From 91e102e79740ae43ded050ccac71aa3371db4f33 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Tue, 1 Oct 2024 23:58:43 +0100 Subject: prctl: arch-agnostic prctl for shadow stack Three architectures (x86, aarch64, riscv) have announced support for shadow stacks with fairly similar functionality. While x86 is using arch_prctl() to control the functionality neither arm64 nor riscv uses that interface so this patch adds arch-agnostic prctl() support to get and set status of shadow stacks and lock the current configuation to prevent further changes, with support for turning on and off individual subfeatures so applications can limit their exposure to features that they do not need. The features are: - PR_SHADOW_STACK_ENABLE: Tracking and enforcement of shadow stacks, including allocation of a shadow stack if one is not already allocated. - PR_SHADOW_STACK_WRITE: Writes to specific addresses in the shadow stack. - PR_SHADOW_STACK_PUSH: Push additional values onto the shadow stack. These features are expected to be inherited by new threads and cleared on exec(), unknown features should be rejected for enable but accepted for locking (in order to allow for future proofing). This is based on a patch originally written by Deepak Gupta but modified fairly heavily, support for indirect landing pads is removed, additional modes added and the locking interface reworked. The set status prctl() is also reworked to just set flags, if setting/reading the shadow stack pointer is required this could be a separate prctl. Reviewed-by: Thiago Jung Bauermann Reviewed-by: Catalin Marinas Acked-by: Yury Khrustalev Signed-off-by: Mark Brown Reviewed-by: Deepak Gupta Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-4-222b78d87eee@kernel.org Signed-off-by: Catalin Marinas --- include/uapi/linux/prctl.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 35791791a879..557a3d2ac1d4 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -328,4 +328,26 @@ struct prctl_mm_map { # define PR_PPC_DEXCR_CTRL_CLEAR_ONEXEC 0x10 /* Clear the aspect on exec */ # define PR_PPC_DEXCR_CTRL_MASK 0x1f +/* + * Get the current shadow stack configuration for the current thread, + * this will be the value configured via PR_SET_SHADOW_STACK_STATUS. + */ +#define PR_GET_SHADOW_STACK_STATUS 74 + +/* + * Set the current shadow stack configuration. Enabling the shadow + * stack will cause a shadow stack to be allocated for the thread. + */ +#define PR_SET_SHADOW_STACK_STATUS 75 +# define PR_SHADOW_STACK_ENABLE (1UL << 0) +# define PR_SHADOW_STACK_WRITE (1UL << 1) +# define PR_SHADOW_STACK_PUSH (1UL << 2) + +/* + * Prevent further changes to the specified shadow stack + * configuration. All bits may be locked via this call, including + * undefined bits. + */ +#define PR_LOCK_SHADOW_STACK_STATUS 76 + #endif /* _LINUX_PRCTL_H */ -- cgit v1.2.3 From 7ec3b57cb29f8371bf12a725b6e8f75831a03f27 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Tue, 1 Oct 2024 23:59:06 +0100 Subject: arm64/ptrace: Expose GCS via ptrace and core files Provide a new register type NT_ARM_GCS reporting the current GCS mode and pointer for EL0. Due to the interactions with allocation and deallocation of Guarded Control Stacks we do not permit any changes to the GCS mode via ptrace, only GCSPR_EL0 may be changed. Reviewed-by: Thiago Jung Bauermann Reviewed-by: Catalin Marinas Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-27-222b78d87eee@kernel.org Signed-off-by: Catalin Marinas --- include/uapi/linux/elf.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h index b9935988da5c..9adc218fb6df 100644 --- a/include/uapi/linux/elf.h +++ b/include/uapi/linux/elf.h @@ -443,6 +443,7 @@ typedef struct elf64_shdr { #define NT_ARM_ZT 0x40d /* ARM SME ZT registers */ #define NT_ARM_FPMR 0x40e /* ARM floating point mode register */ #define NT_ARM_POE 0x40f /* ARM POE registers */ +#define NT_ARM_GCS 0x410 /* ARM GCS state */ #define NT_ARC_V2 0x600 /* ARCv2 accumulator/extra registers */ #define NT_VMCOREDD 0x700 /* Vmcore Device Dump Note */ #define NT_MIPS_DSP 0x800 /* MIPS DSP ASE registers */ -- cgit v1.2.3