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| author | Ard Biesheuvel <ardb@kernel.org> | 2021-09-18 10:44:37 +0200 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2021-09-27 16:54:02 +0200 |
| commit | 50596b7559bf226bb35ad55855ee979453ec06a1 (patch) | |
| tree | 844d4e625c603c1c76ebfd1e21abe9e657e531e0 /arch/arm/Kconfig | |
| parent | 3855ab614df4818c833864572559a97fd9f9a299 (diff) | |
| download | lwn-50596b7559bf226bb35ad55855ee979453ec06a1.tar.gz lwn-50596b7559bf226bb35ad55855ee979453ec06a1.zip | |
ARM: smp: Store current pointer in TPIDRURO register if available
Now that the user space TLS register is assigned on every return to user
space, we can use it to keep the 'current' pointer while running in the
kernel. This removes the need to access it via thread_info, which is
located at the base of the stack, but will be moved out of there in a
subsequent patch.
Use the __builtin_thread_pointer() helper when available - this will
help GCC understand that reloading the value within the same function is
not necessary, even when using the per-task stack protector (which also
generates accesses via the TLS register). For example, the generated
code below loads TPIDRURO only once, and uses it to access both the
stack canary and the preempt_count fields.
<do_one_initcall>:
e92d 41f0 stmdb sp!, {r4, r5, r6, r7, r8, lr}
ee1d 4f70 mrc 15, 0, r4, cr13, cr0, {3}
4606 mov r6, r0
b094 sub sp, #80 ; 0x50
f8d4 34e8 ldr.w r3, [r4, #1256] ; 0x4e8 <- stack canary
9313 str r3, [sp, #76] ; 0x4c
f8d4 8004 ldr.w r8, [r4, #4] <- preempt count
Co-developed-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Diffstat (limited to 'arch/arm/Kconfig')
| -rw-r--r-- | arch/arm/Kconfig | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index ff3e64ae959e..cd195e6f4ea6 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1157,6 +1157,11 @@ config SMP_ON_UP If you don't know what to do here, say Y. + +config CURRENT_POINTER_IN_TPIDRURO + def_bool y + depends on SMP && CPU_32v6K && !CPU_V6 + config ARM_CPU_TOPOLOGY bool "Support cpu topology definition" depends on SMP && CPU_V7 |