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Diffstat (limited to 'arch/x86/kernel/ftrace_64.S')
| -rw-r--r-- | arch/x86/kernel/ftrace_64.S | 354 |
1 files changed, 354 insertions, 0 deletions
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S new file mode 100644 index 000000000..5b2dabedc --- /dev/null +++ b/arch/x86/kernel/ftrace_64.S @@ -0,0 +1,354 @@ +/* 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 .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 + +#ifdef CONFIG_DYNAMIC_FTRACE + +SYM_FUNC_START(__fentry__) + RET +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_caller_end, SYM_L_GLOBAL) + + jmp ftrace_epilogue +SYM_FUNC_END(ftrace_caller); + +SYM_FUNC_START(ftrace_epilogue) +#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. + */ +SYM_INNER_LABEL_ALIGN(ftrace_stub, SYM_L_WEAK) + UNWIND_HINT_FUNC + RET +SYM_FUNC_END(ftrace_epilogue) + +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 */ + +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. + * See arch_ftrace_set_direct_caller(). + */ + movq ORIG_RAX(%rsp), %rax + testq %rax, %rax +SYM_INNER_LABEL(ftrace_regs_caller_jmp, SYM_L_GLOBAL) + jnz 1f + + restore_mcount_regs + /* 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 + + /* 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 + 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) + 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 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 + + RET +SYM_FUNC_END(ftrace_graph_caller) + +SYM_CODE_START(return_to_handler) + UNWIND_HINT_EMPTY + subq $16, %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 $16, %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) + UNWIND_HINT_FUNC + RET +SYM_CODE_END(return_to_handler) +#endif |