Quelle  ftrace-direct.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/module.h>

#include <linux/sched.h> /* for wake_up_process() */
#include <linux/ftrace.h>
#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
#include <asm/asm-offsets.h>
#endif

extern void my_direct_func(struct task_struct *p);

void my_direct_func(struct task_struct *p)
{
 trace_printk("waking up %s-%d\n", p->comm, p->pid);
}

extern void my_tramp(void *);

#ifdef CONFIG_RISCV
#include <asm/asm.h>

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp, @function\n"
" .globl my_tramp\n"
" my_tramp:\n"
" addi sp,sp,-3*"SZREG"\n"
" "REG_S" a0,0*"SZREG"(sp)\n"
" "REG_S" t0,1*"SZREG"(sp)\n"
" "REG_S" ra,2*"SZREG"(sp)\n"
" call my_direct_func\n"
" "REG_L" a0,0*"SZREG"(sp)\n"
" "REG_L" t0,1*"SZREG"(sp)\n"
" "REG_L" ra,2*"SZREG"(sp)\n"
" addi sp,sp,3*"SZREG"\n"
" jr t0\n"
" .size my_tramp, .-my_tramp\n"
" .popsection\n"
);

#endif /* CONFIG_RISCV */

#ifdef CONFIG_X86_64

#include <asm/ibt.h>
#include <asm/nospec-branch.h>

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp, @function\n"
" .globl my_tramp\n"
" my_tramp:"
 ASM_ENDBR
" pushq %rbp\n"
" movq %rsp, %rbp\n"
 CALL_DEPTH_ACCOUNT
" pushq %rdi\n"
" call my_direct_func\n"
" popq %rdi\n"
" leave\n"
 ASM_RET
" .size my_tramp, .-my_tramp\n"
" .popsection\n"
);

#endif /* CONFIG_X86_64 */

#ifdef CONFIG_S390

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp, @function\n"
" .globl my_tramp\n"
" my_tramp:"
" lgr %r1,%r15\n"
" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
" brasl %r14,my_direct_func\n"
" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
" lgr %r1,%r0\n"
" br %r1\n"
" .size my_tramp, .-my_tramp\n"
" .popsection\n"
);

#endif /* CONFIG_S390 */

#ifdef CONFIG_ARM64

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp, @function\n"
" .globl my_tramp\n"
" my_tramp:"
" hint 34\n" // bti c
" sub sp, sp, #32\n"
" stp x9, x30, [sp]\n"
" str x0, [sp, #16]\n"
" bl my_direct_func\n"
" ldp x30, x9, [sp]\n"
" ldr x0, [sp, #16]\n"
" add sp, sp, #32\n"
" ret x9\n"
" .size my_tramp, .-my_tramp\n"
" .popsection\n"
);

#endif /* CONFIG_ARM64 */

#ifdef CONFIG_LOONGARCH

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp, @function\n"
" .globl my_tramp\n"
" my_tramp:\n"
" addi.d $sp, $sp, -32\n"
" st.d $a0, $sp, 0\n"
" st.d $t0, $sp, 8\n"
" st.d $ra, $sp, 16\n"
" bl my_direct_func\n"
" ld.d $a0, $sp, 0\n"
" ld.d $t0, $sp, 8\n"
" ld.d $ra, $sp, 16\n"
" addi.d $sp, $sp, 32\n"
" jr $t0\n"
" .size my_tramp, .-my_tramp\n"
" .popsection\n"
);

#endif /* CONFIG_LOONGARCH */

#ifdef CONFIG_PPC
#include <asm/ppc_asm.h>

#ifdef CONFIG_PPC64
#define STACK_FRAME_SIZE 48
#else
#define STACK_FRAME_SIZE 24
#endif

#if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
#define PPC64_TOC_SAVE_AND_UPDATE   \
" std 2, 24(1)\n"   \
" bcl 20, 31, 1f\n"   \
" 1: mflr 12\n"    \
" ld 2, (99f - 1b)(12)\n"
#define PPC64_TOC_RESTORE    \
" ld 2, 24(1)\n"
#define PPC64_TOC     \
" 99: .quad .TOC.@tocbase\n"
#else
#define PPC64_TOC_SAVE_AND_UPDATE ""
#define PPC64_TOC_RESTORE ""
#define PPC64_TOC ""
#endif

#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
#define PPC_FTRACE_RESTORE_LR    \
 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" \
" mtlr 0\n"
#define PPC_FTRACE_RET     \
" blr\n"
#else
#define PPC_FTRACE_RESTORE_LR    \
 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n" \
" mtctr 0\n"
#define PPC_FTRACE_RET     \
" mtlr 0\n"    \
" bctr\n"
#endif

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp, @function\n"
" .globl my_tramp\n"
" my_tramp:\n"
 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 PPC_STLU" 1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
" mflr 0\n"
 PPC_STL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 PPC_STLU" 1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
 PPC64_TOC_SAVE_AND_UPDATE
 PPC_STL" 3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
" bl my_direct_func\n"
 PPC_LL" 3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
 PPC64_TOC_RESTORE
" addi 1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
 PPC_FTRACE_RESTORE_LR
" addi 1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
 PPC_LL" 0, "__stringify(PPC_LR_STKOFF)"(1)\n"
 PPC_FTRACE_RET
 PPC64_TOC
" .size my_tramp, .-my_tramp\n"
" .popsection\n"
);

#endif /* CONFIG_PPC */

static struct ftrace_ops direct;

static int __init ftrace_direct_init(void)
{
 ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);

 return register_ftrace_direct(&direct, (unsigned long) my_tramp);
}

static void __exit ftrace_direct_exit(void)
{
 unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
}

module_init(ftrace_direct_init);
module_exit(ftrace_direct_exit);

MODULE_AUTHOR("Steven Rostedt");
MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
MODULE_LICENSE("GPL");