[PATCH libpciaccess] Allow building without O_CLOEXEC

Aaron Plattner aplattner at nvidia.com
Mon Sep 22 13:12:11 PDT 2014


On 09/22/2014 12:56 PM, Jasper St. Pierre wrote:
> How old? O_CLOEXEC is part of the 2008 POSIX specification. I really
> wouldn't like to build on anything older than that... :(

As old as possible.  :)

For context, I want to use libpciaccess's device enumeration stuff in 
nvidia-installer to identify legacy devices.  I don't need any of the 
mapping code and I don't need to worry about the application forking, 
which is why not having O_CLOEXEC is safe in my case.

According to our README [1], the minimum supported kernel is 2.6.18. 
The open(2) man page says that O_CLOEXEC was introduced in Linux 2.6.23.

I agree that allowing the library to be built normally (i.e. outside of 
special custom configurations) with the fallback isn't a good idea, 
which is why I didn't wire up ALLOW_NO_O_CLOEXEC to a configure option.


[1] 
http://us.download.nvidia.com/XFree86/Linux-x86/343.22/README/minimumrequirements.html

> On Mon, Sep 22, 2014 at 1:24 PM, Aaron Plattner <aplattner at nvidia.com
> <mailto:aplattner at nvidia.com>> wrote:
>
>     Old versions of Linux don't support O_CLOEXEC, so rather than
>     failing to build,
>     allow building without O_CLOEXEC if a new ALLOW_NO_O_CLOEXEC flag is
>     defined.
>
>     Create a new helper function, pci_open_cloexec that uses O_CLOEXEC
>     when it's
>     available and falls back to open + fcntl when it's not.  Route all
>     calls to open
>     that pass O_CLOEXEC through this new function instead using the
>     following
>     Coccinelle patch:
>
>        @@
>        expression path, flags;
>        @@
>        -open(path, flags | O_CLOEXEC)
>        +pci_open_cloexec(path, flags)
>
>     Signed-off-by: Aaron Plattner <aplattner at nvidia.com
>     <mailto:aplattner at nvidia.com>>
>     ---
>     There are three calls to open() that don't use O_CLOEXEC -- are
>     those bugs?
>
>     src/linux_devmem.c:    fd = open("/dev/mem", O_RDONLY, 0);
>     src/netbsd_pci.c:       fd = open("/dev/ttyE0", O_RDONLY);
>     src/netbsd_pci.c:               pcifd = open(netbsd_devname, O_RDWR);
>
>       src/common_vgaarb.c     |  2 +-
>       src/freebsd_pci.c       | 10 +++++-----
>       src/linux_sysfs.c       | 26 +++++++++++++-------------
>       src/netbsd_pci.c        |  2 +-
>       src/openbsd_pci.c       |  2 +-
>       src/pciaccess_private.h | 33 +++++++++++++++++++++++++++++----
>       src/solx_devfs.c        |  4 ++--
>       src/x86_pci.c           |  4 ++--
>       8 files changed, 54 insertions(+), 29 deletions(-)
>
>     diff --git a/src/common_vgaarb.c b/src/common_vgaarb.c
>     index c59bd788dc5e..f3b523e67c3a 100644
>     --- a/src/common_vgaarb.c
>     +++ b/src/common_vgaarb.c
>     @@ -131,7 +131,7 @@ pci_device_vgaarb_init(void)
>           if (!pci_sys)
>               return -1;
>
>     -    if ((pci_sys->vgaarb_fd = open ("/dev/vga_arbiter", O_RDWR |
>     O_CLOEXEC)) < 0) {
>     +    if ((pci_sys->vgaarb_fd = pci_open_cloexec ("/dev/vga_arbiter",
>     O_RDWR)) < 0) {
>               return errno;
>           }
>
>     diff --git a/src/freebsd_pci.c b/src/freebsd_pci.c
>     index 9505a1c17d21..e40d80847bf0 100644
>     --- a/src/freebsd_pci.c
>     +++ b/src/freebsd_pci.c
>     @@ -112,7 +112,7 @@ pci_device_freebsd_map_range(struct pci_device *dev,
>
>           int fd, err = 0;
>
>     -    fd = open("/dev/mem", O_RDWR | O_CLOEXEC);
>     +    fd = pci_open_cloexec("/dev/mem", O_RDWR);
>           if (fd == -1)
>              return errno;
>
>     @@ -157,7 +157,7 @@ pci_device_freebsd_unmap_range( struct
>     pci_device *dev,
>           if ((map->flags & PCI_DEV_MAP_FLAG_CACHABLE) ||
>              (map->flags & PCI_DEV_MAP_FLAG_WRITE_COMBINE))
