Add a couple of arch_prctl() handles: - ARCH_ENABLE_TAGGED_ADDR enabled LAM. The argument is required number of tag bits. It is rounded up to the nearest LAM mode that can provide it. For now only LAM_U57 is supported, with 6 tag bits. - ARCH_GET_UNTAG_MASK returns untag mask. It can indicates where tag bits located in the address. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> --- arch/x86/include/uapi/asm/prctl.h | 3 +++ arch/x86/kernel/process_64.c | 32 ++++++++++++++++++++++++++++++- 2 files changed, 34 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h index 500b96e71f18..38164a05c23c 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -20,4 +20,7 @@ #define ARCH_MAP_VDSO_32 0x2002 #define ARCH_MAP_VDSO_64 0x2003 +#define ARCH_GET_UNTAG_MASK 0x4001 +#define ARCH_ENABLE_TAGGED_ADDR 0x4002 + #endif /* _ASM_X86_PRCTL_H */ diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 1962008fe743..93c8eba1a66d 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -742,6 +742,32 @@ static long prctl_map_vdso(const struct vdso_image *image, unsigned long addr) } #endif +static int prctl_enable_tagged_addr(unsigned long nr_bits) +{ + struct mm_struct *mm = current->mm; + + /* Already enabled? */ + if (mm->context.lam_cr3_mask) + return -EBUSY; + + /* LAM has to be enabled before spawning threads */ + if (get_nr_threads(current) > 1) + return -EBUSY; + + if (!nr_bits) { + return -EINVAL; + } else if (nr_bits <= 6) { + mm->context.lam_cr3_mask = X86_CR3_LAM_U57; + mm->context.untag_mask = ~GENMASK(62, 57); + } else { + return -EINVAL; + } + + /* Update CR3 to get LAM active */ + switch_mm(current->mm, current->mm, current); + return 0; +} + long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2) { int ret = 0; @@ -829,7 +855,11 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2) case ARCH_MAP_VDSO_64: return prctl_map_vdso(&vdso_image_64, arg2); #endif - + case ARCH_GET_UNTAG_MASK: + return put_user(current->mm->context.untag_mask, + (unsigned long __user *)arg2); + case ARCH_ENABLE_TAGGED_ADDR: + return prctl_enable_tagged_addr(arg2); default: ret = -EINVAL; break; -- 2.35.1