/* 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
/* Save ftrace_regs for function exit context */
subq $(FRAME_SIZE), %rsp
movq %rax, RAX(%rsp)
movq %rdx, RDX(%rsp)
movq %rbp, RBP(%rsp)
movq %rsp, %rdi
call ftrace_return_to_handler
movq %rax, %rdi
movq RDX(%rsp), %rdx
movq RAX(%rsp), %rax
addq $(FRAME_SIZE), %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
