libpayload/libc/time: Fix possible overflow in multiplication

The value from raw_read_cntfrq_el0() could be large enough to cause
overflow when multiplied by USECS_PER_SEC. To prevent this, both
USECS_PER_SEC and hz can be reduced by dividing them by their GCD.

This patch also modifies the return type of `timer_hz()` from
`uint64_t` to `uint32_t`, assuming that in practice the timestamp
counter should never be that fast.

BUG=b:307790895
TEST=boot to kernel and check the timestamps from `cbmem`

Change-Id: Ia55532490651fcf47128b83a8554751f050bcc89
Signed-off-by: Yidi Lin <yidilin@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78888
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
This commit is contained in:
Yidi Lin
2023-11-02 14:17:02 +08:00
committed by Julius Werner
parent e91785dfd8
commit eabdd0252a
5 changed files with 16 additions and 9 deletions

View File

@@ -32,7 +32,7 @@
#include <arch/lib_helpers.h>
#include <libpayload.h>
uint64_t timer_hz(void)
uint32_t timer_hz(void)
{
return raw_read_cntfrq_el0();
}

View File

@@ -33,7 +33,7 @@
#include <assert.h>
#include <libpayload.h>
uint64_t timer_hz(void)
uint32_t timer_hz(void)
{
/* libc/time.c currently requires all timers to be at least 1MHz. */
assert(CONFIG_LP_TIMER_GENERIC_HZ >= 1000000);

View File

@@ -33,10 +33,12 @@
#include <libpayload.h>
#include <arch/rdtsc.h>
#include <assert.h>
uint64_t timer_hz(void)
uint32_t timer_hz(void)
{
return (uint64_t)lib_sysinfo.cpu_khz * 1000;
assert(UINT32_MAX / 1000 >= lib_sysinfo.cpu_khz);
return lib_sysinfo.cpu_khz * 1000;
}
uint64_t timer_raw_value(void)