Roland Dreier found that a section that contained only a weak
function in one of the staging drivers and this caused
recordmcount.pl to spit out a warning and fail.
Although it is strange that a driver would have a weak function, and
this function only be used in one place, it should not be something
to make recordmcount.pl fail.
This patch fixes the issue in a simple manner: if only weak
functions exist in a section, then that section will not be
recorded.
Reported-by: Roland Dreier <rdreier@cisco.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
On Wed, 5 Aug 2009, Ingo Molnar wrote:
> * Dave Airlie <airlied@gmail.com> wrote:
>
> > Hey,
> >
> > So I spent 3-4 hrs today (I'm stupid yes) tracking down a .o
> > breakage by blaming rawhide gcc/binutils as I was using make
> > V=1and seeing only the compiler chain running,
>
> Hm, is this that powerpc related build bug you just reported?
Well we tracked it down and it is powerpc64 specific.
Seems that in drivers/hwmon/lm93.c there's a function called:
LM93_IN_FROM_REG()
But PPC64 has function descriptors and the real function names (the ones
you see in objdump) start with a '.'. Thus this in objdump you have:
Disassembly of section .text:
0000000000000000 <.LM93_IN_FROM_REG>:
0: 7c 08 02 a6 mflr r0
4: fb 81 ff e0 std r28,-32(r1)
The function name used is .LM93_IN_FROM_REG. But gcc considers symbols
that start with ".L" as a special symbol that is used inside the assembly
stage.
The nm passed into recordmcount uses the --synthetic option which shows
the ".L" symbols (my runs outside of the build did not include the
--synthetic option, so my older patch worked). We see the function as a
local.
Now to capture all the locations that use "mcount" we need to have a
reference to link into the object file a list of mcount callers. We need a
reference that will not disappear. We try to use a global function and if
that does not work, we use a local function as a reference. But to relink
the section back into the object, we need to make it global. In this case,
we run objcopy using --globalize-symbol and --localize-symbol to convert
the symbol into a global symbol, link the mcount list, then convert it
back to a local symbol.
This works great except for this case. .L* symbols can not be converted
into a global symbol, and the mcount section referencing it will remain
unresolved.
Reported-by: Dave Airlie <airlied@gmail.com>
LKML-Reference: <alpine.DEB.2.00.0908052011590.5010@gandalf.stny.rr.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The value of $offset should be the offset of $ref_func from the
beginning of the object file. Therefore, we should set both variables
together.
This fixes a bug I was hitting on sh where $offset (which is used to
calcualte the addends for the __mcount_loc entries) was being set
multiple times and didn't correspond to $ref_func's offset in the object
file. The addends in __mcount_loc were calculated incorrectly, resulting
in ftrace dynamically modifying addresses that weren't mcount call
sites.
Signed-off-by: Matt Fleming <matt@console-pimps.org>
LKML-Reference: <1248365775-25196-2-git-send-email-matt@console-pimps.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Fix the conditional that checks if we already have a $ref_func and that
the new function is weak. The code as previously checking whether either
condition was false, and we really need to only update $ref_func is both
cconditions are false.
Signed-off-by: Matt Fleming <matt@console-pimps.org>
LKML-Reference: <1248365775-25196-1-git-send-email-matt@console-pimps.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The only references in the kernel to the .text.sched section are in
recordmcount.pl. Since the code it has is intended to be example code
it should refer to real kernel sections. So change it to .sched.text
instead.
[ Impact: consistency in comments ]
Signed-off-by: Tim Abbott <tabbott@mit.edu>
LKML-Reference: <1241136371-10768-1-git-send-email-tabbott@mit.edu>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Impact: fix failure of dynamic function tracer selftest
In a course of development, a developer does several makes on their
kernel. Sometimes, the make might do something abnormal. In the
case of running the recordmcount.pl script on an object twice,
the script will duplicate all the calls to mcount in the __mcount_loc
section.
On boot up, the dynamic function tracer is careful when it modifies
code, and performs several consistency checks. One is to not modify
the call site if it is not what it expects it to be. If a function
call site is listed twice, the first entry will convert the site
to a nop, and the second will fail because it expected to see a
call to mcount, but instead it sees a nop. Thus, the function tracer
is disabled.
Eric Sesterhenn reported seeing:
[ 1.055440] ftrace: converting mcount calls to 0f 1f 44 00 00
[ 1.055568] ftrace: allocating 29418 entries in 116 pages
[ 1.061000] ------------[ cut here ]------------
[ 1.061000] WARNING: at kernel/trace/ftrace.c:441
[...]
[ 1.060000] ---[ end trace 4eaa2a86a8e2da23 ]---
[ 1.060000] ftrace failed to modify [<c0118072>] check_corruption+0x3/0x2d
[ 1.060000] actual: 0f:1f:44:00:00
This warning shows that check_corruption+0x3 already had a nop in
its place (0x0f1f440000). After compiling another kernel the problem
went away.
