On 31.01.2014 16:50, Peter Oberparleiter wrote:
> On 29.01.2014 21:44, Meelis Roos wrote:
>>>> I do not get very far - it still crashes on startuo. PNG attached.
>>>
>>> I tried to reproduce this behavior a couple of times with no success.
>>> Could you post your kernel configuration? I've also modified the
>>> debugging patch to ensure that the gcov_info structure passed to
>>> gcov_init() is no longer accessed beyond displaying the first 64
>>> bytes. If you could apply this and send dmesg output, this might
>>> hopefully provide a clue as to why the kernel cannot handle these
>>> data structures correctly.
>>
>> This patch makes it boot. dmesg and config are below.
>
> Using your config I was able to reproduce the crash and locate the
> cause. Commit d61931d89b, "x86: Add optimized popcnt variants" adds
> option -fcall-saved-rdi to the compile flags of lib/hweight.c when
> compiling for x86_64. Together with options --coverage and -O2, this
> results in a broken constructor being generated by GCC for this object
> file which in turn causes __gcov_init() to overwrite random memory
> locations (a mutex in your case).
Could you give this patch a try? It is a variation of the approach
proposed in the discussion mentioned earlier and fixes the problem
on my system.
--
diff -Naurp a/arch/x86/include/asm/arch_hweight.h
b/arch/x86/include/asm/arch_hweight.h
--- a/arch/x86/include/asm/arch_hweight.h
+++ b/arch/x86/include/asm/arch_hweight.h
@@ -25,9 +25,18 @@ static inline unsigned int __arch_hweigh
{
unsigned int res = 0;
+#ifdef CONFIG_X86_32
asm (ALTERNATIVE("call __sw_hweight32", POPCNT32, X86_FEATURE_POPCNT)
: "="REG_OUT (res)
: REG_IN (w));
+#else
+ /* Tell gcc that %rdi is clobbered as an input operand */
+ unsigned long dummy;
+
+ asm (ALTERNATIVE("call __sw_hweight32", POPCNT32, X86_FEATURE_POPCNT)
+ : "="REG_OUT (res), "=D" (dummy)
+ : REG_IN (w));
+#endif /* CONFIG_X86_32 */
return res;
}
@@ -50,8 +59,11 @@ static inline unsigned long __arch_hweig
return __arch_hweight32((u32)w) +
__arch_hweight32((u32)(w >> 32));
#else
+ /* Tell gcc that %rdi is clobbered as an input operand */
+ unsigned long dummy;
+
asm (ALTERNATIVE("call __sw_hweight64", POPCNT64, X86_FEATURE_POPCNT)
- : "="REG_OUT (res)
+ : "="REG_OUT (res), "=D" (dummy)
: REG_IN (w));
#endif /* CONFIG_X86_32 */
diff -Naurp a/arch/x86/Kconfig b/arch/x86/Kconfig
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -254,7 +254,7 @@ config X86_32_LAZY_GS
config ARCH_HWEIGHT_CFLAGS
string
default "-fcall-saved-ecx -fcall-saved-edx" if X86_32
- default "-fcall-saved-rdi -fcall-saved-rsi -fcall-saved-rdx
-fcall-saved-rcx -fcall-saved-r8 -fcall-saved-r9 -fcall-saved-r10
-fcall-saved-r11" if X86_64
+ default "-fcall-saved-rsi -fcall-saved-rdx -fcall-saved-rcx
-fcall-saved-r8 -fcall-saved-r9 -fcall-saved-r10 -fcall-saved-r11" if X86_64
config ARCH_SUPPORTS_UPROBES
def_bool y
--
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