| /* SPDX-License-Identifier: GPL-2.0 */ |
| /* |
| * Copyright (C) 2014 Steven Rostedt, Red Hat Inc |
| */ |
| |
| #include <linux/linkage.h> |
| #include <asm/ptrace.h> |
| #include <asm/ftrace.h> |
| #include <asm/export.h> |
| #include <asm/nospec-branch.h> |
| #include <asm/unwind_hints.h> |
| #include <asm/frame.h> |
| |
| .code64 |
| .section .entry.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 (SS+8 + 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 $(MCOUNT_REG_SIZE - MCOUNT_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 |
| |
| #ifdef CONFIG_DYNAMIC_FTRACE |
| |
| SYM_FUNC_START(__fentry__) |
| retq |
| SYM_FUNC_END(__fentry__) |
| EXPORT_SYMBOL(__fentry__) |
| |
| SYM_FUNC_START(ftrace_caller) |
| /* save_mcount_regs fills in first two parameters */ |
| save_mcount_regs |
| |
| SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL) |
| /* Load the ftrace_ops into the 3rd parameter */ |
| movq function_trace_op(%rip), %rdx |
| |
| /* regs go into 4th parameter (but make it NULL) */ |
| movq $0, %rcx |
| |
| SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) |
| call ftrace_stub |
| |
| 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_epilogue, SYM_L_GLOBAL) |
| |
| #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) |
| jmp ftrace_stub |
| #endif |
| |
| /* |
| * This is weak to keep gas from relaxing the jumps. |
| * It is also used to copy the retq for trampolines. |
| */ |
| SYM_INNER_LABEL_ALIGN(ftrace_stub, SYM_L_WEAK) |
| retq |
| SYM_FUNC_END(ftrace_caller) |
| |
| SYM_FUNC_START(ftrace_regs_caller) |
| /* Save the current flags before any operations that can change them */ |
| pushfq |
| |
| UNWIND_HINT_SAVE |
| |
| /* added 8 bytes to save flags */ |
| save_mcount_regs 8 |
| /* save_mcount_regs fills in first two parameters */ |
| |
| SYM_INNER_LABEL(ftrace_regs_caller_op_ptr, SYM_L_GLOBAL) |
| /* 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 |
| |
| SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL) |
| 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 */ |
| movq ORIG_RAX(%rsp), %rax |
| cmpq $0, %rax |
| je 1f |
| |
| /* Swap the flags with orig_rax */ |
| movq MCOUNT_REG_SIZE(%rsp), %rdi |
| movq %rdi, MCOUNT_REG_SIZE-8(%rsp) |
| movq %rax, MCOUNT_REG_SIZE(%rsp) |
| |
| restore_mcount_regs 8 |
| |
| jmp 2f |
| |
| 1: restore_mcount_regs |
| |
| |
| 2: |
| /* |
| * The stack layout is nondetermistic here, depending on which path was |
| * taken. This confuses objtool and ORC, rightfully so. For now, |
| * pretend the stack always looks like the non-direct case. |
| */ |
| UNWIND_HINT_RESTORE |
| |
| /* Restore flags */ |
| popfq |
| |
| /* |
| * As this jmp to ftrace_epilogue can be a short jump |
| * it must not be copied into the trampoline. |
| * The trampoline will add the code to jump |
| * to the return. |
| */ |
| SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL) |
| |
| jmp ftrace_epilogue |
| |
| SYM_FUNC_END(ftrace_regs_caller) |
| |
| |
| #else /* ! CONFIG_DYNAMIC_FTRACE */ |
| |
| SYM_FUNC_START(__fentry__) |
| cmpq $ftrace_stub, ftrace_trace_function |
| jnz trace |
| |
| fgraph_trace: |
| #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| cmpq $ftrace_stub, ftrace_graph_return |
| jnz ftrace_graph_caller |
| |
| cmpq $ftrace_graph_entry_stub, ftrace_graph_entry |
| jnz ftrace_graph_caller |
| #endif |
| |
| SYM_INNER_LABEL(ftrace_stub, SYM_L_GLOBAL) |
| retq |
| |
| 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 fgraph_trace |
| SYM_FUNC_END(__fentry__) |
| EXPORT_SYMBOL(__fentry__) |
| #endif /* CONFIG_DYNAMIC_FTRACE */ |
| |
| #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| SYM_FUNC_START(ftrace_graph_caller) |
| /* Saves rbp into %rdx and fills first parameter */ |
| save_mcount_regs |
| |
| leaq MCOUNT_REG_SIZE+8(%rsp), %rsi |
| movq $0, %rdx /* No framepointers needed */ |
| call prepare_ftrace_return |
| |
| restore_mcount_regs |
| |
| retq |
| SYM_FUNC_END(ftrace_graph_caller) |
| |
| SYM_CODE_START(return_to_handler) |
| UNWIND_HINT_EMPTY |
| subq $24, %rsp |
| |
| /* Save the return values */ |
| movq %rax, (%rsp) |
| movq %rdx, 8(%rsp) |
| movq %rbp, %rdi |
| |
| call ftrace_return_to_handler |
| |
| movq %rax, %rdi |
| movq 8(%rsp), %rdx |
| movq (%rsp), %rax |
| addq $24, %rsp |
| JMP_NOSPEC %rdi |
| SYM_CODE_END(return_to_handler) |
| #endif |
