Update Error Message

[rdhindsa]

Summary

Updates error message for dynamic relocation attempt for read only segments.

[arichardson]

ELF/Relocations.cpp

818

I would not use line continuations here.

819

I think mentioning -z notext is very useful. It is hard to know from the current error message that the build error is due to differing default behaviours in bfd and lld.
However, this message is too long. I don't think we need to mention the default behaviour since the end of the sentence implies it. Also most users will not be invoking lld directly so maybe using -Wl,-z,notext in the message is better?

Maybe ... " in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output"?

[ruiu]

ELF/Relocations.cpp

818

Yes. I think your actual error message contains a lot of spaces between "relocations." and "Recompile object files..." because of the indentation of the next line. In general line continuation should be avoided. You can just write two string literals without any operator or anything to make compiler concatenate the two strings.

[ruiu]

test/ELF/aarch64-fpic-add_abs_lo12_nc.s

4

I think you need to update this test as well. (Your C++ code recommends -Wl,-z,notext but this error message mentions "-z notext".

[ruiu]

LGTM

[rdhindsa]

test/ELF/aarch64-fpic-add_abs_lo12_nc.s

4

Done! Sorry, I missed it earlier.

ELF/Relocations.cpp

if (!Config->Shared && Sym.isUndefWeak()) {
     Sec.Relocations.push_back({Expr, Type, Offset, Addend, &Sym});
     return Expr;
   }
 
   if (!CanWrite && (Config->Pic && !isRelExpr(Expr))) {
     error(
         "can't create dynamic relocation " + toString(Type) + " against " +
         (Sym.getName().empty() ? "local symbol" : "symbol: " + toString(Sym)) +
-        " in readonly segment; recompile object files with -fPIC" +
+        " in readonly segment; recompile object files with -fPIC "
+        "or pass '-Wl,-z,notext' to allow text relocations in the output" +
         getLocation(Sec, Sym, Offset));
     return Expr;
   }
 
   // Copy relocations are only possible if we are creating an executable.
   if (Config->Shared) {
     errorOrWarn("relocation " + toString(Type) +
                 " cannot be used against symbol " + toString(Sym) +
                 "; recompile with -fPIC" + getLocation(Sec, Sym, Offset));

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: can't create dynamic relocation R_AARCH64_ADD_ABS_LO12_NC against symbol: dat
+// CHECK: can't create dynamic relocation R_AARCH64_ADD_ABS_LO12_NC against symbol: dat in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // CHECK: >>> defined in {{.*}}.o
 // CHECK: >>> referenced by {{.*}}.o:(.text+0x0)
 
   add x0, x0, :lo12:dat
 .data
 .globl dat
 dat:
   .word 0

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: can't create dynamic relocation R_AARCH64_LDST32_ABS_LO12_NC against symbol: dat
+// CHECK: can't create dynamic relocation R_AARCH64_LDST32_ABS_LO12_NC against symbol: dat in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // CHECK: >>> defined in {{.*}}.o
 // CHECK: >>> referenced by {{.*}}.o:(.text+0x0)
 
   ldr s4, [x0, :lo12:dat]
 .data
 .globl dat
 dat:
   .word 0

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: can't create dynamic relocation R_AARCH64_LDST64_ABS_LO12_NC against symbol: dat
+// CHECK: can't create dynamic relocation R_AARCH64_LDST64_ABS_LO12_NC against symbol: dat in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // CHECK: >>> defined in {{.*}}.o
 // CHECK: >>> referenced by {{.*}}.o:(.text+0x0)
 
   ldr x0, [x0, :lo12:dat]
 .data
 .globl dat
 dat:
   .word 0

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: can't create dynamic relocation R_AARCH64_LDST8_ABS_LO12_NC against symbol: dat
+// CHECK: can't create dynamic relocation R_AARCH64_LDST8_ABS_LO12_NC against symbol: dat in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // CHECK: >>> defined in {{.*}}.o
 // CHECK: >>> referenced by {{.*}}.o:(.text+0x0)
 
   ldrsb x0, [x1, :lo12:dat]
 .data
 .globl dat
 dat:
   .word 0

test/ELF/arm-target1.s

 // Force generation of $d.0 as section is not all data
   nop
 // RELATIVE: Disassembly of section .text:
 // RELATIVE: $d.0:
 // RELATIVE:     1000:       04 00 00 00     .word   0x00000004
 // RELATIVE: SYMBOL TABLE:
 // RELATIVE: 00001004         .text           00000000 patatino
 
