| 1 | |
| 2 | |
| 3 | * ARM callchain support
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| 4 | *
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| 5 | * Copyright (C) 2009 picoChip Designs, Ltd., Jamie Iles
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| 6 | * Copyright (C) 2010 ARM Ltd., Will Deacon <[email protected]>
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| 7 | *
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| 8 | * This code is based on the ARM OProfile backtrace code.
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| 9 |
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| 10 | #include <linux/perf_event.h>
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| 11 | #include <linux/uaccess.h>
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| 12 |
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| 13 | #include <asm/stacktrace.h>
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| 14 |
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| 15 | |
| 16 | * The registers we're interested in are at the end of the variable
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| 17 | * length saved register structure. The fp points at the end of this
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| 18 | * structure so the address of this struct is:
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| 19 | * (struct frame_tail *)(xxx->fp)-1
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| 20 | *
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| 21 | * This code has been adapted from the ARM OProfile support.
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| 22 |
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| 23 | struct frame_tail {
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| 24 | struct frame_tail __user *fp;
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| 25 | unsigned long sp;
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| 26 | unsigned long lr;
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| 27 | } __attribute__((packed));
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| 28 |
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| 29 | |
| 30 | * Get the return address for a single stackframe and return a pointer to the
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| 31 | * next frame tail.
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| 32 |
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| 33 | static struct frame_tail __user *
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| 34 | user_backtrace(struct frame_tail __user *tail,
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| 35 | struct perf_callchain_entry_ctx *entry)
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| 36 | {
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| 37 | struct frame_tail buftail;
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| 38 | unsigned long err;
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| 39 |
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| 40 | if (!access_ok(tail, sizeof(buftail)))
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| 41 | return NULL;
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| 42 |
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| 43 | pagefault_disable();
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| 44 | err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));
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| 45 | pagefault_enable();
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| 46 |
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| 47 | if (err)
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| 48 | return NULL;
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| 49 |
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| 50 | perf_callchain_store(entry, buftail.lr);
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| 51 |
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| 52 | |
| 53 | * Frame pointers should strictly progress back up the stack
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| 54 | * (towards higher addresses).
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| 55 |
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| 56 | if (tail + 1 >= buftail.fp)
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| 57 | return NULL;
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| 58 |
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| 59 | return buftail.fp - 1;
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| 60 | }
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| 61 |
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| 62 | void
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| 63 | perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
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| 64 | {
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| 65 | struct frame_tail __user *tail;
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| 66 |
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| 67 | perf_callchain_store(entry, regs->ARM_pc);
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| 68 |
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| 69 | if (!current->mm)
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| 70 | return;
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| 71 |
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| 72 | tail = (struct frame_tail __user *)regs->ARM_fp - 1;
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| 73 |
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| 74 | while ((entry->nr < entry->max_stack) &&
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| 75 | tail && !((unsigned long)tail & 0x3))
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| 76 | tail = user_backtrace(tail, entry);
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| 77 | }
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| 78 |
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| 79 | |
| 80 | * Gets called by walk_stackframe() for every stackframe. This will be called
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| 81 | * whist unwinding the stackframe and is like a subroutine return so we use
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| 82 | * the PC.
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| 83 |
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| 84 | static bool
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| 85 | callchain_trace(void *data, unsigned long pc)
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| 86 | {
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| 87 | struct perf_callchain_entry_ctx *entry = data;
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| 88 | return perf_callchain_store(entry, pc) == 0;
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| 89 | }
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| 90 |
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| 91 | void
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| 92 | perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
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| 93 | {
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| 94 | struct stackframe fr;
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| 95 |
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| 96 | arm_get_current_stackframe(regs, &fr);
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| 97 | walk_stackframe(&fr, callchain_trace, entry);
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| 98 | }
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