Later Eric Paris notice the same type of issue. Luckily, he saved
the vmlinux file that caused it. In the file we found a bunch of
duplicate mcount call site records, which lead us to the script.
Perhaps this problem only happens to people named Eric.
This patch changes the script to test if the __mcount_loc already
exists in the object file, and if it does, it will print out
an error message and kill the compile.
Reported-by: Eric Sesterhenn <snakebyte@gmx.de>
Reported-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In IA64, a function pointer isn't a 'unsigned long' but a
'struct {unsigned long ip, unsigned long gp}'. MCOUNT_ADDR is determined
at link time not compile time, so explictly ignore kernel/trace/ftrace.o
in recordmcount.pl.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In IA64, module build and kernel build use different option.
Make recordmcount.pl differentiate the two cases.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: let the function-graph-tracer be aware of the irq entrypoints
Add a new .irqentry.text section to store the irq entrypoints functions
inside the same section. This way, the tracer will be able to signal
an interrupts triggering on output by recognizing these entrypoints.
Also, make this section recordable for dynamic tracing.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: widen the scope of recordmcount.pl
Besides .text section, there are three .text sections that won't
be freed after kernel booting. They are: .sched.text, .spinlock.text
and .kprobes.text, which contain functions we can trace. But the last
section ".kprobes.text" is particular, which has been marked as "notrace",
we ignore it. Thus we add other two sections.
Signed-off-by: Liming Wang <liming.wang@windriver.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: extend scripts/recordmcount.pl to ARM
Arm uses %progbits instead of @progbits and requires only 4 byte alignment.
[ Thanks to Sam Ravnborg for mentioning that ARM uses %progbits ]
Signed-off-by: Jim Radford <radford@galvanix.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: extend scripts/recordmcount.pl with default alignment for SH
Set $alignment=2 for the sh architecture so that a ".align 2" directive
will be emitted for all __mcount_loc sections. Fix a whitspace error
while I'm here (converted spaces to tabs).
Signed-off-by: Matt Fleming <mjf@gentoo.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup of recordmcount.pl
Now that more architectures are being ported to the MCOUNT_RECORD
method, there is no reason to have each declare their own arch
specific variable if most of them share the same value. This patch
creates a set of default values for the arch specific variables
based off of i386.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: Add PowerPC port to recordmcount.pl script
This patch updates the recordmcount.pl script to process
PowerPC.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
First cut at dynamic ftrace support.
[
Steven Rostedt - only updated the recordmcount.pl file.
There are updates for PowerPC that will conflict with this,
and we need to base off of these changes.
]
Signed-off-by: Matt Fleming <mjf@gentoo.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: add alignment option for recordmcount.pl script
Align the __mcount_loc sections so that architectures with strict
alignment requirements need not worry about performing unaligned
accesses.
This fixes an issue where I was seeing unaligned accesses, which are not
supported on our architecture (the results of an unaligned access are
undefined).
Signed-off-by: Matt Fleming <matthew.fleming@imgtec.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The text section stays in memory without ever leaving. With the exception
of modules, but modules know how to handle that case. With the dynamic
ftrace tracer, we need to make sure that it does not try to modify code
that no longer exists. The only safe section is .text.
This patch changes the recordmcount script to only record the mcount calls
in the .text sections.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The recordmcount script requires that the actual arch is passed in.
This works well when ARCH=i386 or ARCH=x86_64 but does not handle the
case of ARCH=x86.
This patch adds a parameter to the function to pass in the number of
bits of the architecture. So that it can determine if x86 should be
run for x86_64 or i386 archs.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The warning messages about old objcopy and local functions spam the
user quite drastically. Remove the warning until we can find a nicer
way of tell the user to upgrade their objcopy.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The --globalize-symbols option came out in objcopy version 2.17.
If the kernel is being compiled on a system with a lower version of
objcopy, then we can not use the globalize / localize trick to
link to symbols pointing to local functions.
This patch tests the version of objcopy and will only use the trick
if the version is greater than or equal to 2.17. Otherwise, if an
object has only local functions within a section, it will give a
nice warning and recommend the user to upgrade their objcopy.
Leaving the symbols unrecorded is not that big of a deal, since the
mcount record method changes the actual mcount code to be a simple
"ret" without recording registers or anything.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
During tests and checks, I've discovered that there were failures to
convert mcount callers into nops. Looking deeper into these failures,
code that was attempted to be changed was not an mcount caller.
The current code only updates if the code being changed is what it expects,
but I still investigate any time there is a failure.
What was happening is that a weak symbol was being used as a reference
for other mcount callers. That weak symbol was also referenced elsewhere
so the offsets were using the strong symbol and not the function symbol
that it was referenced from.
This patch changes the setting up of the mcount_loc section to search
for a global function that is not weak. It will pick a local over a weak
but if only a weak is found in a section, a warning is printed and the
mcount location is not recorded (just to be safe).
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
I'm trying to keep all the arch changes in recordmcount.pl in one place.
I moved your code into that area, by adding the flags to the commands
that were passed in.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
