Proposed patch at https://patchwork.ozlabs.org/patch/1022092/
NB: my guess is that your pwrite on 32-bit arm test is behaving like
that because it isn't going via the pwrite64 syscall, or possibly
because glibc there is dealing with the NULL special case early. Use
QEMU's -strace argument (or strace on real h/w) to see what libc is
actually turning that pwrite() function call into at the syscall level.
** Changed in: qemu
Status: New => In Progress
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https://bugs.launchpad.net/bugs/1810433
Title:
aarch64-linux-user master: inconsistent pwrite behaviour
Status in QEMU:
In Progress
Bug description:
Hello,
I am running aarch64-linux-user from master, commit
20d6c7312f1b812bb9c750f4087f69ac8485cc90
And I've found the following inconsistent emulation of pwrite() call when
buf==NULL and len=0.
Minimal reproducible sample is the following:
#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
/*
System | Result
-------------------------+----------------
Native x86_64 4.12.14 | pwrite ret = 0
Native aarch64 4.4.159 | pwrite ret = 0
qemu-aarch64 at x86_64 | pwrite ret = -1
( 20d6c7312f1b8 ) |
*/
int main(int argc, char** argv) {
int fd = open("test.dat", O_CREAT | O_RDWR, 0644);
if (fd < 0) {
perror("open");
return 1;
}
int ret = fallocate(fd, 0, 0, 1000);
if (ret < 0) {
perror("fallocate");
return 1;
}
ssize_t ret_pwrite = pwrite(fd, NULL, 0, 0);
printf("pwrite ret = %ld\n", ret_pwrite);
close(fd);
return 0;
}
Please note, that the same binary executable prints different output at
native aarch64 platform and under aarch64-linux-user
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