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db8268df09
Dynamically enabled XSTATE features are by default disabled for all
processes. A process has to request permission to use such a feature.
To support this implement a architecture specific prctl() with the options:
- ARCH_GET_XCOMP_SUPP
Copies the supported feature bitmap into the user space provided
u64 storage. The pointer is handed in via arg2
- ARCH_GET_XCOMP_PERM
Copies the process wide permitted feature bitmap into the user space
provided u64 storage. The pointer is handed in via arg2
- ARCH_REQ_XCOMP_PERM
Request permission for a feature set. A feature set can be mapped to a
facility, e.g. AMX, and can require one or more XSTATE components to
be enabled.
The feature argument is the number of the highest XSTATE component
which is required for a facility to work.
The request argument is not a user supplied bitmap because that makes
filtering harder (think seccomp) and even impossible because to
support 32bit tasks the argument would have to be a pointer.
The permission mechanism works this way:
Task asks for permission for a facility and kernel checks whether that's
supported. If supported it does:
1) Check whether permission has already been granted
2) Compute the size of the required kernel and user space buffer
(sigframe) size.
3) Validate that no task has a sigaltstack installed
which is smaller than the resulting sigframe size
4) Add the requested feature bit(s) to the permission bitmap of
current->group_leader->fpu and store the sizes in the group
leaders fpu struct as well.
If that is successful then the feature is still not enabled for any of the
tasks. The first usage of a related instruction will result in a #NM
trap. The trap handler validates the permission bit of the tasks group
leader and if permitted it installs a larger kernel buffer and transfers
the permission and size info to the new fpstate container which makes all
the FPU functions which require per task information aware of the extended
feature set.
[ tglx: Adopted to new base code, added missing serialization,
massaged namings, comments and changelog ]
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211021225527.10184-7-chang.seok.bae@intel.com
45 lines
1 KiB
C
45 lines
1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_PROTO_H
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#define _ASM_X86_PROTO_H
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#include <asm/ldt.h>
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struct task_struct;
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/* misc architecture specific prototypes */
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void syscall_init(void);
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#ifdef CONFIG_X86_64
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void entry_SYSCALL_64(void);
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void entry_SYSCALL_64_safe_stack(void);
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long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2);
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#endif
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#ifdef CONFIG_X86_32
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void entry_INT80_32(void);
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void entry_SYSENTER_32(void);
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void __begin_SYSENTER_singlestep_region(void);
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void __end_SYSENTER_singlestep_region(void);
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#endif
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#ifdef CONFIG_IA32_EMULATION
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void entry_SYSENTER_compat(void);
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void __end_entry_SYSENTER_compat(void);
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void entry_SYSCALL_compat(void);
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void entry_SYSCALL_compat_safe_stack(void);
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void entry_INT80_compat(void);
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#ifdef CONFIG_XEN_PV
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void xen_entry_INT80_compat(void);
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#endif
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#endif
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void x86_configure_nx(void);
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void x86_report_nx(void);
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extern int reboot_force;
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long do_arch_prctl_common(struct task_struct *task, int option,
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unsigned long arg2);
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#endif /* _ASM_X86_PROTO_H */
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