From 579715f830fbbca9e1ecb17dc18176132f5969e7 Mon Sep 17 00:00:00 2001 From: Rami Ylimaki Date: Wed, 17 Mar 2010 12:16:57 +0200 Subject: [PATCH] os: Prevent backtrace from being stopped in noreturn functions. There are two noreturn functions in the X server: FatalError and AbortServer. Having any of those two functions in the middle of a call stack will prevent unwinding the program properly and stops the backtrace at those functions in gdb. The file containing FatalError and AbortServer, os/log.c, has to be compiled with the -mapcs-frame option on ARM to get proper backtraces. Automake imposes its own restrictions on compiling individual source files with different options. The recommended way to do this is to put os/log.c into a convenience library and add this library inside os/libos.la. See the documentation of GNU Automake manual, version 1.11.1, section 27.8 Per-Object Flags Emulation, for details. Signed-off-by: Rami Ylimaki Reviewed-by: Daniel Stone Signed-off-by: Keith Packard --- configure.ac | 13 +++++++++++++ os/Makefile.am | 17 ++++++++++++----- 2 files changed, 25 insertions(+), 5 deletions(-) diff --git a/configure.ac b/configure.ac index d379b3af5..5f086884f 100644 --- a/configure.ac +++ b/configure.ac @@ -315,6 +315,19 @@ AC_CHECK_HEADER([execinfo.h],[ ])] ) +dnl ARM needs additional compiler flags for proper backtraces if GCC is +dnl used. Compile a dummy program with the -mapcs-frame option. If it +dnl succeeds, we know that we are building for ARM with GCC. +old_CFLAGS="$CFLAGS" +CFLAGS="-mapcs-frame" +AC_COMPILE_IFELSE( + AC_LANG_PROGRAM([[ ]]), + ARM_BACKTRACE_CFLAGS="$CFLAGS", + ARM_BACKTRACE_CFLAGS="" +) +CFLAGS="$old_CFLAGS" +AC_SUBST(ARM_BACKTRACE_CFLAGS) + dnl --------------------------------------------------------------------------- dnl Bus options and CPU capabilities. Replaces logic in dnl hw/xfree86/os-support/bus/Makefile.am, among others. diff --git a/os/Makefile.am b/os/Makefile.am index 66a4a0f75..3e4f2c591 100644 --- a/os/Makefile.am +++ b/os/Makefile.am @@ -1,11 +1,19 @@ -noinst_LTLIBRARIES = libos.la +noinst_LTLIBRARIES = libos.la liblog.la AM_CFLAGS = $(DIX_CFLAGS) $(SHA1_CFLAGS) SECURERPC_SRCS = rpcauth.c XDMCP_SRCS = xdmcp.c STRLCAT_SRCS = strlcat.c strlcpy.c -XORG_SRCS = log.c + +# Build a convenience library liblog.la that will be added into +# libos.la. The split is done so that log.c can be built with +# different compiler options. +liblog_la_SOURCES = log.c +# Add flags needed for proper backtraces of functions marked with GCC +# __attribute__((noreturn)). Currently those flags are needed for +# FatalError and AbortServer in log.c. +liblog_la_CFLAGS = $(AM_CFLAGS) $(ARM_BACKTRACE_CFLAGS) libos_la_SOURCES = \ WaitFor.c \ @@ -24,9 +32,8 @@ libos_la_SOURCES = \ xdmauth.c \ xsha1.c \ xstrans.c \ - xprintf.c \ - $(XORG_SRCS) -libos_la_LIBADD = @SHA1_LIBS@ $(DLOPEN_LIBS) + xprintf.c +libos_la_LIBADD = @SHA1_LIBS@ $(DLOPEN_LIBS) liblog.la if SECURE_RPC libos_la_SOURCES += $(SECURERPC_SRCS)