linux/arch/x86/entry/entry.S
Linus Torvalds e2aa39b368 * Make MSR-induced taint easier for users to track down
* Restrict KVM-specific exports to KVM itself
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Merge tag 'x86_misc_for_6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull misc x86 updates from Dave Hansen:
 "The most significant are some changes to ensure that symbols exported
  for KVM are used only by KVM modules themselves, along with some
  related cleanups.

  In true x86/misc fashion, the other patch is completely unrelated and
  just enhances an existing pr_warn() to make it clear to users how they
  have tainted their kernel when something is mucking with MSRs.

  Summary:

   - Make MSR-induced taint easier for users to track down

   - Restrict KVM-specific exports to KVM itself"

* tag 'x86_misc_for_6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86: Restrict KVM-induced symbol exports to KVM modules where obvious/possible
  x86/mm: Drop unnecessary export of "ptdump_walk_pgd_level_debugfs"
  x86/mtrr: Drop unnecessary export of "mtrr_state"
  x86/bugs: Drop unnecessary export of "x86_spec_ctrl_base"
  x86/msr: Add CPU_OUT_OF_SPEC taint name to "unrecognized" pr_warn(msg)
2025-12-02 14:16:42 -08:00

78 lines
2.1 KiB
ArmAsm

/* SPDX-License-Identifier: GPL-2.0 */
/*
* Common place for both 32- and 64-bit entry routines.
*/
#include <linux/export.h>
#include <linux/kvm_types.h>
#include <linux/linkage.h>
#include <linux/objtool.h>
#include <asm/msr-index.h>
#include <asm/unwind_hints.h>
#include <asm/segment.h>
#include <asm/cache.h>
#include <asm/cpufeatures.h>
#include <asm/nospec-branch.h>
#include "calling.h"
.pushsection .noinstr.text, "ax"
/* Clobbers AX, CX, DX */
SYM_FUNC_START(write_ibpb)
ANNOTATE_NOENDBR
movl $MSR_IA32_PRED_CMD, %ecx
movl _ASM_RIP(x86_pred_cmd), %eax
xorl %edx, %edx
wrmsr
/* Make sure IBPB clears return stack preductions too. */
FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_BUG_IBPB_NO_RET
RET
SYM_FUNC_END(write_ibpb)
EXPORT_SYMBOL_FOR_KVM(write_ibpb);
SYM_FUNC_START(__WARN_trap)
ANNOTATE_NOENDBR
ANNOTATE_REACHABLE
ud1 (%edx), %_ASM_ARG1
RET
SYM_FUNC_END(__WARN_trap)
EXPORT_SYMBOL(__WARN_trap)
.popsection
/*
* Define the VERW operand that is disguised as entry code so that
* it can be referenced with KPTI enabled. This ensures VERW can be
* used late in exit-to-user path after page tables are switched.
*/
.pushsection .entry.text, "ax"
.align L1_CACHE_BYTES, 0xcc
SYM_CODE_START_NOALIGN(x86_verw_sel)
UNWIND_HINT_UNDEFINED
ANNOTATE_NOENDBR
.word __KERNEL_DS
.align L1_CACHE_BYTES, 0xcc
SYM_CODE_END(x86_verw_sel);
EXPORT_SYMBOL_FOR_KVM(x86_verw_sel);
.popsection
THUNK warn_thunk_thunk, __warn_thunk
/*
* Clang's implementation of TLS stack cookies requires the variable in
* question to be a TLS variable. If the variable happens to be defined as an
* ordinary variable with external linkage in the same compilation unit (which
* amounts to the whole of vmlinux with LTO enabled), Clang will drop the
* segment register prefix from the references, resulting in broken code. Work
* around this by avoiding the symbol used in -mstack-protector-guard-symbol=
* entirely in the C code, and use an alias emitted by the linker script
* instead.
*/
#if defined(CONFIG_STACKPROTECTOR) && defined(CONFIG_SMP)
EXPORT_SYMBOL(__ref_stack_chk_guard);
#endif