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// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */
#include <linux/perf_event.h>
#include <linux/uaccess.h>
/* Kernel callchain */
struct stackframe {
unsigned long fp;
unsigned long ra;
};
/*
* Get the return address for a single stackframe and return a pointer to the
* next frame tail.
*/
static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
unsigned long fp, unsigned long reg_ra)
{
struct stackframe buftail;
unsigned long ra = 0;
unsigned long __user *user_frame_tail =
(unsigned long __user *)(fp - sizeof(struct stackframe));
/* Check accessibility of one struct frame_tail beyond */
if (!access_ok(user_frame_tail, sizeof(buftail)))
return 0;
if (__copy_from_user_inatomic(&buftail, user_frame_tail,
sizeof(buftail)))
return 0;
if (reg_ra != 0)
ra = reg_ra;
else
ra = buftail.ra;
fp = buftail.fp;
if (ra != 0)
perf_callchain_store(entry, ra);
else
return 0;
return fp;
}
/*
* This will be called when the target is in user mode
* This function will only be called when we use
* "PERF_SAMPLE_CALLCHAIN" in
* kernel/events/core.c:perf_prepare_sample()
*
* How to trigger perf_callchain_[user/kernel] :
* $ perf record -e cpu-clock --call-graph fp ./program
* $ perf report --call-graph
*
* On RISC-V platform, the program being sampled and the C library
* need to be compiled with -fno-omit-frame-pointer, otherwise
* the user stack will not contain function frame.
*/
void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
struct pt_regs *regs)
{
struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
unsigned long fp = 0;
/* RISC-V does not support perf in guest mode. */
if (guest_cbs && guest_cbs->is_in_guest())
return;
fp = regs->s0;
perf_callchain_store(entry, regs->epc);
fp = user_backtrace(entry, fp, regs->ra);
while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
fp = user_backtrace(entry, fp, 0);
}
bool fill_callchain(unsigned long pc, void *entry)
{
return perf_callchain_store(entry, pc) == 0;
}
void notrace walk_stackframe(struct task_struct *task,
struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg);
void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
struct pt_regs *regs)
{
struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
/* RISC-V does not support perf in guest mode. */
if (guest_cbs && guest_cbs->is_in_guest()) {
pr_warn("RISC-V does not support perf in guest mode!");
return;
}
walk_stackframe(NULL, regs, fill_callchain, entry);
}
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