Musl libc realpath implementation calls readlink on a procfs path it computes via __procfdname (code at [1] & [2]).
This is problematic if ubase mount is used in a PID 1 because procfs is not mounted and the kernel passes the rootfs mounted read-only, so the first step is to read-write remount the rootfs, which can't be done because procfs is not mounted. Thus we are in a dependency cycle: procfs can't be mounted because the root is read-only and so on. To break this cycle, don't call readlink on "/" (it doesn't really make sense anyway) so the rootfs can be remounted read-write, after which proc itself can be mounted and the rest of mount calls will succeed so systems running ubase + musl can succesfully boot into userspace. [1] https://git.musl-libc.org/cgit/musl/tree/src/misc/realpath.c?h=v1.1.19 [2] https://git.musl-libc.org/cgit/musl/tree/src/internal/procfdname.c?h=v1.1.19 Signed-off-by: Ioan-Adrian Ratiu <a...@adirat.com> --- mount.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mount.c b/mount.c index 4ce6680..e3d00b8 100644 --- a/mount.c +++ b/mount.c @@ -242,9 +242,11 @@ main(int argc, char *argv[]) if (!target) { target = argv[0]; source = NULL; - if (!(resolvpath = realpath(target, NULL))) - eprintf("realpath %s:", target); - target = resolvpath; + if (strcmp(target, "/") != 0) { + if (!(resolvpath = realpath(target, NULL))) + eprintf("realpath %s:", target); + target = resolvpath; + } } for (i = 0; files[i]; i++) { -- 2.16.3
