Select CONFIG_ARCH_HAS_VARIABLE_STACK_SIZE for arm64 and override arch_vm_stack_pages() to a value set from the command line, this value have the following properties: - Aligned to page size (doesn't need to be a power of 2), so it can be 12kB for example - Min value is chosen to be 8kB - Max value will be the default stack size on arm64 which is used to allocate the VA range for the kernel stack.
Signed-off-by: Mostafa Saleh <[email protected]> --- .../admin-guide/kernel-parameters.txt | 7 ++++++ arch/arm64/Kconfig | 1 + arch/arm64/include/asm/memory.h | 12 ++++++++++ arch/arm64/kernel/entry.S | 10 +++++--- arch/arm64/kernel/setup.c | 24 +++++++++++++++++++ 5 files changed, 51 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 33cd30996e47..e6ef22f01e01 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2920,6 +2920,13 @@ Kernel parameters keepinitrd [HW,ARM] See retain_initrd. + kernel_stack_pages= + [ARM64,EARLY] + Format: <integer> + Number of pages mapped for each task kernel stack. + The virtual area stays THREAD_SIZE and only its top + pages are mapped. + kernelcore= [KNL,X86,PPC,EARLY] Format: nn[KMGTPE] | nn% | "mirror" This parameter specifies the amount of memory usable by diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 020fcaf36b1b..5e09ae904e34 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -58,6 +58,7 @@ config ARM64 select ARCH_HAS_SYSCALL_WRAPPER select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST select ARCH_HAS_ZONE_DMA_SET if EXPERT + select ARCH_HAS_VARIABLE_STACK_SIZE select ARCH_HAVE_ELF_PROT select ARCH_HAVE_NMI_SAFE_CMPXCHG select ARCH_HAVE_TRACE_MMIO_ACCESS diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index 4545d9b39bd5..1d300b16032d 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -113,6 +113,13 @@ #define DIRECT_MAP_PHYSMEM_END __pa(PAGE_END - 1) #define MIN_THREAD_SHIFT (14 + KASAN_THREAD_SHIFT) +#define MIN_KERNEL_STACK_SHIFT (13 + KASAN_THREAD_SHIFT) + +#if (MIN_KERNEL_STACK_SHIFT < PAGE_SHIFT) +#define MIN_KERNEL_STACK_SIZE PAGE_SIZE +#else +#define MIN_KERNEL_STACK_SIZE (UL(1) << MIN_KERNEL_STACK_SHIFT) +#endif /* * VMAP'd stacks are allocated at page granularity, so we must ensure that such @@ -130,6 +137,11 @@ #define THREAD_SIZE (UL(1) << THREAD_SHIFT) +#ifndef __ASSEMBLY__ +extern unsigned long kernel_stack_pages; +#define arch_vm_stack_pages() (kernel_stack_pages) +#endif + #define THREAD_ALIGN THREAD_SIZE #define IRQ_STACK_SIZE THREAD_SIZE diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index ea733b673970..39e68aace0a6 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -76,9 +76,13 @@ msr spsel, #0 mov x1, sp msr spsel, #1 - sub x1, x1, x0 - cmp x1, #THREAD_SIZE - b.lo .Lstack_ok\@ + + add x0, x0, #THREAD_SIZE + sub x1, x0, x1 + adr_l x0, kernel_stack_pages + ldr x0, [x0] + cmp x1, x0, lsl #PAGE_SHIFT + b.ls .Lstack_ok\@ /* Check whether we are on the IRQ, SDEI or EFI stacks. */ stp x2, x30, [sp, #-16]! diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c index 29c6100f0c50..34559048dcca 100644 --- a/arch/arm64/kernel/setup.c +++ b/arch/arm64/kernel/setup.c @@ -278,6 +278,30 @@ u64 cpu_logical_map(unsigned int cpu) return __cpu_logical_map[cpu]; } +unsigned long kernel_stack_pages __ro_after_init = THREAD_SIZE / PAGE_SIZE; + +static int __init setup_kernel_stack_pages(char *str) +{ + unsigned long min = MIN_KERNEL_STACK_SIZE / PAGE_SIZE; + unsigned long max = THREAD_SIZE / PAGE_SIZE; + unsigned long val; + + if (!str) + return -EINVAL; + + if (kstrtoul(str, 10, &val) || val < min || val > max) { + pr_err("Invalid kernel_stack_pages=%s, should be between %lu and %lu\n", + str, min, max); + return 0; + } + + kernel_stack_pages = val; + pr_info("Kernel stack size set to %lu KiB\n", (val * PAGE_SIZE) / SZ_1K); + + return 0; +} +early_param("kernel_stack_pages", setup_kernel_stack_pages); + void __init __no_sanitize_address setup_arch(char **cmdline_p) { setup_initial_init_mm(_text, _etext, _edata, _end); -- 2.56.0.rc1.315.gc6ed9934b7-goog
