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| author | Ard Biesheuvel <ardb@kernel.org> | 2021-11-24 14:08:11 +0100 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2021-12-06 12:49:17 +0100 |
| commit | 9c46929e7989efacc1dd0a1dd662a839897ea2b6 (patch) | |
| tree | e55a231cce8f02eea3be6e7b19627c58bccdee52 /arch/arm/Kconfig | |
| parent | c2755910373bb5dfb9aa68ba2924036686815c9e (diff) | |
| download | linux-9c46929e7989efacc1dd0a1dd662a839897ea2b6.tar.bz2 | |
ARM: implement THREAD_INFO_IN_TASK for uniprocessor systems
On UP systems, only a single task can be 'current' at the same time,
which means we can use a global variable to track it. This means we can
also enable THREAD_INFO_IN_TASK for those systems, as in that case,
thread_info is accessed via current rather than the other way around,
removing the need to store thread_info at the base of the task stack.
This, in turn, permits us to enable IRQ stacks and vmap'ed stacks on UP
systems as well.
To partially mitigate the performance overhead of this arrangement, use
a ADD/ADD/LDR sequence with the appropriate PC-relative group
relocations to load the value of current when needed. This means that
accessing current will still only require a single load as before,
avoiding the need for a literal to carry the address of the global
variable in each function. However, accessing thread_info will now
require this load as well.
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M
Diffstat (limited to 'arch/arm/Kconfig')
| -rw-r--r-- | arch/arm/Kconfig | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 5ad2151c43dd..50ae5286f59b 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -127,8 +127,8 @@ config ARM select PERF_USE_VMALLOC select RTC_LIB select SYS_SUPPORTS_APM_EMULATION - select THREAD_INFO_IN_TASK if CURRENT_POINTER_IN_TPIDRURO - select HAVE_ARCH_VMAP_STACK if MMU && THREAD_INFO_IN_TASK && (!LD_IS_LLD || LLD_VERSION >= 140000) + select THREAD_INFO_IN_TASK + select HAVE_ARCH_VMAP_STACK if MMU && (!LD_IS_LLD || LLD_VERSION >= 140000) select TRACE_IRQFLAGS_SUPPORT if !CPU_V7M # Above selects are sorted alphabetically; please add new ones # according to that. Thanks. @@ -1158,7 +1158,7 @@ config CURRENT_POINTER_IN_TPIDRURO config IRQSTACKS def_bool y - depends on THREAD_INFO_IN_TASK + depends on MMU select HAVE_IRQ_EXIT_ON_IRQ_STACK select HAVE_SOFTIRQ_ON_OWN_STACK @@ -1608,7 +1608,7 @@ config CC_HAVE_STACKPROTECTOR_TLS config STACKPROTECTOR_PER_TASK bool "Use a unique stack canary value for each task" - depends on STACKPROTECTOR && THREAD_INFO_IN_TASK && !XIP_DEFLATED_DATA + depends on STACKPROTECTOR && CURRENT_POINTER_IN_TPIDRURO && !XIP_DEFLATED_DATA depends on GCC_PLUGINS || CC_HAVE_STACKPROTECTOR_TLS select GCC_PLUGIN_ARM_SSP_PER_TASK if !CC_HAVE_STACKPROTECTOR_TLS default y |