-// ABS: can't create dynamic relocation R_ARM_TARGET1 against symbol: patatino
+// ABS: can't create dynamic relocation R_ARM_TARGET1 against symbol: patatino in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // ABS: >>> defined in {{.*}}.o
 // ABS: >>> referenced by {{.*}}.o:(.text+0x0)

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
 
-// CHECK: can't create dynamic relocation R_X86_64_64 against symbol: foo in readonly segment
+// CHECK: can't create dynamic relocation R_X86_64_64 against symbol: foo in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // CHECK: >>> defined in {{.*}}.so
 // CHECK: >>> referenced by {{.*}}.o:(.text+0x0)
 
 .quad foo

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: can't create dynamic relocation R_X86_64_64 against symbol: bar
+// CHECK: can't create dynamic relocation R_X86_64_64 against symbol: bar in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // CHECK: >>> defined in {{.*}}.so
 // CHECK: >>> referenced by {{.*}}.o:(.text+0x0)
 
-// CHECK: can't create dynamic relocation R_X86_64_64 against symbol: foo
+// CHECK: can't create dynamic relocation R_X86_64_64 against symbol: foo in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // CHECK: >>> defined in {{.*}}.so
 // CHECK: >>> referenced by {{.*}}.o:(.text+0x8)
 
 .global _start
 _start:
         .quad bar
         .quad foo

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
 
-// CHECK:      can't create dynamic relocation R_X86_64_64 against local symbol in readonly segment; recompile object files with -fPIC
+// CHECK:      can't create dynamic relocation R_X86_64_64 against local symbol in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // CHECK-NEXT: >>> defined in {{.*}}.o
 // CHECK-NEXT: >>> referenced by {{.*}}.o:(.text+0x0)
 
 foo:
 .quad foo

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
 
-// CHECK: can't create dynamic relocation R_X86_64_64 against symbol: foo
+// CHECK: can't create dynamic relocation R_X86_64_64 against symbol: foo in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 // CHECK: >>> defined in {{.*}}.o
 // CHECK: >>> referenced by {{.*}}.o:(.eh_frame+0x12)
 
 .section bar,"axG",@progbits,foo,comdat
 .cfi_startproc
 .cfi_personality 0x8c, foo
 .cfi_endproc

test/ELF/got32-i386.s

 ## 73728 == 0x12000 == ADDR(.got)
 # CHECK:       _start:
 # CHECK-NEXT:   11001: 8b 1d {{.*}}  movl 73728, %ebx
 # CHECK: Sections:
 # CHECK:  Name Size     Address
 # CHECK:  .got 00000004 0000000000012000
 
 # RUN: not ld.lld %t.o -o %t -pie 2>&1 | FileCheck %s --check-prefix=ERR
-# ERR: error: can't create dynamic relocation R_386_GOT32 against symbol: foo in readonly segment; recompile object files with -fPIC
+# ERR: error: can't create dynamic relocation R_386_GOT32 against symbol: foo in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output

test/ELF/got32x-i386.s

 # CHECK-NEXT:   1100d: 8b 80 {{.*}} movl -4(%eax), %eax
 # CHECK-NEXT:   11013: 8b 83 {{.*}} movl -4(%ebx), %eax
 # CHECK: Sections:
 # CHECK:  Name Size     Address
 # CHECK:  .got 00000004 0000000000013000
 
 # RUN: not ld.lld %S/Inputs/i386-got32x-baseless.elf -o %t1 -pie 2>&1 | \
 # RUN:   FileCheck %s --check-prefix=ERR
-# ERR: error: can't create dynamic relocation R_386_GOT32X against symbol: foo in readonly segment; recompile object files with -fPIC
-# ERR: error: can't create dynamic relocation R_386_GOT32X against symbol: foo in readonly segment; recompile object files with -fPIC
+# ERR: error: can't create dynamic relocation R_386_GOT32X against symbol: foo in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
+# ERR: error: can't create dynamic relocation R_386_GOT32X against symbol: foo in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output

test/ELF/relocation-size-err.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
 
-// CHECK:  error: can't create dynamic relocation R_X86_64_SIZE64 against symbol: foo in readonly segment; recompile object files with -fPIC
+// CHECK:  error: can't create dynamic relocation R_X86_64_SIZE64 against symbol: foo in readonly segment; recompile object files with -fPIC or pass '-Wl,-z,notext' to allow text relocations in the output
 
         .global foo
 foo:
         .quad 42
         .size foo, 8
 
         .quad foo@SIZE