linux/arch
Steven Rostedt 8115f3f0c9 ftrace: use a real variable for ftrace_nop in x86
Impact: avoid section mismatch warning, clean up

The dynamic ftrace determines which nop is safe to use at start up.
When it finds a safe nop for patching, it sets a pointer called ftrace_nop
to point to the code. All call sites are then patched to this nop.

Later, when tracing is turned on, this ftrace_nop variable is again used
to compare the location to make sure it is a nop before we update it to
an mcount call. If this fails just once, a warning is printed and ftrace
is disabled.

Rakib Mullick noted that the code that sets up the nop is a .init section
where as the nop itself is in the .text section. This is needed because
the nop is used later on after boot up. The problem is that the test of the
nop jumps back to the setup code and causes a "section mismatch" warning.

Rakib first recommended to convert the nop to .init.text, but as stated
above, this would fail since that text is used later.

The real solution is to extend Rabik's patch, and to make the ftrace_nop
into an array, and just save the code from the assembly to this array.

Now the section can stay as an init section, and we have a nop to use
later on.

Reported-by: Rakib Mullick <rakib.mullick@gmail.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-27 16:52:01 +01:00
..
alpha Merge branch 'v28-range-hrtimers-for-linus-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2008-10-23 10:53:02 -07:00
arm Merge commit 'v2.6.28-rc2' into tracing/urgent 2008-10-27 10:50:54 +01:00
avr32 Merge branches 'boards' and 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/hskinnemoen/avr32-2.6 2008-10-23 15:24:10 +02:00
blackfin container freezer: implement freezer cgroup subsystem 2008-10-20 08:52:34 -07:00
cris Merge branch 'for-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/dvrabel/uwb 2008-10-23 08:20:34 -07:00
frv container freezer: implement freezer cgroup subsystem 2008-10-20 08:52:34 -07:00
h8300 Merge branch 'for-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/dvrabel/uwb 2008-10-23 08:20:34 -07:00
ia64 Merge branch 'v28-range-hrtimers-for-linus-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2008-10-23 10:53:02 -07:00
m32r Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rric/oprofile 2008-10-23 10:05:40 -07:00
m68k proc: move /proc/stram to m68k-specific code 2008-10-23 14:25:35 +04:00
m68knommu container freezer: implement freezer cgroup subsystem 2008-10-20 08:52:34 -07:00
mips TXx9: Add TX4938 ATA support (v3) 2008-10-23 23:22:08 +02:00
mn10300 mn10300: use bcd2bin/bin2bcd 2008-10-20 08:52:41 -07:00
parisc Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2008-10-23 10:22:40 -07:00
powerpc Merge commit 'v2.6.28-rc2' into tracing/urgent 2008-10-27 10:50:54 +01:00
s390 container freezer: implement freezer cgroup subsystem 2008-10-20 08:52:34 -07:00
sh sh: asm/gpio.h needs linux/kernel.h for might_sleep()/WARN_ON(). 2008-10-23 12:37:20 +09:00
sparc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6 2008-10-23 19:19:14 -07:00
sparc64 Merge commit 'v2.6.28-rc2' into tracing/urgent 2008-10-27 10:50:54 +01:00
um Merge git://git.kernel.org/pub/scm/linux/kernel/git/viro/bdev 2008-10-23 10:23:07 -07:00
x86 ftrace: use a real variable for ftrace_nop in x86 2008-10-27 16:52:01 +01:00
xtensa Merge git://git.kernel.org/pub/scm/linux/kernel/git/czankel/xtensa-2.6 2008-10-23 09:16:56 -07:00
.gitignore
Kconfig Kconfig: eliminate "def_bool n" constructs 2008-10-16 11:21:31 -07:00