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