From 698cc1c137d05f27192d508a068774e4239da59c Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@redhat.com>
Date: Fri, 23 May 2014 10:30:29 -0500
Subject: [PATCH] create-diff-object: support fixup and related sections

Add support for the following sections:

- .fixup
- __ex_table
- .altinstructions
- .altinstr_replacement

Fixes #187.
---
 kpatch-build/create-diff-object.c    | 61 ++++++++++++++++++++++++++++
 test/integration/fixup-section.patch | 12 ++++++
 2 files changed, 73 insertions(+)
 create mode 100644 test/integration/fixup-section.patch

diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
index f817d52..f1400cf 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -995,6 +995,28 @@ void kpatch_reindex_elements(struct kpatch_elf *kelf)
 int bug_table_group_size(struct section *sec, int offset) { return 12; }
 int smp_locks_group_size(struct section *sec, int offset) { return 4; }
 int parainstructions_group_size(struct section *sec, int offset) { return 16; }
+int ex_table_group_size(struct section *sec, int offset) { return 8; }
+int altinstructions_group_size(struct section *sec, int offset) { return 12; }
+
+int fixup_group_size(struct section *sec, int offset)
+{
+	unsigned char *insn, *start, *end;
+
+	/*
+	 * Each fixup group is a collection of instructions.  The last
+	 * instruction is always 'jmpq'.
+	 */
+	start = sec->data->d_buf + offset;
+	end = start + sec->sh.sh_size;
+	for (insn = start; insn < end; insn++) {
+		/* looking for the pattern "e9 00 00 00 00" */
+		if (*insn == 0xe9 && *(uint32_t *)(insn + 1) == 0)
+			return insn + 5 - start;
+	}
+
+	ERROR("can't find jump instruction in .fixup section");
+	return 0;
+}
 
 struct special_section special_sections[] = {
 	{
@@ -1009,6 +1031,18 @@ struct special_section special_sections[] = {
 		.name		= ".parainstructions",
 		.group_size	= parainstructions_group_size,
 	},
+	{
+		.name		= "__ex_table",
+		.group_size	= ex_table_group_size,
+	},
+	{
+		.name		= ".altinstructions",
+		.group_size	= altinstructions_group_size,
+	},
+	{
+		.name		= ".fixup",
+		.group_size	= fixup_group_size,
+	},
 	{},
 };
 
@@ -1117,6 +1151,8 @@ void kpatch_process_special_sections(struct kpatch_elf *kelf)
 {
 	struct special_section *special;
 	struct section *sec;
+	struct symbol *sym;
+	struct rela *rela;
 
 	for (special = special_sections; special->name; special++) {
 		sec = find_section_by_name(&kelf->sections, special->name);
@@ -1129,6 +1165,31 @@ void kpatch_process_special_sections(struct kpatch_elf *kelf)
 
 		kpatch_regenerate_special_section(special, sec);
 	}
+
+	/*
+	 * The following special section doesn't have relas which reference
+	 * non-included symbols, so its entire rela section can be included.
+	 */
+	list_for_each_entry(sec, &kelf->sections, list) {
+		if (strcmp(sec->name, ".altinstr_replacement"))
+			continue;
+
+		/* include base section */
+		sec->include = 1;
+
+		/* include all symbols in the section */
+		list_for_each_entry(sym, &kelf->symbols, list)
+			if (sym->sec == sec)
+				sym->include = 1;
+
+		/* include rela section */
+		if (sec->rela) {
+			sec->rela->include = 1;
+			/* include all symbols referenced by relas */
+			list_for_each_entry(rela, &sec->rela->relas, list)
+				rela->sym->include = 1;
+		}
+	}
 }
 
 void print_strtab(char *buf, size_t size)
diff --git a/test/integration/fixup-section.patch b/test/integration/fixup-section.patch
new file mode 100644
index 0000000..cdcd99f
--- /dev/null
+++ b/test/integration/fixup-section.patch
@@ -0,0 +1,12 @@
+Index: src/fs/readdir.c
+===================================================================
+--- src.orig/fs/readdir.c
++++ src/fs/readdir.c
+@@ -169,6 +169,7 @@ static int filldir(void * __buf, const c
+ 			goto efault;
+ 	}
+ 	dirent = buf->current_dir;
++	printk("kpatch-test: testing .fixup section changes\n");
+ 	if (__put_user(d_ino, &dirent->d_ino))
+ 		goto efault;
+ 	if (__put_user(reclen, &dirent->d_reclen))