linux.git/arch/x86/kernel/process_64.c, branch v6.15 Linux kernel source tree x86/percpu: Move current_task to percpu hot section 2025-03-04T19:30:33+00:00 Brian Gerst brgerst@gmail.com 2025-03-03T16:52:44+00:00 a1e4cc0155ad577adc3a2c563fc5eec625945ce7 No functional change. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Uros Bizjak <ubizjak@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20250303165246.2175811-10-brgerst@gmail.com 
No functional change.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-10-brgerst@gmail.com
x86/percpu: Move top_of_stack to percpu hot section 2025-03-04T19:30:33+00:00 Brian Gerst brgerst@gmail.com 2025-03-03T16:52:43+00:00 385f72c83eb609652f02dc9ee415520c23bda629 No functional change. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Uros Bizjak <ubizjak@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20250303165246.2175811-9-brgerst@gmail.com 
No functional change.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-9-brgerst@gmail.com
x86/irq: Move irq stacks to percpu hot section 2025-03-04T19:30:33+00:00 Brian Gerst brgerst@gmail.com 2025-03-03T16:52:42+00:00 c6a0918072eaa97df268c00c05822ea982a321b6 No functional change. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Uros Bizjak <ubizjak@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20250303165246.2175811-8-brgerst@gmail.com 
No functional change.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-8-brgerst@gmail.com
x86/asm: Merge KSTK_ESP() implementations 2025-03-03T19:28:33+00:00 Brian Gerst brgerst@gmail.com 2025-03-03T18:31:11+00:00 399fd7a26441586021ca3722f6a98ff33ed32caf Commit: 263042e4630a ("Save user RSP in pt_regs->sp on SYSCALL64 fastpath") simplified the 64-bit implementation of KSTK_ESP() which is now identical to 32-bit. Merge them into a common definition. No functional change. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20250303183111.2245129-1-brgerst@gmail.com 
Commit:

  263042e4630a ("Save user RSP in pt_regs->sp on SYSCALL64 fastpath")

simplified the 64-bit implementation of KSTK_ESP() which is
now identical to 32-bit.  Merge them into a common definition.

No functional change.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250303183111.2245129-1-brgerst@gmail.com
x86/arch_prctl/64: Clean up ARCH_MAP_VDSO_32 2025-02-21T21:32:25+00:00 Brian Gerst brgerst@gmail.com 2025-02-02T20:23:23+00:00 684b12916a107157633311f07bb74307221eff92 process_64.c is not built on native 32-bit, so CONFIG_X86_32 will never be set. No change in functionality intended. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Link: https://lore.kernel.org/r/20250202202323.422113-3-brgerst@gmail.com 
process_64.c is not built on native 32-bit, so CONFIG_X86_32 will never
be set.

No change in functionality intended.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20250202202323.422113-3-brgerst@gmail.com
x86/arch_prctl: Simplify sys_arch_prctl() 2025-02-21T21:32:25+00:00 Brian Gerst brgerst@gmail.com 2025-02-02T20:23:22+00:00 2df1ad0d25803399056d439425e271802cd243f6 Use in_ia32_syscall() instead of a compat syscall entry. No change in functionality intended. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Link: https://lore.kernel.org/r/20250202202323.422113-2-brgerst@gmail.com 
Use in_ia32_syscall() instead of a compat syscall entry.

No change in functionality intended.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20250202202323.422113-2-brgerst@gmail.com
x86/mm: Cleanup prctl_enable_tagged_addr() nr_bits error checking 2024-07-02T18:33:44+00:00 Yosry Ahmed yosryahmed@google.com 2024-07-02T13:21:39+00:00 b7c35279e0da414e7d90eba76f58a16223a734cb There are two separate checks in prctl_enable_tagged_addr() that nr_bits is in the correct range. The checks are arranged such the correct case is sandwiched between both error cases, which do exactly the same thing. Simplify the if condition and pull the correct case outside with the rest of the success code path. Signed-off-by: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Link: https://lore.kernel.org/all/20240702132139.3332013-4-yosryahmed%40google.com 
There are two separate checks in prctl_enable_tagged_addr() that nr_bits
is in the correct range. The checks are arranged such the correct case
is sandwiched between both error cases, which do exactly the same thing.

