/* SPDX-License-Identifier: GPL-2.0 */ /* * Copyright (C) 2014 Steven Rostedt, Red Hat Inc */ #include <linux/export.h> #include <linux/cfi_types.h> #include <linux/linkage.h> #include <asm/asm-offsets.h> #include <asm/ptrace.h> #include <asm/ftrace.h> #include <asm/nospec-branch.h> #include <asm/unwind_hints.h> #include <asm/frame.h> .code64 .section .text, "ax" #ifdef CONFIG_FRAME_POINTER /* Save parent and function stack frames (rip and rbp) */ # define MCOUNT_FRAME_SIZE (8+16*2) #else /* No need to save a stack frame */ # define MCOUNT_FRAME_SIZE 0 #endif /* CONFIG_FRAME_POINTER */ /* Size of stack used to save mcount regs in save_mcount_regs */ #define MCOUNT_REG_SIZE (FRAME_SIZE + MCOUNT_FRAME_SIZE) /* * gcc -pg option adds a call to 'mcount' in most functions. * When -mfentry is used, the call is to 'fentry' and not 'mcount' * and is done before the function's stack frame is set up. * They both require a set of regs to be saved before calling * any C code and restored before returning back to the function. * * On boot up, all these calls are converted into nops. When tracing * is enabled, the call can jump to either ftrace_caller or * ftrace_regs_caller. Callbacks (tracing functions) that require * ftrace_regs_caller (like kprobes) need to have pt_regs passed to * it. For this reason, the size of the pt_regs structure will be * allocated on the stack and the required mcount registers will * be saved in the locations that pt_regs has them in. */ /* * @added: the amount of stack added before calling this * * After this is called, the following registers contain: * * %rdi - holds the address that called the trampoline * %rsi - holds the parent function (traced function's return address) * %rdx - holds the original %rbp */ .macro save_mcount_regs added=0 #ifdef CONFIG_FRAME_POINTER /* Save the original rbp */ pushq %rbp /* * Stack traces will stop at the ftrace trampoline if the frame pointer * is not set up properly. If fentry is used, we need to save a frame * pointer for the parent as well as the function traced, because the * fentry is called before the stack frame is set up, where as mcount * is called afterward. */ /* Save the parent pointer (skip orig rbp and our return address) */ pushq \added+8*2(%rsp) pushq %rbp movq %rsp, %rbp /* Save the return address (now skip orig rbp, rbp and parent) */ pushq \added+8*3(%rsp) pushq %rbp movq %rsp, %rbp #endif /* CONFIG_FRAME_POINTER */ /* * We add enough stack to save all regs. */ subq $(FRAME_SIZE), %rsp movq %rax, RAX(%rsp) movq %rcx, RCX(%rsp) movq %rdx, RDX(%rsp) movq %rsi, RSI(%rsp) movq %rdi, RDI(%rsp) movq %r8, R8(%rsp) movq %r9, R9(%rsp) movq $0, ORIG_RAX(%rsp) /* * Save the original RBP. Even though the mcount ABI does not * require this, it helps out callers. */ #ifdef CONFIG_FRAME_POINTER movq MCOUNT_REG_SIZE-8(%rsp), %rdx #else movq %rbp, %rdx #endif movq %rdx, RBP(%rsp) /* Copy the parent address into %rsi (second parameter) */ movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi /* Move RIP to its proper location */ movq MCOUNT_REG_SIZE+\added(%rsp), %rdi movq %rdi, RIP(%rsp) /* * Now %rdi (the first parameter) has the return address of * where ftrace_call returns. But the callbacks expect the * address of the call itself. */ subq $MCOUNT_INSN_SIZE, %rdi .endm .macro restore_mcount_regs save=0 /* ftrace_regs_caller or frame pointers require this */ movq RBP(%rsp), %rbp movq R9(%rsp), %r9 movq R8(%rsp), %r8 movq RDI(%rsp), %rdi movq RSI(%rsp), %rsi movq RDX(%rsp), %rdx movq RCX(%rsp), %rcx movq RAX(%rsp), %rax addq $MCOUNT_REG_SIZE-\save, %rsp .endm SYM_TYPED_FUNC_START(ftrace_stub) CALL_DEPTH_ACCOUNT RET SYM_FUNC_END(ftrace_stub) #ifdef CONFIG_FUNCTION_GRAPH_TRACER SYM_TYPED_FUNC_START(ftrace_stub_graph) CALL_DEPTH_ACCOUNT RET SYM_FUNC_END(ftrace_stub_graph) #endif #ifdef CONFIG_DYNAMIC_FTRACE SYM_FUNC_START(__fentry__) CALL_DEPTH_ACCOUNT RET SYM_FUNC_END(__fentry__) EXPORT_SYMBOL(__fentry__) SYM_FUNC_START(ftrace_caller) /* save_mcount_regs fills in first two parameters */ save_mcount_regs CALL_DEPTH_ACCOUNT /* Stack - skipping return address of ftrace_caller */ leaq MCOUNT_REG_SIZE+8(%rsp), %rcx movq %rcx, RSP(%rsp) SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL) ANNOTATE_NOENDBR /* Load the ftrace_ops into the 3rd parameter */ movq function_trace_op(%rip), %rdx /* regs go into 4th parameter */ leaq (%rsp), %rcx /* Only ops with REGS flag set should have CS register set */ movq $0, CS(%rsp) /* Account for the function call below */ CALL_DEPTH_ACCOUNT SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) ANNOTATE_NOENDBR call ftrace_stub /* Handlers can change the RIP */ movq RIP(%rsp), %rax movq %rax, MCOUNT_REG_SIZE(%rsp) restore_mcount_regs /* * The code up to this label is copied into trampolines so * think twice before adding any new code or changing the * layout here. */ SYM_INNER_LABEL(ftrace_caller_end, SYM_L_GLOBAL) ANNOTATE_NOENDBR RET SYM_FUNC_END(ftrace_caller); STACK_FRAME_NON_STANDARD_FP(ftrace_caller) SYM_FUNC_START(ftrace_regs_caller) /* Save the current flags before any operations that can change them */ pushfq /* added 8 bytes to save flags */ save_mcount_regs 8 /* save_mcount_regs fills in first two parameters */ CALL_DEPTH_ACCOUNT SYM_INNER_LABEL(ftrace_regs_caller_op_ptr, SYM_L_GLOBAL) ANNOTATE_NOENDBR /* Load the ftrace_ops into the 3rd parameter */ movq function_trace_op(%rip), %rdx /* Save the rest of pt_regs */ movq %r15, R15(%rsp) movq %r14, R14(%rsp) movq %r13, R13(%rsp) movq %r12, R12(%rsp) movq %r11, R11(%rsp) movq %r10, R10(%rsp) movq %rbx, RBX(%rsp) /* Copy saved flags */ movq MCOUNT_REG_SIZE(%rsp), %rcx movq %rcx, EFLAGS(%rsp) /* Kernel segments */ movq $__KERNEL_DS, %rcx movq %rcx, SS(%rsp) movq $__KERNEL_CS, %rcx movq %rcx, CS(%rsp) /* Stack - skipping return address and flags */ leaq MCOUNT_REG_SIZE+8*2(%rsp), %rcx movq %rcx, RSP(%rsp) ENCODE_FRAME_POINTER /* regs go into 4th parameter */ leaq (%rsp), %rcx /* Account for the function call below */ CALL_DEPTH_ACCOUNT SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL) ANNOTATE_NOENDBR call ftrace_stub /* Copy flags back to SS, to restore them */ movq EFLAGS(%rsp), %rax movq %rax, MCOUNT_REG_SIZE(%rsp) /* Handlers can change the RIP */ movq RIP(%rsp), %rax movq %rax, MCOUNT_REG_SIZE+8(%rsp) /* restore the rest of pt_regs */ movq R15(%rsp), %r15 movq R14(%rsp), %r14 movq R13(%rsp), %r13 movq R12(%rsp), %r12 movq R10(%rsp), %r10 movq RBX(%rsp), %rbx movq ORIG_RAX(%rsp), %rax movq %rax, MCOUNT_REG_SIZE-8(%rsp) /* * If ORIG_RAX is anything but zero, make this a call to that. * See arch_ftrace_set_direct_caller(). */ testq %rax, %rax SYM_INNER_LABEL(ftrace_regs_caller_jmp, SYM_L_GLOBAL) ANNOTATE_NOENDBR jnz 1f restore_mcount_regs /* Restore flags */ popfq /* * The trampoline will add the return. */ SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL) ANNOTATE_NOENDBR RET /* Swap the flags with orig_rax */ 1: movq MCOUNT_REG_SIZE(%rsp), %rdi movq %rdi, MCOUNT_REG_SIZE-8(%rsp) movq %rax, MCOUNT_REG_SIZE(%rsp) restore_mcount_regs 8 /* Restore flags */ popfq UNWIND_HINT_FUNC /* * The above left an extra return value on the stack; effectively * doing a tail-call without using a register. This PUSH;RET * pattern unbalances the RSB, inject a pointless CALL to rebalance. */ ANNOTATE_INTRA_FUNCTION_CALL CALL .Ldo_rebalance int3 .Ldo_rebalance: add $8, %rsp ALTERNATIVE __stringify(RET), \ __stringify(ANNOTATE_UNRET_SAFE; ret; int3), \ X86_FEATURE_CALL_DEPTH SYM_FUNC_END(ftrace_regs_caller) STACK_FRAME_NON_STANDARD_FP(ftrace_regs_caller) SYM_FUNC_START(ftrace_stub_direct_tramp) CALL_DEPTH_ACCOUNT RET SYM_FUNC_END(ftrace_stub_direct_tramp) #else /* ! CONFIG_DYNAMIC_FTRACE */ SYM_FUNC_START(__fentry__) CALL_DEPTH_ACCOUNT cmpq $ftrace_stub, ftrace_trace_function jnz trace RET trace: /* save_mcount_regs fills in first two parameters */ save_mcount_regs /* * When DYNAMIC_FTRACE is not defined, ARCH_SUPPORTS_FTRACE_OPS is not * set (see include/asm/ftrace.h and include/linux/ftrace.h). Only the * ip and parent ip are used and the list function is called when * function tracing is enabled. */ movq ftrace_trace_function, %r8 CALL_NOSPEC r8 restore_mcount_regs jmp ftrace_stub SYM_FUNC_END(__fentry__) EXPORT_SYMBOL(__fentry__) STACK_FRAME_NON_STANDARD_FP(__fentry__) #endif /* CONFIG_DYNAMIC_FTRACE */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER SYM_CODE_START(return_to_handler) UNWIND_HINT_UNDEFINED ANNOTATE_NOENDBR subq $24, %rsp /* Save the return values */ movq %rax, (%rsp) movq %rdx, 8(%rsp) movq %rbp, 16(%rsp) movq %rsp, %rdi call ftrace_return_to_handler movq %rax, %rdi movq 8(%rsp), %rdx movq (%rsp), %rax addq $24, %rsp /* * Jump back to the old return address. This cannot be JMP_NOSPEC rdi * since IBT would demand that contain ENDBR, which simply isn't so for * return addresses. Use a retpoline here to keep the RSB balanced. */ ANNOTATE_INTRA_FUNCTION_CALL call .Ldo_rop int3 .Ldo_rop: mov %rdi, (%rsp) ALTERNATIVE __stringify(RET), \ __stringify(ANNOTATE_UNRET_SAFE; ret; int3), \ X86_FEATURE_CALL_DEPTH SYM_CODE_END(return_to_handler) #endif
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