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Subject[PATCH 06/14] kbuild: introduce __init_refok/__initdata_refok to supress section mismatch warnings
From 9ea9840b8258e81ea88548bc22b2cb2871e2b1c4 Mon Sep 17 00:00:00 2001
From: Sam Ravnborg <sam@ravnborg.org>
Date: Thu, 17 May 2007 20:14:48 +0200
Subject: [PATCH 06/14] kbuild: introduce __init_refok/__initdata_refok to supress section mismatch warnings

Throughout the kernel there are a few legitimite references
to init or exit sections. Most of these are covered by the
patterns included in modpost but a few nees special attention.
To avoid hardcoding a lot of function names in modpost introduce
a marker so relevant function/data can be marked.
When modpost see a reference to a init/exit function from
a function/data marked no warning will be issued.

Idea from: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
include/asm-generic/vmlinux.lds.h | 6 ++++--
include/linux/init.h | 13 +++++++++++++
scripts/mod/modpost.c | 11 +++++++++++
3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 52e2d69..8307b1b 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -11,7 +11,8 @@

/* .data section */
#define DATA_DATA \
- *(.data)
+ *(.data) \
+ *(.data.init.refok)

#define RODATA \
. = ALIGN(4096); \
@@ -147,7 +148,8 @@
* during second ld run in second ld pass when generating System.map */
#define TEXT_TEXT \
ALIGN_FUNCTION(); \
- *(.text)
+ *(.text) \
+ *(.text.init.refok)

/* sched.text is aling to function alignment to secure we have same
* address even at second ld pass when generating System.map */
diff --git a/include/linux/init.h b/include/linux/init.h
index e007ae4..c39f3d3 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -45,6 +45,19 @@
#define __exitdata __attribute__ ((__section__(".exit.data")))
#define __exit_call __attribute_used__ __attribute__ ((__section__ (".exitcall.exit")))

+/* modpost check for section mismatches during the kernel build.
+ * A section mismatch happens when there are references from a
+ * code or data section to an init section (both code or data).
+ * The init sections are (for most archs) discarded by the kernel
+ * when early init has completed so all such references are potential bugs.
+ * For exit sections the same issue exists.
+ * The follwoing markers are used for the cases where the reference to
+ * the init/exit section (code or data) is valid and will teach modpost
+ * not to issue a warning.
+ * The markers follow same syntax rules as __init / __initdata. */
+#define __init_refok noinline __attribute__ ((__section__ (".text.init.refok")))
+#define __initdata_refok __attribute__ ((__section__ (".data.init.refok")))
+
#ifdef MODULE
#define __exit __attribute__ ((__section__(".exit.text")))
#else
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index b394629..f4d9edf 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -583,6 +583,12 @@ static int strrcmp(const char *s, const char *sub)

/**
* Whitelist to allow certain references to pass with no warning.
+ *
+ * Pattern 0:
+ * Do not warn if funtion/data are marked with __init_refok/__initdata_refok.
+ * The pattern is identified by:
+ * fromsec = .text.init.refok | .data.init.refok
+ *
* Pattern 1:
* If a module parameter is declared __initdata and permissions=0
* then this is legal despite the warning generated.
@@ -686,6 +692,11 @@ static int secref_whitelist(const char *modname, const char *tosec,
NULL
};

+ /* Check for pattern 0 */
+ if ((strcmp(fromsec, ".text.init.refok") == 0) ||
+ (strcmp(fromsec, ".data.init.refok") == 0))
+ return 1;
+
/* Check for pattern 1 */
if (strcmp(tosec, ".init.data") != 0)
f1 = 0;
--
1.5.1.rc3.20.gaa453
-
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