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 static inline unsigned long 14 get_ex_fixup(const struct exception_table_entry *ex) 15 { 16 return ((unsigned long)&ex->fixup + ex->fixup); 17 } 18 19 static bool ex_handler_fixup(const struct exception_table_entry *ex, 20 struct pt_regs *regs) 21 { 22 regs->pc = get_ex_fixup(ex); 23 return true; 24 } 25 26 static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex, 27 struct pt_regs *regs) 28 { 29 int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data); 30 int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data); 31 32 pt_regs_write_reg(regs, reg_err, -EFAULT); 33 pt_regs_write_reg(regs, reg_zero, 0); 34 35 regs->pc = get_ex_fixup(ex); 36 return true; 37 } 38 39 static bool 40 ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, 41 struct pt_regs *regs) 42 { 43 int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->type); 44 int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->type); 45 unsigned long data, addr, offset; 46 47 addr = pt_regs_read_reg(regs, reg_addr); 48 49 offset = addr & 0x7UL; 50 addr &= ~0x7UL; 51 52 data = *(unsigned long*)addr; 53 54 #ifndef __AARCH64EB__ 55 data >>= 8 * offset; 56 #else 57 data <<= 8 * offset; 58 #endif 59 60 pt_regs_write_reg(regs, reg_data, data); 61 62 regs->pc = get_ex_fixup(ex); 63 return true; 64 } 65 66 bool fixup_exception(struct pt_regs *regs) 67 { 68 const struct exception_table_entry *ex; 69 70 ex = search_exception_tables(instruction_pointer(regs)); 71 if (!ex) 72 return false; 73 74 switch (ex->type) { 75 case EX_TYPE_FIXUP: 76 return ex_handler_fixup(ex, regs); 77 case EX_TYPE_BPF: 78 return ex_handler_bpf(ex, regs); 79 case EX_TYPE_UACCESS_ERR_ZERO: 80 return ex_handler_uaccess_err_zero(ex, regs); 81 case EX_TYPE_LOAD_UNALIGNED_ZEROPAD: 82 return ex_handler_load_unaligned_zeropad(ex, regs); 83 } 84 85 BUG(); 86 } 87