Simplify the if condition and pull the correct case outside with the
rest of the success code path.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/all/20240702132139.3332013-4-yosryahmed%40google.com
x86/mm: Fix LAM inconsistency during context switch 2024-07-02T18:32:16+00:00 Yosry Ahmed yosryahmed@google.com 2024-07-02T13:21:38+00:00 ec225f8c255fd0f256c282cc73d211550cb08b34 LAM can only be enabled when a process is single-threaded. But _kernel_ threads can temporarily use a single-threaded process's mm. That means that a context-switching kernel thread can race and observe the mm's LAM metadata (mm->context.lam_cr3_mask) change. The context switch code does two logical things with that metadata: populate CR3 and populate 'cpu_tlbstate.lam'. If it hits this race, 'cpu_tlbstate.lam' and CR3 can end up out of sync. This de-synchronization is currently harmless. But it is confusing and might lead to warnings or real bugs. Update set_tlbstate_lam_mode() to take in the LAM mask and untag mask instead of an mm_struct pointer, and while we are at it, rename it to cpu_tlbstate_update_lam(). This should also make it clearer that we are updating cpu_tlbstate. In switch_mm_irqs_off(), read the LAM mask once and use it for both the cpu_tlbstate update and the CR3 update. Signed-off-by: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Link: https://lore.kernel.org/all/20240702132139.3332013-3-yosryahmed%40google.com 
LAM can only be enabled when a process is single-threaded.  But _kernel_
threads can temporarily use a single-threaded process's mm.  That means
that a context-switching kernel thread can race and observe the mm's LAM
metadata (mm->context.lam_cr3_mask) change.

The context switch code does two logical things with that metadata:
populate CR3 and populate 'cpu_tlbstate.lam'.  If it hits this race,
'cpu_tlbstate.lam' and CR3 can end up out of sync.

This de-synchronization is currently harmless.  But it is confusing and
might lead to warnings or real bugs.

Update set_tlbstate_lam_mode() to take in the LAM mask and untag mask
instead of an mm_struct pointer, and while we are at it, rename it to
cpu_tlbstate_update_lam(). This should also make it clearer that we are
updating cpu_tlbstate. In switch_mm_irqs_off(), read the LAM mask once
and use it for both the cpu_tlbstate update and the CR3 update.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/all/20240702132139.3332013-3-yosryahmed%40google.com
x86/mm: Use IPIs to synchronize LAM enablement 2024-07-02T18:31:51+00:00 Yosry Ahmed yosryahmed@google.com 2024-07-02T13:21:37+00:00 3b299b99556c1753923f8d9bbd9304bcd139282f LAM can only be enabled when a process is single-threaded. But _kernel_ threads can temporarily use a single-threaded process's mm. If LAM is enabled by a userspace process while a kthread is using its mm, the kthread will not observe LAM enablement (i.e. LAM will be disabled in CR3). This could be fine for the kthread itself, as LAM only affects userspace addresses. However, if the kthread context switches to a thread in the same userspace process, CR3 may or may not be updated because the mm_struct doesn't change (based on pending TLB flushes). If CR3 is not updated, the userspace thread will run incorrectly with LAM disabled, which may cause page faults when using tagged addresses. Example scenario: CPU 1 CPU 2 /* kthread */ kthread_use_mm() /* user thread */ prctl_enable_tagged_addr() /* LAM enabled on CPU 2 */ /* LAM disabled on CPU 1 */ context_switch() /* to CPU 1 */ /* Switching to user thread */ switch_mm_irqs_off() /* CR3 not updated */ /* LAM is still disabled on CPU 1 */ Synchronize LAM enablement by sending an IPI to all CPUs running with the mm_struct to enable LAM. This makes sure LAM is enabled on CPU 1 in the above scenario before prctl_enable_tagged_addr() returns and userspace starts using tagged addresses, and before it's possible to run the userspace process on CPU 1. In switch_mm_irqs_off(), move reading the LAM mask until after mm_cpumask() is updated. This ensures that if an outdated LAM mask is written to CR3, an IPI is received to update it right after IRQs are re-enabled. [ dhansen: Add a LAM enabling helper and comment it ] Fixes: 82721d8b25d7 ("x86/mm: Handle LAM on context switch") Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Link: https://lore.kernel.org/all/20240702132139.3332013-2-yosryahmed%40google.com 
LAM can only be enabled when a process is single-threaded.  But _kernel_
threads can temporarily use a single-threaded process's mm.

