root/arch/powerpc/kernel/trace/ftrace_32.S

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * Split from entry_32.S
   4  */
   5 
   6 #include <linux/magic.h>
   7 #include <asm/reg.h>
   8 #include <asm/ppc_asm.h>
   9 #include <asm/asm-offsets.h>
  10 #include <asm/ftrace.h>
  11 #include <asm/export.h>
  12 
  13 _GLOBAL(mcount)
  14 _GLOBAL(_mcount)
  15         /*
  16          * It is required that _mcount on PPC32 must preserve the
  17          * link register. But we have r0 to play with. We use r0
  18          * to push the return address back to the caller of mcount
  19          * into the ctr register, restore the link register and
  20          * then jump back using the ctr register.
  21          */
  22         mflr    r0
  23         mtctr   r0
  24         lwz     r0, 4(r1)
  25         mtlr    r0
  26         bctr
  27 
  28 _GLOBAL(ftrace_caller)
  29         MCOUNT_SAVE_FRAME
  30         /* r3 ends up with link register */
  31         subi    r3, r3, MCOUNT_INSN_SIZE
  32 .globl ftrace_call
  33 ftrace_call:
  34         bl      ftrace_stub
  35         nop
  36 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  37 .globl ftrace_graph_call
  38 ftrace_graph_call:
  39         b       ftrace_graph_stub
  40 _GLOBAL(ftrace_graph_stub)
  41 #endif
  42         MCOUNT_RESTORE_FRAME
  43         /* old link register ends up in ctr reg */
  44         bctr
  45 
  46 EXPORT_SYMBOL(_mcount)
  47 
  48 _GLOBAL(ftrace_stub)
  49         blr
  50 
  51 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  52 _GLOBAL(ftrace_graph_caller)
  53         addi    r5, r1, 48
  54         /* load r4 with local address */
  55         lwz     r4, 44(r1)
  56         subi    r4, r4, MCOUNT_INSN_SIZE
  57 
  58         /* Grab the LR out of the caller stack frame */
  59         lwz     r3,52(r1)
  60 
  61         bl      prepare_ftrace_return
  62         nop
  63 
  64         /*
  65          * prepare_ftrace_return gives us the address we divert to.
  66          * Change the LR in the callers stack frame to this.
  67          */
  68         stw     r3,52(r1)
  69 
  70         MCOUNT_RESTORE_FRAME
  71         /* old link register ends up in ctr reg */
  72         bctr
  73 
  74 _GLOBAL(return_to_handler)
  75         /* need to save return values */
  76         stwu    r1, -32(r1)
  77         stw     r3, 20(r1)
  78         stw     r4, 16(r1)
  79         stw     r31, 12(r1)
  80         mr      r31, r1
  81 
  82         bl      ftrace_return_to_handler
  83         nop
  84 
  85         /* return value has real return address */
  86         mtlr    r3
  87 
  88         lwz     r3, 20(r1)
  89         lwz     r4, 16(r1)
  90         lwz     r31,12(r1)
  91         lwz     r1, 0(r1)
  92 
  93         /* Jump back to real return address */
  94         blr
  95 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */