diff options
Diffstat (limited to 'arch/x86/entry/entry_64_fred.S')
| -rw-r--r-- | arch/x86/entry/entry_64_fred.S | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S new file mode 100644 index 000000000000..894f7f16eb80 --- /dev/null +++ b/arch/x86/entry/entry_64_fred.S @@ -0,0 +1,151 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * The actual FRED entry points. + */ + +#include <linux/export.h> +#include <linux/kvm_types.h> + +#include <asm/asm.h> +#include <asm/fred.h> +#include <asm/segment.h> + +#include "calling.h" + + .code64 + .section .noinstr.text, "ax" + +.macro FRED_ENTER + UNWIND_HINT_END_OF_STACK + ANNOTATE_NOENDBR + PUSH_AND_CLEAR_REGS + movq %rsp, %rdi /* %rdi -> pt_regs */ +.endm + +.macro FRED_EXIT + UNWIND_HINT_REGS + POP_REGS +.endm + +/* + * The new RIP value that FRED event delivery establishes is + * IA32_FRED_CONFIG & ~FFFH for events that occur in ring 3. + * Thus the FRED ring 3 entry point must be 4K page aligned. + */ + .align 4096 + +SYM_CODE_START_NOALIGN(asm_fred_entrypoint_user) + FRED_ENTER + call fred_entry_from_user +SYM_INNER_LABEL(asm_fred_exit_user, SYM_L_GLOBAL) + FRED_EXIT +1: ERETU + + _ASM_EXTABLE_TYPE(1b, asm_fred_entrypoint_user, EX_TYPE_ERETU) +SYM_CODE_END(asm_fred_entrypoint_user) + +/* + * The new RIP value that FRED event delivery establishes is + * (IA32_FRED_CONFIG & ~FFFH) + 256 for events that occur in + * ring 0, i.e., asm_fred_entrypoint_user + 256. + */ + .org asm_fred_entrypoint_user + 256, 0xcc +SYM_CODE_START_NOALIGN(asm_fred_entrypoint_kernel) + FRED_ENTER + call fred_entry_from_kernel + FRED_EXIT + ERETS +SYM_CODE_END(asm_fred_entrypoint_kernel) + +#if IS_ENABLED(CONFIG_KVM_INTEL) +SYM_FUNC_START(asm_fred_entry_from_kvm) + ANNOTATE_NOENDBR + push %rbp + mov %rsp, %rbp + + UNWIND_HINT_SAVE + + /* + * Both IRQ and NMI from VMX can be handled on current task stack + * because there is no need to protect from reentrancy and the call + * stack leading to this helper is effectively constant and shallow + * (relatively speaking). Do the same when FRED is active, i.e., no + * need to check current stack level for a stack switch. + * + * Emulate the FRED-defined redzone and stack alignment. + */ + sub $(FRED_CONFIG_REDZONE_AMOUNT << 6), %rsp + and $FRED_STACK_FRAME_RSP_MASK, %rsp + + /* + * Start to push a FRED stack frame, which is always 64 bytes: + * + * +--------+-----------------+ + * | Bytes | Usage | + * +--------+-----------------+ + * | 63:56 | Reserved | + * | 55:48 | Event Data | + * | 47:40 | SS + Event Info | + * | 39:32 | RSP | + * | 31:24 | RFLAGS | + * | 23:16 | CS + Aux Info | + * | 15:8 | RIP | + * | 7:0 | Error Code | + * +--------+-----------------+ + */ + push $0 /* Reserved, must be 0 */ + push $0 /* Event data, 0 for IRQ/NMI */ + push %rdi /* fred_ss handed in by the caller */ + push %rbp + pushf + push $__KERNEL_CS + + /* + * Unlike the IDT event delivery, FRED _always_ pushes an error code + * after pushing the return RIP, thus the CALL instruction CANNOT be + * used here to push the return RIP, otherwise there is no chance to + * push an error code before invoking the IRQ/NMI handler. + * + * Use LEA to get the return RIP and push it, then push an error code. + */ + lea 1f(%rip), %rax + push %rax /* Return RIP */ + push $0 /* Error code, 0 for IRQ/NMI */ + + PUSH_AND_CLEAR_REGS clear_callee=0 unwind_hint=0 + + movq %rsp, %rdi /* %rdi -> pt_regs */ + /* + * At this point: {rdi, rsi, rdx, rcx, r8, r9}, {r10, r11}, {rax, rdx} + * are clobbered, which corresponds to: arguments, extra caller-saved + * and return. All registers a C function is allowed to clobber. + * + * Notably, the callee-saved registers: {rbx, r12, r13, r14, r15} + * are untouched, with the exception of rbp, which carries the stack + * frame and will be restored before exit. + * + * Further calling another C function will not alter this state. + */ + call __fred_entry_from_kvm /* Call the C entry point */ + + /* + * When FRED, use ERETS to potentially clear NMIs, otherwise simply + * restore the stack pointer. + */ + ALTERNATIVE "nop; nop; mov %rbp, %rsp", \ + __stringify(add $C_PTREGS_SIZE, %rsp; ERETS), \ + X86_FEATURE_FRED + +1: /* + * Objtool doesn't understand ERETS, and the cfi register state is + * different from initial_func_cfi due to PUSH_REGS. Tell it the state + * is similar to where UNWIND_HINT_SAVE is. + */ + UNWIND_HINT_RESTORE + + pop %rbp + RET + +SYM_FUNC_END(asm_fred_entry_from_kvm) +EXPORT_SYMBOL_FOR_KVM(asm_fred_entry_from_kvm); +#endif |