This is a slightly odd series of 2 patches. The two patches are actually alternative solutions to the same problem. I'm keen to see one of these merged, but I don't know which method would be preferred.
This commit aims to address an issue that was introduced / mentioned in commit 20554a78a9bba278c6b9cbbb4cfc5bde3772c56d (ARC: Conditionalise certain relocations as provided by TLS tools only).
The problem is that not all historic versions of binutils have supported the @pcl relocation type. This problem is compounded by the fact that the arithmetic construct that was previously used to synthesise an @pcl like behaviour, does not work on recent versions of binutils.
In the commit 20554a78a code was added that selects between the new style @pcl relocations, and the old style arithmetic construct, however, this selection is done based on whether the uClibc user has configured with native threads or not.
Of course, a uClibc user could choose to use a modern version of binutils AND configure without native thread support, in which case uClibc will not compile.
I have two proposed solutions. In patch 1/2 I simply drop support for the older versions of binutils in favour of the new @pcl relocation type. This feels the cleanest solution, but I don't know how strongly the uClibc(-ng) community feels about maintaining compatibility for older versions of the tools.
Given that I anticipated push back against the first patch I took a look at how I might maintain compatibility. It turns out to be pretty easy, and that is patch 2/2. In this patch I drew inspiration from similar examples in the Rules.mak file to check if the toolchain supports @pcl relocations or not. With this done we have a new define based on the specific toolchain feature being supported or not, which can then be used to conditionalise the code.
Would you consider merging one of these patches?
Thanks, Andrew
Some old versions of binutils did not support @pcl relocations. This commit adds a new flag to the uClibc configuration system that detects if the toolchain supports @pcl relocations or not.
If this relocation is supported then the define ARC_HAS_AT_PCL_RELOC will be passed to the compiler, which is then used in the arc ldso to choose between generating old or new style code.
This commit addresses and issue that was worked around in commit 181d410ad00cddd1d6c9f4835e129136b74c5187 (ARC: Conditionalise certain relocations as provided by TLS tools only). In this commit the choice between old or new style relocations was made based on whether uClibc was configured with native threads or not. The problem is that a user of a new toolchain might choose to configure without native threads. --- Rules.mak | 2 ++ ldso/ldso/arc/dl-startup.h | 2 +- ldso/ldso/arc/dl-sysdep.h | 4 ++++ 3 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/Rules.mak b/Rules.mak index 3c80016..04ff02f 100644 --- a/Rules.mak +++ b/Rules.mak @@ -507,9 +507,11 @@ ifeq ($(TARGET_ARCH),c6x) endif
ifeq ($(TARGET_ARCH),arc) + ARC_HAS_AT_PCL_RELOC:=$(shell echo -e "\t.text\n\tadd r0,pcl,_symbol@pcl" | $(CC) -c -x assembler -o /dev/null - 2> /dev/null && echo -n y || echo -n n) CPU_CFLAGS-y += -mlock -mswape CPU_CFLAGS-$(CONFIG_ARC_CPU_700) += -mA7 CPU_CFLAGS-$(CONFIG_ARC_CPU_HS) += -mcpu=archs + CPU_CFLAGS-$(ARC_HAS_AT_PCL_RELOC) += -DARC_HAS_AT_PCL_RELOC CPU_LDFLAGS-y += $(CPU_CFLAGS) -marclinux endif
diff --git a/ldso/ldso/arc/dl-startup.h b/ldso/ldso/arc/dl-startup.h index ef89b53..80ffd79 100644 --- a/ldso/ldso/arc/dl-startup.h +++ b/ldso/ldso/arc/dl-startup.h @@ -34,7 +34,7 @@ __asm__( " ; skip the extra args calc by dl_start() \n" " ld_s r1, [sp] ; orig argc from aux-vec Tbl \n"
-#ifdef __UCLIBC_HAS_THREADS_NATIVE__ +#ifdef ARC_HAS_AT_PCL_RELOC " ld r12, [pcl, _dl_skip_args@pcl] \n"
" add r2, pcl, _dl_fini@pcl ; finalizer \n" diff --git a/ldso/ldso/arc/dl-sysdep.h b/ldso/ldso/arc/dl-sysdep.h index caece99..27463f0 100644 --- a/ldso/ldso/arc/dl-sysdep.h +++ b/ldso/ldso/arc/dl-sysdep.h @@ -154,7 +154,11 @@ static __always_inline Elf32_Addr elf_machine_load_address(void) Elf32_Addr addr, tmp; __asm__ ( "ld %1, [pcl, _dl_start@gotpc] ;build addr of _dl_start \n" +#ifdef ARC_HAS_AT_PCL_RELOC + "add %0, pcl, _dl_start@pcl ;runtime addr of _dl_start \n" +#else "add %0, pcl, _dl_start-.+(.&2) ;runtime addr of _dl_start \n" +#endif /* ARC_HAS_AT_PCL_RELOC */ "sub %0, %0, %1 ;delta \n" : "=&r" (addr), "=r"(tmp) );
Hi Andrew, Andrew Burgess wrote,
Some old versions of binutils did not support @pcl relocations. This commit adds a new flag to the uClibc configuration system that detects if the toolchain supports @pcl relocations or not.
