Commit 0e0d314e authored by Sam Ravnborg's avatar Sam Ravnborg

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: default avatarSam Ravnborg <sam@ravnborg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
parent ca967258
......@@ -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 */
......
......@@ -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 following 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
......
......@@ -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;
......
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