x86, arm64 and risc-v support cpu assisted shadow stack. x86 was first one and most of the shadow stack related code is in x86 arch directory. arm64 guarded control stack (GCS) patches from Mark Brown are in -next. This led to obvious discussion many how to merge certain common flows in generic code. Recent one being [1]. Goes without saying having generic code helps with bug management as well (not having to fix same bug for 3 different arches). High level common flow between x86, riscv and arm64: - Enabling is via prctl. Enabling and book keeping per task_struct in thread data strutures differ on each architecture. This version of patchset doesn't try to merge those flows. - Managing virtual memory for shadow stack handled similarly. From kernel's perspective shadow stack writeable memory which can be written by only certain selected store operations (depending on arch) This patch converges this notion between different architecture to allocate, map and free shadow stack. - Virtual memory management of shadow stack on clone/fork is similar. Treatment of copy-on-write (COW) or using parent's stack (CLONE_VFORK) or allocating new shadow stack (CLONE_VM) are similar in all arch. Thus logic to setup shadow stack should be similar on clone/fork Mark brown introduced `ARCH_HAS_SHADOW_STACK` as part of arm64 gcs series [2] and this patch set depends on it. This patchset uses same config to move as much as possible common code in generic kernel. Additionaly this patchset introduces wrapper abstractions where arch specific handling is required. Generic code and arch specific code for shadow stack are independent modules and can call into each other. This is by design because each architecture's enabling mechanisms are different but at the same time from kernel's perspective it's a special memory which is writeable from certain selected store operations. I've not tested this. Only compiled for x86 with shadow stack enable. Thus this is a RFC and possible looking for some help to test as well on x86. [1] - https://lore.kernel.org/all/20241008-v5_user_cfi_series-v6-0-60d9fe073f37@xxxxxxxxxxxx/T/#m98d14237663150778a3f8df59a76a3fe6318624a [2] - https://lore.kernel.org/linux-arm-kernel/20241001-arm64-gcs-v13-0-222b78d87eee@xxxxxxxxxx/T/#m1ff65a49873b0e770e71de7af178f581c72be7ad To: Thomas Gleixner <tglx@xxxxxxxxxxxxx> To: Ingo Molnar <mingo@xxxxxxxxxx> To: Borislav Petkov <bp@xxxxxxxxx> To: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> To: x86@xxxxxxxxxx To: H. Peter Anvin <hpa@xxxxxxxxx> To: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> To: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> To: Vlastimil Babka <vbabka@xxxxxxx> To: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> To: Arnd Bergmann <arnd@xxxxxxxx> Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: linux-fsdevel@xxxxxxxxxxxxxxx Cc: linux-mm@xxxxxxxxx Cc: linux-arch@xxxxxxxxxxxxxxx Cc: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> Cc: Mark Brown <broonie@xxxxxxxxxx> Signed-off-by: Deepak Gupta <debug@xxxxxxxxxxxx> --- Changes in v2: - Doesn't carry patch which introduces `ARCH_HAS_SHADOW_STACK`. Most likely it'll be merged as part of arm64 gcs patch series. - moves shstk_setup back into x86 portion. Primary reason is that entire arch specific prctl specific handling can't be made generic easily due to arch differences. - Due to prctl handling code remaining arch specific, removed generic wrappers to set thread status and shstk enabling - Removed x86 specific comment - Added `SHADOW_STACK_SET_MARKER` - Link to v1: https://lore.kernel.org/r/20241010-shstk_converge-v1-0-631beca676e7@xxxxxxxxxxxx --- Deepak Gupta (2): mm: helper `is_shadow_stack_vma` to check shadow stack vma kernel: converge common shadow stack flow agnostic to arch arch/x86/include/asm/shstk.h | 7 + arch/x86/include/uapi/asm/mman.h | 3 - arch/x86/kernel/shstk.c | 223 +++++--------------------------- include/linux/usershstk.h | 22 ++++ include/uapi/asm-generic/mman-common.h | 5 + kernel/Makefile | 2 + kernel/usershstk.c | 230 +++++++++++++++++++++++++++++++++ mm/gup.c | 2 +- mm/mmap.c | 2 +- mm/vma.h | 10 +- 10 files changed, 305 insertions(+), 201 deletions(-) --- base-commit: 4e0105ad0161b4262b51f034a757c4899c647487 change-id: 20241010-shstk_converge-aefbcbef5d71 -- - debug
