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 */
read_user_stack_slow(const void __user * ptr,void * buf,int nb)26 int 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
read_user_stack_64(const unsigned long __user * ptr,unsigned long * ret)47 static 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 */
55 struct 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
is_sigreturn_64_address(unsigned long nip,unsigned long fp)66 static 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 */
sane_signal_64_frame(unsigned long sp)80 static 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
perf_callchain_user_64(struct perf_callchain_entry_ctx * entry,struct pt_regs * regs)93 void 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