1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Based on arch/arm/mm/extable.c 4 */ 5 6 #include <linux/bitfield.h> 7 #include <linux/extable.h> 8 #include <linux/uaccess.h> 9 10 #include <asm/asm-extable.h> 11 #include <asm/ptrace.h> 12 13 typedef bool (*ex_handler_t)(const struct exception_table_entry *, 14 struct pt_regs *); 15 16 static inline unsigned long 17 get_ex_fixup(const struct exception_table_entry *ex) 18 { 19 return ((unsigned long)&ex->fixup + ex->fixup); 20 } 21 22 static bool ex_handler_fixup(const struct exception_table_entry *ex, 23 struct pt_regs *regs) 24 { 25 regs->pc = get_ex_fixup(ex); 26 return true; 27 } 28 29 static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex, 30 struct pt_regs *regs) 31 { 32 int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data); 33 int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data); 34 35 pt_regs_write_reg(regs, reg_err, -EFAULT); 36 pt_regs_write_reg(regs, reg_zero, 0); 37 38 regs->pc = get_ex_fixup(ex); 39 return true; 40 } 41 42 static bool 43 ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, 44 struct pt_regs *regs) 45 { 46 int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->type); 47 int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->type); 48 unsigned long data, addr, offset; 49 50 addr = pt_regs_read_reg(regs, reg_addr); 51 52 offset = addr & 0x7UL; 53 addr &= ~0x7UL; 54 55 data = *(unsigned long*)addr; 56 57 #ifndef __AARCH64EB__ 58 data >>= 8 * offset; 59 #else 60 data <<= 8 * offset; 61 #endif 62 63 pt_regs_write_reg(regs, reg_data, data); 64 65 regs->pc = get_ex_fixup(ex); 66 return true; 67 } 68 69 bool fixup_exception(struct pt_regs *regs) 70 { 71 const struct exception_table_entry *ex; 72 73 ex = search_exception_tables(instruction_pointer(regs)); 74 if (!ex) 75 return false; 76 77 switch (ex->type) { 78 case EX_TYPE_FIXUP: 79 return ex_handler_fixup(ex, regs); 80 case EX_TYPE_BPF: 81 return ex_handler_bpf(ex, regs); 82 case EX_TYPE_UACCESS_ERR_ZERO: 83 return ex_handler_uaccess_err_zero(ex, regs); 84 case EX_TYPE_LOAD_UNALIGNED_ZEROPAD: 85 return ex_handler_load_unaligned_zeropad(ex, regs); 86 } 87 88 BUG(); 89 } 90