Forgot adding related ARCH mailing list or people to CC, add them. On 08/12/25 at 08:49pm, Baoquan He wrote: > Currently only hw_tags mode of kasan can be enabled or disabled with > kernel parameter kasan=on|off for built kernel. For kasan generic and > sw_tags mode, there's no way to disable them once kernel is built. > This is not convenient sometime, e.g in system kdump is configured. > When the 1st kernel has KASAN enabled and crash triggered to switch to > kdump kernel, the generic or sw_tags mode will cost much extra memory > for kasan shadow while in fact it's meaningless to have kasan in kdump > kernel. > > So this patchset moves the kasan=on|off out of hw_tags scope and into > common code to make it visible in generic and sw_tags mode too. Then we > can add kasan=off in kdump kernel to reduce the unneeded meomry cost for > kasan. > > Changelog: > ==== > v1->v2: > - Add __ro_after_init for __ro_after_init, and remove redundant blank > lines in mm/kasan/common.c. Thanks to Marco. > - Fix a code bug in <linux/kasan-enabled.h> when CONFIG_KASAN is unset, > this is found out by SeongJae and Lorenzo, and also reported by LKP > report, thanks to them. > - Add a missing kasan_enabled() checking in kasan_report(). This will > cause below KASAN report info even though kasan=off is set: > ================================================================== > BUG: KASAN: stack-out-of-bounds in tick_program_event+0x130/0x150 > Read of size 4 at addr ffff00005f747778 by task swapper/0/1 > > CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.16.0+ #8 > PREEMPT(voluntary) > Hardware name: GIGABYTE R272-P30-JG/MP32-AR0-JG, BIOS F31n (SCP: > 2.10.20220810) 09/30/2022 > Call trace: > show_stack+0x30/0x90 (C) > dump_stack_lvl+0x7c/0xa0 > print_address_description.constprop.0+0x90/0x310 > print_report+0x104/0x1f0 > kasan_report+0xc8/0x110 > __asan_report_load4_noabort+0x20/0x30 > tick_program_event+0x130/0x150 > ......snip... > ================================================================== > > - Add jump_label_init() calling before kasan_init() in setup_arch() in these > architectures: xtensa, arm. Because they currenly rely on > jump_label_init() in main() which is a little late. Then the early static > key kasan_flag_enabled in kasan_init() won't work. > > - In UML architecture, change to enable kasan_flag_enabled in > arch_mm_preinit() > because kasan_init() is enabled before main(), there's no chance to operate > on static key in kasan_init(). > > Test: > ===== > In v1, I took test on x86_64 for generic mode, and on arm64 for > generic, sw_tags and hw_tags mode. All of them works well. > > In v2, I only tested on arm64 for generic, sw_tags and hw_tags mode, it > works. For powerpc, I got a BOOK3S/64 machine, while it says > 'KASAN not enabled as it requires radix' and KASAN is disabled. Will > look for other POWER machine to test this. > ==== > > Baoquan He (12): > mm/kasan: add conditional checks in functions to return directly if > kasan is disabled > mm/kasan: move kasan= code to common place > mm/kasan/sw_tags: don't initialize kasan if it's disabled > arch/arm: don't initialize kasan if it's disabled > arch/arm64: don't initialize kasan if it's disabled > arch/loongarch: don't initialize kasan if it's disabled > arch/powerpc: don't initialize kasan if it's disabled > arch/riscv: don't initialize kasan if it's disabled > arch/x86: don't initialize kasan if it's disabled > arch/xtensa: don't initialize kasan if it's disabled > arch/um: don't initialize kasan if it's disabled > mm/kasan: make kasan=on|off take effect for all three modes > > arch/arm/kernel/setup.c | 6 +++++ > arch/arm/mm/kasan_init.c | 6 +++++ > arch/arm64/mm/kasan_init.c | 7 ++++++ > arch/loongarch/mm/kasan_init.c | 5 ++++ > arch/powerpc/mm/kasan/init_32.c | 8 +++++- > arch/powerpc/mm/kasan/init_book3e_64.c | 6 +++++ > arch/powerpc/mm/kasan/init_book3s_64.c | 6 +++++ > arch/riscv/mm/kasan_init.c | 6 +++++ > arch/um/kernel/mem.c | 6 +++++ > arch/x86/mm/kasan_init_64.c | 6 +++++ > arch/xtensa/kernel/setup.c | 1 + > arch/xtensa/mm/kasan_init.c | 6 +++++ > include/linux/kasan-enabled.h | 18 ++++++------- > mm/kasan/common.c | 25 ++++++++++++++++++ > mm/kasan/generic.c | 20 +++++++++++++-- > mm/kasan/hw_tags.c | 35 ++------------------------ > mm/kasan/init.c | 6 +++++ > mm/kasan/quarantine.c | 3 +++ > mm/kasan/report.c | 4 ++- > mm/kasan/shadow.c | 23 ++++++++++++++++- > mm/kasan/sw_tags.c | 9 +++++++ > 21 files changed, 165 insertions(+), 47 deletions(-) > > -- > 2.41.0 >
