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20380bb390
Function graph tracer modifies a return address (LR) in a stack frame to hook a function return. This will result in many useless entries (return_to_handler) showing up in a) a stack tracer's output b) perf call graph (with perf record -g) c) dump_backtrace (at panic et al.) For example, in case of a), $ echo function_graph > /sys/kernel/debug/tracing/current_tracer $ echo 1 > /proc/sys/kernel/stack_trace_enabled $ cat /sys/kernel/debug/tracing/stack_trace Depth Size Location (54 entries) ----- ---- -------- 0) 4504 16 gic_raise_softirq+0x28/0x150 1) 4488 80 smp_cross_call+0x38/0xb8 2) 4408 48 return_to_handler+0x0/0x40 3) 4360 32 return_to_handler+0x0/0x40 ... In case of b), $ echo function_graph > /sys/kernel/debug/tracing/current_tracer $ perf record -e mem:XXX:x -ag -- sleep 10 $ perf report ... | | |--0.22%-- 0x550f8 | | | 0x10888 | | | el0_svc_naked | | | sys_openat | | | return_to_handler | | | return_to_handler ... In case of c), $ echo function_graph > /sys/kernel/debug/tracing/current_tracer $ echo c > /proc/sysrq-trigger ... Call trace: [<ffffffc00044d3ac>] sysrq_handle_crash+0x24/0x30 [<ffffffc000092250>] return_to_handler+0x0/0x40 [<ffffffc000092250>] return_to_handler+0x0/0x40 ... This patch replaces such entries with real addresses preserved in current->ret_stack[] at unwind_frame(). This way, we can cover all the cases. Reviewed-by: Jungseok Lee <jungseoklee85@gmail.com> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> [will: fixed minor context changes conflicting with irq stack bits] Signed-off-by: Will Deacon <will.deacon@arm.com>
200 lines
5.0 KiB
C
200 lines
5.0 KiB
C
/*
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* arm64 callchain support
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*
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* Copyright (C) 2015 ARM Limited
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/perf_event.h>
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#include <linux/uaccess.h>
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#include <asm/stacktrace.h>
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struct frame_tail {
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struct frame_tail __user *fp;
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unsigned long lr;
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} __attribute__((packed));
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/*
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* Get the return address for a single stackframe and return a pointer to the
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* next frame tail.
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*/
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static struct frame_tail __user *
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user_backtrace(struct frame_tail __user *tail,
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struct perf_callchain_entry *entry)
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{
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struct frame_tail buftail;
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unsigned long err;
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/* Also check accessibility of one struct frame_tail beyond */
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if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
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return NULL;
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pagefault_disable();
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err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));
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pagefault_enable();
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if (err)
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return NULL;
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perf_callchain_store(entry, buftail.lr);
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/*
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* Frame pointers should strictly progress back up the stack
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* (towards higher addresses).
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*/
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if (tail >= buftail.fp)
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return NULL;
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return buftail.fp;
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}
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#ifdef CONFIG_COMPAT
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/*
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* The registers we're interested in are at the end of the variable
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* length saved register structure. The fp points at the end of this
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* structure so the address of this struct is:
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* (struct compat_frame_tail *)(xxx->fp)-1
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*
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* This code has been adapted from the ARM OProfile support.
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*/
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struct compat_frame_tail {
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compat_uptr_t fp; /* a (struct compat_frame_tail *) in compat mode */
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u32 sp;
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u32 lr;
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} __attribute__((packed));
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static struct compat_frame_tail __user *
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compat_user_backtrace(struct compat_frame_tail __user *tail,
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struct perf_callchain_entry *entry)
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{
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struct compat_frame_tail buftail;
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unsigned long err;
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/* Also check accessibility of one struct frame_tail beyond */
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if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
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return NULL;
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pagefault_disable();
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err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));
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pagefault_enable();
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if (err)
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return NULL;
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perf_callchain_store(entry, buftail.lr);
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/*
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* Frame pointers should strictly progress back up the stack
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* (towards higher addresses).
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*/
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if (tail + 1 >= (struct compat_frame_tail __user *)
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compat_ptr(buftail.fp))
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return NULL;
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return (struct compat_frame_tail __user *)compat_ptr(buftail.fp) - 1;
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}
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#endif /* CONFIG_COMPAT */
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void perf_callchain_user(struct perf_callchain_entry *entry,
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struct pt_regs *regs)
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{
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if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
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/* We don't support guest os callchain now */
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return;
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}
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perf_callchain_store(entry, regs->pc);
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if (!compat_user_mode(regs)) {
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/* AARCH64 mode */
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struct frame_tail __user *tail;
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tail = (struct frame_tail __user *)regs->regs[29];
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while (entry->nr < PERF_MAX_STACK_DEPTH &&
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tail && !((unsigned long)tail & 0xf))
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tail = user_backtrace(tail, entry);
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} else {
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#ifdef CONFIG_COMPAT
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/* AARCH32 compat mode */
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struct compat_frame_tail __user *tail;
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tail = (struct compat_frame_tail __user *)regs->compat_fp - 1;
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while ((entry->nr < PERF_MAX_STACK_DEPTH) &&
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tail && !((unsigned long)tail & 0x3))
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tail = compat_user_backtrace(tail, entry);
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#endif
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}
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}
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/*
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* Gets called by walk_stackframe() for every stackframe. This will be called
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* whist unwinding the stackframe and is like a subroutine return so we use
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* the PC.
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*/
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static int callchain_trace(struct stackframe *frame, void *data)
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{
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struct perf_callchain_entry *entry = data;
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perf_callchain_store(entry, frame->pc);
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return 0;
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}
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void perf_callchain_kernel(struct perf_callchain_entry *entry,
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struct pt_regs *regs)
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{
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struct stackframe frame;
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if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
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/* We don't support guest os callchain now */
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return;
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}
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frame.fp = regs->regs[29];
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frame.sp = regs->sp;
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frame.pc = regs->pc;
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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frame.graph = current->curr_ret_stack;
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#endif
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walk_stackframe(current, &frame, callchain_trace, entry);
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}
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unsigned long perf_instruction_pointer(struct pt_regs *regs)
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{
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if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
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return perf_guest_cbs->get_guest_ip();
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return instruction_pointer(regs);
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}
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unsigned long perf_misc_flags(struct pt_regs *regs)
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{
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int misc = 0;
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if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
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if (perf_guest_cbs->is_user_mode())
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misc |= PERF_RECORD_MISC_GUEST_USER;
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else
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misc |= PERF_RECORD_MISC_GUEST_KERNEL;
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} else {
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if (user_mode(regs))
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misc |= PERF_RECORD_MISC_USER;
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else
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misc |= PERF_RECORD_MISC_KERNEL;
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}
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return misc;
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}
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