On Fri, Feb 16, 2024 at 07:19:20PM +0100, Uwe Kleine-König wrote: > A phandle in an overlay is not supposed to overwrite a phandle that > already exists in the base dtb as this breaks references to the > respective node in the base. > > So add another iteration over the fdto that checks for such overwrites > and fixes the fdto phandle's value to match the fdt's. > > A test is added that checks that newly added phandles and existing > phandles work as expected. > > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> > --- > Hello, > > last year I already tried to address the issue of phandle overwriting in > overlays. See > https://lore.kernel.org/all/20230426100231.484497-1-u.kleine-koenig@xxxxxxxxxxxxxx > > The approach I took back then required allocating a mapping. This isn't > suiteable for libfdt though because it's expected to be embedded in code > that cannot allocate dynamic memory. So here I implement an algorithm > that doesn't allocate memory at the cost of a higher run time because it > iterates over the whole dtbo for each conflict found. But there isn't a > better way to do it without allocating memory. Thanks for following this up. I think I finally got my head around what's going on here. I really wish there were a more elegant way of dealing with it, but I don't think there is. That said, there are some smaller improvements that I think can be made, detailed comments below. > libfdt/fdt_overlay.c | 230 ++++++++++++++++++++++++++++++ > tests/overlay_base_phandle.dts | 21 +++ > tests/overlay_overlay_phandle.dts | 30 ++++ > tests/run_tests.sh | 23 +++ > 4 files changed, 304 insertions(+) > create mode 100644 tests/overlay_base_phandle.dts > create mode 100644 tests/overlay_overlay_phandle.dts > > diff --git a/libfdt/fdt_overlay.c b/libfdt/fdt_overlay.c > index 5c0c3981b89d..914acc5b14a6 100644 > --- a/libfdt/fdt_overlay.c > +++ b/libfdt/fdt_overlay.c > @@ -520,6 +520,228 @@ static int overlay_fixup_phandles(void *fdt, void *fdto) > return 0; > } > All of these new functions could do with descriptive comments saying what they do (see the existing code for examples). > +static int overlay_adjust_node_conflicting_phandle(void *fdto, int node, > + uint32_t fdt_phandle, > + uint32_t fdto_phandle) > +{ > + const fdt32_t *php; > + int len, ret; > + int child; > + > + php = fdt_getprop(fdto, node, "phandle", &len); > + if (php && len == sizeof(*php) && fdt32_to_cpu(*php) == fdto_phandle) { > + ret = fdt_setprop_inplace_u32(fdto, node, "phandle", fdt_phandle); > + if (ret) > + return ret; > + } > + > + php = fdt_getprop(fdto, node, "linux,phandle", &len); > + if (php && len == sizeof(*php) && fdt32_to_cpu(*php) == fdto_phandle) { > + ret = fdt_setprop_inplace_u32(fdto, node, "linux,phandle", fdt_phandle); > + if (ret) > + return ret; > + } > + > + fdt_for_each_subnode(child, fdto, node) { > + ret = overlay_adjust_node_conflicting_phandle(fdto, child, > + fdt_phandle, fdto_phandle); > + if (ret) > + return ret; > + } > + > + return 0; > +} > + > +static int overlay_adjust_local_conflicting_phandle(void *fdto, > + uint32_t fdt_phandle, > + uint32_t fdto_phandle) > +{ > + return overlay_adjust_node_conflicting_phandle(fdto, 0, fdt_phandle, > + fdto_phandle); > +} I don't believe you need the above two functions: see further comments at the call site. > +static int overlay_update_node_conflicting_references(void *fdto, int tree_node, > + int fixup_node, > + uint32_t fdt_phandle, > + uint32_t fdto_phandle) > +{ > + int fixup_prop; > + int fixup_child; > + int ret; > + > + fdt_for_each_property_offset(fixup_prop, fdto, fixup_node) { > + Extraneous blank line. > + const fdt32_t *fixup_val; > + const char *tree_val; libfdt style is to use tab indents, looks like most of this block has space indents instead. > + const char *name; > + int fixup_len; > + int tree_len; > + int i; > + > + fixup_val = fdt_getprop_by_offset(fdto, fixup_prop, > + &name, &fixup_len); > + if (!fixup_val) > + return fixup_len; > + > + if (fixup_len % sizeof(uint32_t)) > + return -FDT_ERR_BADOVERLAY; > + fixup_len /= sizeof(uint32_t); > + > + tree_val = fdt_getprop(fdto, tree_node, name, &tree_len); > + if (!tree_val) { > + if (tree_len == -FDT_ERR_NOTFOUND) > + return -FDT_ERR_BADOVERLAY; > + > + return tree_len; > + } > + > + for (i = 0; i < fixup_len; i++) { > + fdt32_t adj_val; > + uint32_t poffset; > + > + poffset = fdt32_to_cpu(fixup_val[i]); You can use fdt32_ld_() here to slightly simplify this > + > + /* > + * phandles to fixup can be unaligned. > + * > + * Use a memcpy for the architectures that do > + * not support unaligned accesses. > + */ > + memcpy(&adj_val, tree_val + poffset, sizeof(adj_val)); And here you can use fdt32_ld() which has unaligned access handling built in. > + > + if (fdt32_to_cpu(adj_val) == fdto_phandle) { > + > + adj_val = cpu_to_fdt32(fdt_phandle); > + > + ret = fdt_setprop_inplace_namelen_partial(fdto, > + tree_node, > + name, > + strlen(name), > + poffset, > + &adj_val, > + sizeof(adj_val)); > + if (ret == -FDT_ERR_NOSPACE) > + return -FDT_ERR_BADOVERLAY; > + > + if (ret) > + return ret; And here you can use fdt32_st() on (tree_val + poffset), avoiding quite some complexity. > + } > + } > + } > + > + fdt_for_each_subnode(fixup_child, fdto, fixup_node) { > + const char *fixup_child_name = fdt_get_name(fdto, fixup_child, NULL); > + int tree_child; > + > + tree_child = fdt_subnode_offset(fdto, tree_node, fixup_child_name); > + > + if (tree_child == -FDT_ERR_NOTFOUND) > + return -FDT_ERR_BADOVERLAY; > + if (tree_child < 0) > + return tree_child; > + > + ret = overlay_update_node_conflicting_references(fdto, tree_child, > + fixup_child, > + fdt_phandle, > + fdto_phandle); > + } > + > + return 0; > +} > + > +static int overlay_update_local_conflicting_references(void *fdto, > + uint32_t fdt_phandle, > + uint32_t fdto_phandle) > +{ > + int fixups; > + > + fixups = fdt_path_offset(fdto, "/__local_fixups__"); > + if (fixups == -FDT_ERR_NOTFOUND) > + return 0; > + if (fixups < 0) > + return fixups; > + > + return overlay_update_node_conflicting_references(fdto, 0, fixups, > + fdt_phandle, > + fdto_phandle); > +} > + > +static int overlay_prevent_phandle_overwrite_node(void *fdt, int fdtnode, > + void *fdto, int fdtonode) Maybe "overlay_resolve_phandle_conflict()" for a slightly shorter function name. > +{ > + uint32_t fdt_phandle, fdto_phandle; > + int fdtochild; > + > + fdt_phandle = fdt_get_phandle(fdt, fdtnode); > + fdto_phandle = fdt_get_phandle(fdto, fdtonode); > + > + if (fdt_phandle && fdto_phandle) { > + int ret; > + > + ret = overlay_adjust_local_conflicting_phandle(fdto, > + fdt_phandle, > + fdto_phandle); > + if (ret) > + return ret; So while, as you've seen, there can be conflicting phandles between the fdt and the fdto, within the fdto a particular phandle should only appear on a single node. If a phandle is duplicated across nodes witin a single fdto, you have bigger problems. Therefore, having found a conflict, you're already found the only place you need to change the phandle property itself - you don't need to scan the full fdto again. So I believe you can replace the above call with just setting the phandle property on fdtonode. > + > + ret = overlay_update_local_conflicting_references(fdto, > + fdt_phandle, > + fdto_phandle); > + if (ret) > + return ret; You do, of course, have to scan the whole fdto to update references. > + } > + > + fdt_for_each_subnode(fdtochild, fdto, fdtonode) { > + const char *name = fdt_get_name(fdto, fdtochild, NULL); > + int fdtchild; > + int ret; > + > + fdtchild = fdt_subnode_offset(fdt, fdtnode, name); > + if (fdtchild == -FDT_ERR_NOTFOUND) > + /* > + * no further overwrites possible here as this node is > + * new > + */ > + continue; > + > + ret = overlay_prevent_phandle_overwrite_node(fdt, fdtchild, > + fdto, fdtochild); > + if (ret) > + return ret; > + } > + > + return 0; > +} > + > +static int overlay_prevent_phandle_overwrite(void *fdt, void *fdto) > +{ > + int fragment; > + > + fdt_for_each_subnode(fragment, fdto, 0) { > + int overlay; > + int target; > + int ret; > + > + overlay = fdt_subnode_offset(fdto, fragment, "__overlay__"); > + if (overlay == -FDT_ERR_NOTFOUND) > + continue; > + > + if (overlay < 0) > + return