[igt-dev] [PATCH i-g-t] Fix global symbol loading failure in resolve function

[Hong, Brandon]

> On 28 Sep 2019, at 2:26 AM, Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:
> 
> On Tue, Sep 24, 2019 at 10:02:29PM +0800, brandon.hong at intel.com wrote:
>> From: Brandon Hong <brandon.hong at intel.com>
>> 
>> 270 out of 284 tests get failed with SIGSEGV on ClearLinux because the ifunc
>> resolver resolve_half_to_float() tries to call unbound global function
>> igt_x86_features(). This patch fixes the issue by adding a F16C checking
>> local function.
> 
> The rules for this stuff seem to be poorly documented. But I did find
> some docs that support this. So generally lgtm, just a few nitpicks
> below…
> 
>> 
>> Signed-off-by: Brandon Hong <brandon.hong at intel.com>
>> ---
>> lib/igt_halffloat.c | 22 ++++++++++++++++++++--
>> 1 file changed, 20 insertions(+), 2 deletions(-)
>> 
>> diff --git a/lib/igt_halffloat.c b/lib/igt_halffloat.c
>> index 08ab05fc..fa7ad2e0 100644
>> --- a/lib/igt_halffloat.c
>> +++ b/lib/igt_halffloat.c
>> @@ -24,6 +24,7 @@
>> 
>> #include <assert.h>
>> #include <math.h>
>> +#include <stdbool.h>
>> 
>> #include "igt_halffloat.h"
>> #include "igt_x86.h"
>> @@ -163,6 +164,8 @@ static inline float _half_to_float(uint16_t val)
>> }
>> 
>> #if defined(__x86_64__) && !defined(__clang__)
>> +#include <cpuid.h>
> 
> igt_x86.c has HAVE_CPUID_H protection around this stuff.
> I suppose we'd want the same here?

Thanks for pointing it out. Will add HAVE_CPUID_H as same as igt_x86.c file.

> 
>> +
>> #pragma GCC push_options
>> #pragma GCC target("f16c")
>> 
>> @@ -182,6 +185,20 @@ static void half_to_float_f16c(const uint16_t *h, float *f, unsigned int num)
>> 
>> #pragma GCC pop_options
>> 
>> +static bool f16c_is_supported(void)
>> +{
>> +	unsigned max = __get_cpuid_max(0, NULL);
>> +	unsigned eax, ebx, ecx, edx;
>> +
>> +	if (max >= 1) {
>> +		__cpuid(1, eax, ebx, ecx, edx);
>> +
>> +		if (ecx & bit_F16C)
>> +			return true;
>> +	}
>> +	return false;
>> +}
>> +
>> static void float_to_half(const float *f, uint16_t *h, unsigned int num)
>> {
>> 	for (int i = 0; i < num; i++)
>> @@ -194,9 +211,10 @@ static void half_to_float(const uint16_t *h, float *f, unsigned int num)
>> 		f[i] = _half_to_float(h[i]);
>> }
>> 
>> +
> 
> Spurious newline.
Will remove it and re-submit.

> 
>> static void (*resolve_float_to_half(void))(const float *f, uint16_t *h, unsigned int num)
>> {
>> -	if (igt_x86_features() & F16C)
>> +	if (f16c_is_supported())
>> 		return float_to_half_f16c;
>> 
>> 	return float_to_half;
>> @@ -207,7 +225,7 @@ void igt_float_to_half(const float *f, uint16_t *h, unsigned int num)
>> 
>> static void (*resolve_half_to_float(void))(const uint16_t *h, float *f, unsigned int num)
>> {
>> -	if (igt_x86_features() & F16C)
>> +	if (f16c_is_supported())
>> 		return half_to_float_f16c;
>> 
>> 	return half_to_float;
>> -- 
>> 2.23.0
>> 
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>> igt-dev at lists.freedesktop.org
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> 
> -- 
> Ville Syrjälä
> Intel