From 7136836e14e5286afe74a354c289601375bd472d Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 17 Oct 2018 22:28:51 -0400 Subject: document and make explicit desired noinline property for __init_libc on multiple occasions I've started to flatten/inline the code in __init_libc, only to rediscover the reason it was not inlined: GCC fails to deallocate its stack (and now, with the changes in commit 4390383b32250a941ec616e8bff6f568a801b1c0, fails to produce a tail call to the stage 2 function; see PR #87639) before calling main if it was inlined. document this with a comment and use an explicit noinline attribute if __GNUC__ is defined so that even with CFLAGS that heavily favor inlining it won't get inlined. --- src/env/__libc_start_main.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'src/env') diff --git a/src/env/__libc_start_main.c b/src/env/__libc_start_main.c index ba4d2135..2e5f9dcb 100644 --- a/src/env/__libc_start_main.c +++ b/src/env/__libc_start_main.c @@ -17,6 +17,9 @@ weak_alias(dummy1, __init_ssp); #define AUX_CNT 38 +#ifdef __GNUC__ +__attribute__((__noinline__)) +#endif void __init_libc(char **envp, char *pn) { size_t i, *auxv, aux[AUX_CNT] = { 0 }; @@ -69,6 +72,9 @@ int __libc_start_main(int (*main)(int,char **,char **), int argc, char **argv) { char **envp = argv+argc+1; + /* External linkage, and explicit noinline attribute if available, + * are used to prevent the stack frame used during init from + * persisting for the entire process lifetime. */ __init_libc(envp, argv[0]); /* Barrier against hoisting application code or anything using ssp -- cgit v1.2.1