diff options
| author | Yidi Lin <yidilin@chromium.org> | 2023-11-02 14:17:02 +0800 |
|---|---|---|
| committer | Julius Werner <jwerner@chromium.org> | 2023-11-07 19:25:23 +0000 |
| commit | eabdd0252a2c3f8fb03b83781019243d47737e80 (patch) | |
| tree | 2b3665eb5e1cebfa09aaa7151d02378d1797a9ad /payloads/libpayload/libc/time.c | |
| parent | e91785dfd8fd29a2f39a1f0ceb143015536706fb (diff) | |
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>
Diffstat (limited to 'payloads/libpayload/libc/time.c')
| -rw-r--r-- | payloads/libpayload/libc/time.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/payloads/libpayload/libc/time.c b/payloads/libpayload/libc/time.c index 6780008d4c..c38dbfdde8 100644 --- a/payloads/libpayload/libc/time.c +++ b/payloads/libpayload/libc/time.c @@ -38,6 +38,7 @@ #if CONFIG(LP_ARCH_X86) && CONFIG(LP_NVRAM) #include <arch/rdtsc.h> #endif +#include <commonlib/bsd/gcd.h> #include <inttypes.h> extern u32 cpu_khz; @@ -170,17 +171,21 @@ void arch_ndelay(uint64_t ns) u64 timer_us(u64 base) { - static u64 hz; + static u32 hz, mult = USECS_PER_SEC; + u32 div; // Only check timer_hz once. Assume it doesn't change. if (hz == 0) { hz = timer_hz(); - if (hz < 1000000) { - printf("Timer frequency %" PRIu64 " is too low, " + if (hz < mult) { + printf("Timer frequency %" PRIu32 " is too low, " "must be at least 1MHz.\n", hz); halt(); } + div = gcd32(hz, mult); + hz /= div; + mult /= div; } - return (1000000 * timer_raw_value()) / hz - base; + return (mult * timer_raw_value()) / hz - base; } |