Am 14.07.25 um 11:39 schrieb Paul Floyd via oi-dev:
Hi
I'm working on an issue related to an exe opening its own binary file
with flags like O_WRONLY|O_CREAT|O_TRUNC. Any writing is going to be
bad, and truncation even worse.
On FreeBSD and Linux this is not allowed. 'open' will fail and set
errno to ETXTBSY.
I haven't yet tried this on Solaris. My testcase just opens and
truncates the exe and core dumps on the first call to open.
If I read open's explanation in the man page (man -s 2 open) I cannot
find a hint that what you do is forbidden on illumos. So I think what
you see is the expected behavior. Maybe nobody thought about your
special case when it was designed.
Andreas
Under gdb I get
Dwarf Error: wrong version in compilation unit header (is 0, should be
2, 3, 4 or 5) [in module
/export/home/paulf/scratch/valgrind/memcheck/tests/solaris/open_client]
I guess that;s because it's failing to rread the Dwarf from the 0 byte
file.
Here is my testcase, works fine on FreeBSD
// For Bug 505673
// Valgrind crashes with an internal error and SIGBUS when the guest
tries to open its own file with O_WRONLY|O_CREAT|O_TRUNC
#include <fcntl.h>
#include <cerrno>
#include <stdexcept>
#include <vector>
#include <unistd.h>
#include <sys/syscall.h>
#include <unistd.h>
int main(int argc, char** argv)
{
std::vector<int> flags{O_WRONLY|O_CREAT|O_TRUNC, O_WRONLY, O_RDWR};
// On FreeBSD libc open uses syscall openat (at least on 14.2)
for (auto f : flags)
{
int res = open(argv[0], f, 0666);
if (-1 != res)
{
throw std::runtime_error("open should have failed");
}
else
{
if (errno != ETXTBSY)
{
throw std::runtime_error("errno should be ETXTBSY");
}
}
}
// repeat the above, but with syscall(SYS_OPEN
for (auto f : flags)
{
int res = syscall(SYS_open, argv[0], f, 0666);
if (-1 != res)
{
throw std::runtime_error("open should have failed");
}
else
{
if (errno != ETXTBSY)
{
throw std::runtime_error("errno should be ETXTBSY");
}
}
}
chdir("..");
// check that relative paths work
for (auto f : flags)
{
int res = open("solaris/open_client", f, 0666);
if (-1 != res)
{
throw std::runtime_error("open should have failed");
}
else
{
if (errno != ETXTBSY)
{
throw std::runtime_error("errno should be ETXTBSY");
}
}
}
for (auto f : flags)
{
int res = syscall(SYS_open, "solaris/open_client", f, 0666);
if (-1 != res)
{
throw std::runtime_error("open should have failed");
}
else
{
if (errno != ETXTBSY)
{
throw std::runtime_error("errno should be ETXTBSY");
}
}
}
}
A+
Paul
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