On Fri, Apr 01, 2011 at 11:00:51AM +0900, Simon Horman wrote:
> On Thu, Mar 31, 2011 at 05:21:15PM +0000, Chris Leech wrote:
> > Simon Horman <horms at ...> writes:
> >
> > >
> > > On Tue, Mar 29, 2011 at 09:04:53AM +0000, WANG Cong wrote:
> > > > On Mon, 28 Mar 2011 14:50:11 -0700, Chris Leech wrote:
> > > >
> > > > > kexec needs to keep the subarch setting the same as the running kernel
> > > > > in the boot parameters, or the kernel will die in early setup. I ran
> > > > > into this with X86_SUBARCH_MRST, but it should apply to CE4100 and any
> > > > > future subarch that uses non-default early setup code.
> > > > >
> > > > > This patch requires debugfs mounted at /sys/kernel/debug, as that's the
> > > > > only way I know of to get at the running kernels boot_params. Without
> > > > > debugfs mounted it falls back to the current behavior of assuming
> > > > > subarch 0.
> > > > >
> > > > ...
> > > > >
> > > > > +#define BOOT_PARAMS_DBGFS "/sys/kernel/debug/boot_params/data"
> > > >
> > > > A minor issue here is that you are using a hard-coded debugfs path,
> > > > debugfs can be also mounted to /debug too, so it is better that if we can
> > > > search the path dynamically here.
> > >
> > > Do you think it would be better for the code to loop through
> > > a few common alternatives for the path?
> > >
> >
> > Not fully tested, but instead of looping through possible mount points maybe
> > look through mtab in search of debugfs by fs type.
> >
> > Something like this?
>
> This approach looks good to me.
> Could you do some more testing?
Ping.
> > kexec, x86: search for debugfs mountpoint in /etc/mtab
> >
> > From: Chris Leech <christopher.leech at linux.intel.com>
> >
> > Signed-off-by: Chris Leech <christopher.leech at linux.intel.com>
> > ---
> > kexec/arch/i386/x86-linux-setup.c | 35 +++++++++++++++++++++++++++++++++--
> > 1 files changed, 33 insertions(+), 2 deletions(-)
> >
> > diff --git a/kexec/arch/i386/x86-linux-setup.c b/kexec/arch/i386/x86-linux-
> > setup.c
> > index 50b32be..0528cea 100644
> > --- a/kexec/arch/i386/x86-linux-setup.c
> > +++ b/kexec/arch/i386/x86-linux-setup.c
> > @@ -30,6 +30,7 @@
> > #include <linux/fb.h>
> > #include <unistd.h>
> > #include <dirent.h>
> > +#include <mntent.h>
> > #include <x86/x86-linux.h>
> > #include "../../kexec.h"
> > #include "kexec-x86.h"
> > @@ -397,14 +398,44 @@ out:
> > real_mode->eddbuf_entries);
> > }
> >
> > -#define BOOT_PARAMS_DBGFS "/sys/kernel/debug/boot_params/data"
> > +/*
> > + * This really only makes sense for virtual filesystems that are only expected
> > + * to be mounted once (sysfs, debugsfs, proc), as it will return the first
> > + * instance listed in mtab.
> > + */
> > +char *find_mnt_by_fsname(char *fsname)
> > +{
> > + FILE *mtab;
> > + struct mntent *mnt;
> > + char *mntdir;
> > +
> > + mtab = setmntent("/etc/mtab", "r");
> > + if (!mtab)
> > + return NULL;
> > + for(mnt = getmntent(mtab); mnt; mnt = getmntent(mtab)) {
> > + if (strcmp(mnt->mnt_fsname, fsname) == 0)
> > + break;
> > + }
> > + mntdir = mnt ? strdup(mnt->mnt_dir) : NULL;
> > + endmntent(mtab);
> > + return mntdir;
> > +}
> >
> > void setup_subarch(struct x86_linux_param_header *real_mode)
> > {
> > int data_file;
> > const off_t offset = offsetof(typeof(*real_mode), hardware_subarch);
> > + char *debugfs_mnt;
> > + char filename[PATH_MAX];
> > +
> > + debugfs_mnt = find_mnt_by_fsname("debugfs");
> > + if (!debugfs_mnt)
> > + return;
> > + snprintf(filename, PATH_MAX, "%s/%s", debugfs_mnt, "boot_params/data");
>
> It might be worth bailing out on truncation here.
> Perhaps with an error message?
>
> > + filename[PATH_MAX-1] = 0;
> > + free(debugfs_mnt);
> >
> > - data_file = open(BOOT_PARAMS_DBGFS, O_RDONLY);
> > + data_file = open(filename, O_RDONLY);
> > if (data_file < 0)
> > return;
> > if (lseek(data_file, offset, SEEK_SET) < 0)
>
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