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[rng] Check for TSC support before using RTC entropy source

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Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2021-05-12 10:24:00 +01:00
parent 13c1abe10a
commit 05fcf1a2f0
2 changed files with 14 additions and 0 deletions
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11
src/arch/x86/interface/pcbios/rtc_entropy.c
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@@ -36,6 +36,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <biosint.h>
#include <pic8259.h>
#include <rtc.h>
#include <ipxe/cpuid.h>
#include <ipxe/entropy.h>
/** Maximum time to wait for an RTC interrupt, in milliseconds */
@@ -174,8 +175,17 @@ static int rtc_entropy_check ( void ) {
* @ret rc Return status code
*/
static int rtc_entropy_enable ( void ) {
struct x86_features features;
int rc;
/* Check that TSC is supported */
x86_features ( &features );
if ( ! ( features.intel.edx & CPUID_FEATURES_INTEL_EDX_TSC ) ) {
DBGC ( &rtc_flag, "RTC has no TSC\n" );
rc = -ENOTSUP;
goto err_no_tsc;
}
/* Hook ISR and enable RTC interrupts */
rtc_hook_isr();
enable_irq ( RTC_IRQ );
@@ -191,6 +201,7 @@ static int rtc_entropy_enable ( void ) {
rtc_disable_int();
disable_irq ( RTC_IRQ );
rtc_unhook_isr();
err_no_tsc:
return rc;
}