If LAM is enabled by a userspace process while a kthread is using its
mm, the kthread will not observe LAM enablement (i.e.  LAM will be
disabled in CR3). This could be fine for the kthread itself, as LAM only
affects userspace addresses. However, if the kthread context switches to
a thread in the same userspace process, CR3 may or may not be updated
because the mm_struct doesn't change (based on pending TLB flushes). If
CR3 is not updated, the userspace thread will run incorrectly with LAM
disabled, which may cause page faults when using tagged addresses.
Example scenario:

CPU 1                                   CPU 2
/* kthread */
kthread_use_mm()
                                        /* user thread */
                                        prctl_enable_tagged_addr()
                                        /* LAM enabled on CPU 2 */
/* LAM disabled on CPU 1 */
                                        context_switch() /* to CPU 1 */
/* Switching to user thread */
switch_mm_irqs_off()
/* CR3 not updated */
/* LAM is still disabled on CPU 1 */

Synchronize LAM enablement by sending an IPI to all CPUs running with
the mm_struct to enable LAM. This makes sure LAM is enabled on CPU 1
in the above scenario before prctl_enable_tagged_addr() returns and
userspace starts using tagged addresses, and before it's possible to
run the userspace process on CPU 1.

In switch_mm_irqs_off(), move reading the LAM mask until after
mm_cpumask() is updated. This ensures that if an outdated LAM mask is
written to CR3, an IPI is received to update it right after IRQs are
re-enabled.

[ dhansen: Add a LAM enabling helper and comment it ]

Fixes: 82721d8b25d7 ("x86/mm: Handle LAM on context switch")
Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/all/20240702132139.3332013-2-yosryahmed%40google.com
x86/cpu: Fix check for RDPKRU in __show_regs() 2024-04-24T12:30:21+00:00 David Kaplan david.kaplan@amd.com 2024-04-21T19:17:28+00:00 b53c6bd5d271d023857174b8fd3e32f98ae51372 cpu_feature_enabled(X86_FEATURE_OSPKE) does not necessarily reflect whether CR4.PKE is set on the CPU. In particular, they may differ on non-BSP CPUs before setup_pku() is executed. In this scenario, RDPKRU will #UD causing the system to hang. Fix by checking CR4 for PKE enablement which is always correct for the current CPU. The scenario happens by inserting a WARN* before setup_pku() in identiy_cpu() or some other diagnostic which would lead to calling __show_regs(). [ bp: Massage commit message. ] Signed-off-by: David Kaplan <david.kaplan@amd.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20240421191728.32239-1-bp@kernel.org 
cpu_feature_enabled(X86_FEATURE_OSPKE) does not necessarily reflect
whether CR4.PKE is set on the CPU.  In particular, they may differ on
non-BSP CPUs before setup_pku() is executed.  In this scenario, RDPKRU
will #UD causing the system to hang.

Fix by checking CR4 for PKE enablement which is always correct for the
current CPU.

The scenario happens by inserting a WARN* before setup_pku() in
identiy_cpu() or some other diagnostic which would lead to calling
__show_regs().

  [ bp: Massage commit message. ]

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240421191728.32239-1-bp@kernel.org