>           {
>     -       fd = open("/dev/mem", O_RDWR | O_CLOEXEC);
>     +       fd = pci_open_cloexec("/dev/mem", O_RDWR);
>              if (fd != -1) {
>                  mrd.mr_base = map->base;
>                  mrd.mr_len = map->size;
>     @@ -297,7 +297,7 @@ pci_device_freebsd_read_rom( struct pci_device *
>     dev, void * buffer )
>           }
>
>           printf("Using rom_base = 0x%lx\n", (long)rom_base);
>     -    memfd = open( "/dev/mem", O_RDONLY | O_CLOEXEC );
>     +    memfd = pci_open_cloexec( "/dev/mem", O_RDONLY );
>           if ( memfd == -1 )
>              return errno;
>
>     @@ -574,7 +574,7 @@ pci_device_freebsd_open_legacy_io(struct
>     pci_io_handle *ret,
>           struct pci_device *dev, pciaddr_t base, pciaddr_t size)
>       {
>       #if defined(__i386__) || defined(__amd64__)
>     -       ret->fd = open("/dev/io", O_RDWR | O_CLOEXEC);
>     +       ret->fd = pci_open_cloexec("/dev/io", O_RDWR);
>
>              if (ret->fd < 0)
>                      return NULL;
>     @@ -735,7 +735,7 @@ pci_system_freebsd_create( void )
>           int i;
>
>           /* Try to open the PCI device */
>     -    pcidev = open( "/dev/pci", O_RDWR | O_CLOEXEC );
>     +    pcidev = pci_open_cloexec( "/dev/pci", O_RDWR );
>           if ( pcidev == -1 )
>              return ENXIO;
>
>     diff --git a/src/linux_sysfs.c b/src/linux_sysfs.c
>     index 08c99719bcba..120cd6411893 100644
>     --- a/src/linux_sysfs.c
>     +++ b/src/linux_sysfs.c
>     @@ -100,7 +100,7 @@ pci_system_linux_sysfs_create( void )
>              if ( pci_sys != NULL ) {
>                  pci_sys->methods = & linux_sysfs_methods;
>       #ifdef HAVE_MTRR
>     -           pci_sys->mtrr_fd = open("/proc/mtrr", O_WRONLY | O_CLOEXEC);
>     +           pci_sys->mtrr_fd = pci_open_cloexec("/proc/mtrr", O_WRONLY);
>       #endif
>                  err = populate_entries(pci_sys);
>              }
>     @@ -247,7 +247,7 @@ pci_device_linux_sysfs_probe( struct pci_device
>     * dev )
>                        dev->bus,
>                        dev->dev,
>                        dev->func );
>     -       fd = open( name, O_RDONLY | O_CLOEXEC);
>     +       fd = pci_open_cloexec(name, O_RDONLY);
>              if ( fd != -1 ) {
>                  char * next;
>                  pciaddr_t  low_addr;
>     @@ -309,7 +309,7 @@ pci_device_linux_sysfs_read_rom( struct
>     pci_device * dev, void * buffer )
>                    dev->dev,
>                    dev->func );
>
>     -    fd = open( name, O_RDWR | O_CLOEXEC);
>     +    fd = pci_open_cloexec(name, O_RDWR);
>           if ( fd == -1 ) {
>       #ifdef LINUX_ROM
>              /* If reading the ROM using sysfs fails, fall back to the old
>     @@ -390,7 +390,7 @@ pci_device_linux_sysfs_read( struct pci_device *
>     dev, void * data,
>                    dev->dev,
>                    dev->func );
>
>     -    fd = open( name, O_RDONLY | O_CLOEXEC);
>     +    fd = pci_open_cloexec(name, O_RDONLY);
>           if ( fd == -1 ) {
>              return errno;
>           }
>     @@ -450,7 +450,7 @@ pci_device_linux_sysfs_write( struct pci_device
>     * dev, const void * data,
>                    dev->dev,
>                    dev->func );
>
>     -    fd = open( name, O_WRONLY | O_CLOEXEC);
>     +    fd = pci_open_cloexec(name, O_WRONLY);
>           if ( fd == -1 ) {
>              return errno;
>           }
>     @@ -501,7 +501,7 @@ pci_device_linux_sysfs_map_range_wc(struct
>     pci_device *dev,
>                   dev->dev,
>                   dev->func,
>                   map->region);
>     -    fd = open(name, open_flags | O_CLOEXEC);
>     +    fd = pci_open_cloexec(name, open_flags);
>           if (fd == -1)
>                  return errno;
>
>     @@ -566,7 +566,7 @@ pci_device_linux_sysfs_map_range(struct
