[PATCH] Fix IFUNC symbols assembly mode.

[Roman Divacky]

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
+  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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