Messages in this thread Patch in this message | | | Date | Thu, 24 Feb 2022 15:51:56 +0100 | From | Peter Zijlstra <> | Subject | [PATCH v2 18/39] x86/ibt: Add IBT feature, MSR and #CP handling |
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The bits required to make the hardware go.. Of note is that, provided the syscall entry points are covered with ENDBR, #CP doesn't need to be an IST because we'll never hit the syscall gap.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- arch/x86/include/asm/cpu.h | 4 + arch/x86/include/asm/cpufeatures.h | 1 arch/x86/include/asm/idtentry.h | 5 ++ arch/x86/include/asm/msr-index.h | 20 +++++++- arch/x86/include/asm/traps.h | 2 arch/x86/include/uapi/asm/processor-flags.h | 2 arch/x86/kernel/cpu/common.c | 28 ++++++++++- arch/x86/kernel/idt.c | 4 + arch/x86/kernel/machine_kexec_64.c | 2 arch/x86/kernel/traps.c | 70 ++++++++++++++++++++++++++++ 10 files changed, 136 insertions(+), 2 deletions(-)
--- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -7,6 +7,7 @@ #include <linux/topology.h> #include <linux/nodemask.h> #include <linux/percpu.h> +#include <asm/ibt.h> #ifdef CONFIG_SMP @@ -72,4 +73,7 @@ void init_ia32_feat_ctl(struct cpuinfo_x #else static inline void init_ia32_feat_ctl(struct cpuinfo_x86 *c) {} #endif + +extern __noendbr void cet_disable(void); + #endif /* _ASM_X86_CPU_H */ --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -387,6 +387,7 @@ #define X86_FEATURE_TSXLDTRK (18*32+16) /* TSX Suspend Load Address Tracking */ #define X86_FEATURE_PCONFIG (18*32+18) /* Intel PCONFIG */ #define X86_FEATURE_ARCH_LBR (18*32+19) /* Intel ARCH LBR */ +#define X86_FEATURE_IBT (18*32+20) /* Indirect Branch Tracking */ #define X86_FEATURE_AMX_BF16 (18*32+22) /* AMX bf16 Support */ #define X86_FEATURE_AVX512_FP16 (18*32+23) /* AVX512 FP16 */ #define X86_FEATURE_AMX_TILE (18*32+24) /* AMX tile Support */ --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -617,6 +617,11 @@ DECLARE_IDTENTRY_DF(X86_TRAP_DF, exc_dou DECLARE_IDTENTRY_RAW_ERRORCODE(X86_TRAP_DF, xenpv_exc_double_fault); #endif +/* #CP */ +#ifdef CONFIG_X86_KERNEL_IBT +DECLARE_IDTENTRY_ERRORCODE(X86_TRAP_CP, exc_control_protection); +#endif + /* #VC */ #ifdef CONFIG_AMD_MEM_ENCRYPT DECLARE_IDTENTRY_VC(X86_TRAP_VC, exc_vmm_communication); --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -362,11 +362,29 @@ #define MSR_ATOM_CORE_TURBO_RATIOS 0x0000066c #define MSR_ATOM_CORE_TURBO_VIDS 0x0000066d - #define MSR_CORE_PERF_LIMIT_REASONS 0x00000690 #define MSR_GFX_PERF_LIMIT_REASONS 0x000006B0 #define MSR_RING_PERF_LIMIT_REASONS 0x000006B1 +/* Control-flow Enforcement Technology MSRs */ +#define MSR_IA32_U_CET 0x000006a0 /* user mode cet */ +#define MSR_IA32_S_CET 0x000006a2 /* kernel mode cet */ +#define CET_SHSTK_EN BIT_ULL(0) +#define CET_WRSS_EN BIT_ULL(1) +#define CET_ENDBR_EN BIT_ULL(2) +#define CET_LEG_IW_EN BIT_ULL(3) +#define CET_NO_TRACK_EN BIT_ULL(4) +#define CET_SUPPRESS_DISABLE BIT_ULL(5) +#define CET_RESERVED (BIT_ULL(6) | BIT_ULL(7) | BIT_ULL(8) | BIT_ULL(9)) +#define CET_SUPPRESS BIT_ULL(10) +#define CET_WAIT_ENDBR BIT_ULL(11) + +#define MSR_IA32_PL0_SSP 0x000006a4 /* ring-0 shadow stack pointer */ +#define MSR_IA32_PL1_SSP 0x000006a5 /* ring-1 shadow stack pointer */ +#define MSR_IA32_PL2_SSP 0x000006a6 /* ring-2 shadow stack pointer */ +#define MSR_IA32_PL3_SSP 0x000006a7 /* ring-3 shadow stack pointer */ +#define MSR_IA32_INT_SSP_TAB 0x000006a8 /* exception shadow stack table */ + /* Hardware P state interface */ #define MSR_PPERF 0x0000064e #define MSR_PERF_LIMIT_REASONS 0x0000064f --- a/arch/x86/include/asm/traps.h +++ b/arch/x86/include/asm/traps.h @@ -18,6 +18,8 @@ void __init trap_init(void); asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *eregs); #endif +extern bool ibt_selftest(void); + #ifdef CONFIG_X86_F00F_BUG /* For handling the FOOF bug */ void handle_invalid_op(struct pt_regs *regs); --- a/arch/x86/include/uapi/asm/processor-flags.h +++ b/arch/x86/include/uapi/asm/processor-flags.h @@ -130,6 +130,8 @@ #define X86_CR4_SMAP _BITUL(X86_CR4_SMAP_BIT) #define X86_CR4_PKE_BIT 22 /* enable Protection Keys support */ #define X86_CR4_PKE _BITUL(X86_CR4_PKE_BIT) +#define