overlay; > + > + target = fdt_overlay_target_offset(fdt, fdto, fragment, NULL); > + if (target < 0) > + return target; > + > + ret = overlay_prevent_phandle_overwrite_node(fdt, target, > + fdto, overlay); > + if (ret) > + return ret; > + } > + > + return 0; > +} > + > /** > * overlay_apply_node - Merges a node into the base device tree > * @fdt: Base Device Tree blob > @@ -824,18 +1046,26 @@ int fdt_overlay_apply(void *fdt, void *fdto) > if (ret) > goto err; > > + /* Increase all phandles in the fdto by delta */ > ret = overlay_adjust_local_phandles(fdto, delta); > if (ret) > goto err; > > + /* Adapt the phandle values in fdto to the above increase */ > ret = overlay_update_local_references(fdto, delta); > if (ret) > goto err; > > + /* Update fdto's phandles using symbols from fdt */ > ret = overlay_fixup_phandles(fdt, fdto); > if (ret) > goto err; > > + /* Don't overwrite phandles in fdt */ > + ret = overlay_prevent_phandle_overwrite(fdt, fdto); > + if (ret) > + goto err; I think this should go above overlay_fixup_phandles(), so that we're completing all the __local_fixups__ based adjustments before going to the __fixups__ based adjustments. > + > ret = overlay_merge(fdt, fdto); > if (ret) > goto err; > diff --git a/tests/overlay_base_phandle.dts b/tests/overlay_base_phandle.dts > new file mode 100644 > index 000000000000..36f013c772a2 > --- /dev/null > +++ b/tests/overlay_base_phandle.dts > @@ -0,0 +1,21 @@ > +/* > + * Copyright (c) 2024 Uwe Kleine-König > + * > + * SPDX-License-Identifier: GPL-2.0+ > + */ > + > +/dts-v1/; > + > +/ { > + node_a: a { > + value = <17>; > + }; > + > + node_b: b { > + a = <&node_a>; > + }; > + > + node_c: c { > + b = <&node_b>; > + }; > +}; > diff --git a/tests/overlay_overlay_phandle.dts b/tests/overlay_overlay_phandle.dts > new file mode 100644 > index 000000000000..218e5266b992 > --- /dev/null > +++ b/tests/overlay_overlay_phandle.dts > @@ -0,0 +1,30 @@ > +/* > + * Copyright (c) 2024 Uwe Kleine-König > + * > + * SPDX-License-Identifier: GPL-2.0+ > + */ > + > +/dts-v1/; > +/plugin/; > + > +&{/} { > + /* /a already has a label "node_a" in the base dts */ > + node_b2: b { > + value = <42>; > + c = <&node_c>; > + }; > + > + c { > + a = <&node_a>; > + d = <&node_d>; > + }; > + > + node_d: d { > + value = <23>; > + b = <&node_b2>; > + }; > +}; > + > +&node_a { > + value = <32>; > +}; > diff --git a/tests/run_tests.sh b/tests/run_tests.sh > index 3225a12bbb06..256472b623a3 100755 > --- a/tests/run_tests.sh > +++ b/tests/run_tests.sh > @@ -1040,6 +1040,28 @@ fdtoverlay_tests() { > run_dtc_test -@ -I dts -O dtb -o $stacked_addlabeldtb $stacked_addlabel > > run_fdtoverlay_test baz "/foonode/barnode/baznode" "baz-property" "-ts" ${stacked_base_nolabeldtb} ${stacked_addlabel_targetdtb} ${stacked_addlabeldtb} ${stacked_bardtb} ${stacked_bazdtb} > + > + # verify that labels are not overwritten > + run_dtc_test -@ -I dts -O dtb -o overlay_base_phandle.test.dtb "$SRCDIR/overlay_base_phandle.dts" > + run_dtc_test -@ -I dts -O dtb -o overlay_overlay_phandle.test.dtb "$SRCDIR/overlay_overlay_phandle.dts" > + run_wrap_test $FDTOVERLAY -i overlay_base_phandle.test.dtb -o overlay_base_phandleO.test.dtb overlay_overlay_phandle.test.dtb > + > + pa=$($DTGET overlay_base_phandleO.test.dtb /a phandle) > + pb=$($DTGET overlay_base_phandleO.test.dtb /b phandle) > + pc=$($DTGET overlay_base_phandleO.test.dtb /c phandle) > + pd=$($DTGET overlay_base_phandleO.test.dtb /d phandle) > + ba=$($DTGET overlay_base_phandleO.test.dtb /b a) > + bc=$($DTGET overlay_base_phandleO.test.dtb /b c) > + ca=$($DTGET overlay_base_phandleO.test.dtb /c a) > + cb=$($DTGET overlay_base_phandleO.test.dtb /c b) > + cd=$($DTGET overlay_base_phandleO.test.dtb /c d) > + db=$($DTGET overlay_base_phandleO.test.dtb /d b) > + shorten_echo "check phandle wasn't overwritten: " > + if test "$ba-$bc-$ca-$cb-$cd-$db" = "$pa-$pc-$pa-$pb-$pd-$pb"; then I'd prefer to see each of these pairs as a separate test case. > + PASS > + else > + FAIL > + fi > } > > pylibfdt_tests () { -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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