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// SPDX-License-Identifier: GPL-2.0
/*
* Based on arch/arm/mm/extable.c
*/
#include <linux/bitfield.h>
#include <linux/extable.h>
#include <linux/uaccess.h>
#include <asm/asm-extable.h>
#include <asm/ptrace.h>
typedef bool (*ex_handler_t)(const struct exception_table_entry *,
struct pt_regs *);
static inline unsigned long
get_ex_fixup(const struct exception_table_entry *ex)
{
return ((unsigned long)&ex->fixup + ex->fixup);
}
static bool ex_handler_fixup(const struct exception_table_entry *ex,
struct pt_regs *regs)
{
regs->pc = get_ex_fixup(ex);
return true;
}
static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
struct pt_regs *regs)
{
int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
pt_regs_write_reg(regs, reg_err, -EFAULT);
pt_regs_write_reg(regs, reg_zero, 0);
regs->pc = get_ex_fixup(ex);
return true;
}
static bool
ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex,
struct pt_regs *regs)
{
int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->type);
int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->type);
unsigned long data, addr, offset;
addr = pt_regs_read_reg(regs, reg_addr);
offset = addr & 0x7UL;
addr &= ~0x7UL;
data = *(unsigned long*)addr;
#ifndef __AARCH64EB__
data >>= 8 * offset;
#else
data <<= 8 * offset;
#endif
pt_regs_write_reg(regs, reg_data, data);
regs->pc = get_ex_fixup(ex);
return true;
}
bool fixup_exception(struct pt_regs *regs)
{
const struct exception_table_entry *ex;
ex = search_exception_tables(instruction_pointer(regs));
if (!ex)
return false;
switch (ex->type) {
case EX_TYPE_FIXUP:
return ex_handler_fixup(ex, regs);
case EX_TYPE_BPF:
return ex_handler_bpf(ex, regs);
case EX_TYPE_UACCESS_ERR_ZERO:
return ex_handler_uaccess_err_zero(ex, regs);
case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
return ex_handler_load_unaligned_zeropad(ex, regs);
}
BUG();
}
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