On 25/06/2018 19:35, Matthias Kaehlcke wrote:
> commit e2a5dca753d1cdc3212519023ed8a13e13f5495b
> Author: Borislav Petkov <bp@xxxxxxx>
> Date: Thu Nov 23 10:19:51 2017 +0100
>
> x86/umip: Fix insn_get_code_seg_params()'s return value
So this is the closest thing to a bug (it could have been a real bug
if the caller checked ret < 0 instead of ret == -EINVAL). *However*
the warning there is a bit misleading too.
The compiler does absolutely nothing to tell you that the return value
is in the [-EINVAL,132] range and therefore it should have been int.
_That_ would have been a useful warning. Instead, it says:
arch/x86/lib/insn-eval.c:780:10: warning: implicit conversion from 'int' to 'char'
changes value from 132 to -124 [-Wconstant-conversion]
return INSN_CODE_SEG_PARAMS(4, 8);
~~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~~~
./arch/x86/include/asm/insn-eval.h:16:57: note: expanded from macro 'INSN_CODE_SEG_PARAMS'
#define INSN_CODE_SEG_PARAMS(oper_sz, addr_sz) (oper_sz | (addr_sz << 4))
If you changed the return value from char to u8, you'd break the "return
-EINVAL;" case. The compiler would probably complain in turn that this
is not the right fix, by signaling a warning on "return -EINVAL;", but the
warning could really be done better.
Thanks,
Paolo
