linux.git/arch/x86/kernel/process_64.c, branch v6.0

x86/prctl: Remove pointless task argument

2022-05-13T10:56:28+00:00

The functions invoked via do_arch_prctl_common() can only operate on
the current task and none of these function uses the task argument.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lore.kernel.org/r/87lev7vtxj.ffs@tglx

x86: Remove toolchain check for X32 ABI capability

2022-03-15T09:32:48+00:00

Commit 0bf6276392e9 ("x32: Warn and disable rather than error if
binutils too old") added a small test in arch/x86/Makefile because
binutils 2.22 or newer is needed to properly support elf32-x86-64. This
check is no longer necessary, as the minimum supported version of
binutils is 2.23, which is enforced at configuration time with
scripts/min-tool-version.sh.

Remove this check and replace all uses of CONFIG_X86_X32 with
CONFIG_X86_X32_ABI, as two symbols are no longer necessary.

[nathan: Rebase, fix up a few places where CONFIG_X86_X32 was still
         used, and simplify commit message to satisfy -tip requirements]

Signed-off-by: Masahiro Yamada 
Signed-off-by: Nathan Chancellor 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20220314194842.3452-2-nathan@kernel.org

x86/fpu: Move context switch and exit to user inlines into sched.h

2021-10-20T13:27:27+00:00

internal.h is a kitchen sink which needs to get out of the way to prepare
for the upcoming changes.

Move the context switch and exit to user inlines into a separate header,
which is all that code needs.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211015011539.349132461@linutronix.de

x86/fpu: Remove pointless argument from switch_fpu_finish()

2021-10-20T13:27:25+00:00

Unused since the FPU switching rework.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211015011538.433135710@linutronix.de

x86/fpu: Add PKRU storage outside of task XSAVE buffer

2021-06-23T17:37:45+00:00

PKRU is currently partly XSAVE-managed and partly not. It has space
in the task XSAVE buffer and is context-switched by XSAVE/XRSTOR.
However, it is switched more eagerly than FPU because there may be a
need for PKRU to be up-to-date for things like copy_to/from_user() since
PKRU affects user-permission memory accesses, not just accesses from
userspace itself.

This leaves PKRU in a very odd position. XSAVE brings very little value
to the table for how Linux uses PKRU except for signal related XSTATE
handling.

Prepare to move PKRU away from being XSAVE-managed. Allocate space in
the thread_struct for it and save/restore it in the context-switch path
separately from the XSAVE-managed features. task->thread_struct.pkru
is only valid when the task is scheduled out. For the current task the
authoritative source is the hardware, i.e. it has to be retrieved via
rdpkru().

Leave the XSAVE code in place for now to ensure bisectability.

Signed-off-by: Dave Hansen 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Reviewed-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210623121456.399107624@linutronix.de

x86/cpu: Sanitize X86_FEATURE_OSPKE

2021-06-23T16:59:44+00:00

X86_FEATURE_OSPKE is enabled first on the boot CPU and the feature flag is
set. Secondary CPUs have to enable CR4.PKE as well and set their per CPU
feature flag. That's ineffective because all call sites have checks for
boot_cpu_data.

Make it smarter and force the feature flag when PKU is enabled on the boot
cpu which allows then to use cpu_feature_enabled(X86_FEATURE_OSPKE) all
over the place. That either compiles the code out when PKEY support is
disabled in Kconfig or uses a static_cpu_has() for the feature check which
makes a significant difference in hotpaths, e.g. context switch.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Reviewed-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210623121455.305113644@linutronix.de

x86/pkeys: Move read_pkru() and write_pkru()

2021-06-23T16:52:57+00:00

write_pkru() was originally used just to write to the PKRU register.  It
was mercifully short and sweet and was not out of place in pgtable.h with
some other pkey-related code.

But, later work included a requirement to also modify the task XSAVE
buffer when updating the register.  This really is more related to the
XSAVE architecture than to paging.

Move the read/write_pkru() to asm/pkru.h.  pgtable.h won't miss them.

Signed-off-by: Dave Hansen 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210623121455.102647114@linutronix.de

x86/irq: Sanitize irq stack tracking

2021-02-10T22:34:13+00:00

The recursion protection for hard interrupt stacks is an unsigned int per
CPU variable initialized to -1 named __irq_count. 

The irq stack switching is only done when the variable is -1, which creates
worse code than just checking for 0. When the stack switching happens it
uses this_cpu_add/sub(1), but there is no reason to do so. It simply can
use straight writes. This is a historical leftover from the low level ASM
code which used inc and jz to make a decision.

Rename it to hardirq_stack_inuse, make it a bool and use plain stores.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Kees Cook 
Link: https://lore.kernel.org/r/20210210002512.228830141@linutronix.de

x86: Reclaim TIF_IA32 and TIF_X32

2020-10-26T12:46:47+00:00

Now that these flags are no longer used, reclaim those TIF bits.

Signed-off-by: Gabriel Krisman Bertazi 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20201004032536.1229030-11-krisman@collabora.com

x86/mm: Convert mmu context ia32_compat into a proper flags field

2020-10-26T12:46:47+00:00

The ia32_compat attribute is a weird thing.  It mirrors TIF_IA32 and
TIF_X32 and is used only in two very unrelated places: (1) to decide if
the vsyscall page is accessible (2) for uprobes to find whether the
patched instruction is 32 or 64 bit.

In preparation to remove the TIF flags, a new mechanism is required for
ia32_compat, but given its odd semantics, adding a real flags field which
configures these specific behaviours is the best option.

So, set_personality_x64() can ask for the vsyscall page, which is not
available in x32/ia32 and set_personality_ia32() can configure the uprobe
code as needed.

uprobe cannot rely on other methods like user_64bit_mode() to decide how
to patch, so it needs some specific flag like this.

Signed-off-by: Gabriel Krisman Bertazi 
Signed-off-by: Thomas Gleixner 
Acked-by: Andy Lutomirski
Link: https://lore.kernel.org/r/20201004032536.1229030-10-krisman@collabora.com