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Peter Anvin (Intel)" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/fred] x86/fred: Add FRED initialization functions Cc: "H. Peter Anvin (Intel)" , Xin Li , Thomas Gleixner , "Borislav Petkov (AMD)" , Shan Kang , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20231205105030.8698-35-xin3.li@intel.com> References: <20231205105030.8698-35-xin3.li@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <170673567962.398.15247656787676456855.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit The following commit has been merged into the x86/fred branch of tip: Commit-ID: cdd99dd873cb11c40adf1ef70693f72c622ac8f3 Gitweb: https://git.kernel.org/tip/cdd99dd873cb11c40adf1ef70693f72c622ac8f3 Author: H. Peter Anvin (Intel) AuthorDate: Tue, 05 Dec 2023 02:50:23 -08:00 Committer: Borislav Petkov (AMD) CommitterDate: Wed, 31 Jan 2024 22:03:32 +01:00 x86/fred: Add FRED initialization functions Add cpu_init_fred_exceptions() to: - Set FRED entrypoints for events happening in ring 0 and 3. - Specify the stack level for IRQs occurred ring 0. - Specify dedicated event stacks for #DB/NMI/#MCE/#DF. - Enable FRED and invalidtes IDT. - Force 32-bit system calls to use "int $0x80" only. Add fred_complete_exception_setup() to: - Initialize system_vectors as done for IDT systems. - Set unused sysvec_table entries to fred_handle_spurious_interrupt(). Co-developed-by: Xin Li Signed-off-by: H. Peter Anvin (Intel) Signed-off-by: Xin Li Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Tested-by: Shan Kang Link: https://lore.kernel.org/r/20231205105030.8698-35-xin3.li@intel.com --- arch/x86/entry/entry_fred.c | 21 +++++++++++++- arch/x86/include/asm/fred.h | 5 +++- arch/x86/kernel/Makefile | 1 +- arch/x86/kernel/fred.c | 59 ++++++++++++++++++++++++++++++++++++- 4 files changed, 86 insertions(+) create mode 100644 arch/x86/kernel/fred.c diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_fred.c index 6ecc08b..ac120cb 100644 --- a/arch/x86/entry/entry_fred.c +++ b/arch/x86/entry/entry_fred.c @@ -133,6 +133,27 @@ void __init fred_install_sysvec(unsigned int sysvec, idtentry_t handler) sysvec_table[sysvec - FIRST_SYSTEM_VECTOR] = handler; } +static noinstr void fred_handle_spurious_interrupt(struct pt_regs *regs) +{ + spurious_interrupt(regs, regs->fred_ss.vector); +} + +void __init fred_complete_exception_setup(void) +{ + unsigned int vector; + + for (vector = 0; vector < FIRST_EXTERNAL_VECTOR; vector++) + set_bit(vector, system_vectors); + + for (vector = 0; vector < NR_SYSTEM_VECTORS; vector++) { + if (sysvec_table[vector]) + set_bit(vector + FIRST_SYSTEM_VECTOR, system_vectors); + else + sysvec_table[vector] = fred_handle_spurious_interrupt; + } + fred_setup_done = true; +} + static noinstr void fred_extint(struct pt_regs *regs) { unsigned int vector = regs->fred_ss.vector; diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h index 2fa9f34..e86c7ba 100644 --- a/arch/x86/include/asm/fred.h +++ b/arch/x86/include/asm/fred.h @@ -83,8 +83,13 @@ static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int asm_fred_entry_from_kvm(ss); } +void cpu_init_fred_exceptions(void); +void fred_complete_exception_setup(void); + #else /* CONFIG_X86_FRED */ static __always_inline unsigned long fred_event_data(struct pt_regs *regs) { return 0; } +static inline void cpu_init_fred_exceptions(void) { } +static inline void fred_complete_exception_setup(void) { } static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int vector) { } #endif /* CONFIG_X86_FRED */ #endif /* !__ASSEMBLY__ */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 0000325..0dcbfc1 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -48,6 +48,7 @@ obj-y += platform-quirks.o obj-y += process_$(BITS).o signal.o signal_$(BITS).o obj-y += traps.o idt.o irq.o irq_$(BITS).o dumpstack_$(BITS).o obj-y += time.o ioport.o dumpstack.o nmi.o +obj-$(CONFIG_X86_FRED) += fred.o obj-$(CONFIG_MODIFY_LDT_SYSCALL) += ldt.o obj-$(CONFIG_X86_KERNEL_IBT) += ibt_selftest.o obj-y += setup.o x86_init.o i8259.o irqinit.o diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c new file mode 100644 index 0000000..4bcd879 --- /dev/null +++ b/arch/x86/kernel/fred.c @@ -0,0 +1,59 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include + +#include +#include +#include +#include + +/* #DB in the kernel would imply the use of a kernel debugger. */ +#define FRED_DB_STACK_LEVEL 1UL +#define FRED_NMI_STACK_LEVEL 2UL +#define FRED_MC_STACK_LEVEL 2UL +/* + * #DF is the highest level because a #DF means "something went wrong + * *while delivering an exception*." The number of cases for which that + * can happen with FRED is drastically reduced and basically amounts to + * "the stack you pointed me to is broken." Thus, always change stacks + * on #DF, which means it should be at the highest level. + */ +#define FRED_DF_STACK_LEVEL 3UL + +#define FRED_STKLVL(vector, lvl) ((lvl) << (2 * (vector))) + +void cpu_init_fred_exceptions(void) +{ + /* When FRED is enabled by default, remove this log message */ + pr_info("Initialize FRED on CPU%d\n", smp_processor_id()); + + wrmsrl(MSR_IA32_FRED_CONFIG, + /* Reserve for CALL emulation */ + FRED_CONFIG_REDZONE | + FRED_CONFIG_INT_STKLVL(0) | + FRED_CONFIG_ENTRYPOINT(asm_fred_entrypoint_user)); + + /* + * The purpose of separate stacks for NMI, #DB and #MC *in the kernel* + * (remember that user space faults are always taken on stack level 0) + * is to avoid overflowing the kernel stack. + */ + wrmsrl(MSR_IA32_FRED_STKLVLS, + FRED_STKLVL(X86_TRAP_DB, FRED_DB_STACK_LEVEL) | + FRED_STKLVL(X86_TRAP_NMI, FRED_NMI_STACK_LEVEL) | + FRED_STKLVL(X86_TRAP_MC, FRED_MC_STACK_LEVEL) | + FRED_STKLVL(X86_TRAP_DF, FRED_DF_STACK_LEVEL)); + + /* The FRED equivalents to IST stacks... */ + wrmsrl(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB)); + wrmsrl(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI)); + wrmsrl(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF)); + + /* Enable FRED */ + cr4_set_bits(X86_CR4_FRED); + /* Any further IDT use is a bug */ + idt_invalidate(); + + /* Use int $0x80 for 32-bit system calls in FRED mode */ + setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); + setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); +}