[U-Boot] fs/fat: device not booting since conversion to dir iterators

[Patrick Brünn]

Hi Simon,

>From: sjg at google.com [mailto:sjg at google.com] On Behalf Of Simon Glass
>Sent: Dienstag, 19. Dezember 2017 16:42
>Hi Patrick,
>
>On 13 December 2017 at 03:15, Patrick Brünn <P.Bruenn at beckhoff.com>
>wrote:
>>>From: Patrick Brünn
>>>Sent: Donnerstag, 30. November 2017 12:22
>>>
>>>Since commit 8eafae209c35932d9a6560809c55ee4641534236
>>>my mx53cx9020_defconfig stopped booting.
>>>...
>>>It seems important to read into do_fat_read_at_block. If I
>>>allocate a temporary buffer and read into that one, I still
>>>can't boot. That seems strange to me as, I couldn't find
>>>any uninitialized access to do_fat_read_at_block anywhere.
>>>
>> I believe I finally tracked it down to the linker.
>>
>> Without accessing do_fat_read_at_block within fat.c, I find
>> .bss. do_fat_read_at_block as "discarded input section" in
>> my u-boot.map
>>
>> With a patch like this:
>> diff --git a/fs/fat/fat.c b/fs/fat/fat.c
>> index d16883fa10..8e70fdbc8d 100644
>> --- a/fs/fat/fat.c
>> +++ b/fs/fat/fat.c
>> @@ -1157,6 +1157,7 @@ int fat_opendir(const char *filename, struct
>fs_dir_stream **dirsp)
>>                 return -ENOMEM;
>>         memset(dir, 0, sizeof(*dir));
>>
>> +       if (do_fat_read_at_block[0])
>> +               printf("value doesn't matter, the access is important\n");
>> +
>>         ret = fat_itr_root(&dir->itr, &dir->fsdata);
>>         if (ret)
>>                 goto fail_free_dir;
>>
>> The section isn't discarded and my board boots again.
>>
>>
>> Another workaround would be:
>> diff --git a/arch/arm/config.mk b/arch/arm/config.mk
>> index 124b44a337..02f61fcc3c 100644
>> --- a/arch/arm/config.mk
>> +++ b/arch/arm/config.mk
>> @@ -17,7 +17,7 @@ CFLAGS_NON_EFI := -fno-pic -ffixed-r9 -ffunction-
>sections -fdata-sections
>>  CFLAGS_EFI := -fpic -fshort-wchar
>>
>>  LDFLAGS_FINAL += --gc-sections
>> -PLATFORM_RELFLAGS += -ffunction-sections -fdata-sections \
>> +PLATFORM_RELFLAGS += -ffunction-sections \
>>                      -fno-common -ffixed-r9
>>  PLATFORM_RELFLAGS += $(call cc-option, -msoft-float) \
>>        $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,))
>>
>> Or a hack like:
>> diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds
>> index 37d4c605ac..b916cbc733 100644
>> --- a/arch/arm/cpu/u-boot.lds
>> +++ b/arch/arm/cpu/u-boot.lds
>> @@ -219,6 +219,7 @@ SECTIONS
>>         }
>>
>>         .bss_end __bss_limit (OVERLAY) : {
>> +               KEEP(*(.bss.do_fat_read_at_block));
>>                 KEEP(*(.__bss_end));
>>         }
>>
>> I also tried to mark do_fat_read_at_block as:
>> volatile, __used and/or __attribute__((externally_visible))
>>
>> This doesn't help.
>>
>> Moving it into fat_write.c doesn't help either(with/without static)
>>
>> My toolchain is:
>> ~/u-boot$ arm-linux-gnueabihf-gcc -v
>> Using built-in specs.
>> COLLECT_GCC=arm-linux-gnueabihf-gcc
>> COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/arm-linux-gnueabihf/6/lto-
>wrapper
>> Target: arm-linux-gnueabihf
>> Configured with: ../src/configure -v --with-pkgversion='Debian 6.3.0-18' --
>with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs --enable-
>languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-
>suffix=-6 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --
>without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls
>--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-
>libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-
>object --disable-libitm --disable-libquadmath --enable-plugin --enable-
>default-pie --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk
>--enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-armhf-
>cross/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-
>6-armhf-cross --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-armhf-
>cross --with-arch-directory=arm --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
>--disable-libgcj --with-target-system-zlib --enable-objc-gc=auto --enable-
>multiarch --disable-sjlj-exceptions --with-arch=armv7-a --with-fpu=vfpv3-d16
>--with-float=hard --with-mode=thumb --enable-checking=release --
>build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=arm-linux-
>gnueabihf --program-prefix=arm-linux-gnueabihf- --includedir=/usr/arm-
>linux-gnueabihf/include
>> Thread model: posix
>> gcc version 6.3.0 20170516 (Debian 6.3.0-18)
>>
>> ~/u-boot$ arm-linux-gnueabihf-ld -v
>> GNU ld (GNU Binutils for Debian) 2.28
>>
>>
>> Does anyone have an idea what else I can try to prevent my linker from
>removing
>> do_fat_read_at_block?
>
>This doesn't seem to be used unless you have enabled CONFIG_FAT_WRITE.
>Have you?
>
>I wonder if the problem is somewhere else, and the presence of this
>buffer is just moving things apart in the data space, and thus masking
>the problem?
>
Yes, I hope I finally found it. Please see the first patch of this series[1].
Don't using that global variable anymore fixes my problem, according to the
documentation it makes sense. Even if I am still not 100% sure. I just don't understand
why this thing was working for so long for at least two boards.
Does it make sense to you?

Thanks for your input,
Patrick

[1] https://www.mail-archive.com/u-boot@lists.denx.de/msg272444.html

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