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/esr.h> 12 #include <asm/ptrace.h> 13 14 static bool cpy_faulted_on_uaccess(const struct exception_table_entry *ex, 15 unsigned long esr) 16 { 17 bool uaccess_is_write = FIELD_GET(EX_DATA_UACCESS_WRITE, ex->data); 18 bool fault_on_write = esr & ESR_ELx_WNR; 19 20 return uaccess_is_write == fault_on_write; 21 } 22 23 bool insn_may_access_user(unsigned long addr, unsigned long esr) 24 { 25 const struct exception_table_entry *ex = search_exception_tables(addr); 26 27 if (!ex) 28 return false; 29 30 switch (ex->type) { 31 case EX_TYPE_UACCESS_CPY: 32 return cpy_faulted_on_uaccess(ex, esr); 33 default: 34 return true; 35 } 36 } 37 38 static inline unsigned long 39 get_ex_fixup(const struct exception_table_entry *ex) 40 { 41 return ((unsigned long)&ex->fixup + ex->fixup); 42 } 43 44 static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex, 45 struct pt_regs *regs) 46 { 47 int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data); 48 int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data); 49 50 pt_regs_write_reg(regs, reg_err, -EFAULT); 51 pt_regs_write_reg(regs, reg_zero, 0); 52 53 regs->pc = get_ex_fixup(ex); 54 return true; 55 } 56 57 static bool ex_handler_uaccess_cpy(const struct exception_table_entry *ex, 58 struct pt_regs *regs, unsigned long esr) 59 { 60 /* Do not fix up faults on kernel memory accesses */ 61 if (!cpy_faulted_on_uaccess(ex, esr)) 62 return false; 63 64 regs->pc = get_ex_fixup(ex); 65 return true; 66 } 67 68 static bool 69 ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, 70 struct pt_regs *regs) 71 { 72 int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->data); 73 int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data); 74 unsigned long data, addr, offset; 75 76 addr = pt_regs_read_reg(regs, reg_addr); 77 78 offset = addr & 0x7UL; 79 addr &= ~0x7UL; 80 81 data = *(unsigned long*)addr; 82 83 #ifndef __AARCH64EB__ 84 data >>= 8 * offset; 85 #else 86 data <<= 8 * offset; 87 #endif 88 89 pt_regs_write_reg(regs, reg_data, data); 90 91 regs->pc = get_ex_fixup(ex); 92 return true; 93 } 94 95 bool fixup_exception(struct pt_regs *regs, unsigned long esr) 96 { 97 const struct exception_table_entry *ex; 98 99 ex = search_exception_tables(instruction_pointer(regs)); 100 if (!ex) 101 return false; 102 103 switch (ex->type) { 104 case EX_TYPE_BPF: 105 return ex_handler_bpf(ex, regs); 106 case EX_TYPE_UACCESS_ERR_ZERO: 107 case EX_TYPE_KACCESS_ERR_ZERO: 108 return ex_handler_uaccess_err_zero(ex, regs); 109 case EX_TYPE_UACCESS_CPY: 110 return ex_handler_uaccess_cpy(ex, regs, esr); 111 case EX_TYPE_LOAD_UNALIGNED_ZEROPAD: 112 return ex_handler_load_unaligned_zeropad(ex, regs); 113 } 114 115 BUG(); 116 } 117