>     pci_device *dev,
>                    dev->func,
>                    map->region);
>
>     -    fd = open(name, open_flags | O_CLOEXEC);
>     +    fd = pci_open_cloexec(name, open_flags);
>           if (fd == -1) {
>               return errno;
>           }
>     @@ -689,7 +689,7 @@ static void pci_device_linux_sysfs_enable(struct
>     pci_device *dev)
>                    dev->dev,
>                    dev->func );
>
>     -    fd = open( name, O_RDWR | O_CLOEXEC);
>     +    fd = pci_open_cloexec(name, O_RDWR);
>           if (fd == -1)
>              return;
>
>     @@ -711,7 +711,7 @@ static int
>     pci_device_linux_sysfs_boot_vga(struct pci_device *dev)
>                    dev->dev,
>                    dev->func );
>
>     -    fd = open( name, O_RDONLY | O_CLOEXEC);
>     +    fd = pci_open_cloexec(name, O_RDONLY);
>           if (fd == -1)
>              return 0;
>
>     @@ -754,7 +754,7 @@ pci_device_linux_sysfs_open_device_io(struct
>     pci_io_handle *ret,
>           snprintf(name, PATH_MAX, "%s/%04x:%02x:%02x.%1u/resource%d",
>                   SYS_BUS_PCI, dev->domain, dev->bus, dev->dev,
>     dev->func, bar);
>
>     -    ret->fd = open(name, O_RDWR | O_CLOEXEC);
>     +    ret->fd = pci_open_cloexec(name, O_RDWR);
>
>           if (ret->fd < 0)
>              return NULL;
>     @@ -778,7 +778,7 @@ pci_device_linux_sysfs_open_legacy_io(struct
>     pci_io_handle *ret,
>              snprintf(name, PATH_MAX,
>     "/sys/class/pci_bus/%04x:%02x/legacy_io",
>                       dev->domain, dev->bus);
>
>     -       ret->fd = open(name, O_RDWR | O_CLOEXEC);
>     +       ret->fd = pci_open_cloexec(name, O_RDWR);
>              if (ret->fd >= 0)
>                  break;
>
>     @@ -925,7 +925,7 @@ pci_device_linux_sysfs_map_legacy(struct
>     pci_device *dev, pciaddr_t base,
>              snprintf(name, PATH_MAX,
>     "/sys/class/pci_bus/%04x:%02x/legacy_mem",
>                       dev->domain, dev->bus);
>
>     -       fd = open(name, flags | O_CLOEXEC);
>     +       fd = pci_open_cloexec(name, flags);
>              if (fd >= 0)
>                  break;
>
>     @@ -934,7 +934,7 @@ pci_device_linux_sysfs_map_legacy(struct
>     pci_device *dev, pciaddr_t base,
>
>           /* If not, /dev/mem is the best we can do */
>           if (!dev)
>     -       fd = open("/dev/mem", flags | O_CLOEXEC);
>     +       fd = pci_open_cloexec("/dev/mem", flags);
>
>           if (fd < 0)
>              return errno;
>     diff --git a/src/netbsd_pci.c b/src/netbsd_pci.c
>     index 52591b08f737..87bb2feb2504 100644
>     --- a/src/netbsd_pci.c
>     +++ b/src/netbsd_pci.c
>     @@ -909,7 +909,7 @@ pci_system_netbsd_create(void)
>              ndevs = 0;
>              nbuses = 0;
>              snprintf(netbsd_devname, 32, "/dev/pci%d", nbuses);
>     -       pcifd = open(netbsd_devname, O_RDWR | O_CLOEXEC);
>     +       pcifd = pci_open_cloexec(netbsd_devname, O_RDWR);
>              while (pcifd > 0) {
>                      ioctl(pcifd, PCI_IOC_BUSINFO, &businfo);
>                      buses[nbuses].fd = pcifd;
>     diff --git a/src/openbsd_pci.c b/src/openbsd_pci.c
>     index fe034f3b046b..3d66598b5b77 100644
>     --- a/src/openbsd_pci.c
>     +++ b/src/openbsd_pci.c
>     @@ -571,7 +571,7 @@ pci_system_openbsd_create(void)
>
>              for (domain = 0; domain < sizeof(pcifd) / sizeof(pcifd[0]);
>     domain++) {
>                      snprintf(path, sizeof(path), "/dev/pci%d", domain);
>     -               pcifd[domain] = open(path, O_RDWR | O_CLOEXEC);
>     +               pcifd[domain] = pci_open_cloexec(path, O_RDWR);
>                      if (pcifd[domain] == -1)
>                              break;
>                      ndomains++;
>     diff --git a/src/pciaccess_private.h b/src/pciaccess_private.h
