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b=RCbwxEBiwPj2HK6Jbgin3F3Xh33Hvant+am5S9Whfl9mOT4coCat7ZyLNF0NMDRYwa xSDB4gjSZEciEX5AUk3jKKEjGA1AqHTp4dHJHy+U66L4C5IjU5exmBgiUyZyYOElE78r 3ILlLIHXQQEF2AtVlAZEISvUh7mWYiyPLBTuoHwS3vxO15i5/hIn93zuVsGI1KvoPL9+ B658HDq43TYOY9HNc+bzNNpqKDp/ouBbSADHnwo0o8rC3rTv3pJ77lY2Ekge5Su0ifYW pjk/XT5+m6kLd/syv14bPiXcgcE/lukby7wmZTxrVExKOf2M9O/Ih3r64cRtIXSowvj2 2IdA== X-Forwarded-Encrypted: i=1; AKwUvBwODVpC7ZM6P+ULsRLBg6SnRzrNqzv4+9g9cyof2se88Rycna7FNGzsumFaNAwWgIGt0wQKOfBKOg==@kvack.org X-Gm-Message-State: AFuF++mE/Gpx5isAbAxSY4QO1ZS1t56pN1f/JB8Hj0AlwRGF2ztNn/aE YmwSihB3v97Ov7IMFzLmJJNittGALnPg2DkLU8rJiA/qHUKLlrP9s75TVI0KSjkawtE8LpSfDQv n5HXxnNqE8nTIDA== X-Received: from wmpr40.prod.google.com ([2002:a05:600c:3228:b0:49f:fde6:649f]) (user=smostafa job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:6287:b0:49d:827:e5b6 with SMTP id 5b1f17b1804b1-49fe7babaadmr223084505e9.20.1790617327143; Mon, 28 Sep 2026 10:42:07 -0700 (PDT) Date: Mon, 28 Sep 2026 17:41:22 +0000 In-Reply-To: <20260928174122.3380703-1-smostafa@google.com> Mime-Version: 1.0 References: <20260928174122.3380703-1-smostafa@google.com> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20260928174122.3380703-16-smostafa@google.com> Subject: [RFC PATCH 15/15] arm64: mm: Set stack size from the kernel command line From: Mostafa Saleh To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, linux-rt-devel@lists.linux.dev Cc: corbet@lwn.net, skhan@linuxfoundation.org, rdunlap@infradead.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, akpm@linux-foundation.org, urezki@gmail.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, kees@kernel.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, gustavoars@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, Mostafa Saleh Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: 5ephx5ob3y1qc4mctc4fokxytdiockk7 X-Rspamd-Queue-Id: BCF1CC000C X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1790617328-9112 X-HE-Meta: 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 P4MgC5nu 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 --- .../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: + 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