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KVM: x86: do not fail if software breakpoint has already been removed 

If kvm_arch_remove_sw_breakpoint finds that a software breakpoint does not
have an INT3 instruction, it fails.  This can happen if one sets a
software breakpoint in a kernel module and then reloads it.  gdb then
thinks the breakpoint cannot be deleted and there is no way to add it
back.

Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2021-03-01 12:02:44 +01:00
parent e586edcb41
commit c6986f16a7
1 changed files with 7 additions and 2 deletions
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9
target/i386/kvm/kvm.c
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@ -4352,8 +4352,13 @@ int kvm_arch_remove_sw_breakpoint(CPUState *cs, struct kvm_sw_breakpoint *bp)
{
uint8_t int3;
if (cpu_memory_rw_debug(cs, bp->pc, &int3, 1, 0) || int3 != 0xcc ||
cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&bp->saved_insn, 1, 1)) {
if (cpu_memory_rw_debug(cs, bp->pc, &int3, 1, 0)) {
return -EINVAL;
}
if (int3 != 0xcc) {
return 0;
}
if (cpu_memory_rw_debug(cs, bp->pc, (uint8_t *)&bp->saved_insn, 1, 1)) {
return -EINVAL;
}
return 0;