X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/316670eb35587141e969394ae8537d66b9211e80..490019cf9519204c5fb36b2fba54ceb983bb6b72:/osfmk/x86_64/machine_routines_asm.s?ds=inline diff --git a/osfmk/x86_64/machine_routines_asm.s b/osfmk/x86_64/machine_routines_asm.s index 362887586..af962f2f4 100644 --- a/osfmk/x86_64/machine_routines_asm.s +++ b/osfmk/x86_64/machine_routines_asm.s @@ -39,9 +39,7 @@ /* ** ml_get_timebase() ** -** Entry - %rdi contains pointer to 64 bit structure. -** -** Exit - 64 bit structure filled in. +** Returns TSC in RAX ** */ ENTRY(ml_get_timebase) @@ -51,7 +49,6 @@ ENTRY(ml_get_timebase) lfence shlq $32,%rdx orq %rdx,%rax - movq %rax, (%rdi) ret @@ -81,10 +78,15 @@ ENTRY(ml_get_timebase) * */ ENTRY(tmrCvt) + cmpq $1,%rsi /* check for unity fastpath */ + je 1f movq %rdi,%rax mulq %rsi /* result is %rdx:%rax */ shrdq $32,%rdx,%rax /* %rdx:%rax >>= 32 */ ret +1: + mov %rdi,%rax + ret /* * void _rtc_nanotime_adjust( @@ -104,28 +106,36 @@ ENTRY(_rtc_nanotime_adjust) ret /* - * unint64_t _rtc_nanotime_read(rtc_nanotime_t *rntp, int slow); + * uint64_t _rtc_nanotime_read(rtc_nanotime_t *rntp); * * This is the same as the commpage nanotime routine, except that it uses the * kernel internal "rtc_nanotime_info" data instead of the commpage data. * These two copies of data are kept in sync by rtc_clock_napped(). * - * Warning! There is another copy of this code in osfmk/x86_64/idt64.s. - * These are kept in sync by both using the RTC_NANOTIME_READ() macro. + * Warning! There are several copies of this code in the trampolines found in + * osfmk/x86_64/idt64.s, coming from the various TIMER macros in rtclock_asm.h. + * They're all kept in sync by using the RTC_NANOTIME_READ() macro. + * + * The algorithm we use is: + * + * ns = ((((rdtsc - rnt_tsc_base)< SLOW_TSC_THRESHOLD * - * ns = (((rdtsc - rnt_tsc_base)*rnt_tsc_scale) / 2**32) + rnt_ns_base; + * Where SLOW_TSC_THRESHOLD is about 10e9. Since most processor's tscFreqs are greater + * than 1GHz, rnt_shift is usually 0. rnt_tsc_scale is also a 32-bit constant: * - * Of course, the divide by 2**32 is a nop. rnt_tsc_scale is a constant - * computed during initialization: + * rnt_tsc_scale = (10e9 * 2**32) / (tscFreq << rnt_shift); * - * rnt_tsc_scale = (10e9 * 2**32) / tscFreq; + * On 64-bit processors this algorithm could be simplified by doing a 64x64 bit + * multiply of rdtsc by tscFCvtt2n: * - * The "slow" algorithm uses long division: + * ns = (((rdtsc - rnt_tsc_base) * tscFCvtt2n) / 2**32) + rnt_ns_base; * - * ns = (((rdtsc - rnt_tsc_base) * 10e9) / tscFreq) + rnt_ns_base; + * We don't do so in order to use the same algorithm in 32- and 64-bit mode. + * When U32 goes away, we should reconsider. * * Since this routine is not synchronized and can be called in any context, * we use a generation count to guard against seeing partially updated data. @@ -136,33 +146,36 @@ ENTRY(_rtc_nanotime_adjust) * the generation is zero. * * unint64_t _rtc_nanotime_read( - * rtc_nanotime_t *rntp, // %rdi - * int slow); // %rsi + * rtc_nanotime_t *rntp); // %rdi * */ ENTRY(_rtc_nanotime_read) - test %rsi,%rsi - jnz Lslow - - /* - * Processor whose TSC frequency is faster than SLOW_TSC_THRESHOLD - */ + PAL_RTC_NANOTIME_READ_FAST() ret + +/* + * extern uint64_t _rtc_tsc_to_nanoseconds( + * uint64_t value, // %rdi + * pal_rtc_nanotime_t *rntp); // %rsi + * + * Converts TSC units to nanoseconds, using an abbreviated form of the above + * algorithm. Note that while we could have simply used tmrCvt(value,tscFCvtt2n), + * which would avoid the need for this asm, doing so is a bit more risky since + * we'd be using a different algorithm with possibly different rounding etc. + */ - /* - * Processor whose TSC frequency is not faster than SLOW_TSC_THRESHOLD - * But K64 doesn't support this... - */ -Lslow: - lea 1f(%rip),%rdi - xorb %al,%al - call EXT(panic) - hlt - .data -1: String "_rtc_nanotime_read() - slow algorithm not supported" - .text +ENTRY(_rtc_tsc_to_nanoseconds) + movq %rdi,%rax /* copy value (in TSC units) to convert */ + movl RNT_SHIFT(%rsi),%ecx + movl RNT_SCALE(%rsi),%edx + shlq %cl,%rax /* tscUnits << shift */ + mulq %rdx /* (tscUnits << shift) * scale */ + shrdq $32,%rdx,%rax /* %rdx:%rax >>= 32 */ + ret + + Entry(call_continuation) movq %rdi,%rcx /* get continuation */ @@ -179,45 +192,6 @@ Entry(x86_init_wrapper) movq %rsi, %rsp callq *%rdi - /* - * Generate a 64-bit quantity with possibly random characteristics, intended for use - * before the kernel entropy pool is available. The processor's RNG is used if - * available, and a value derived from the Time Stamp Counter is returned if not. - * Multiple invocations may result in well-correlated values if sourced from the TSC. - */ -Entry(ml_early_random) - mov %rbx, %rsi - mov $1, %eax - cpuid - mov %rsi, %rbx - test $(1 << 30), %ecx - jz Lnon_rdrand - RDRAND_RAX /* RAX := 64 bits of DRBG entropy */ - jnc Lnon_rdrand - ret -Lnon_rdrand: - rdtsc /* EDX:EAX := TSC */ - /* Distribute low order bits */ - mov %eax, %ecx - xor %al, %ah - shl $16, %rcx - xor %rcx, %rax - xor %eax, %edx - - /* Incorporate ASLR entropy, if any */ - lea (%rip), %rcx - shr $21, %rcx - movzbl %cl, %ecx - shl $16, %ecx - xor %ecx, %edx - - mov %ah, %cl - ror %cl, %edx /* Right rotate EDX (TSC&0xFF ^ (TSC>>8 & 0xFF))&1F */ - shl $32, %rdx - xor %rdx, %rax - mov %cl, %al - ret - #if CONFIG_VMX /* @@ -257,3 +231,14 @@ Entry(__vmxoff) ret #endif /* CONFIG_VMX */ + +/* + * mfence -- Memory Barrier + * Use out-of-line assembly to get + * standard x86-64 ABI guarantees + * about what the caller's codegen + * has in registers vs. memory + */ +Entry(do_mfence) + mfence + ret