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Re: [PATCH] grub-install: Add backup and restore
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From: |
Dimitri John Ledkov |
|
Subject: |
Re: [PATCH] grub-install: Add backup and restore |
|
Date: |
Wed, 12 May 2021 19:20:37 +0100 |
On Tue, 4 May 2021 at 18:41, Daniel Kiper <dkiper@net-space.pl> wrote:
>
> Hey,
>
> In general much better but...
>
> On Thu, Apr 29, 2021 at 12:36:37PM +0100, Dimitri John Ledkov wrote:
> > Refactor clean_grub_dir to create a backup of all the files, instead
> > of just irrevocably removing them as the first action. If available,
> > register atexit handle to restore the backup if errors occur before
> > point of no return, or remove the backup if everything was
> > successful. If atexit is not available, the backup remains on disk for
> > manual recovery.
> >
> > Some platforms defined a point of no return, i.e. after modules & core
> > images were updated. Failures from any commands after that stage are
> > ignored, and backup is cleanedup. For example, on EFI platforms update
> > is not reverted when efibootmgr fails.
> >
> > Extra care is taken to ensure atexit handler is only invoked by the
> > parent process and not any children forks. Some older grub codebases
> > can invoke parent atexit hooks from forks, which can mess up the
> > backup.
> >
> > This allows safer upgrades of MBR & modules, such that
> > modules/images/fonts/translations are consistent with MBR in case of
> > errors. For example accidental grub-install /dev/non-existent-disk
> > currently clobbers and upgrades modules in /boot/grub, despite not
> > actually updating any MBR. This increases peak disk-usage slightly, by
> > requiring temporarily twice the disk space to complete grub-install.
>
> I think this last sentence does not parse with the rest of paragraph.
>
simply dropped.
> Additionally, may I ask you to add a blurb here about the blocklist?
> I think about most important things from the email exchange between
> Micheal and you.
>
Added a summary.
> > Also add modinfo.sh and *.efi to the cleanup/backup/restore codepath,
> > to ensure it is also cleaned / backed up / restored.
> >
> > Signed-off-by: Dimitri John Ledkov <xnox@ubuntu.com>
> > ---
> >
> > Changes since v2:
> > - switch from on_exit, to atexit
> > - introduce point of no return flag, as atexit doesn't know about
> > exit status and at times it is desired to declare point of no
> > return earlier and ignore some error.
> > - address review feedback wrt styling
> > - improve reliablity, verify that only parent process calls atexit
> > hook
> >
> > configure.ac | 2 +-
> > include/grub/util/install.h | 11 +++
> > util/grub-install-common.c | 142 ++++++++++++++++++++++++++++++++----
> > util/grub-install.c | 33 +++++++--
> > util/grub-mknetdir.c | 3 +
> > util/grub-mkrescue.c | 3 +
> > util/grub-mkstandalone.c | 2 +
> > 7 files changed, 172 insertions(+), 24 deletions(-)
> >
> > diff --git a/configure.ac b/configure.ac
> > index 74719416c4..a5e94f360e 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -419,7 +419,7 @@ else
> > fi
> >
> > # Check for functions and headers.
> > -AC_CHECK_FUNCS(posix_memalign memalign getextmntent)
> > +AC_CHECK_FUNCS(posix_memalign memalign getextmntent atexit)
> > AC_CHECK_HEADERS(sys/param.h sys/mount.h sys/mnttab.h limits.h)
> >
> > # glibc 2.25 still includes sys/sysmacros.h in sys/types.h but emits
> > deprecation
> > diff --git a/include/grub/util/install.h b/include/grub/util/install.h
> > index b93c73caac..d729060ce7 100644
> > --- a/include/grub/util/install.h
> > +++ b/include/grub/util/install.h
> > @@ -275,4 +275,15 @@ extern char *grub_install_copy_buffer;
> > int
> > grub_install_is_short_mbrgap_supported (void);
> >
> > +/* grub-install-common tries to make backups of modules & auxilary
> > +files, and restore the backup upon failure to install core.img. There
> > +are platforms with additional actions after modules & core got
> > +installed in place. It is a point of no return, as core.img cannot be
> > +reverted from this point onwards, and new modules should be kept
> > +installed. Before performing these additional actions raise
> > +grub_install_backup_ponr flag, this way failure to perform additional
> > +actions will not result in reverting new modules to the old
> > +ones. (i.e. in case efivars updates fails) */
>
> Could you format comments like it is documented here:
> https://www.gnu.org/software/grub/manual/grub-dev/grub-dev.html#Comments
>
done.
