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Linux/arch/arm/kernel/perf_callchain.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * ARM callchain support
  4  *
  5  * Copyright (C) 2009 picoChip Designs, Ltd., Jamie Iles
  6  * Copyright (C) 2010 ARM Ltd., Will Deacon <will.deacon@arm.com>
  7  *
  8  * This code is based on the ARM OProfile backtrace code.
  9  */
 10 #include <linux/perf_event.h>
 11 #include <linux/uaccess.h>
 12 
 13 #include <asm/stacktrace.h>
 14 
 15 /*
 16  * The registers we're interested in are at the end of the variable
 17  * length saved register structure. The fp points at the end of this
 18  * structure so the address of this struct is:
 19  * (struct frame_tail *)(xxx->fp)-1
 20  *
 21  * This code has been adapted from the ARM OProfile support.
 22  */
 23 struct frame_tail {
 24         struct frame_tail __user *fp;
 25         unsigned long sp;
 26         unsigned long lr;
 27 } __attribute__((packed));
 28 
 29 /*
 30  * Get the return address for a single stackframe and return a pointer to the
 31  * next frame tail.
 32  */
 33 static struct frame_tail __user *
 34 user_backtrace(struct frame_tail __user *tail,
 35                struct perf_callchain_entry_ctx *entry)
 36 {
 37         struct frame_tail buftail;
 38         unsigned long err;
 39 
 40         if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
 41                 return NULL;
 42 
 43         pagefault_disable();
 44         err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));
 45         pagefault_enable();
 46 
 47         if (err)
 48                 return NULL;
 49 
 50         perf_callchain_store(entry, buftail.lr);
 51 
 52         /*
 53          * Frame pointers should strictly progress back up the stack
 54          * (towards higher addresses).
 55          */
 56         if (tail + 1 >= buftail.fp)
 57                 return NULL;
 58 
 59         return buftail.fp - 1;
 60 }
 61 
 62 void
 63 perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 64 {
 65         struct frame_tail __user *tail;
 66 
 67         if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
 68                 /* We don't support guest os callchain now */
 69                 return;
 70         }
 71 
 72         perf_callchain_store(entry, regs->ARM_pc);
 73 
 74         if (!current->mm)
 75                 return;
 76 
 77         tail = (struct frame_tail __user *)regs->ARM_fp - 1;
 78 
 79         while ((entry->nr < entry->max_stack) &&
 80                tail && !((unsigned long)tail & 0x3))
 81                 tail = user_backtrace(tail, entry);
 82 }
 83 
 84 /*
 85  * Gets called by walk_stackframe() for every stackframe. This will be called
 86  * whist unwinding the stackframe and is like a subroutine return so we use
 87  * the PC.
 88  */
 89 static int
 90 callchain_trace(struct stackframe *fr,
 91                 void *data)
 92 {
 93         struct perf_callchain_entry_ctx *entry = data;
 94         perf_callchain_store(entry, fr->pc);
 95         return 0;
 96 }
 97 
 98 void
 99 perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
100 {
101         struct stackframe fr;
102 
103         if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
104                 /* We don't support guest os callchain now */
105                 return;
106         }
107 
108         arm_get_current_stackframe(regs, &fr);
109         walk_stackframe(&fr, callchain_trace, entry);
110 }
111 
112 unsigned long perf_instruction_pointer(struct pt_regs *regs)
113 {
114         if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
115                 return perf_guest_cbs->get_guest_ip();
116 
117         return instruction_pointer(regs);
118 }
119 
120 unsigned long perf_misc_flags(struct pt_regs *regs)
121 {
122         int misc = 0;
123 
124         if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
125                 if (perf_guest_cbs->is_user_mode())
126                         misc |= PERF_RECORD_MISC_GUEST_USER;
127                 else
128                         misc |= PERF_RECORD_MISC_GUEST_KERNEL;
129         } else {
130                 if (user_mode(regs))
131                         misc |= PERF_RECORD_MISC_USER;
132                 else
133                         misc |= PERF_RECORD_MISC_KERNEL;
134         }
135 
136         return misc;
137 }
138 

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