mirror of
https://github.com/FEX-Emu/FEX.git
synced 2026-10-06 18:00:17 +02:00
Ryan Houdek
0f54369f9b
This is an interesting vdso implementation because it only exists in x86-64 with kernel v6.11. For Arm64 the implementation is likely to land in a couple kernel versions from now. Some differences with vdso_getrandom versus the regular getrandom syscall - Has two additional arguments, opaque_state and opaque_len - Expects the userspace to mmap/munmap this opaque state structure - Lets userspace query information about this structure upfront - If the opaque data structure isn't provided then it falls back to regular SYS_getrandom With the "glibc" implementation, we can tell the interface to allocate a single page that gets unused (otherwise glibc ends up not using the interface), and fallback to the regular SYS_getrandom. In the case of the vdso interface, currently the arguments just get passed through. Keeping this as a WIP until the ARM64 kernel patches land and I can actually test the things. Running the "glibc" path works today with the selftest, but the vdso path is currently completely untested.
65 lines
1.6 KiB
C++
65 lines
1.6 KiB
C++
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/*
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$info$
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tags: thunklibs|VDSO
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desc: Linux VDSO thunking
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$end_info$
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*/
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#include <stdio.h>
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#include <cstring>
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#include <sched.h>
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#include <sys/time.h>
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#include <time.h>
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#include "Types.h"
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#include "common/Guest.h"
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#include "thunkgen_guest_libVDSO.inl"
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extern "C" {
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time_t __vdso_time(time_t* tloc) __attribute__((alias("fexfn_pack_time")));
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int __vdso_gettimeofday(struct timeval* tv, struct timezone* tz) __attribute__((alias("fexfn_pack_gettimeofday")));
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int __vdso_clock_gettime(clockid_t, struct timespec*) __attribute__((alias("fexfn_pack_clock_gettime")));
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int __vdso_clock_getres(clockid_t, struct timespec*) __attribute__((alias("fexfn_pack_clock_getres")));
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int __vdso_getcpu(uint32_t*, uint32_t*) __attribute__((alias("fexfn_pack_getcpu")));
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#if __SIZEOF_POINTER__ == 4
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int __vdso_clock_gettime64(clockid_t, struct timespec64*) __attribute__((alias("fexfn_pack_clock_gettime64")));
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__attribute__((naked)) int __kernel_vsyscall() {
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asm volatile(R"(
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.intel_syntax noprefix
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int 0x80;
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ret;
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.att_syntax prefix
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)" ::
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: "memory");
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}
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__attribute__((naked)) void __kernel_sigreturn() {
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asm volatile(R"(
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.intel_syntax noprefix
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pop eax;
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mov eax, 0x77;
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int 0x80;
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nop;
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.att_syntax prefix
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)" ::
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: "memory");
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}
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__attribute__((naked)) void __kernel_rt_sigreturn() {
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asm volatile(R"(
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.intel_syntax noprefix
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mov eax, 0xad;
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int 0x80;
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.att_syntax prefix
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)" ::
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: "memory");
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}
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#else
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ssize_t __vdso_getrandom(void*, size_t, uint32_t, void*, size_t) __attribute__((alias("fexfn_pack_getrandom")));
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#endif
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}
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