If this relocation is supported then the define ARC_HAS_AT_PCL_RELOC will be passed to the compiler, which is then used in the arc ldso to choose between generating old or new style code.
This commit addresses and issue that was worked around in commit 181d410ad00cddd1d6c9f4835e129136b74c5187 (ARC: Conditionalise certain relocations as provided by TLS tools only). In this commit the choice between old or new style relocations was made based on whether uClibc was configured with native threads or not. The problem is that a user of a new toolchain might choose to configure without native threads.
Rules.mak | 2 ++ ldso/ldso/arc/dl-startup.h | 2 +- ldso/ldso/arc/dl-sysdep.h | 4 ++++ 3 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/Rules.mak b/Rules.mak index 3c80016..04ff02f 100644 --- a/Rules.mak +++ b/Rules.mak @@ -507,9 +507,11 @@ ifeq ($(TARGET_ARCH),c6x) endif
ifeq ($(TARGET_ARCH),arc)
- ARC_HAS_AT_PCL_RELOC:=$(shell echo -e "\t.text\n\tadd r0,pcl,_symbol@pcl" | $(CC) -c -x assembler -o /dev/null - 2> /dev/null && echo -n y || echo -n n) CPU_CFLAGS-y += -mlock -mswape CPU_CFLAGS-$(CONFIG_ARC_CPU_700) += -mA7 CPU_CFLAGS-$(CONFIG_ARC_CPU_HS) += -mcpu=archs
- CPU_CFLAGS-$(ARC_HAS_AT_PCL_RELOC) += -DARC_HAS_AT_PCL_RELOC CPU_LDFLAGS-y += $(CPU_CFLAGS) -marclinux
endif
I tried the patch, but get this with arc 2016.03 (ARC700, LE):
/home/wbx/embedded-test/openadk/toolchain_nsim-arcv1_uclibc-ng_arc700/usr/bin/arc-openadk-linux-uclibc-gcc -c libc/sysdeps/linux/common/pause.c -o libc/sysdeps/linux/common/pause.os -Wall -Wstrict-prototypes -Wstrict-aliasing -funsigned-char -fno-builtin -fno-asm -fmerge-all-constants -std=gnu99 -mlock -mswape -mA7 -fno-stack-protector -nostdinc -I./include -I./include -include libc-symbols.h -I./libc/sysdeps/linux/arc -I./libc/sysdeps/linux -I./ldso/ldso/arc -I./ldso/include -I. -Os -fstrict-aliasing -fwrapv -fno-ident -mcpu=arc700 -Os -pipe -fomit-frame-pointer -fno-unwind-tables -fno-asynchronous-unwind-tables -D__USE_STDIO_FUTEXES__ -DHAVE_FORCED_UNWIND -D_LIBC_REENTRANT -I./libpthread/nptl -I./libpthread/nptl -I./libpthread/nptl/sysdeps/unix/sysv/linux/arc -I./libpthread/nptl/sysdeps/arc -I./libpthread/nptl/sysdeps/arc -I./libpthread/nptl/sysdeps/unix/sysv/linux -I./libpthread/nptl/sysdeps/unix/sysv/linux -I./libpthread/nptl/sysdeps/pthread -I./libpthread/nptl/sysdeps/pthread/bits -I./libpthread/nptl/sysdeps/generic -I./libc/sysdeps/linux/common -isystem /home/wbx/embedded-test/openadk/toolchain_nsim-arcv1_uclibc-ng_arc700/usr/lib/gcc/arc-openadk-linux-uclibc/4.8.5/include-fixed -isystem /home/wbx/embedded-test/openadk/toolchain_nsim-arcv1_uclibc-ng_arc700/usr/lib/gcc/arc-openadk-linux-uclibc/4.8.5/include -I/home/wbx/embedded-test/openadk/target_nsim-arcv1_uclibc-ng_arc700/usr/include/ -DNDEBUG -DIN_LIB=libc -fPIC -fexceptions -fasynchronous-unwind-tables -MT libc/sysdeps/linux/common/pause.os -MD -MP -MF libc/sysdeps/linux/common/.pause.os.dep {standard input}: Assembler messages: {standard input}:15: Error: invalid operands (.bss and .text sections) for `-' {standard input}:15: Error: invalid operands (.text and *ABS* sections) for `&' {standard input}:17: Error: invalid operands (.text.exit and .text sections) for `-' {standard input}:17: Error: invalid operands (.text and *ABS* sections) for `&' Makerules:385: recipe for target 'ldso/ldso/ldso.oS' failed make[6]: *** [ldso/ldso/ldso.oS] Error 1
It seems ARC_HAS_AT_PCL_RELOC isn't set. I tracked it down, it seems a combination of my shell and echo -e usage. I know there is another echo -e usage in Rules.mak and I will fix it later. Can you please resend the patch with printf instead of echo -e, if the Synopsis ARC developers agree on this patch? I added the trailing "\n" to avoid a unnecessary warning when trying just the command in a shell, sth like that:
diff --git a/Rules.mak b/Rules.mak index 04ff02f..8b962b4 100644 --- a/Rules.mak +++ b/Rules.mak @@ -507,7 +507,7 @@ ifeq ($(TARGET_ARCH),c6x) endif
ifeq ($(TARGET_ARCH),arc) - ARC_HAS_AT_PCL_RELOC:=$(shell echo -e "\t.text\n\tadd r0,pcl,_symbol@pcl" | $(CC) -c -x assembler -o /dev/null - 2> /dev/null && echo -n y || echo -n n) + ARC_HAS_AT_PCL_RELOC:=$(shell printf "\t.text\n\tadd r0,pcl,_symbol@pcl\n" | $(CC) -c -x assembler -o /dev/null - 2> /dev/null && echo -n y || echo -n n) CPU_CFLAGS-y += -mlock -mswape CPU_CFLAGS-$(CONFIG_ARC_CPU_700) += -mA7 CPU_CFLAGS-$(CONFIG_ARC_CPU_HS) += -mcpu=archs
Otherwise looks good to me and fixes my problem with a nothread build :)
thanks Waldemar
This commit reverses a change introduced in commit 20554a78a9bba that split some of the ARC code into two based on whether uClibc was configured with native threads or not.
The native thread code was updated to use the relocation syntax of modern binutils, while the non-native code path used a syntax only accepted in older versions of binutils.
The problem with this is that the choice of old binutils or not is orthogonal to the choice of native threads or not, and so, inevitably a user with a recent version of binutils can make the choice to configure uClibc with non-native thread support, and run into code that will not assemble.
The solution is either to abandon support for the old tools completely, or to add a new compile time flag for ARC that is set when the version of binutils being used is old; this new flag would allow the old relocation structure to be selected.
