* Kprobes build failure
@ 2014-09-25 23:37 Russell King - ARM Linux
2014-09-26 9:57 ` Jon Medhurst (Tixy)
0 siblings, 1 reply; 3+ messages in thread
From: Russell King - ARM Linux @ 2014-09-25 23:37 UTC (permalink / raw)
To: linux-arm-kernel
So, Olof's kbuild found this while building my rc5 based for-next tree:
arm.allmodconfig:
/tmp/ccoT403o.s:21439: Error: bad immediate value for offset (4168)
/tmp/ccoT403o.s:21440: Error: bad immediate value for offset (4176)
/tmp/ccoT403o.s:21475: Error: bad immediate value for offset (4260)
/tmp/ccoT403o.s:21476: Error: bad immediate value for offset (4260)
/tmp/ccoT403o.s:23566: Error: bad immediate value for offset (4132)
/tmp/ccoT403o.s:23567: Error: bad immediate value for offset (4148)
/tmp/ccoT403o.s:23606: Error: bad immediate value for offset (4236)
/tmp/ccoT403o.s:23607: Error: bad immediate value for offset (4248)
which, when looking at the logs, appears to be:
/tmp/ccoT403o.s:47583: Error: bad immediate value for offset (5464)
make[3]: *** [arch/arm/kernel/kprobes-test-arm.o] Error 1
make[3]: Target `__build' not remade because of errors.
make[2]: *** [arch/arm/kernel] Error 2
Any ideas?
--
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according to speedtest.net.
^ permalink raw reply [flat|nested] 3+ messages in thread* Kprobes build failure
2014-09-25 23:37 Kprobes build failure Russell King - ARM Linux
@ 2014-09-26 9:57 ` Jon Medhurst (Tixy)
2014-09-26 11:53 ` Jon Medhurst (Tixy)
0 siblings, 1 reply; 3+ messages in thread
From: Jon Medhurst (Tixy) @ 2014-09-26 9:57 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, 2014-09-26 at 00:37 +0100, Russell King - ARM Linux wrote:
> So, Olof's kbuild found this while building my rc5 based for-next tree:
>
> arm.allmodconfig:
> /tmp/ccoT403o.s:21439: Error: bad immediate value for offset (4168)
> /tmp/ccoT403o.s:21440: Error: bad immediate value for offset (4176)
> /tmp/ccoT403o.s:21475: Error: bad immediate value for offset (4260)
> /tmp/ccoT403o.s:21476: Error: bad immediate value for offset (4260)
> /tmp/ccoT403o.s:23566: Error: bad immediate value for offset (4132)
> /tmp/ccoT403o.s:23567: Error: bad immediate value for offset (4148)
> /tmp/ccoT403o.s:23606: Error: bad immediate value for offset (4236)
> /tmp/ccoT403o.s:23607: Error: bad immediate value for offset (4248)
>
> which, when looking at the logs, appears to be:
>
> /tmp/ccoT403o.s:47583: Error: bad immediate value for offset (5464)
> make[3]: *** [arch/arm/kernel/kprobes-test-arm.o] Error 1
> make[3]: Target `__build' not remade because of errors.
> make[2]: *** [arch/arm/kernel] Error 2
>
> Any ideas?
Sounds vaguely familiar as a problem I hit before. Google finds someone
else hitting similar problem [1] and the symptoms and cause match my
memories of the old kprobe issue.
Where can I find a clue of to the config and compiler used in Olof's
build, so I can have a go at reproducing and debugging?
[1] https://lkml.org/lkml/2012/9/24/223
The relevant explanation of the above post copied below...
------------------------------------------------------------------------
The compiler uses a pretty dumb heuristic to guess the size of asms:
4 * (number of ; or \n in the string)
Directives that the compiler can't predict the size of are not safe if
they output into any segment that the compiler uses. .fill/.skip are
obvious candidates, but macro expansions, .rept, .irp etc. can cause
these problems too.
For example:
void g(int);
void f(void)
{
g(0xd00dfeed);
asm(".skip 0x1000");
}
If you try building this with gcc -marm -Os for example:
/tmp/ccXYm1uP.s: Assembler messages:
/tmp/ccXYm1uP.s:21: Error: bad immediate value for offset (4100)
...because the assembler assumes that it can dump a literal at the end
of the function and reference it from the g() callsite.