> > +extern size_t grub_install_backup_ponr;
> > +
> > #endif
> > diff --git a/util/grub-install-common.c b/util/grub-install-common.c
> > index b4f28840f1..db7feae7d3 100644
> > --- a/util/grub-install-common.c
> > +++ b/util/grub-install-common.c
> > @@ -185,38 +185,150 @@ grub_install_mkdir_p (const char *dst)
> > free (t);
> > }
> >
> > +static int
> > +strcmp_ext (const char *a, const char *b, const char *ext)
> > +{
> > + char *bsuffix = grub_util_path_concat_ext (1, b, ext);
> > + int r = strcmp (a, bsuffix);
> > +
> > + free (bsuffix);
> > + return r;
> > +}
> > +
> > +enum clean_grub_dir_mode
> > +{
> > + CLEAN,
>
> CLEAN what? s/CLEAN/CLEAN_NEW/?
>
CLEAN_NEW it is.
> > + CLEAN_BACKUP,
> > + CREATE_BACKUP,
> > + RESTORE_BACKUP,
>
> Please drop this redundant "," at the end.
>
done.
> > +};
> > +
> > +static size_t backup_dirs_len = 0;
>
> s/backup_dirs_len/backup_dirs_nr/?
>
> or
>
> s/backup_dirs_len/backup_dirs_size/?
>
git grep '_nr;' | wc
1 3 40
git grep '_len;' | wc
172 848 10494
git grep '_size;' | wc
749 3138 47413
_size it is.
> > +static char **backup_dirs;
> > +static pid_t backup_process = 0;
> > +size_t grub_install_backup_ponr = 0;
> > +
> > static void
> > -clean_grub_dir (const char *di)
> > +clean_grub_dir_real (const char *di, enum clean_grub_dir_mode mode)
> > {
> > grub_util_fd_dir_t d;
> > grub_util_fd_dirent_t de;
> > + char suffix[2] = "";
>
> const char *suffix = "";
>
done.
> > + if ((mode == CLEAN_BACKUP) || (mode == RESTORE_BACKUP))
> > + strcpy (suffix, "~");
>
> suffix = "~";
>
done.
> > d = grub_util_fd_opendir (di);
> > if (!d)
> > - grub_util_error (_("cannot open directory `%s': %s"),
> > - di, grub_util_fd_strerror ());
> > + {
> > + if (mode == CLEAN_BACKUP)
> > + return;
> > + grub_util_error (_("cannot open directory `%s': %s"),
> > + di, grub_util_fd_strerror ());
> > + }
> >
> > while ((de = grub_util_fd_readdir (d)))
> > {
> > const char *ext = strrchr (de->d_name, '.');
> > - if ((ext && (strcmp (ext, ".mod") == 0
> > - || strcmp (ext, ".lst") == 0
> > - || strcmp (ext, ".img") == 0
> > - || strcmp (ext, ".mo") == 0)
> > - && strcmp (de->d_name, "menu.lst") != 0)
> > - || strcmp (de->d_name, "efiemu32.o") == 0
> > - || strcmp (de->d_name, "efiemu64.o") == 0)
> > +
> > + if ((ext && (strcmp_ext (ext, ".mod", suffix) == 0
> > + || strcmp_ext (ext, ".lst", suffix) == 0
> > + || strcmp_ext (ext, ".img", suffix) == 0
> > + || strcmp_ext (ext, ".efi", suffix) == 0
> > + || strcmp_ext (ext, ".mo", suffix) == 0)
> > + && strcmp_ext (de->d_name, "menu.lst", suffix) != 0)
> > + || strcmp_ext (de->d_name, "modinfo.sh", suffix) == 0
> > + || strcmp_ext (de->d_name, "efiemu32.o", suffix) == 0
> > + || strcmp_ext (de->d_name, "efiemu64.o", suffix) == 0)
