1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/compat.h> 3 #include <linux/errno.h> 4 #include <linux/kernel.h> 5 #include <linux/perf_event.h> 6 #include <linux/bug.h> 7 #include <linux/sched/task_stack.h> 8 9 #include <asm/perf_regs.h> 10 #include <asm/ptrace.h> 11 12 u64 perf_reg_value(struct pt_regs *regs, int idx) 13 { 14 if (WARN_ON_ONCE((u32)idx >= PERF_REG_ARM64_MAX)) 15 return 0; 16 17 /* 18 * Our handling of compat tasks (PERF_SAMPLE_REGS_ABI_32) is weird, but 19 * we're stuck with it for ABI compatibility reasons. 20 * 21 * For a 32-bit consumer inspecting a 32-bit task, then it will look at 22 * the first 16 registers (see arch/arm/include/uapi/asm/perf_regs.h). 23 * These correspond directly to a prefix of the registers saved in our 24 * 'struct pt_regs', with the exception of the PC, so we copy that down 25 * (x15 corresponds to SP_hyp in the architecture). 26 * 27 * So far, so good. 28 * 29 * The oddity arises when a 64-bit consumer looks at a 32-bit task and 30 * asks for registers beyond PERF_REG_ARM_MAX. In this case, we return 31 * SP_usr, LR_usr and PC in the positions where the AArch64 SP, LR and 32 * PC registers would normally live. The initial idea was to allow a 33 * 64-bit unwinder to unwind a 32-bit task and, although it's not clear 34 * how well that works in practice, somebody might be relying on it. 35 * 36 * At the time we make a sample, we don't know whether the consumer is 37 * 32-bit or 64-bit, so we have to cater for both possibilities. 38 */ 39 if (compat_user_mode(regs)) { 40 if ((u32)idx == PERF_REG_ARM64_SP) 41 return regs->compat_sp; 42 if ((u32)idx == PERF_REG_ARM64_LR) 43 return regs->compat_lr; 44 if (idx == 15) 45 return regs->pc; 46 } 47 48 if ((u32)idx == PERF_REG_ARM64_SP) 49 return regs->sp; 50 51 if ((u32)idx == PERF_REG_ARM64_PC) 52 return regs->pc; 53 54 return regs->regs[idx]; 55 } 56 57 #define REG_RESERVED (~((1ULL << PERF_REG_ARM64_MAX) - 1)) 58 59 int perf_reg_validate(u64 mask) 60 { 61 if (!mask || mask & REG_RESERVED) 62 return -EINVAL; 63 64 return 0; 65 } 66 67 u64 perf_reg_abi(struct task_struct *task) 68 { 69 if (is_compat_thread(task_thread_info(task))) 70 return PERF_SAMPLE_REGS_ABI_32; 71 else 72 return PERF_SAMPLE_REGS_ABI_64; 73 } 74 75 void perf_get_regs_user(struct perf_regs *regs_user, 76 struct pt_regs *regs) 77 { 78 regs_user->regs = task_pt_regs(current); 79 regs_user->abi = perf_reg_abi(current); 80 } 81