linux-stable/arch/csky/kernel/perf_callchain.c
Sean Christopherson 84af21d850 perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscv
Drop "support" for guest callbacks from architectures that don't implement
the guest callbacks.  Future patches will convert the callbacks to
static_call; rather than churn a bunch of arch code (that was presumably
copy+pasted from x86), remove it wholesale as it's useless and at best
wasting cycles.

A future patch will also add a Kconfig to force architcture to opt into
the callbacks to make it more difficult for uses "support" to sneak in in
the future.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20211111020738.2512932-6-seanjc@google.com
2021-11-17 14:49:07 +01:00

115 lines
2.8 KiB
C

// 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;
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;
fr.fp = regs->regs[4];
fr.lr = regs->lr;
walk_stackframe(&fr, entry);
}