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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, unsigned long regs, 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, 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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