------------------------------------------------------------------------
--
Tixy
^ permalink raw reply [flat|nested] 3+ messages in thread* Kprobes build failure
2014-09-26 9:57 ` Jon Medhurst (Tixy)
@ 2014-09-26 11:53 ` Jon Medhurst (Tixy)
0 siblings, 0 replies; 3+ messages in thread
From: Jon Medhurst (Tixy) @ 2014-09-26 11:53 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, 2014-09-26 at 10:57 +0100, Jon Medhurst (Tixy) wrote:
> On Fri, 2014-09-26 at 00:37 +0100, Russell King - ARM Linux wrote:
> > So, Olof's kbuild found this while building my rc5 based for-next tree:
> >
> > arm.allmodconfig:
> > /tmp/ccoT403o.s:21439: Error: bad immediate value for offset (4168)
> > /tmp/ccoT403o.s:21440: Error: bad immediate value for offset (4176)
> > /tmp/ccoT403o.s:21475: Error: bad immediate value for offset (4260)
> > /tmp/ccoT403o.s:21476: Error: bad immediate value for offset (4260)
> > /tmp/ccoT403o.s:23566: Error: bad immediate value for offset (4132)
> > /tmp/ccoT403o.s:23567: Error: bad immediate value for offset (4148)
> > /tmp/ccoT403o.s:23606: Error: bad immediate value for offset (4236)
> > /tmp/ccoT403o.s:23607: Error: bad immediate value for offset (4248)
> >
> > which, when looking at the logs, appears to be:
> >
> > /tmp/ccoT403o.s:47583: Error: bad immediate value for offset (5464)
> > make[3]: *** [arch/arm/kernel/kprobes-test-arm.o] Error 1
> > make[3]: Target `__build' not remade because of errors.
> > make[2]: *** [arch/arm/kernel] Error 2
> >
> > Any ideas?
>
> Sounds vaguely familiar as a problem I hit before. Google finds someone
> else hitting similar problem [1] and the symptoms and cause match my
> memories of the old kprobe issue.
>
> Where can I find a clue of to the config and compiler used in Olof's
> build, so I can have a go at reproducing and debugging?
I've now reproduced this and the cause _is_ the problem mentioned at the
bottom of this email because the following diff fixes the issue (now
need to try and think of a nicer and more robust fix...)
diff --git a/arch/arm/kernel/kprobes-test.h
b/arch/arm/kernel/kprobes-test.h
index eecc90a..783072d 100644
--- a/arch/arm/kernel/kprobes-test.h
+++ b/arch/arm/kernel/kprobes-test.h
@@ -113,7 +113,7 @@ struct test_arg_end {
"bl __kprobes_test_case_start \n\t" \
/* don't use .asciz here as 'title' may be */ \
/* multiple strings to be concatenated. */ \
- ".ascii "#title" \n\t" \
+ ".ascii "#title";;;;;;;;;;;;;;;;;;;; \n\t" \
".byte 0 \n\t" \
".align 2, 0 \n\t"
>
> [1] https://lkml.org/lkml/2012/9/24/223
>
> The relevant explanation of the above post copied below...
>
> ------------------------------------------------------------------------
>
> The compiler uses a pretty dumb heuristic to guess the size of asms:
> 4 * (number of ; or \n in the string)
>
> Directives that the compiler can't predict the size of are not safe if
> they output into any segment that the compiler uses. .fill/.skip are
> obvious candidates, but macro expansions, .rept, .irp etc. can cause
> these problems too.
>
> For example:
>
> void g(int);
> void f(void)
> {
> g(0xd00dfeed);
> asm(".skip 0x1000");
> }
> If you try building this with gcc -marm -Os for example:
>
> /tmp/ccXYm1uP.s: Assembler messages:
> /tmp/ccXYm1uP.s:21: Error: bad immediate value for offset (4100)
>
> ...because the assembler assumes that it can dump a literal at the end
> of the function and reference it from the g() callsite.
>
> ------------------------------------------------------------------------
>
>
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2014-09-26 9:57 ` Jon Medhurst (Tixy)
2014-09-26 11:53 ` Jon Medhurst (Tixy)
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