> > {
> > - char *x = grub_util_path_concat (2, di, de->d_name);
> > - if (grub_util_unlink (x) < 0)
> > - grub_util_error (_("cannot delete `%s': %s"), x,
> > - grub_util_fd_strerror ());
> > - free (x);
> > + char *srcf = grub_util_path_concat (2, di, de->d_name);
> > +
> > + if (mode == CREATE_BACKUP)
> > + {
> > + char *dstf = grub_util_path_concat_ext (2, di, de->d_name, "~");
> > +
> > + if (grub_util_rename (srcf, dstf) < 0)
> > + grub_util_error (_("cannot backup `%s': %s"), srcf,
> > + grub_util_fd_strerror ());
> > + free (dstf);
> > + }
> > + else if (mode == RESTORE_BACKUP)
> > + {
> > + char *dstf = grub_util_path_concat (2, di, de->d_name);
> > +
> > + dstf[strlen (dstf) - 1] = 0;
>
> s/0/'\0'/
>
> The final result is the same but it is a bit clearer what you mean...
>
done.
> > + if (grub_util_rename (srcf, dstf) < 0)
> > + grub_util_error (_("cannot restore `%s': %s"), dstf,
> > + grub_util_fd_strerror ());
> > + free (dstf);
> > + }
> > + else
> > + {
> > + if (grub_util_unlink (srcf) < 0)
> > + grub_util_error (_("cannot delete `%s': %s"), srcf,
> > + grub_util_fd_strerror ());
> > + }
> > + free (srcf);
> > }
> > }
> > grub_util_fd_closedir (d);
> > }
> >
> > +static void
> > +restore_backup_atexit (void)
> > +{
> > + /* some child inherited atexit handler, did not clear it, and
> > + * called it, skip clean or restore logic */
>
> Please fix this comment as I mentioned above...
>
done.
> > + if (backup_process != getpid ())
> > + return;
> > +
> > + for (size_t i = 0; i < backup_dirs_len; i++)
> > + {
> > + /* if past point of no return simply clean the
> > + backups. Otherwise cleanup newly installed files,
> > + and restore the backups */
> > + if (grub_install_backup_ponr == 1)
>
> I would drop "== 1" here.
>
done.
> > + clean_grub_dir_real (backup_dirs[i], CLEAN_BACKUP);
> > + else
> > + {
> > + clean_grub_dir_real (backup_dirs[i], CLEAN);
> > + clean_grub_dir_real (backup_dirs[i], RESTORE_BACKUP);
> > + }
> > + free (backup_dirs[i]);
> > + }
> > +
> > + backup_dirs_len = 0;
> > +
> > + free (backup_dirs);
> > +}
> > +
> > +static void
> > +append_to_backup_dirs (const char *dir)
> > +{
> > + if (backup_dirs_len == 0)
> > + backup_dirs = xmalloc (sizeof (char *) * (backup_dirs_len + 1));
> > + else
> > + backup_dirs =
> > + xrealloc (backup_dirs, sizeof (char *) * (backup_dirs_len + 1));
>
> backup_dirs = xrealloc (backup_dirs, sizeof (char *) * (backup_dirs_len + 1));
>
> You do not need "if (backup_dirs_len == 0)" because xrealloc() is able
> to serve you properly in both cases you care about. And even more... :-)
>
yes.
> > + backup_dirs[backup_dirs_len] = strdup (dir);
> > + backup_dirs_len++;
> > + if (backup_process == 0)
>
> if (!backup_process)
>
done.
