Quelle  ftrace-direct-modify.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/ftrace.h>
#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
#include <asm/asm-offsets.h>
#endif

extern void my_direct_func1(void);
extern void my_direct_func2(void);

void my_direct_func1(void)
{
 trace_printk("my direct func1\n");
}

void my_direct_func2(void)
{
 trace_printk("my direct func2\n");
}

extern void my_tramp1(void *);
extern void my_tramp2(void *);

static unsigned long my_ip = (unsigned long)schedule;

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

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp1, @function\n"
" .globl my_tramp1\n"
" my_tramp1:\n"
" addi sp,sp,-2*"SZREG"\n"
" "REG_S" t0,0*"SZREG"(sp)\n"
" "REG_S" ra,1*"SZREG"(sp)\n"
" call my_direct_func1\n"
" "REG_L" t0,0*"SZREG"(sp)\n"
" "REG_L" ra,1*"SZREG"(sp)\n"
" addi sp,sp,2*"SZREG"\n"
" jr t0\n"
" .size my_tramp1, .-my_tramp1\n"
" .type my_tramp2, @function\n"
" .globl my_tramp2\n"

" my_tramp2:\n"
" addi sp,sp,-2*"SZREG"\n"
" "REG_S" t0,0*"SZREG"(sp)\n"
" "REG_S" ra,1*"SZREG"(sp)\n"
" call my_direct_func2\n"
" "REG_L" t0,0*"SZREG"(sp)\n"
" "REG_L" ra,1*"SZREG"(sp)\n"
" addi sp,sp,2*"SZREG"\n"
" jr t0\n"
" .size my_tramp2, .-my_tramp2\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_tramp1, @function\n"
" .globl my_tramp1\n"
" my_tramp1:"
 ASM_ENDBR
" pushq %rbp\n"
" movq %rsp, %rbp\n"
 CALL_DEPTH_ACCOUNT
" call my_direct_func1\n"
" leave\n"
 ASM_RET
" .size my_tramp1, .-my_tramp1\n"

" .type my_tramp2, @function\n"
" .globl my_tramp2\n"
" my_tramp2:"
 ASM_ENDBR
" pushq %rbp\n"
" movq %rsp, %rbp\n"
 CALL_DEPTH_ACCOUNT
" call my_direct_func2\n"
" leave\n"
 ASM_RET
" .size my_tramp2, .-my_tramp2\n"
" .popsection\n"
);

#endif /* CONFIG_X86_64 */

#ifdef CONFIG_S390

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp1, @function\n"
" .globl my_tramp1\n"
" my_tramp1:"
" 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_func1\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_tramp1, .-my_tramp1\n"
" .type my_tramp2, @function\n"
" .globl my_tramp2\n"
" my_tramp2:"
" 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_func2\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_tramp2, .-my_tramp2\n"
" .popsection\n"
);

#endif /* CONFIG_S390 */

#ifdef CONFIG_ARM64

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp1, @function\n"
" .globl my_tramp1\n"
" my_tramp1:"
" hint 34\n" // bti c
" sub sp, sp, #16\n"
" stp x9, x30, [sp]\n"
" bl my_direct_func1\n"
" ldp x30, x9, [sp]\n"
" add sp, sp, #16\n"
" ret x9\n"
" .size my_tramp1, .-my_tramp1\n"

" .type my_tramp2, @function\n"
" .globl my_tramp2\n"
" my_tramp2:"
" hint 34\n" // bti c
" sub sp, sp, #16\n"
" stp x9, x30, [sp]\n"
" bl my_direct_func2\n"
" ldp x30, x9, [sp]\n"
" add sp, sp, #16\n"
" ret x9\n"
" .size my_tramp2, .-my_tramp2\n"
" .popsection\n"
);

#endif /* CONFIG_ARM64 */

#ifdef CONFIG_LOONGARCH

asm (
" .pushsection .text, \"ax\", @progbits\n"
" .type my_tramp1, @function\n"
" .globl my_tramp1\n"
" my_tramp1:\n"
" addi.d $sp, $sp, -16\n"
" st.d $t0, $sp, 0\n"
" st.d $ra, $sp, 8\n"
" bl my_direct_func1\n"
" ld.d $t0, $sp, 0\n"
" ld.d $ra, $sp, 8\n"
" addi.d $sp, $sp, 16\n"
" jr $t0\n"
" .size my_tramp1, .-my_tramp1\n"

" .type my_tramp2, @function\n"
" .globl my_tramp2\n"
" my_tramp2:\n"
" addi.d $sp, $sp, -16\n"
" st.d $t0, $sp, 0\n"
" st.d $ra, $sp, 8\n"
" bl my_direct_func2\n"
" ld.d $t0, $sp, 0\n"
" ld.d $ra, $sp, 8\n"
" addi.d $sp, $sp, 16\n"
" jr $t0\n"
" .size my_tramp2, .-my_tramp2\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_tramp1, @function\n"
" .globl my_tramp1\n"
" my_tramp1:\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
" bl my_direct_func1\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
" .size my_tramp1, .-my_tramp1\n"

" .type my_tramp2, @function\n"
" .globl my_tramp2\n"
" my_tramp2:\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
" bl my_direct_func2\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_tramp2, .-my_tramp2\n"
" .popsection\n"
);

#endif /* CONFIG_PPC */

static struct ftrace_ops direct;

static unsigned long my_tramp = (unsigned long)my_tramp1;
static unsigned long tramps[2] = {
 (unsigned long)my_tramp1,
 (unsigned long)my_tramp2,
};

static int simple_thread(void *arg)
{
 static int t;
 int ret = 0;

 while (!kthread_should_stop()) {
  set_current_state(TASK_INTERRUPTIBLE);
  schedule_timeout(2 * HZ);

  if (ret)
   continue;
  t ^= 1;
  ret = modify_ftrace_direct(&direct, tramps[t]);
  if (!ret)
   my_tramp = tramps[t];
  WARN_ON_ONCE(ret);
 }

 return 0;
}

static struct task_struct *simple_tsk;

static int __init ftrace_direct_init(void)
{
 int ret;

 ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0);
 ret = register_ftrace_direct(&direct, my_tramp);

 if (!ret)
  simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
 return ret;
}

static void __exit ftrace_direct_exit(void)
{
 kthread_stop(simple_tsk);
 unregister_ftrace_direct(&direct, my_tramp, true);
}

module_init(ftrace_direct_init);
module_exit(ftrace_direct_exit);

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