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Kernel: Add g_cpu_supports_rdseed

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CPUs which support RDRAND do not necessarily support RDSEED. This
introduces a flag g_cpu_supports_rdseed which is set appropriately
by CPUID. This causes Haswell CPUs in particular (and probably a lot
of AMD chips) to now fail to boot with #2634, rather than an illegal
instruction.

It seems like the KernelRng needs either an initial reseed call or
more random events added before the first call to get_good_random,
but I don't feel qualified to make that kind of change.
This commit is contained in:
3541 2020-06-27 15:15:54 +10:00 committed by Andreas Kling
parent ebbcef926a
commit 4fa6301523
Notes: sideshowbarker 2024-07-19 05:21:50 +09:00 
Author: https://github.com/3541 🔰
Commit: https://github.com/SerenityOS/serenity/commit/4fa6301523b
Pull-request: https://github.com/SerenityOS/serenity/pull/2641
3 changed files with 4 additions and 1 deletions
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2
Kernel/Arch/i386/CPU.cpp
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@ -714,6 +714,7 @@ bool g_cpu_supports_nx;
bool g_cpu_supports_pae;
bool g_cpu_supports_pge;
bool g_cpu_supports_rdrand;
bool g_cpu_supports_rdseed;
bool g_cpu_supports_smap;
bool g_cpu_supports_smep;
bool g_cpu_supports_sse;
@ -736,6 +737,7 @@ void cpu_detect()
g_cpu_supports_smap = (extended_features.ebx() & (1 << 20));
g_cpu_supports_smep = (extended_features.ebx() & (1 << 7));
g_cpu_supports_umip = (extended_features.ecx() & (1 << 2));
g_cpu_supports_rdseed = (extended_features.ebx() & (1 << 18));
}
void cpu_setup()

1
Kernel/Arch/i386/CPU.h
View file

@ -588,6 +588,7 @@ extern bool g_cpu_supports_nx;
extern bool g_cpu_supports_pae;
extern bool g_cpu_supports_pge;
extern bool g_cpu_supports_rdrand;
extern bool g_cpu_supports_rdseed;
extern bool g_cpu_supports_smap;
extern bool g_cpu_supports_smep;
extern bool g_cpu_supports_sse;

2
Kernel/Random.cpp
View file

@ -44,7 +44,7 @@ KernelRng& KernelRng::the()
KernelRng::KernelRng()
{
if (g_cpu_supports_rdrand) {
if (g_cpu_supports_rdseed) {
for (size_t i = 0; i < resource().pool_count * resource().reseed_threshold; ++i) {
u32 value = 0;
asm volatile(