arm/kernel/perf_callchain.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * ARM callchain support
0004  *
0005  * Copyright (C) 2009 picoChip Designs, Ltd., Jamie Iles
0006  * Copyright (C) 2010 ARM Ltd., Will Deacon <will.deacon@arm.com>
0007  *
0008  * This code is based on the ARM OProfile backtrace code.
0009  */
0010 #include <linux/perf_event.h>
0011 #include <linux/uaccess.h>
0012
0013 #include <asm/stacktrace.h>
0014
0015 /*
0016  * The registers we're interested in are at the end of the variable
0017  * length saved register structure. The fp points at the end of this
0018  * structure so the address of this struct is:
0019  * (struct frame_tail *)(xxx->fp)-1
0020  *
0021  * This code has been adapted from the ARM OProfile support.
0022  */
0023 struct frame_tail {
0024     struct frame_tail __user *fp;
0025     unsigned long sp;
0026     unsigned long lr;
0027 } __attribute__((packed));
0028
0029 /*
0030  * Get the return address for a single stackframe and return a pointer to the
0031  * next frame tail.
0032  */
0033 static struct frame_tail __user *
0034 user_backtrace(struct frame_tail __user *tail,
0035            struct perf_callchain_entry_ctx *entry)
0036 {
0037     struct frame_tail buftail;
0038     unsigned long err;
0039
0040     if (!access_ok(tail, sizeof(buftail)))
0041         return NULL;
0042
0043     pagefault_disable();
0044     err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));
0045     pagefault_enable();
0046
0047     if (err)
0048         return NULL;
0049
0050     perf_callchain_store(entry, buftail.lr);
0051
0052     /*
0053      * Frame pointers should strictly progress back up the stack
0054      * (towards higher addresses).
0055      */
0056     if (tail + 1 >= buftail.fp)
0057         return NULL;
0058
0059     return buftail.fp - 1;
0060 }
0061
0062 void
0063 perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
0064 {
0065     struct frame_tail __user *tail;
0066
0067     perf_callchain_store(entry, regs->ARM_pc);
0068
0069     if (!current->mm)
0070         return;
0071
0072     tail = (struct frame_tail __user *)regs->ARM_fp - 1;
0073
0074     while ((entry->nr < entry->max_stack) &&
0075            tail && !((unsigned long)tail & 0x3))
0076         tail = user_backtrace(tail, entry);
0077 }
0078
0079 /*
0080  * Gets called by walk_stackframe() for every stackframe. This will be called
0081  * whist unwinding the stackframe and is like a subroutine return so we use
0082  * the PC.
0083  */
0084 static int
0085 callchain_trace(struct stackframe *fr,
0086         void *data)
0087 {
0088     struct perf_callchain_entry_ctx *entry = data;
0089     perf_callchain_store(entry, fr->pc);
0090     return 0;
0091 }
0092
0093 void
0094 perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
0095 {
0096     struct stackframe fr;
0097
0098     arm_get_current_stackframe(regs, &fr);
0099     walk_stackframe(&fr, callchain_trace, entry);
0100 }
0101
0102 unsigned long perf_instruction_pointer(struct pt_regs *regs)
0103 {
0104     return instruction_pointer(regs);
0105 }
0106
0107 unsigned long perf_misc_flags(struct pt_regs *regs)
0108 {
0109     int misc = 0;
0110
0111     if (user_mode(regs))
0112         misc |= PERF_RECORD_MISC_USER;
0113     else
0114         misc |= PERF_RECORD_MISC_KERNEL;
0115
0116     return misc;
0117 }