>     index 9f4e8f9ab573..0de989bceab4 100644
>     --- a/src/pciaccess_private.h
>     +++ b/src/pciaccess_private.h
>     @@ -40,13 +40,16 @@
>       /*
>        * O_CLOEXEC fixes an fd leak case (see 'man 2 open' for details).
>     I don't
>        * know of any OS we support where this isn't available in a
>     sufficiently
>     - * new version, so warn unconditionally.
>     + * new version, so fail if ALLOW_NO_O_CLOEXEC is not defined.
>        */
>       #include <sys/fcntl.h>
>
>     -#ifndef O_CLOEXEC
>     -#warning O_CLOEXEC not available, please upgrade.
>     -#define O_CLOEXEC 0
>     +#if !defined(O_CLOEXEC)
>     +# if defined(ALLOW_NO_O_CLOEXEC)
>     +#  include <unistd.h>
>     +# else
>     +#  error O_CLOEXEC not available, please upgrade.
>     +# endif
>       #endif
>
>
>     @@ -191,3 +194,25 @@ extern void pci_system_openbsd_init_dev_mem( int );
>       extern int pci_system_solx_devfs_create( void );
>       extern int pci_system_x86_create( void );
>       extern void pci_io_cleanup( void );
>     +
>     +static inline int pci_open_cloexec( const char *path, int flags )
>     +{
>     +#if defined(O_CLOEXEC)
>     +    return open(path, flags | O_CLOEXEC);
>     +#else
>     +    int fd = open(path, flags);
>     +    if (fd >= 0) {
>     +       int flags = fcntl(fd, F_GETFD);
>     +       if (flags == -1) {
>     +           close(fd);
>     +           return -1;
>     +       }
>     +       flags |= FD_CLOEXEC;
>     +       if (fcntl(fd, F_SETFD, flags) == -1) {
>     +           close(fd);
>     +           return -1;
>     +       }
>     +    }
>     +    return fd;
>     +#endif
>     +}
>     diff --git a/src/solx_devfs.c b/src/solx_devfs.c
>     index f57239304a43..2d4b102f8cf1 100644
>     --- a/src/solx_devfs.c
>     +++ b/src/solx_devfs.c
>     @@ -415,7 +415,7 @@ probe_nexus_node(di_node_t di_node, di_minor_t
>     minor, void *arg)
>                  nexus_path, first_bus, last_bus);
>       #endif
>
>     -    if ((fd = open(nexus_path, O_RDWR | O_CLOEXEC)) >= 0) {
>     +    if ((fd = pci_open_cloexec(nexus_path, O_RDWR)) >= 0) {
>              probe_args_t args;
>
>              nexus->fd = fd;
>     @@ -718,7 +718,7 @@ pci_device_solx_devfs_map_range(struct
>     pci_device *dev,
>       #endif
>
>           if (map_fd < 0) {
>     -       if ((map_fd = open(map_dev, O_RDWR | O_CLOEXEC)) < 0) {
>     +       if ((map_fd = pci_open_cloexec(map_dev, O_RDWR)) < 0) {
>                  err = errno;
>                  (void) fprintf(stderr, "can not open %s: %s\n", map_dev,
>                                 strerror(errno));
>     diff --git a/src/x86_pci.c b/src/x86_pci.c
>     index 49c1cabc3c6c..7088ff9a016d 100644
>     --- a/src/x86_pci.c
>     +++ b/src/x86_pci.c
>     @@ -457,7 +457,7 @@ pci_device_x86_read_rom(struct pci_device *dev,
>     void *buffer)
>              return ENOSYS;
>           }
>
>     -    memfd = open("/dev/mem", O_RDONLY | O_CLOEXEC);
>     +    memfd = pci_open_cloexec("/dev/mem", O_RDONLY);
>           if (memfd == -1)
>              return errno;
>
>     @@ -637,7 +637,7 @@ static int
>       pci_device_x86_map_range(struct pci_device *dev,
>           struct pci_device_mapping *map)
>       {
>     -    int memfd = open("/dev/mem", O_RDWR | O_CLOEXEC);
>     +    int memfd = pci_open_cloexec("/dev/mem", O_RDWR);
>           int prot = PROT_READ;
>
>           if (memfd == -1)
>     --
>     2.1.0
>
>     _______________________________________________
>     xorg-devel at lists.x.org <mailto:xorg-devel at lists.x.org>: X.Org
>     development
>     Archives: http://lists.x.org/archives/xorg-devel
>     Info: http://lists.x.org/mailman/listinfo/xorg-devel
>
>
>
>
> --
>    Jasper


-- 
Aaron


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