1 files changed, 104 insertions, 6 deletions

diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
index 81e694af5f8c..6e0528831cd3 100644
--- a/arch/arm64/mm/extable.c
+++ b/arch/arm64/mm/extable.c
@@ -3,16 +3,114 @@
  * Based on arch/arm/mm/extable.c
  */
 
+#include <linux/bitfield.h>
 #include <linux/extable.h>
 #include <linux/uaccess.h>
 
-int fixup_exception(struct pt_regs *regs)
+#include <asm/asm-extable.h>
+#include <asm/esr.h>
+#include <asm/ptrace.h>
+
+static bool cpy_faulted_on_uaccess(const struct exception_table_entry *ex,
+				   unsigned long esr)
+{
+	bool uaccess_is_write = FIELD_GET(EX_DATA_UACCESS_WRITE, ex->data);
+	bool fault_on_write = esr & ESR_ELx_WNR;
+
+	return uaccess_is_write == fault_on_write;
+}
+
+bool insn_may_access_user(unsigned long addr, unsigned long esr)
+{
+	const struct exception_table_entry *ex = search_exception_tables(addr);
+
+	if (!ex)
+		return false;
+
+	switch (ex->type) {
+	case EX_TYPE_UACCESS_CPY:
+		return cpy_faulted_on_uaccess(ex, esr);
+	default:
+		return true;
+	}
+}
+
+static inline unsigned long
+get_ex_fixup(const struct exception_table_entry *ex)
+{
+	return ((unsigned long)&ex->fixup + ex->fixup);
+}
+
+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_uaccess_cpy(const struct exception_table_entry *ex,
+				   struct pt_regs *regs, unsigned long esr)
+{
+	/* Do not fix up faults on kernel memory accesses */
+	if (!cpy_faulted_on_uaccess(ex, esr))
+		return false;
+
+	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->data);
+	int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data);
+	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, unsigned long esr)
 {
-	const struct exception_table_entry *fixup;
+	const struct exception_table_entry *ex;
+
+	ex = search_exception_tables(instruction_pointer(regs));
+	if (!ex)
+		return false;
 
-	fixup = search_exception_tables(instruction_pointer(regs));
-	if (fixup)
-		regs->pc = (unsigned long)&fixup->fixup + fixup->fixup;
+	switch (ex->type) {
+	case EX_TYPE_BPF:
+		return ex_handler_bpf(ex, regs);
+	case EX_TYPE_UACCESS_ERR_ZERO:
+	case EX_TYPE_KACCESS_ERR_ZERO:
+		return ex_handler_uaccess_err_zero(ex, regs);
+	case EX_TYPE_UACCESS_CPY:
+		return ex_handler_uaccess_cpy(ex, regs, esr);
+	case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
+		return ex_handler_load_unaligned_zeropad(ex, regs);
+	}
 
-	return fixup != NULL;
+	BUG();
 }