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 */ 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 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 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 */ 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 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