> > + {
> > + atexit (restore_backup_atexit);
> > + backup_process = getpid ();
> > + }
> > +}
> > +
> > +static void
> > +clean_grub_dir (const char *di)
> > +{
> > + clean_grub_dir_real (di, CLEAN_BACKUP);
> > + clean_grub_dir_real (di, CREATE_BACKUP);
> > +#if defined(HAVE_ATEXIT)
> > + append_to_backup_dirs (di);
> > +#endif
> > +}
> > +
> > struct install_list
> > {
> > int is_default;
> > diff --git a/util/grub-install.c b/util/grub-install.c
> > index a0babe3eff..f85cf473ff 100644
> > --- a/util/grub-install.c
> > +++ b/util/grub-install.c
> > @@ -1719,10 +1719,14 @@ main (int argc, char *argv[])
> >
> > /* Now perform the installation. */
> > if (install_bootsector)
> > - grub_util_bios_setup (platdir, "boot.img", "core.img",
> > - install_drive, force,
> > - fs_probe, allow_floppy, add_rs_codes,
> > - !grub_install_is_short_mbrgap_supported ());
> > + {
> > + grub_util_bios_setup (platdir, "boot.img", "core.img",
> > + install_drive, force,
> > + fs_probe, allow_floppy, add_rs_codes,
> > + !grub_install_is_short_mbrgap_supported ());
> > +
> > + grub_install_backup_ponr = 1;
> > + }
> > break;
> > }
> > case GRUB_INSTALL_PLATFORM_SPARC64_IEEE1275:
> > @@ -1746,10 +1750,14 @@ main (int argc, char *argv[])
> >
> > /* Now perform the installation. */
> > if (install_bootsector)
> > - grub_util_sparc_setup (platdir, "boot.img", "core.img",
> > - install_drive, force,
> > - fs_probe, allow_floppy,
> > - 0 /* unused */, 0 /* unused */ );
> > + {
> > + grub_util_sparc_setup (platdir, "boot.img", "core.img",
> > + install_drive, force,
> > + fs_probe, allow_floppy,
> > + 0 /* unused */, 0 /* unused */ );
> > +
> > + grub_install_backup_ponr = 1;
> > + }
> > break;
> > }
> >
> > @@ -1776,6 +1784,8 @@ main (int argc, char *argv[])
> > grub_elf = grub_util_path_concat (2, core_services, "grub.elf");
> > grub_install_copy_file (imgfile, grub_elf, 1);
> >
> > + grub_install_backup_ponr = 1;
> > +
> > f = grub_util_fopen (mach_kernel, "a+");
> > if (!f)
> > grub_util_error (_("Can't create file: %s"), strerror (errno));
> > @@ -1878,6 +1888,8 @@ main (int argc, char *argv[])
> > boot_efi = grub_util_path_concat (2, core_services, "boot.efi");
> > grub_install_copy_file (imgfile, boot_efi, 1);
> >
> > + grub_install_backup_ponr = 1;
> > +
> > f = grub_util_fopen (mach_kernel, "r+");
> > if (!f)
> > grub_util_error (_("Can't create file: %s"), strerror (errno));
> > @@ -1916,6 +1928,9 @@ main (int argc, char *argv[])
> > {
> > char *dst = grub_util_path_concat (2, efidir, efi_file);
> > grub_install_copy_file (imgfile, dst, 1);
> > +
> > + grub_install_backup_ponr = 1;
> > +
> > free (dst);
> > }
> > if (!removable && update_nvram)
> > @@ -1967,6 +1982,8 @@ main (int argc, char *argv[])
> > break;
> > }
> >
> > + grub_install_backup_ponr = 1;
> > +
>
> Do we really need this one?
Yes. Many platforms only conditionally set ponr, or don't set ponr at
all as they have no platform specific code.
Thus yes, at this point core is installed, and ponr should be set.
Otherwise we would suddenly start reverting files for all the
platforms without a platform specific code.
>
> > fprintf (stderr, "%s\n", _("Installation finished. No error reported."));
> >
> > /* Free resources. */
>
> Daniel
--
Regards,
Dimitri.