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
21/*
22 * On 64-bit we don't want to invoke hash_page on user addresses from
23 * interrupt context, so if the access faults, we read the page tables
24 * to find which page (if any) is mapped and access it directly.
25 */
26int read_user_stack_slow(const void __user *ptr, void *buf, int nb)
27{
28
29	unsigned long addr = (unsigned long) ptr;
30	unsigned long offset;
31	struct page *page;
32	void *kaddr;
33
34	if (get_user_page_fast_only(addr, FOLL_WRITE, &page)) {
35		kaddr = page_address(page);
36
37		/* align address to page boundary */
38		offset = addr & ~PAGE_MASK;
39
40		memcpy(buf, kaddr + offset, nb);
41		put_page(page);
42		return 0;
43	}
44	return -EFAULT;
45}
46
47static int read_user_stack_64(const unsigned long __user *ptr, unsigned long *ret)
48{
49	return __read_user_stack(ptr, ret, sizeof(*ret));
50}
51
52/*
53 * 64-bit user processes use the same stack frame for RT and non-RT signals.
54 */
55struct signal_frame_64 {
56	char		dummy[__SIGNAL_FRAMESIZE];
57	struct ucontext	uc;
58	unsigned long	unused[2];
59	unsigned int	tramp[6];
60	struct siginfo	*pinfo;
61	void		*puc;
62	struct siginfo	info;
63	char		abigap[288];
64};
65
66static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
67{
68	if (nip == fp + offsetof(struct signal_frame_64, tramp))
69		return 1;
70	if (vdso64_rt_sigtramp && current->mm->context.vdso_base &&
71	    nip == current->mm->context.vdso_base + vdso64_rt_sigtramp)
72		return 1;
73	return 0;
74}
75
76/*
77 * Do some sanity checking on the signal frame pointed to by sp.
78 * We check the pinfo and puc pointers in the frame.
79 */
80static int sane_signal_64_frame(unsigned long sp)
81{
82	struct signal_frame_64 __user *sf;
83	unsigned long pinfo, puc;
84
85	sf = (struct signal_frame_64 __user *) sp;
86	if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
87	    read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
88		return 0;
89	return pinfo == (unsigned long) &sf->info &&
90		puc == (unsigned long) &sf->uc;
91}
92
93void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
94			    struct pt_regs *regs)
95{
96	unsigned long sp, next_sp;
97	unsigned long next_ip;
98	unsigned long lr;
99	long level = 0;
100	struct signal_frame_64 __user *sigframe;
101	unsigned long __user *fp, *uregs;
102
103	next_ip = perf_instruction_pointer(regs);
104	lr = regs->link;
105	sp = regs->gpr[1];
106	perf_callchain_store(entry, next_ip);
107
108	while (entry->nr < entry->max_stack) {
109		fp = (unsigned long __user *) sp;
110		if (invalid_user_sp(sp) || read_user_stack_64(fp, &next_sp))
111			return;
112		if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
113			return;
114
115		/*
116		 * Note: the next_sp - sp >= signal frame size check
117		 * is true when next_sp < sp, which can happen when
118		 * transitioning from an alternate signal stack to the
119		 * normal stack.
120		 */
121		if (next_sp - sp >= sizeof(struct signal_frame_64) &&
122		    (is_sigreturn_64_address(next_ip, sp) ||
123		     (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
124		    sane_signal_64_frame(sp)) {
125			/*
126			 * This looks like an signal frame
127			 */
128			sigframe = (struct signal_frame_64 __user *) sp;
129			uregs = sigframe->uc.uc_mcontext.gp_regs;
130			if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
131			    read_user_stack_64(&uregs[PT_LNK], &lr) ||
132			    read_user_stack_64(&uregs[PT_R1], &sp))
133				return;
134			level = 0;
135			perf_callchain_store_context(entry, PERF_CONTEXT_USER);
136			perf_callchain_store(entry, next_ip);
137			continue;
138		}
139
140		if (level == 0)
141			next_ip = lr;
142		perf_callchain_store(entry, next_ip);
143		++level;
144		sp = next_sp;
145	}
146}
147