From c5547c14990823b041ccdd5e2f671817e8347d89 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Cl=C3=A9ment=20Chigot?= Date: Wed, 11 Aug 2021 10:07:39 +0200 Subject: [PATCH] aix: force reference to __tls_get_addr when needed 64bit XCOFF files will generated TLS access, with local-exec or global-exec models, by an access to R13. Thus, there isn't any reference to a TLS symbol. The problem is that it allows programs with TLS to be compiled and linked even without -pthread. Most of the time, it will result in a segfault when trying to access a TLS variable. But sometimes, it might create a memory corruption. This patch forces a reference to __tls_get_addr() to ensure link will fail without -pthread. --- gcc/config/rs6000/rs6000.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c index 2de5a96e1b6..cdb34feddbd 100644 @@ -117,6 +117,12 @@ int dot_symbols; of this machine mode. */ scalar_int_mode rs6000_pmode; +/* Programs with __thread might be able to link in 64bit on AIX, + even without -pthread when exec models are used. + In order to avoid that, a .ref to __tls_get_addr must be + added. */ +static bool xcoff_tls_exec_model_detected = false; + /* Width in bits of a pointer. */ unsigned rs6000_pointer_size; @@ -9422,7 +9428,10 @@ rs6000_legitimize_tls_address_aix (rtx a emit_insn (gen_tls_get_tpointer (tlsreg)); } else - tlsreg = gen_rtx_REG (DImode, 13); + { + xcoff_tls_exec_model_detected = true; + tlsreg = gen_rtx_REG (DImode, 13); + } /* Load the TOC value into temporary register. */ tmpreg = gen_reg_rtx (Pmode); @@ -21237,6 +21246,12 @@ rs6000_xcoff_file_end (void) { switch_to_section (text_section); fputs ("_section_.text:\n", asm_out_file); + if (xcoff_tls_exec_model_detected) + { + /* Add a .ref to __tls_get_addr to ensure that link + fails if -pthread is provided. */ + fputs ("\t.ref __tls_get_addr\n", asm_out_file); + } switch_to_section (data_section); fputs (TARGET_32BIT ? "\t.long _section_.text\n" : "\t.llong _section_.text\n", 2.31.1