/* 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__)
        ANNOTATE_NOENDBR
        CALL_DEPTH_ACCOUNT
        RET
SYM_FUNC_END(__fentry__)
EXPORT_SYMBOL(__fentry__)

SYM_FUNC_START(ftrace_caller)
        ANNOTATE_NOENDBR
        /* 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)
        ANNOTATE_NOENDBR
        /* 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

1:
        testb   $1, %al
        jz      2f
        andq $0xfffffffffffffffe, %rax
        movq %rax, MCOUNT_REG_SIZE+8(%rsp)
        restore_mcount_regs
        /* Restore flags */
        popfq
        RET

        /* Swap the flags with orig_rax */
2:      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)
        ANNOTATE_NOENDBR
        CALL_DEPTH_ACCOUNT
        RET
SYM_FUNC_END(ftrace_stub_direct_tramp)

#else /* ! CONFIG_DYNAMIC_FTRACE */

SYM_FUNC_START(__fentry__)
        ANNOTATE_NOENDBR
        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

        /* Store original rsp for pt_regs.sp value. */
        movq %rsp, %rdi

        /* Restore return_to_handler value that got eaten by previous ret instruction. */
        subq $8, %rsp
        UNWIND_HINT_FUNC

        /* Save ftrace_regs for function exit context  */
        subq $(FRAME_SIZE), %rsp

        movq %rax, RAX(%rsp)
        movq %rdx, RDX(%rsp)
        movq %rbp, RBP(%rsp)
        movq %rdi, RSP(%rsp)
        movq %rsp, %rdi

        call ftrace_return_to_handler

        movq %rax, %rdi
        movq RDX(%rsp), %rdx
        movq RAX(%rsp), %rax

        addq $(FRAME_SIZE) + 8, %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