In this commit I have simply dropped support for older versions of the tools. --- ldso/ldso/arc/dl-startup.h | 7 ------- ldso/ldso/arc/dl-sysdep.h | 2 +- 2 files changed, 1 insertion(+), 8 deletions(-)
diff --git a/ldso/ldso/arc/dl-startup.h b/ldso/ldso/arc/dl-startup.h index ef89b53..664b860 100644 --- a/ldso/ldso/arc/dl-startup.h +++ b/ldso/ldso/arc/dl-startup.h @@ -34,15 +34,8 @@ __asm__( " ; skip the extra args calc by dl_start() \n" " ld_s r1, [sp] ; orig argc from aux-vec Tbl \n"
-#ifdef __UCLIBC_HAS_THREADS_NATIVE__ " ld r12, [pcl, _dl_skip_args@pcl] \n" - " add r2, pcl, _dl_fini@pcl ; finalizer \n" -#else - " add r12, pcl, _dl_skip_args-.+(.&2) \n" - " ld r12, [r12] \n" - " add r2, pcl, _dl_fini-.+(.&2) ; finalizer \n" -#endif
" add2 sp, sp, r12 ; discard argv entries from stack\n" " sub_s r1, r1, r12 ; adjusted argc, on stack \n" diff --git a/ldso/ldso/arc/dl-sysdep.h b/ldso/ldso/arc/dl-sysdep.h index caece99..aadf624 100644 --- a/ldso/ldso/arc/dl-sysdep.h +++ b/ldso/ldso/arc/dl-sysdep.h @@ -154,7 +154,7 @@ static __always_inline Elf32_Addr elf_machine_load_address(void) Elf32_Addr addr, tmp; __asm__ ( "ld %1, [pcl, _dl_start@gotpc] ;build addr of _dl_start \n" - "add %0, pcl, _dl_start-.+(.&2) ;runtime addr of _dl_start \n" + "add %0, pcl, _dl_start@pcl ;runtime addr of _dl_start \n" "sub %0, %0, %1 ;delta \n" : "=&r" (addr), "=r"(tmp) );
Hi Andrew,
On 07/28/2016 11:20 AM, Andrew Burgess wrote:
This is a slightly odd series of 2 patches. The two patches are actually alternative solutions to the same problem. I'm keen to see one of these merged, but I don't know which method would be preferred.
This commit aims to address an issue that was introduced / mentioned in commit 20554a78a9bba278c6b9cbbb4cfc5bde3772c56d (ARC: Conditionalise certain relocations as provided by TLS tools only).
The problem is that not all historic versions of binutils have supported the @pcl relocation type. This problem is compounded by the fact that the arithmetic construct that was previously used to synthesise an @pcl like behaviour, does not work on recent versions of binutils.
In the commit 20554a78a code was added that selects between the new style @pcl relocations, and the old style arithmetic construct, however, this selection is done based on whether the uClibc user has configured with native threads or not.
Right - the idea at the time was @pcl was added to tools for TLS/NPTL support and thus uClibc NPTL loosely implied that your tools will have that support - but this was not the ideal choice I agree.
Of course, a uClibc user could choose to use a modern version of binutils AND configure without native thread support, in which case uClibc will not compile.
I have two proposed solutions. In patch 1/2 I simply drop support for the older versions of binutils in favour of the new @pcl relocation type. This feels the cleanest solution, but I don't know how strongly the uClibc(-ng) community feels about maintaining compatibility for older versions of the tools.
So this was reported recently by Waldemar's build service too.
http://mailman.uclibc-ng.org/pipermail/devel/2016-July/001072.html
And we have an exact same patch floated internally which Vlad sent out earlier this week
Given that I anticipated push back against the first patch I took a look at how I might maintain compatibility.
Not really - while indeed 1/2 opens up a non-compatibilty window, there is less likelihood people will mix-n-match different baselines of uclibc and gcc/gas. So Vlad's patch does exactly that.
It turns out to be pretty easy, and that is patch 2/2. In this patch I drew inspiration from similar examples in the Rules.mak file to check if the toolchain supports @pcl relocations or not. With this done we have a new define based on the specific toolchain feature being supported or not, which can then be used to conditionalise the code.
Indeed your 2/2 seems to be the most "past-proof" code change. So I would think it is indeed better and is something I should have done in the first place.
@Alexey, @Vlad what say you ?
-Vineet
Would you consider merging one of these patches?
Thanks, Andrew
-
Andrew Burgess -
Vineet Gupta -
Waldemar Brodkorb