diff options
| author | Ian Moffett <ian@osmora.org> | 2025-08-12 23:31:41 -0400 |
|---|---|---|
| committer | Ian Moffett <ian@osmora.org> | 2025-08-12 23:31:41 -0400 |
| commit | 60af87ead21331501d3eac54648122f5ec6a4082 (patch) | |
| tree | 4e0b6ee76b6deffe579a4fd41bdf1788dfaa2eb2 | |
| parent | 466e8e091704c2b5ef1003c36b9538a61e037f6d (diff) | |
kernel/amd64: conf: Add boolean USER_TSC option
Introduce the USER_TSC kernel config option to control whether or not
the 'rdtsc' instruction should be accessible in a user context.
Signed-off-by: Ian Moffett <ian@osmora.org>
| -rw-r--r-- | sys/arch/amd64/amd64/tsc.c | 24 | ||||
| -rw-r--r-- | sys/arch/amd64/conf/GENERIC | 1 |
2 files changed, 25 insertions, 0 deletions
diff --git a/sys/arch/amd64/amd64/tsc.c b/sys/arch/amd64/amd64/tsc.c index e9070c5..1880821 100644 --- a/sys/arch/amd64/amd64/tsc.c +++ b/sys/arch/amd64/amd64/tsc.c @@ -32,6 +32,14 @@ #include <sys/driver.h> #include <sys/syslog.h> #include <machine/tsc.h> +#include <machine/asm.h> + +/* See kconf(9) */ +#if defined(__USER_TSC) +#define USER_TSC __USER_TSC +#else +#define USER_TSC 0 +#endif /* __USER_TSC */ #define pr_trace(fmt, ...) kprintf("tsc: " fmt, ##__VA_ARGS__) #define pr_error(...) pr_trace(__VA_ARGS__) @@ -47,8 +55,24 @@ rdtsc_rel(void) static int tsc_init(void) { + uint64_t cr4; + + cr4 = amd64_read_cr4(); tsc_i = rdtsc(); pr_trace("initial count @ %d\n", rdtsc_rel()); + + /* + * If we USER_TSC is configured to "yes" then + * we'll need to enable the 'rdtsc' instruction + * in user mode. + */ + if (!USER_TSC) { + cr4 &= ~CR4_TSD; + } else { + cr4 |= CR4_TSD; + } + + amd64_write_cr4(cr4); return 0; } diff --git a/sys/arch/amd64/conf/GENERIC b/sys/arch/amd64/conf/GENERIC index 6f573f3..9411999 100644 --- a/sys/arch/amd64/conf/GENERIC +++ b/sys/arch/amd64/conf/GENERIC @@ -8,5 +8,6 @@ option SPECTRE_IBRS no // Enable the IBRS CPU feature option SERIAL_DEBUG yes // Enable kmsg serial logging option USER_KMSG no // Show kmsg in user consoles +option USER_TSC no // Enable 'rdtsc' in user mode option CPU_SMEP yes // Supervisor Memory Exec Protection option I8042_POLL yes // Use polling for the i8042 |