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path: root/libc/sysdeps/linux/common/fallocate.c
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2015-10-05libc: fix sign extension in fallocate()Yuriy Kolerov
For common generic syscall ABI fallocate syscall handler in kernel expects a 64-bit signed arguments for offset and len. However uClibc has 2 wrappers for this syscall: fallocate and fallocate64. On 32-bit machines fallocate (not fallocate64) expects 32-bit values of offset and len. Thus in this case uClibc's fallocate must pass to the syscall those values with sign extension. High word of 64-bit value must be 0 or 0xFFFFFFFF depending on sign of the original 32-bit value (offset or len). It is how sign extansion works - all high bits of the negative value must be 1. So on 32-bit machines uClibc's fallocate does sign extension incorrectly when 32-bit values are passed (offset or len). It just fills the second word of 64-bit value by zeros. E.g. fallocate works incorrectly when offset or length is negative value - in this case kernel thinks that positive values are passed. Solution is to call fallocate64 from fallocate and pass 32-bit values of offset and len to fallocate64. off_t type is automatically converted to off64_t with an appropriate sign extension. Then fallocate64 invokes kernel's system call properly. This error is detected in LTP's test kernel/syscalls/fallocate02: ----------->8---------- fallocate(..., 1, -1024, 1024) failed, expected errno:22: TEST_ERRNO=0 fallocate(..., 1, 1024, -1024) failed, expected errno:22: TEST_ERRNO=0 fallocate(..., 1, 12288, -1024) failed, expected errno:22: TEST_ERRNO=0 fallocate(..., 1, -24576, 1024) failed, expected errno:22: TEST_ERRNO=0 ----------->8---------- fallocate does not emit an error because negative values are passed to the kernel without sign extension and kernel thinks that it got valid positive values. Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
2015-10-05libc: fix setting return value and errno in fallocate()Yuriy Kolerov
fallocate system call must return 0 on success. On error, -1 is returned and errno is set to indicate the error. However there is an error in fallocate which is fixed by this patch - it does not set errno and returns invalid value on error (it returns error code instead of -1). This error is detected in LTP's test kernel/syscalls/fallocate02: ----------->8---------- fallocate(..., 1, 0, 1024) failed, expected errno:9: TEST_ERRNO=0 fallocate(..., 1, -1024, 1024) failed, expected errno:22: TEST_ERRNO=0 fallocate(..., 1, 1024, -1024) failed, expected errno:22: TEST_ERRNO=0 fallocate(..., 1, 12288, 0) failed, expected errno:22: TEST_ERRNO=0 fallocate(..., 1, 12288, -1024) failed, expected errno:22: TEST_ERRNO=0 fallocate(..., 1, -24576, 1024) failed, expected errno:22: TEST_ERRNO=0 ----------->8---------- Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
2014-09-09libc: add fallocate() and fallocate64()Anthony G. Basile
We add the Linux-specific function fallocate() which allows the user to directly manipulate allocate space for a file. fallocate() can operate in different modes, but the default mode is equivalent to posix_fallocate() which is specified in POSIX.1. Recent releases of e2fsprogs 1.42.11 and above expect fallocate64() to be available. Signed-off-by: Anthony G. Basile <blueness@gentoo.org> Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>