[PATCH] Fix IFUNC symbols assembly mode.

[Rafael Espíndola]

On 6 January 2014 13:50, Roman Divacky <rdivacky at freebsd.org> wrote:
> Actually, the merging rules are not so simple, this is my attempt to simulate
> what gnu as is doing:
>
> Index: lib/MC/ELFObjectWriter.cpp
> ===================================================================
> --- lib/MC/ELFObjectWriter.cpp  (revision 198593)
> +++ lib/MC/ELFObjectWriter.cpp  (working copy)
> @@ -546,6 +546,35 @@
>    // Binding and Type share the same byte as upper and lower nibbles
>    uint8_t Binding = MCELF::GetBinding(OrigData);
>    uint8_t Type = MCELF::GetType(Data);
> +
> +  // Propagation rules:
> +  // IFUNC > FUNC > OBJECT > NOTYPE
> +  // TLS_OBJECT > OBJECT > NOTYPE
> +  //
> +  // dont let the new type degrade the old type

These need tests. Can IFUNC or FUNC show up in a comparison with
TLS_OBJECT?  Please try to refactor this into a pair of functions like

unsigned getTypePreference(uint8_t Type) {....}
bool compareTypes(uint8_t TypeA, uint8_t TypeB) { return
getTypePreference(TypeA) > getTypePreference(TypeB); }


> +  switch (MCELF::GetType(OrigData)) {
> +  default:
> +    break;
> +  case ELF::STT_GNU_IFUNC:
> +    if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
> +        Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
> +      Type = ELF::STT_GNU_IFUNC;
> +    break;
> +  case ELF::STT_FUNC:
> +    if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
> +        Type == ELF::STT_TLS)
> +      Type = ELF::STT_FUNC;
> +    break;
> +  case ELF::STT_OBJECT:
> +    if (Type == ELF::STT_NOTYPE)
> +      Type = ELF::STT_OBJECT;
> +    break;
> +  case ELF::STT_TLS:
> +    if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
> +        Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
> +      Type = ELF::STT_TLS;
> +    break;
> +  }
>    uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
>
>    // Other and Visibility share the same byte with Visibility using the lower
>
>
> On Sat, Jan 04, 2014 at 03:49:28PM +0100, Roman Divacky wrote:
>> Hi,
>>
>> .globl  memcpy
>> .type   memcpy, @gnu_indirect_function
>> .set    memcpy,resolve_memcpy
>>
>> is currently misassembled (the memcpy is of type STT_FUNC instead of
>> STT_GNU_IFUNC).
>>
>> This patch fixes it:
>>
>> Index: lib/MC/ELFObjectWriter.cpp
>> ===================================================================
>> --- lib/MC/ELFObjectWriter.cpp  (revision 198480)
>> +++ lib/MC/ELFObjectWriter.cpp  (working copy)
>> @@ -546,6 +546,9 @@
>>    // Binding and Type share the same byte as upper and lower nibbles
>>    uint8_t Binding = MCELF::GetBinding(OrigData);
>>    uint8_t Type = MCELF::GetType(Data);
>> +  // Keep IFUNC type.
>> +  if (Type == ELF::STT_FUNC && MCELF::GetType(OrigData) == ELF::STT_GNU_IFUNC)
>> +    Type = ELF::STT_GNU_IFUNC;
>>    uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
>>
>>    // Other and Visibility share the same byte with Visibility using the lower
>> Index: test/MC/ELF/type.s
>> ===================================================================
>> --- test/MC/ELF/type.s  (revision 198480)
>> +++ test/MC/ELF/type.s  (working copy)
>> @@ -22,9 +22,9 @@
>>          .type func, at function
>>          .type func, at object
>>
>> -ifunc:
>>          .global ifunc
>>          .type ifunc, at gnu_indirect_function
>> +        .set ifunc,func
>>
>>  tls:
>>          .global tls
>>
>> I track this in #18372. Is the patch ok to commit?
>>
>> Roman
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