM_SEL(4, 8) "\n\t" + ".type int3_selftest_ip, @object\n\t" + ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t" + "int3_selftest_ip:\n\t" + __ASM_SEL(.long, .quad) " 1b\n\t" + ".popsection\n\t" + : : __ASM_SEL_RAW(a, D) (&val) : "memory"); + + BUG_ON(val != 1); + + unregister_die_notifier(&int3_exception_nb); +} + void __init alternative_instructions(void) { - /* The patching is not fully atomic, so try to avoid local interruptions - that might execute the to be patched code. - Other CPUs are not running. */ + int3_selftest(); + + /* + * The patching is not fully atomic, so try to avoid local + * interruptions that might execute the to be patched code. + * Other CPUs are not running. + */ stop_nmi(); /* @@ -645,10 +717,11 @@ void __init alternative_instructions(void) _text, _etext); } - if (!uniproc_patched || num_possible_cpus() == 1) + if (!uniproc_patched || num_possible_cpus() == 1) { free_init_pages("SMP alternatives", (unsigned long)__smp_locks, (unsigned long)__smp_locks_end); + } #endif apply_paravirt(__parainstructions, __parainstructions_end); |