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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 lr;
};
static int unwind_frame_kernel(struct stackframe *frame)
{
unsigned long low = (unsigned long)task_stack_page(current);
unsigned long high = low + THREAD_SIZE;
if (unlikely(frame->fp < low || frame->fp > high))
return -EPERM;
if (kstack_end((void *)frame->fp) || frame->fp & 0x3)
return -EPERM;
*frame = *(struct stackframe *)frame->fp;
if (__kernel_text_address(frame->lr)) {
int graph = 0;
frame->lr = ftrace_graph_ret_addr(NULL, &graph, frame->lr,
NULL);
}
return 0;
}
static void notrace walk_stackframe(struct stackframe *fr,
struct perf_callchain_entry_ctx *entry)
{
do {
perf_callchain_store(entry, fr->lr);
} while (unwind_frame_kernel(fr) >= 0);
}
/*
* 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_lr)
{
struct stackframe buftail;
unsigned long lr = 0;
unsigned long *user_frame_tail = (unsigned long *)fp;
/* 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_lr != 0)
lr = reg_lr;
else
lr = buftail.lr;
fp = buftail.fp;
perf_callchain_store(entry, lr);
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 C-SKY platform, the program being sampled and the C library
* need to be compiled with * -mbacktrace, otherwise the user
* stack will not contain function frame.
*/
void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
struct pt_regs *regs)
{
unsigned long fp = 0;
/* C-SKY does not support virtualization. */
if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
return;
fp = regs->regs[4];
perf_callchain_store(entry, regs->pc);
/*
* While backtrace from leaf function, lr is normally
* not saved inside frame on C-SKY, so get lr from pt_regs
* at the sample point. However, lr value can be incorrect if
* lr is used as temp register
*/
fp = user_backtrace(entry, fp, regs->lr);
while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
fp = user_backtrace(entry, fp, 0);
}
void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
struct pt_regs *regs)
{
struct stackframe fr;
/* C-SKY does not support virtualization. */
if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
pr_warn("C-SKY does not support perf in guest mode!");
return;
}
fr.fp = regs->regs[4];
fr.lr = regs->lr;
walk_stackframe(&fr, entry);
}
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