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We allocate our IRQ stacks using a percpu array. This allows us to generate our IRQ stack pointers with adr_this_cpu, but bloats the kernel Image with the boot CPU's IRQ stack. Additionally, these are packed with other percpu variables, and aren't guaranteed to have guard pages. When we enable VMAP_STACK we'll want to vmap our IRQ stacks also, in order to provide guard pages and to permit more stringent alignment requirements. Doing so will require that we use a percpu pointer to each IRQ stack, rather than allocating a percpu IRQ stack in the kernel image. This patch updates our IRQ stack code to use a percpu pointer to the base of each IRQ stack. This will allow us to change the way the stack is allocated with minimal changes elsewhere. In some cases we may try to backtrace before the IRQ stack pointers are initialised, so on_irq_stack() is updated to account for this. In testing with cyclictest, there was no measureable difference between using adr_this_cpu (for irq_stack) and ldr_this_cpu (for irq_stack_ptr) in the IRQ entry path. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Will Deacon <will.deacon@arm.com> Tested-by: Laura Abbott <labbott@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: James Morse <james.morse@arm.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.