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From 46b54db1427ac7a58f986ae3506ce23c068d94e0 Mon Sep 17 00:00:00 2001
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From: Josh Poimboeuf <jpoimboe@redhat.com>
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Date: Tue, 23 Jun 2020 22:20:33 -0500
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Subject: [PATCH] create-diff-object: change rela_equal() to return bool
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Change rela_equal's return value to bool to make its return semantics
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more clear.
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Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
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create-diff-object: Ignore changes to .altinstr_aux
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On x86, .altinstr_aux is used to store temporary code which allows
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static_cpu_has() to work before apply_alternatives() has run. This code
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is completely inert for modules, because apply_alternatives() runs
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during module init, before the module is fully formed. Any changed
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references to it (i.e. changed addend) can be ignored. As long as
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they're both references to .altinstr_aux, they can be considered equal,
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even if the addends differ.
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Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
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---
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kpatch-build/create-diff-object.c | 21 +++++++++++++++++----
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1 file changed, 17 insertions(+), 4 deletions(-)
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diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
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index aedd07d..b7332b1 100644
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--- a/kpatch-build/create-diff-object.c
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+++ b/kpatch-build/create-diff-object.c
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@@ -327,14 +327,27 @@ static int kpatch_mangled_strcmp(char *s1, char *s2)
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return 1;
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}
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-static int rela_equal(struct rela *rela1, struct rela *rela2)
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+static bool rela_equal(struct rela *rela1, struct rela *rela2)
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{
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struct rela *rela_toc1, *rela_toc2;
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unsigned long toc_data1 = 0, toc_data2 = 0; /* = 0 to prevent gcc warning */
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if (rela1->type != rela2->type ||
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rela1->offset != rela2->offset)
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- return 0;
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+ return false;
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+
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+ /*
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+ * On x86, .altinstr_aux is used to store temporary code which allows
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+ * static_cpu_has() to work before apply_alternatives() has run. This
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+ * code is completely inert for modules, because apply_alternatives()
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+ * runs during module init, before the module is fully formed. Any
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+ * changed references to it (i.e. changed addend) can be ignored. As
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+ * long as they're both references to .altinstr_aux, they can be
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+ * considered equal, even if the addends differ.
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+ */
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+ if (!strcmp(rela1->sym->name, ".altinstr_aux") &&
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+ !strcmp(rela2->sym->name, ".altinstr_aux"))
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+ return true;
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/*
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* With -mcmodel=large on ppc64le, GCC might generate entries in the .toc
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@@ -393,13 +406,13 @@ static int rela_equal(struct rela *rela1, struct rela *rela2)
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return toc_data1 == toc_data2;
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if (!rela_toc1 || !rela_toc2)
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- return 0;
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+ return false;
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if (rela_toc1->string)
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return rela_toc2->string && !strcmp(rela_toc1->string, rela_toc2->string);
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if (rela_toc1->addend != rela_toc2->addend)
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- return 0;
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+ return false;
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return !kpatch_mangled_strcmp(rela_toc1->sym->name, rela_toc2->sym->name);
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}
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--
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2.21.3
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