1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Performance counter callchain support - powerpc architecture code
4 *
5 * Copyright �� 2009 Paul Mackerras, IBM Corporation.
6 */
7#include <linux/kernel.h>
8#include <linux/sched.h>
9#include <linux/perf_event.h>
10#include <linux/percpu.h>
11#include <linux/uaccess.h>
12#include <linux/mm.h>
13#include <asm/ptrace.h>
14#include <asm/sigcontext.h>
15#include <asm/ucontext.h>
16#include <asm/vdso.h>
17#include <asm/pte-walk.h>
18
19#include "callchain.h"
20
21static int read_user_stack_64(const unsigned long __user *ptr, unsigned long *ret)
22{
23	return __read_user_stack(ptr, ret, sizeof(*ret));
24}
25
26/*
27 * 64-bit user processes use the same stack frame for RT and non-RT signals.
28 */
29struct signal_frame_64 {
30	char		dummy[__SIGNAL_FRAMESIZE];
31	struct ucontext	uc;
32	unsigned long	unused[2];
33	unsigned int	tramp[6];
34	struct siginfo	*pinfo;
35	void		*puc;
36	struct siginfo	info;
37	char		abigap[288];
38};
39
40static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
41{
42	if (nip == fp + offsetof(struct signal_frame_64, tramp))
43		return 1;
44	if (current->mm->context.vdso &&
45	    nip == VDSO64_SYMBOL(current->mm->context.vdso, sigtramp_rt64))
46		return 1;
47	return 0;
48}
49
50/*
51 * Do some sanity checking on the signal frame pointed to by sp.
52 * We check the pinfo and puc pointers in the frame.
53 */
54static int sane_signal_64_frame(unsigned long sp)
55{
56	struct signal_frame_64 __user *sf;
57	unsigned long pinfo, puc;
58
59	sf = (struct signal_frame_64 __user *) sp;
60	if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
61	    read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
62		return 0;
63	return pinfo == (unsigned long) &sf->info &&
64		puc == (unsigned long) &sf->uc;
65}
66
67void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
68			    struct pt_regs *regs)
69{
70	unsigned long sp, next_sp;
71	unsigned long next_ip;
72	unsigned long lr;
73	long level = 0;
74	struct signal_frame_64 __user *sigframe;
75	unsigned long __user *fp, *uregs;
76
77	next_ip = perf_instruction_pointer(regs);
78	lr = regs->link;
79	sp = regs->gpr[1];
80	perf_callchain_store(entry, next_ip);
81
82	while (entry->nr < entry->max_stack) {
83		fp = (unsigned long __user *) sp;
84		if (invalid_user_sp(sp) || read_user_stack_64(fp, &next_sp))
85			return;
86		if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
87			return;
88
89		/*
90		 * Note: the next_sp - sp >= signal frame size check
91		 * is true when next_sp < sp, which can happen when
92		 * transitioning from an alternate signal stack to the
93		 * normal stack.
94		 */
95		if (next_sp - sp >= sizeof(struct signal_frame_64) &&
96		    (is_sigreturn_64_address(next_ip, sp) ||
97		     (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
98		    sane_signal_64_frame(sp)) {
99			/*
100			 * This looks like an signal frame
101			 */
102			sigframe = (struct signal_frame_64 __user *) sp;
103			uregs = sigframe->uc.uc_mcontext.gp_regs;
104			if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
105			    read_user_stack_64(&uregs[PT_LNK], &lr) ||
106			    read_user_stack_64(&uregs[PT_R1], &sp))
107				return;
108			level = 0;
109			perf_callchain_store_context(entry, PERF_CONTEXT_USER);
110			perf_callchain_store(entry, next_ip);
111			continue;
112		}
113
114		if (level == 0)
115			next_ip = lr;
116		perf_callchain_store(entry, next_ip);
117		++level;
118		sp = next_sp;
119	}
120}
121