static bool __kprobes aarch64_insn_is_steppable(u32 insn)
{
if (aarch64_get_insn_class(insn) == AARCH64_INSN_CLS_BR_SYS) {
if (aarch64_insn_is_branch(insn))
return false;
/* modification of daif creates issues */
if (aarch64_insn_is_daif_access(insn))
return false;
if (aarch64_insn_is_exception(insn))
return false;
if (aarch64_insn_is_hint(insn))
return aarch64_insn_is_nop(insn);
return true;
}
if (aarch64_insn_uses_literal(insn))
return false;
if (aarch64_insn_is_exclusive(insn))
return false;
return true;
}
static bool __kprobes __aarch64_insn_hotpatch_safe(u32 insn)
{
if (aarch64_get_insn_class(insn) != AARCH64_INSN_CLS_BR_SYS)
return false;
return aarch64_insn_is_b(insn) ||
aarch64_insn_is_bl(insn) ||
aarch64_insn_is_svc(insn) ||
aarch64_insn_is_hvc(insn) ||
aarch64_insn_is_smc(insn) ||
aarch64_insn_is_brk(insn) ||
aarch64_insn_is_nop(insn);
}
static bool __kprobes aarch64_insn_is_steppable(u32 insn)
{
/*
* Branch instructions will write a new value into the PC which is
* likely to be relative to the XOL address and therefore invalid.
* Deliberate generation of an exception during stepping is also not
* currently safe. Lastly, MSR instructions can do any number of nasty
* things we can't handle during single-stepping.
*/
if (aarch64_get_insn_class(insn) == AARCH64_INSN_CLS_BR_SYS) {
if (aarch64_insn_is_branch(insn) ||
aarch64_insn_is_msr_imm(insn) ||
aarch64_insn_is_msr_reg(insn) ||
aarch64_insn_is_exception(insn) ||
aarch64_insn_is_eret(insn))
return false;
/*
* The MRS instruction may not return a correct value when
* executing in the single-stepping environment. We do make one
* exception, for reading the DAIF bits.
*/
if (aarch64_insn_is_mrs(insn))
return aarch64_insn_extract_system_reg(insn)
!= AARCH64_INSN_SPCLREG_DAIF;
/*
* The HINT instruction is is problematic when single-stepping,
* except for the NOP case.
*/
if (aarch64_insn_is_hint(insn))
return aarch64_insn_is_nop(insn);
return true;
}
/*
* Instructions which load PC relative literals are not going to work
* when executed from an XOL slot. Instructions doing an exclusive
* load/store are not going to complete successfully when single-step
* exception handling happens in the middle of the sequence.
*/
if (aarch64_insn_uses_literal(insn) ||
aarch64_insn_is_exclusive(insn))
return false;
return true;
}