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x86: fix tsc unification buglet with ftrace and stackprotector

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Yinghai Lu reported crashes on 64-bit x86:

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
 IP: [<ffffffff80253b17>] hrtick_start_fair+0x89/0x173
 [...]

And with a long session of debugging and a lot of difficulty, tracked it down
to this commit:

 --------------->
 8fbbc4b45c is first bad commit
 commit 8fbbc4b45c
 Author: Alok Kataria <akataria@vmware.com>
 Date:   Tue Jul 1 11:43:34 2008 -0700

     x86: merge tsc_init and clocksource code
 <--------------

The problem is that the TSC unification missed these Makefile rules
in arch/x86/kernel/Makefile:

  # Do not profile debug and lowlevel utilities
  CFLAGS_REMOVE_tsc_64.o = -pg
  CFLAGS_REMOVE_tsc_32.o = -pg
  ...
  CFLAGS_tsc_64.o         := $(nostackp)
  ...

which rules make sure that various instrumentation and debugging
facilities are disabled for code that might end up in a VDSO - such as
the TSC code.

Reported-and-bisected-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Conflicts:

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2008-07-11 15:09:15 +02:00
parent f361a450bf
commit 3d0decc4f4
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kernel/Makefile
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@ -13,7 +13,7 @@ CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE)
nostackp := $(call cc-option, -fno-stack-protector)
CFLAGS_vsyscall_64.o := $(PROFILING) -g0 $(nostackp)
CFLAGS_hpet.o := $(nostackp)
CFLAGS_tsc_64.o := $(nostackp)
CFLAGS_tsc.o := $(nostackp)
obj-y := process_$(BITS).o signal_$(BITS).o entry_$(BITS).o
obj-y += traps_$(BITS).o irq_$(BITS).o