[Bug binutils/18276] New: AArch64: readelf, gas do not support TLSLD relocations

[jingyuuiuc at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18276

            Bug ID: 18276
           Summary: AArch64: readelf, gas do not support TLSLD relocations
           Product: binutils
           Version: 2.26 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: jingyuuiuc at gmail dot com

Clang aarch64 backend generates some TLSLD relocations that readelf and gas do
not support.

For example,
$cat tlsld.c
extern int __thread v_ld1a __attribute__ ((tls_model("local-dynamic")));
extern int __thread v_ld1b __attribute__ ((tls_model("local-dynamic")));
int f_ld1 () { return v_ld1a + v_ld1b; }
void s (int i) { v_ld1a = v_ld1b = i; }
int main(int argc, char** argv) {
  s(argc);
  return f_ld1();
}

$ clang tlsld.c -fPIC -mllvm -aarch64-elf-ldtls-generation -c -o tlsld.o

readelf does not recognize some relocations.
$ readelf -r tlsld.o
...
00000000001c  000d00000210 unrecognized: 210     0000000000000000 v_ld1a + 0
000000000020  000d00000212 unrecognized: 212     0000000000000000 v_ld1a + 0
...
000000000044  000e00000210 unrecognized: 210     0000000000000000 v_ld1b + 0
000000000048  000e00000212 unrecognized: 212     0000000000000000 v_ld1b + 0
...

GAS does not support them either.
$ clang tlsld.c -fPIC -mllvm -aarch64-elf-ldtls-generation -S -o tlsld.s
$ gcc tlsld.s
tlsld.s: Assembler messages:
tlsld.s:16: Error: unknown relocation modifier at operand 3 -- `add
x0,x0,:dtprel_hi12:v_ld1a'
tlsld.s:17: Error: unknown relocation modifier at operand 3 -- `add
x0,x0,:dtprel_lo12_nc:v_ld1a'
tlsld.s:27: Error: unknown relocation modifier at operand 3 -- `add
x8,x0,:dtprel_hi12:v_ld1b'
tlsld.s:28: Error: unknown relocation modifier at operand 3 -- `add
x8,x8,:dtprel_lo12_nc:v_ld1b'
tlsld.s:56: Error: unknown relocation modifier at operand 3 -- `add
x0,x0,:dtprel_hi12:v_ld1b'
tlsld.s:57: Error: unknown relocation modifier at operand 3 -- `add
x0,x0,:dtprel_lo12_nc:v_ld1b'
tlsld.s:67: Error: unknown relocation modifier at operand 3 -- `add
x8,x0,:dtprel_hi12:v_ld1a'
tlsld.s:68: Error: unknown relocation modifier at operand 3 -- `add
x8,x8,:dtprel_lo12_nc:v_ld1a'

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