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Re: [PATCH v4] Fix Linux fcntl OFD locks for non-LFS architectures (BZ#20251)
- From: Szabolcs Nagy <nsz at port70 dot net>
- To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: libc-alpha at sourceware dot org
- Date: Sat, 30 Jun 2018 14:26:21 +0200
- Subject: Re: [PATCH v4] Fix Linux fcntl OFD locks for non-LFS architectures (BZ#20251)
- References: <1529530993-20897-1-git-send-email-adhemerval.zanella@linaro.org>
* Adhemerval Zanella <adhemerval.zanella@linaro.org> [2018-06-20 18:43:13 -0300]:
> This patch fixes the OFD ("file private") locks for architectures that
> support non-LFS flock definition (__USE_FILE_OFFSET64 not defined). The
> issue in this case is both F_OFD_{GETLK,SETLK,SETLKW} and
> F_{SET,GET}L{W}K64 expects a flock64 argument and when using old
> F_OFD_* flags with a non LFS flock argument the kernel might interpret
> the underlying data wrongly. Kernel idea originally was to avoid using
> such flags in non-LFS syscall, but since GLIBC uses fcntl with LFS
> semantic as default it is possible to provide the functionality and
> avoid the bogus struct kernel passing by adjusting the struct manually
> for the required flags.
>
> The idea follows other LFS interfaces that provide two symbols:
>
> 1. A new LFS fcntl64 is added on default ABI with the usual macros to
> select it for FILE_OFFSET_BITS=64.
>
> 2. The Linux non-LFS fcntl use a stack allocated struct flock64 for
> F_OFD_{GETLK,SETLK,SETLKW} copy the results on the user provided
> struct.
>
> 3. Keep a compat symbol with old broken semantic for architectures
> that do not define __OFF_T_MATCHES_OFF64_T.
>
> So for architectures which defines __USE_FILE_OFFSET64, fcntl64 will
> aliased to fcntl and no adjustment would be required. So to actually
> use F_OFD_* with LFS support the source must be built with LFS support
> (_FILE_OFFSET_BITS=64).
>
> Also F_OFD_SETLKW command is handled a cancellation point, as for
> F_SETLKW{64}.
>
> Checked on x86_64-linux-gnu and i686-linux-gnu.
>
build-many-glibcs fails for me on i686
in logs/glibcs/i686-gnu/010-glibcs-i686-gnu-check-log.txt i see
FAIL: elf/check-abi-libc
FAIL: elf/check-execstack
FAIL: hurd/check-installed-headers-c
FAIL: hurd/check-installed-headers-cxx
FAIL: mach/check-installed-headers-c
FAIL: mach/check-installed-headers-cxx
the libc abi failure is
--- ../sysdeps/mach/hurd/i386/libc.abilist 2018-06-29 18:53:06.105524353 +0100
+++ /B/build/glibcs/i686-gnu/glibc/libc.symlist 2018-06-30 13:02:53.044456983 +0100
@@ -2036 +2035,0 @@ GLIBC_2.27 wcstof64x_l F
-GLIBC_2.28 fcntl F
but i don't know if hurd is supposed to work...