diff options
| -rw-r--r-- | arch/x86/include/asm/fpu/regset.h | 7 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/regset.c | 81 | ||||
| -rw-r--r-- | arch/x86/kernel/ptrace.c | 12 | ||||
| -rw-r--r-- | include/uapi/linux/elf.h | 2 |
4 files changed, 99 insertions, 3 deletions
diff --git a/arch/x86/include/asm/fpu/regset.h b/arch/x86/include/asm/fpu/regset.h index 4f928d6a367b..697b77e96025 100644 --- a/arch/x86/include/asm/fpu/regset.h +++ b/arch/x86/include/asm/fpu/regset.h @@ -7,11 +7,12 @@ #include <linux/regset.h> -extern user_regset_active_fn regset_fpregs_active, regset_xregset_fpregs_active; +extern user_regset_active_fn regset_fpregs_active, regset_xregset_fpregs_active, + ssp_active; extern user_regset_get2_fn fpregs_get, xfpregs_get, fpregs_soft_get, - xstateregs_get; + xstateregs_get, ssp_get; extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set, - xstateregs_set; + xstateregs_set, ssp_set; /* * xstateregs_active == regset_fpregs_active. Please refer to the comment diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index 6d056b68f4ed..6bc1eb2a21bd 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -8,6 +8,7 @@ #include <asm/fpu/api.h> #include <asm/fpu/signal.h> #include <asm/fpu/regset.h> +#include <asm/prctl.h> #include "context.h" #include "internal.h" @@ -174,6 +175,86 @@ out: return ret; } +#ifdef CONFIG_X86_USER_SHADOW_STACK +int ssp_active(struct task_struct *target, const struct user_regset *regset) +{ + if (target->thread.features & ARCH_SHSTK_SHSTK) + return regset->n; + + return 0; +} + +int ssp_get(struct task_struct *target, const struct user_regset *regset, + struct membuf to) +{ + struct fpu *fpu = &target->thread.fpu; + struct cet_user_state *cetregs; + + if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK)) + return -ENODEV; + + sync_fpstate(fpu); + cetregs = get_xsave_addr(&fpu->fpstate->regs.xsave, XFEATURE_CET_USER); + if (WARN_ON(!cetregs)) { + /* + * This shouldn't ever be NULL because shadow stack was + * verified to be enabled above. This means + * MSR_IA32_U_CET.CET_SHSTK_EN should be 1 and so + * XFEATURE_CET_USER should not be in the init state. + */ + return -ENODEV; + } + + return membuf_write(&to, (unsigned long *)&cetregs->user_ssp, + sizeof(cetregs->user_ssp)); +} + +int ssp_set(struct task_struct *target, const struct user_regset *regset, + unsigned int pos, unsigned int count, + const void *kbuf, const void __user *ubuf) +{ + struct fpu *fpu = &target->thread.fpu; + struct xregs_state *xsave = &fpu->fpstate->regs.xsave; + struct cet_user_state *cetregs; + unsigned long user_ssp; + int r; + + if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK) || + !ssp_active(target, regset)) + return -ENODEV; + + if (pos != 0 || count != sizeof(user_ssp)) + return -EINVAL; + + r = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &user_ssp, 0, -1); + if (r) + return r; + + /* + * Some kernel instructions (IRET, etc) can cause exceptions in the case + * of disallowed CET register values. Just prevent invalid values. + */ + if (user_ssp >= TASK_SIZE_MAX || !IS_ALIGNED(user_ssp, 8)) + return -EINVAL; + + fpu_force_restore(fpu); + + cetregs = get_xsave_addr(xsave, XFEATURE_CET_USER); + if (WARN_ON(!cetregs)) { + /* + * This shouldn't ever be NULL because shadow stack was + * verified to be enabled above. This means + * MSR_IA32_U_CET.CET_SHSTK_EN should be 1 and so + * XFEATURE_CET_USER should not be in the init state. + */ + return -ENODEV; + } + + cetregs->user_ssp = user_ssp; + return 0; +} +#endif /* CONFIG_X86_USER_SHADOW_STACK */ + #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION /* diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index dfaa270a7cc9..095f04bdabdc 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -58,6 +58,7 @@ enum x86_regset_64 { REGSET64_FP, REGSET64_IOPERM, REGSET64_XSTATE, + REGSET64_SSP, }; #define REGSET_GENERAL \ @@ -1267,6 +1268,17 @@ static struct user_regset x86_64_regsets[] __ro_after_init = { .active = ioperm_active, .regset_get = ioperm_get }, +#ifdef CONFIG_X86_USER_SHADOW_STACK + [REGSET64_SSP] = { + .core_note_type = NT_X86_SHSTK, + .n = 1, + .size = sizeof(u64), + .align = sizeof(u64), + .active = ssp_active, + .regset_get = ssp_get, + .set = ssp_set + }, +#endif }; static const struct user_regset_view user_x86_64_view = { diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h index 0c8cf359ea5b..786d51727e74 100644 --- a/include/uapi/linux/elf.h +++ b/include/uapi/linux/elf.h @@ -409,6 +409,8 @@ typedef struct elf64_shdr { #define NT_386_TLS 0x200 /* i386 TLS slots (struct user_desc) */ #define NT_386_IOPERM 0x201 /* x86 io permission bitmap (1=deny) */ #define NT_X86_XSTATE 0x202 /* x86 extended state using xsave */ +/* Old binutils treats 0x203 as a CET state */ +#define NT_X86_SHSTK 0x204 /* x86 SHSTK state */ #define NT_S390_HIGH_GPRS 0x300 /* s390 upper register halves */ #define NT_S390_TIMER 0x301 /* s390 timer register */ #define NT_S390_TODCMP 0x302 /* s390 TOD clock comparator register */ |