From 03eabfe65e1e2c36f4d26c78a730fa19a3bdada3 Mon Sep 17 00:00:00 2001 From: David 'Digit' Turner Date: Thu, 28 May 2009 15:54:03 +0200 Subject: Fix the C library initialization to avoid calling static C++ constructors twice. The problem was due to the fact that, in the case of dynamic executables, the dynamic linker calls the DT_PREINIT_ARRAY, DT_INIT and DT_INIT_ARRAY constructors when loading shared libraries and dynamic executables, *before* calling the executable's entry point (i.e. arch-$ARCH/bionic/crtbegin_dynamic.c) which in turns call __libc_init() in libc.so, as defined by bionic/libc_init_dynamic.c The latter did call these constructors array again, mistakenly. The patch also updates the documentation of many related functions. Also adds a new section to linker/README.TXT explaining restrictions on C library usage. The patch has been tested on a Dream for stability issues with proprietary blobs: - H264 decoding works - Camera + Video recording works - GPS works - Sensors work The tests in system/extra/tests/bionic/libc/common/test_static_cpp_mutex.cpp has been run and shows the static C++ constructor being called only once. --- libc/arch-x86/bionic/crtbegin_dynamic.S | 24 +++++++++++++++++------- libc/arch-x86/bionic/crtbegin_static.S | 24 +++++++++++++----------- 2 files changed, 30 insertions(+), 18 deletions(-) (limited to 'libc/arch-x86/bionic') diff --git a/libc/arch-x86/bionic/crtbegin_dynamic.S b/libc/arch-x86/bionic/crtbegin_dynamic.S index 3b47b18..b013641 100644 --- a/libc/arch-x86/bionic/crtbegin_dynamic.S +++ b/libc/arch-x86/bionic/crtbegin_dynamic.S @@ -29,25 +29,35 @@ .type _start, @function .globl _start -# this is the small startup code that is first run when -# any executable that is statically-linked with Bionic -# runs. +# This is the small startup code that is called from +# the dynamic linker to execute an executable once all +# dependent shared libraries have been loaded and +# initialized. # -# it's purpose is to call __libc_init with appropriate +# It's purpose is to call __libc_init as defined in +# bionic/libc_init_dynamic.c with appropriate # arguments, which are: # # - the address of the raw data block setup by the Linux # kernel ELF loader # -# - address of an "onexit" function, not used on any -# platform supported by Bionic +# - address of an "onexit" function (not used on any +# platform supported by Bionic) # # - address of the "main" function of the program. We # can't hard-code it in the adr pseudo instruction # so we use a tiny trampoline that will get relocated # by the dynamic linker before this code runs # -# - address of the constructor list +# - address of the constructors table, i.e. a table +# that points to various initialization and +# finalization sections for the program. +# +# NOTE: This code is currently placed in shared libraries +# by the build system, but will be ignored. +# +# On the other hand, the arrays defined below are +# required and will be parsed by the dynamic linker. # _start: mov %esp, %eax diff --git a/libc/arch-x86/bionic/crtbegin_static.S b/libc/arch-x86/bionic/crtbegin_static.S index eb4acee..a6c9ebf 100644 --- a/libc/arch-x86/bionic/crtbegin_static.S +++ b/libc/arch-x86/bionic/crtbegin_static.S @@ -29,25 +29,27 @@ .type _start, @function .globl _start -# this is the small startup code that is first run when -# any executable that is statically-linked with Bionic -# runs. +# This is the small startup code that is first run when +# any static executable runs. A static executable is one +# that is started directly by the Linux kernel, not from +# the dynamic linker, it thus cannot depend on any shared +# library. # -# it's purpose is to call __libc_init with appropriate +# It's purpose is to call __libc_init as defined in +# bionic/libc_init_static.c with appropriate # arguments, which are: # # - the address of the raw data block setup by the Linux # kernel ELF loader # -# - address of an "onexit" function, not used on any -# platform supported by Bionic +# - address of an "onexit" function (not used on any +# platform supported by Bionic). # -# - address of the "main" function of the program. We -# can't hard-code it in the adr pseudo instruction -# so we use a tiny trampoline that will get relocated -# by the dynamic linker before this code runs +# - address of the "main" function of the program. # -# - address of the constructor list +# - address of the constructors table, i.e. a table +# that points to various initialization and +# finalization sections for the program. # _start: mov %esp, %eax -- cgit v1.1