X86_CR4_CET_BIT 23 /* enable Control-flow Enforcement Technology */ +#define X86_CR4_CET _BITUL(X86_CR4_CET_BIT) /* * x86-64 Task Priority Register, CR8 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -59,6 +59,7 @@ #include <asm/cpu_device_id.h> #include <asm/uv/uv.h> #include <asm/sigframe.h> +#include <asm/traps.h> #include "cpu.h" @@ -438,7 +439,8 @@ static __always_inline void setup_umip(s /* These bits should not change their value after CPU init is finished. */ static const unsigned long cr4_pinned_mask = - X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP | X86_CR4_FSGSBASE; + X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP | + X86_CR4_FSGSBASE | X86_CR4_CET; static DEFINE_STATIC_KEY_FALSE_RO(cr_pinning); static unsigned long cr4_pinned_bits __ro_after_init; @@ -592,6 +594,29 @@ static __init int setup_disable_pku(char __setup("nopku", setup_disable_pku); #endif /* CONFIG_X86_64 */ +static __always_inline void setup_cet(struct cpuinfo_x86 *c) +{ + u64 msr = CET_ENDBR_EN; + + if (!HAS_KERNEL_IBT || + !cpu_feature_enabled(X86_FEATURE_IBT)) + return; + + wrmsrl(MSR_IA32_S_CET, msr); + cr4_set_bits(X86_CR4_CET); + + if (!ibt_selftest()) { + pr_err("IBT selftest: Failed!\n"); + setup_clear_cpu_cap(X86_FEATURE_IBT); + } +} + +__noendbr void cet_disable(void) +{ + if (cpu_feature_enabled(X86_FEATURE_IBT)) + wrmsrl(MSR_IA32_S_CET, 0); +} + /* * Some CPU features depend on higher CPUID levels, which may not always * be available due to CPUID level capping or broken virtualization @@ -1709,6 +1734,7 @@ static void identify_cpu(struct cpuinfo_ x86_init_rdrand(c); setup_pku(c); + setup_cet(c); /* * Clear/Set all flags overridden by options, need do it --- a/arch/x86/kernel/idt.c +++ b/arch/x86/kernel/idt.c @@ -104,6 +104,10 @@ static const __initconst struct idt_data ISTG(X86_TRAP_MC, asm_exc_machine_check, IST_INDEX_MCE), #endif +#ifdef CONFIG_X86_KERNEL_IBT + INTG(X86_TRAP_CP, asm_exc_control_protection), +#endif + #ifdef CONFIG_AMD_MEM_ENCRYPT ISTG(X86_TRAP_VC, asm_exc_vmm_communication, IST_INDEX_VC), #endif --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -27,6 +27,7 @@ #include <asm/kexec-bzimage64.h> #include <asm/setup.h> #include <asm/set_memory.h> +#include <asm/cpu.h> #ifdef CONFIG_ACPI /* @@ -310,6 +311,7 @@ void machine_kexec(struct kimage *image) /* Interrupts aren't acceptable while we reboot */ local_irq_disable(); hw_breakpoint_disable(); + cet_disable(); if (image->preserve_context) { #ifdef CONFIG_X86_IO_APIC --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -210,6 +210,76 @@ DEFINE_IDTENTRY(exc_overflow) do_error_trap(regs, 0, "overflow", X86_TRAP_OF, SIGSEGV, 0, NULL); } +#ifdef CONFIG_X86_KERNEL_IBT + +static __ro_after_init bool ibt_fatal = true; + +extern const unsigned long ibt_selftest_ip; /* defined in asm beow */ + +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection) +{ + if (!cpu_feature_enabled(X86_FEATURE_IBT)) { + pr_err("Unexpected #CP\n"); + BUG(); + } + + if (WARN_ON_ONCE(user_mode(regs) || error_code != 3)) + return; + + if (unlikely(regs->ip == ibt_selftest_ip)) { + regs->ax = 0; + return; + } + + pr_err("Missing ENDBR: %pS\n", (void *)instruction_pointer(regs)); + if (!ibt_fatal) { + printk(KERN_DEFAULT CUT_HERE); + __warn(__FILE__, __LINE__, (void *)regs->ip, TAINT_WARN, regs, NULL); + return; + } + BUG(); +} + +bool ibt_selftest(void) +{ + unsigned long ret; + + asm ("1: lea 2f(%%rip), %%rax\n\t" + ANNOTATE_RETPOLINE_SAFE + " jmp *%%rax\n\t" + ASM_REACHABLE + ANNOTATE_NOENDBR + "2: nop\n\t" + + /* unsigned ibt_selftest_ip = 2b */ + ".pushsection .rodata,\"a\"\n\t" + ".align 8\n\t" + ".type ibt_selftest_ip, @object\n\t" + ".size ibt_selftest_ip, 8\n\t" + "ibt_selftest_ip:\n\t" + ".quad 2b\n\t" + ".popsection\n\t" + + : "=a" (ret) : : "memory"); + + return !ret; +} + +static int __init ibt_setup(char *str) +{ + if (!strcmp(str, "off")) + setup_clear_cpu_cap(X86_FEATURE_IBT); + + if (!strcmp(str, "warn")) + ibt_fatal = false; + + return 1; +} + +__setup("ibt=", ibt_setup); + +#endif /* CONFIG_X86_KERNEL_IBT */ + #ifdef CONFIG_X86_F00F_BUG void handle_invalid_op(struct pt_regs *regs) #else
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