arch/riscv/kernel/mcount.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /* Copyright (C) 2017 Andes Technology Corporation */
   3
   4 #include <linux/init.h>
   5 #include <linux/linkage.h>
   6 #include <asm/asm.h>
   7 #include <asm/csr.h>
   8 #include <asm/unistd.h>
   9 #include <asm/thread_info.h>
  10 #include <asm/asm-offsets.h>
  11 #include <asm-generic/export.h>
  12 #include <asm/ftrace.h>
  13
  14         .text
  15
  16         .macro SAVE_ABI_STATE
  17         addi    sp, sp, -16
  18         sd      s0, 0(sp)
  19         sd      ra, 8(sp)
  20         addi    s0, sp, 16
  21         .endm
  22
  23         /*
  24          * The call to ftrace_return_to_handler would overwrite the return
  25          * register if a0 was not saved.
  26          */
  27         .macro SAVE_RET_ABI_STATE
  28         addi    sp, sp, -32
  29         sd      s0, 16(sp)
  30         sd      ra, 24(sp)
  31         sd      a0, 8(sp)
  32         addi    s0, sp, 32
  33         .endm
  34
  35         .macro RESTORE_ABI_STATE
  36         ld      ra, 8(sp)
  37         ld      s0, 0(sp)
  38         addi    sp, sp, 16
  39         .endm
  40
  41         .macro RESTORE_RET_ABI_STATE
  42         ld      ra, 24(sp)
  43         ld      s0, 16(sp)
  44         ld      a0, 8(sp)
  45         addi    sp, sp, 32
  46         .endm
  47
  48 ENTRY(ftrace_stub)
  49 #ifdef CONFIG_DYNAMIC_FTRACE
  50        .global MCOUNT_NAME
  51        .set    MCOUNT_NAME, ftrace_stub
  52 #endif
  53         ret
  54 ENDPROC(ftrace_stub)
  55
  56 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  57 ENTRY(return_to_handler)
  58 /*
  59  * On implementing the frame point test, the ideal way is to compare the
  60  * s0 (frame pointer, if enabled) on entry and the sp (stack pointer) on return.
  61  * However, the psABI of variable-length-argument functions does not allow this.
  62  *
  63  * So alternatively we check the *old* frame pointer position, that is, the
  64  * value stored in -16(s0) on entry, and the s0 on return.
  65  */
  66 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
  67         mv      t6, s0
  68 #endif
  69         SAVE_RET_ABI_STATE
  70 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
  71         mv      a0, t6
  72 #endif
  73         call    ftrace_return_to_handler
  74         mv      a1, a0
  75         RESTORE_RET_ABI_STATE
  76         jalr    a1
  77 ENDPROC(return_to_handler)
  78 EXPORT_SYMBOL(return_to_handler)
  79 #endif
  80
  81 #ifndef CONFIG_DYNAMIC_FTRACE
  82 ENTRY(MCOUNT_NAME)
  83         la      t4, ftrace_stub
  84 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  85         la      t0, ftrace_graph_return
  86         ld      t1, 0(t0)
  87         bne     t1, t4, do_ftrace_graph_caller
  88
  89         la      t3, ftrace_graph_entry
  90         ld      t2, 0(t3)
  91         la      t6, ftrace_graph_entry_stub
  92         bne     t2, t6, do_ftrace_graph_caller
  93 #endif
  94         la      t3, ftrace_trace_function
  95         ld      t5, 0(t3)
  96         bne     t5, t4, do_trace
  97         ret
  98
  99 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 100 /*
 101  * A pseudo representation for the function graph tracer:
 102  * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller)
 103  */
 104 do_ftrace_graph_caller:
 105         addi    a0, s0, -8
 106         mv      a1, ra
 107 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 108         ld      a2, -16(s0)
 109 #endif
 110         SAVE_ABI_STATE
 111         call    prepare_ftrace_return
 112         RESTORE_ABI_STATE
 113         ret
 114 #endif
 115
 116 /*
 117  * A pseudo representation for the function tracer:
 118  * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller)
 119  */
 120 do_trace:
 121         ld      a1, -8(s0)
 122         mv      a0, ra
 123
 124         SAVE_ABI_STATE
 125         jalr    t5
 126         RESTORE_ABI_STATE
 127         ret
 128 ENDPROC(MCOUNT_NAME)
 129 #endif
 130 EXPORT_SYMBOL(MCOUNT_NAME)