[ELF] - Inform user that we do not support relocations against text segment.

[grimar]

Summary

It was reported in PR28020, that lld does not link code which
gold do. But in fact that is expected behavior as we do not
support DT_TEXTREL.

This patch changes error message as it can report about relocations against
text segments exclusively, other dynamic relocations errors can
be handled separately.

[ruiu]

I don't think the error message is easy to understand as it now contains two types of errors. Can you separate them out?

[grimar]

• Updated error text.

[grimar]

In D21133#452235, @ruiu wrote:

I don't think the error message is easy to understand as it now contains two types of errors. Can you separate them out?

It looks that place can report about relocations against text segments exclusively,
other dynamic relocations errors can be handled separately (please see D21184)

[• rafael]

I think this is a nice improvement as some of the relocations (R_X86_64_64) *can* be used, just not on a read only segment.

lld/trunk/ELF/Relocations.cpp

static RelExpr adjustExpr(const elf::ObjectFile<ELFT> &File, SymbolBody &Body,
 
   if (IsWrite || isStaticLinkTimeConstant<ELFT>(Expr, Type, Body))
     return Expr;
 
   // This relocation would require the dynamic linker to write a value to read
   // only memory. We can hack around it if we are producing an executable and
   // the refered symbol can be preemepted to refer to the executable.
   if (Config->Shared || (Config->Pic && !isRelExpr(Expr))) {
-    error("relocation " + getRelName(Type) +
-          " cannot be used when making a shared object; recompile with -fPIC.");
+    error("can't create dynamic relocation " + getRelName(Type) +
+          " against readonly segment");
     return Expr;
   }
   if (Body.getVisibility() != STV_DEFAULT) {
     error("Cannot preempt symbol");
     return Expr;
   }
   if (Body.isObject()) {
     // Produce a copy relocation.

lld/trunk/test/ELF/aarch64-fpic-add_abs_lo12_nc.s

 // REQUIRES: aarch64
 // RUN: llvm-mc -filetype=obj -triple=aarch64-none-freebsd %s -o %t.o
 // RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
-// CHECK: relocation R_AARCH64_ADD_ABS_LO12_NC cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_AARCH64_ADD_ABS_LO12_NC against readonly segment
 
   add x0, x0, :lo12:dat
 .data
 .globl dat
 dat:
   .word 0

lld/trunk/test/ELF/aarch64-fpic-adr_prel_lo21.s

 // REQUIRES: aarch64
 // RUN: llvm-mc -filetype=obj -triple=aarch64-none-freebsd %s -o %t.o
 // RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
-// CHECK: relocation R_AARCH64_ADR_PREL_LO21 cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_AARCH64_ADR_PREL_LO21 against readonly segment
 
   adr x0, dat
 .data
 .globl dat
 dat:
   .word 0

lld/trunk/test/ELF/aarch64-fpic-adr_prel_pg_hi21.s

 // REQUIRES: aarch64
 // RUN: llvm-mc -filetype=obj -triple=aarch64-none-freebsd %s -o %t.o
 // RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
-// CHECK: relocation R_AARCH64_ADR_PREL_PG_HI21 cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_AARCH64_ADR_PREL_PG_HI21 against readonly segment
 
   adrp x0, dat
 .data
 .globl dat
 dat:
   .word 0

lld/trunk/test/ELF/aarch64-fpic-ldst32_abs_lo12_nc.s

 // REQUIRES: aarch64
 // RUN: llvm-mc -filetype=obj -triple=aarch64-none-freebsd %s -o %t.o
 // RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
-// CHECK: relocation R_AARCH64_LDST32_ABS_LO12_NC cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_AARCH64_LDST32_ABS_LO12_NC against readonly segment
 
   ldr s4, [x0, :lo12:dat]
 .data
 .globl dat
 dat:
   .word 0

lld/trunk/test/ELF/aarch64-fpic-ldst64_abs_lo12_nc.s

 // REQUIRES: aarch64
 // RUN: llvm-mc -filetype=obj -triple=aarch64-none-freebsd %s -o %t.o
 // RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
-// CHECK: relocation R_AARCH64_LDST64_ABS_LO12_NC cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_AARCH64_LDST64_ABS_LO12_NC against readonly segment
 
   ldr x0, [x0, :lo12:dat]
 .data
 .globl dat
 dat:
   .word 0

lld/trunk/test/ELF/aarch64-fpic-ldst8_abs_lo12_nc.s

 // REQUIRES: aarch64
 // RUN: llvm-mc -filetype=obj -triple=aarch64-none-freebsd %s -o %t.o
 // RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
-// CHECK: relocation R_AARCH64_LDST8_ABS_LO12_NC cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_AARCH64_LDST8_ABS_LO12_NC against readonly segment
 
   ldrsb x0, [x1, :lo12:dat]
 .data
 .globl dat
 dat:
   .word 0

lld/trunk/test/ELF/copy-in-shared.s

 // REQUIRES: x86
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/copy-in-shared.s -o %t1.o
 // RUN: ld.lld -shared %t1.o -o %t1.so
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t2.o
 // RUN: not ld.lld %t2.o %t1.so -o %t2.so -shared 2>&1 | FileCheck %s
 
 
 .quad foo
 
-// CHECK: relocation R_X86_64_64 cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_X86_64_64 against readonly segment

lld/trunk/test/ELF/copy-rel-pie-error.s

 // RUN: llvm-mc %s -o %t.o -filetype=obj -triple=x86_64-pc-linux
 // RUN: llvm-mc %p/Inputs/copy-rel-pie.s -o %t2.o -filetype=obj -triple=x86_64-pc-linux
 // RUN: ld.lld %t2.o -o %t2.so -shared
 // RUN: not ld.lld %t.o %t2.so -o %t.exe -pie 2>&1 | FileCheck %s
 
-// CHECK: relocation R_X86_64_64 cannot be used when making a shared object; recompile with -fPIC.
-// CHECK: relocation R_X86_64_64 cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_X86_64_64 against readonly segment
+// CHECK: can't create dynamic relocation R_X86_64_64 against readonly segment
 
 .global _start
 _start:
         .quad bar
         .quad foo

lld/trunk/test/ELF/dynamic-reloc-in-ro.s

 // REQUIRES: x86
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 // RUN: not ld.lld %t.o -o %t.so -shared 2>&1 | FileCheck %s
 
 foo:
 .quad foo
 
-// CHECK: relocation R_X86_64_64 cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_X86_64_64 against readonly segment

lld/trunk/test/ELF/eh-frame-dyn-rel.s

 // REQUIRES: x86
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 // RUN: not ld.lld %t.o %t.o -o %t -shared 2>&1 | FileCheck %s
 
         .section        bar,"axG",@progbits,foo,comdat
         .cfi_startproc
         .cfi_personality 0x8c, foo
         .cfi_endproc
 
-// CHECK: relocation R_X86_64_64 cannot be used when making a shared object; recompile with -fPIC.
+// CHECK: can't create dynamic relocation R_X86_64_64 against readonly segment

lld/trunk/test/ELF/x86-64-reloc-32-fpic.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
 # RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
-# CHECK: relocation R_X86_64_32 cannot be used when making a shared object; recompile with -fPIC.
+# CHECK: can't create dynamic relocation R_X86_64_32 against readonly segment
 
 .long _shared

lld/trunk/test/ELF/x86-64-reloc-pc32-fpic.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
 # RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
-# CHECK: relocation R_X86_64_PC32 cannot be used when making a shared object; recompile with -fPIC.
+# CHECK: can't create dynamic relocation R_X86_64_PC32 against readonly segment
 
 call _shared