Re: [PATCH] gcov: support GCC 7.1
From: Peter Oberparleiter
Date: Thu Dec 08 2016 - 07:52:54 EST
On 24.11.2016 13:46, Martin LiÅka wrote:
> On 11/09/2016 10:21 AM, Peter Oberparleiter wrote:
>> On 31.10.2016 10:35, Martin LiÅka wrote:
>>> Starting from GCC 7.1, __gcov_exit is a new symbol expected
>>> to be implemented in a profiling runtime.
>> I tested your patch with kernel 4.9-rc4 compiled with GCC 7.0.0 20161107
>> (experimental) and validated that it fixes the build error due to a
>> missing __gcov_exit symbol.
>> An attempt to read from one of the .gcda files generated by a kernel
>> compiled this way resulted in a crash though. It appears that the number
>> of GCOV_COUNTERS has changed again for GCC 7.x and must be adjusted in
>> the kernel as well. Could you add that to your patch as well?
> Sorry, this is fixed in second version of the patch.
>> Given that GCC 7.1 has not yet been released, I'm wondering if it is
>> safe to program against interfaces that have not yet been fully
>> finalized. Can you provide an indication on whether these gcov-related
>> aspects of GCC might still be changed until release?
> Well, we just flipped to stage3 which means that any new features should
> be added to current master. If you prefer we can commit the patch after
> a release of 7.1 will be done?
I've given this some more thought: if your patch is not applied, GCOV
kernel profiling will definitely not work with GCC 7.x. If it is
applied, there is a high probability that it will work, and a small
chance that additional patches will be required. Overall I would say
this justifies applying the patch now.
>> As a side note, please post your patches inline instead of as attachment
>> as that helps quoting them in replies. See also
> Sure, thanks for info. I'm attaching new version:
> Starting from GCC 7.1, __gcov_exit is a new symbol expected
> to be implemented in a profiling runtime. Update number of profile
> Signed-off-by: Martin Liska <mliska@xxxxxxx>
Looks good, thanks! Tested successfully with GCC 7.0.0 20161208
(experimental) on Linux kernel 4.9-rc8 (compiles successfully and
produces valid kernel .gcda files).
Andrew, could you pick this change up via your tree?
Reviewed-by: Peter Oberparleiter <oberpar@xxxxxxxxxxxxxxxxxx>
Tested-by: Peter Oberparleiter <oberpar@xxxxxxxxxxxxxxxxxx>
> kernel/gcov/base.c | 6 ++++++
> kernel/gcov/gcc_4_7.c | 4 +++-
> 2 files changed, 9 insertions(+), 1 deletion(-)
> diff --git a/kernel/gcov/base.c b/kernel/gcov/base.c
> index 2f9df37..85dca5d 100644
> --- a/kernel/gcov/base.c
> +++ b/kernel/gcov/base.c
> @@ -98,6 +98,12 @@ void __gcov_merge_icall_topn(gcov_type *counters, unsigned int n_counters)
> +void __gcov_exit (void)
> + /* Unused. */
> * gcov_enable_events - enable event reporting through gcov_event()
> diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
> index 6a5c239..46a18e7 100644
> --- a/kernel/gcov/gcc_4_7.c
> +++ b/kernel/gcov/gcc_4_7.c
> @@ -18,7 +18,9 @@
> #include <linux/vmalloc.h>
> #include "gcov.h"
> -#if (__GNUC__ > 5) || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)
> +#if (__GNUC__ >= 7)
> +#define GCOV_COUNTERS 9
> +#elif (__GNUC__ > 5) || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)
> #define GCOV_COUNTERS 10
> #elif __GNUC__ == 4 && __GNUC_MINOR__ >= 9
> #define GCOV_COUNTERS 9
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