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mount: don't call realpath on root target - ubase - suckless linux base utils |
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commit 4f5837147a14e0fb8ec1a2a46a9c4045bdb75696 |
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parent 11d2d1faaf9cd0e2b6796c17390137dedcdc90bb |
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Author: Ioan-Adrian Ratiu <[email protected]> |
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Date: Sat, 7 Apr 2018 05:33:30 +0300 |
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mount: don't call realpath on root target |
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Musl libc realpath implementation calls readlink on a procfs |
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path it computes via __procfdname (code at [1] & [2]). |
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This is problematic if ubase mount is used in a PID 1 because procfs |
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is not mounted and the kernel passes the rootfs mounted read-only, so |
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the first step is to read-write remount the rootfs, which can't be |
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done because procfs is not mounted. Thus we are in a dependency cycle: |
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procfs can't be mounted because the root is read-only and so on. |
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To break this cycle, don't call readlink on "/" (it doesn't really make |
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sense anyway) so the rootfs can be remounted read-write, after which |
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proc itself can be mounted and the rest of mount calls will succeed |
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so systems running ubase + musl can succesfully boot into userspace. |
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[1] https://git.musl-libc.org/cgit/musl/tree/src/misc/realpath.c?h=v1.1.19 |
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[2] https://git.musl-libc.org/cgit/musl/tree/src/internal/procfdname.c?h=v1.1.19 |
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Signed-off-by: Ioan-Adrian Ratiu <[email protected]> |
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Diffstat: |
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M mount.c | 8 +++++--- |
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1 file changed, 5 insertions(+), 3 deletions(-) |
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--- |
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diff --git a/mount.c b/mount.c |
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@@ -242,9 +242,11 @@ main(int argc, char *argv[]) |
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if (!target) { |
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target = argv[0]; |
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source = NULL; |
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- if (!(resolvpath = realpath(target, NULL))) |
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- eprintf("realpath %s:", target); |
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- target = resolvpath; |
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+ if (strcmp(target, "/") != 0) { |
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+ if (!(resolvpath = realpath(target, NULL))) |
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+ eprintf("realpath %s:", target); |
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+ target = resolvpath; |
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+ } |
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} |
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for (i = 0; files[i]; i++) { |
