cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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entry-common.h (3092B)

      1/* SPDX-License-Identifier: GPL-2.0-only */
      2#ifndef _ASM_X86_ENTRY_COMMON_H
      3#define _ASM_X86_ENTRY_COMMON_H
      4
      5#include <linux/randomize_kstack.h>
      6#include <linux/user-return-notifier.h>
      7
      8#include <asm/nospec-branch.h>
      9#include <asm/io_bitmap.h>
     10#include <asm/fpu/api.h>
     11
     12/* Check that the stack and regs on entry from user mode are sane. */
     13static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs)
     14{
     15	if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {
     16		/*
     17		 * Make sure that the entry code gave us a sensible EFLAGS
     18		 * register.  Native because we want to check the actual CPU
     19		 * state, not the interrupt state as imagined by Xen.
     20		 */
     21		unsigned long flags = native_save_fl();
     22		unsigned long mask = X86_EFLAGS_DF | X86_EFLAGS_NT;
     23
     24		/*
     25		 * For !SMAP hardware we patch out CLAC on entry.
     26		 */
     27		if (boot_cpu_has(X86_FEATURE_SMAP) ||
     28		    (IS_ENABLED(CONFIG_64BIT) && boot_cpu_has(X86_FEATURE_XENPV)))
     29			mask |= X86_EFLAGS_AC;
     30
     31		WARN_ON_ONCE(flags & mask);
     32
     33		/* We think we came from user mode. Make sure pt_regs agrees. */
     34		WARN_ON_ONCE(!user_mode(regs));
     35
     36		/*
     37		 * All entries from user mode (except #DF) should be on the
     38		 * normal thread stack and should have user pt_regs in the
     39		 * correct location.
     40		 */
     41		WARN_ON_ONCE(!on_thread_stack());
     42		WARN_ON_ONCE(regs != task_pt_regs(current));
     43	}
     44}
     45#define arch_enter_from_user_mode arch_enter_from_user_mode
     46
     47static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
     48						  unsigned long ti_work)
     49{
     50	if (ti_work & _TIF_USER_RETURN_NOTIFY)
     51		fire_user_return_notifiers();
     52
     53	if (unlikely(ti_work & _TIF_IO_BITMAP))
     54		tss_update_io_bitmap();
     55
     56	fpregs_assert_state_consistent();
     57	if (unlikely(ti_work & _TIF_NEED_FPU_LOAD))
     58		switch_fpu_return();
     59
     60#ifdef CONFIG_COMPAT
     61	/*
     62	 * Compat syscalls set TS_COMPAT.  Make sure we clear it before
     63	 * returning to user mode.  We need to clear it *after* signal
     64	 * handling, because syscall restart has a fixup for compat
     65	 * syscalls.  The fixup is exercised by the ptrace_syscall_32
     66	 * selftest.
     67	 *
     68	 * We also need to clear TS_REGS_POKED_I386: the 32-bit tracer
     69	 * special case only applies after poking regs and before the
     70	 * very next return to user mode.
     71	 */
     72	current_thread_info()->status &= ~(TS_COMPAT | TS_I386_REGS_POKED);
     73#endif
     74
     75	/*
     76	 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
     77	 * but not enough for x86 stack utilization comfort. To keep
     78	 * reasonable stack head room, reduce the maximum offset to 8 bits.
     79	 *
     80	 * The actual entropy will be further reduced by the compiler when
     81	 * applying stack alignment constraints (see cc_stack_align4/8 in
     82	 * arch/x86/Makefile), which will remove the 3 (x86_64) or 2 (ia32)
     83	 * low bits from any entropy chosen here.
     84	 *
     85	 * Therefore, final stack offset entropy will be 5 (x86_64) or
     86	 * 6 (ia32) bits.
     87	 */
     88	choose_random_kstack_offset(rdtsc() & 0xFF);
     89}
     90#define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare
     91
     92static __always_inline void arch_exit_to_user_mode(void)
     93{
     94	mds_user_clear_cpu_buffers();
     95}
     96#define arch_exit_to_user_mode arch_exit_to_user_mode
     97
     98#endif