59 lines
2.1 KiB
Diff
59 lines
2.1 KiB
Diff
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From ae03bc6effdffe145c871d70ce346f93faefc71b Mon Sep 17 00:00:00 2001
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From: Johannes Berg <johannes.berg@intel.com>
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Date: Thu, 28 Feb 2019 21:34:03 +0100
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Subject: [PATCH 49/50] iw: fix cmd_size determination with LTO
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Use a separate section to determine the cmd_size as in LTO
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the entries in __cmd get freely rearranged, leading to a
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(usually) very large cmd_size, and thus to the whole thing
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not working.
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Change-Id: I3437ad34de1d927961a3e98f109794d7a884327f
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Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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---
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iw.c | 21 ++++++++++++++++++++-
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1 file changed, 20 insertions(+), 1 deletion(-)
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diff --git a/iw.c b/iw.c
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index 76f152d..afc8118 100644
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--- a/iw.c
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+++ b/iw.c
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@@ -542,6 +542,25 @@ int handle_cmd(struct nl80211_state *state, enum id_input idby,
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return __handle_cmd(state, idby, argc, argv, NULL);
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}
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+/*
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+ * Unfortunately, I don't know how densely the linker packs the struct cmd.
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+ * For example, if you have a 72-byte struct cmd, the linker will pad each
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+ * out to 96 bytes before putting them together in the section. There must
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+ * be some algorithm, but I haven't found it yet.
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+ *
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+ * We used to calculate this by taking the (abs value of) the difference
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+ * between __section_get and __section_set, but if LTO is enabled then this
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+ * stops working because the entries of the "__cmd" section get rearranged
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+ * freely by the compiler/linker.
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+ *
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+ * Fix this by using yet another "__sizer" section that only contains these
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+ * two entries - then the (abs value of) the difference between them will
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+ * be how they get packed and that can be used to iterate the __cmd section
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+ * as well.
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+ */
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+static struct cmd sizer1 __attribute__((used,section("__sizer"))) = {};
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+static struct cmd sizer2 __attribute__((used,section("__sizer"))) = {};
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+
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int main(int argc, char **argv)
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{
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struct nl80211_state nlstate;
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@@ -549,7 +568,7 @@ int main(int argc, char **argv)
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const struct cmd *cmd = NULL;
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/* calculate command size including padding */
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- cmd_size = labs((long)&__section_set - (long)&__section_get);
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+ cmd_size = labs((uintptr_t)&sizer2 - (uintptr_t)&sizer1);
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/* strip off self */
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argc--;
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argv0 = *argv++;
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--
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1.8.3.1
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