[binutils-gdb] PR32387 ppc64 TLS optimization bug with -fno-plt code

[Alan Modra]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=1686dc7079f1c03bdaffd2f779b92aa2b7ad97b5

commit 1686dc7079f1c03bdaffd2f779b92aa2b7ad97b5
Author: Alan Modra <amodra@gmail.com>
Date:   Tue Nov 26 08:24:19 2024 +1030

    PR32387 ppc64 TLS optimization bug with -fno-plt code
    
    The inline plt code emitted by gcc is incompatible with the
    linker/ld.so --tls-get-addr-optimize scheme.  This is the runtime
    optimisation where the first call to __tls_get_addr results in
    __tls_get_addr updating the tls_index pair, then the special linker
    stub using that to short-circuit second and subsequent calls for a
    given tls symbol.  Enabled by default when the linker sees
    __tls_get_addr_opt is preseent, and enabled in ld.so when DT_PPC64_OPT
    has PPC64_OPT_TLS set.  Note that this is distinct from link-time tls
    optimisation.
    
            PR 32387
            * elf64-ppc.c (ppc64_elf_check_relocs): Disable tls_get_addr_opt
            on detecting inline plt calls to __tls_get_addr.

Diff:
---
 bfd/elf64-ppc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/bfd/elf64-ppc.c b/bfd/elf64-ppc.c
index 9674fcdd6be..f7debc1edbc 100644
--- a/bfd/elf64-ppc.c
+++ b/bfd/elf64-ppc.c
@@ -4915,6 +4915,15 @@ ppc64_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
       tls_type = 0;
       switch (r_type)
 	{
+	case R_PPC64_PLTSEQ:
+	case R_PPC64_PLTSEQ_NOTOC:
+	  /* Inline plt call code emitted by gcc doesn't support
+	     modifying the tls_index words to short-circuit
+	     __tls_get_addr calls.  See PR32387.  */
+	  if (h != NULL && (h == tga || h == dottga))
+	    htab->params->tls_get_addr_opt = 0;
+	  break;
+
 	case R_PPC64_TLSGD:
 	case R_PPC64_TLSLD:
 	  /* These special tls relocs tie a call to __tls_get_addr with