Jérôme Duval
bdd7dae89c
* install syscall handlers in compatibility mode. * copy the syscall entry in the compatibility commpage, ATM only for Intel SYSENTER. * copy the thread exit handler in the compatibility commpage. Change-Id: Ic350799938815194377d8a4560cb106fe7366cc6
152 lines
4.0 KiB
C++
152 lines
4.0 KiB
C++
/*
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* Copyright 2018, Jérôme Duval, [email protected].
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* Copyright 2012, Alex Smith, [email protected].
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* Distributed under the terms of the MIT License.
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*/
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#include "x86_syscalls.h"
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#include <KernelExport.h>
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#ifdef _COMPAT_MODE
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# include <commpage_compat.h>
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#endif
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#include <cpu.h>
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#ifdef _COMPAT_MODE
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# include <elf.h>
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#endif
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#include <smp.h>
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// SYSCALL handler (in interrupts.S).
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extern "C" void x86_64_syscall_entry(void);
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#ifdef _COMPAT_MODE
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// SYSCALL/SYSENTER handlers (in entry_compat.S).
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extern "C" {
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void x86_64_syscall32_entry(void);
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void x86_64_sysenter32_entry(void);
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}
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void (*gX86SetSyscallStack)(addr_t stackTop) = NULL;
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// user syscall assembly stubs
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extern "C" void x86_user_syscall_sysenter(void);
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extern unsigned int x86_user_syscall_sysenter_end;
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extern "C" void x86_user_syscall_syscall(void);
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extern unsigned int x86_user_syscall_syscall_end;
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extern "C" void x86_sysenter32_userspace_thread_exit(void);
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extern unsigned int x86_sysenter32_userspace_thread_exit_end;
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#endif // _COMPAT_MODE
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static void
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init_syscall_registers(void* dummy, int cpuNum)
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{
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// Enable SYSCALL (EFER.SCE = 1).
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x86_write_msr(IA32_MSR_EFER, x86_read_msr(IA32_MSR_EFER)
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| IA32_MSR_EFER_SYSCALL);
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// Flags to clear upon entry. Want interrupts disabled and the direction
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// flag cleared.
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x86_write_msr(IA32_MSR_FMASK, X86_EFLAGS_INTERRUPT | X86_EFLAGS_DIRECTION
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| X86_EFLAGS_ALIGNMENT_CHECK);
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// Entry point address.
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x86_write_msr(IA32_MSR_LSTAR, (addr_t)x86_64_syscall_entry);
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#ifdef _COMPAT_MODE
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// Syscall compat entry point address.
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x86_write_msr(IA32_MSR_CSTAR, (addr_t)x86_64_syscall32_entry);
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#endif
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// Segments that will be set upon entry and return. This is very strange
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// and requires a specific ordering of segments in the GDT. Upon entry:
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// - CS is set to IA32_STAR[47:32]
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// - SS is set to IA32_STAR[47:32] + 8
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// Upon return:
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// - CS is set to IA32_STAR[63:48] + 16
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// - SS is set to IA32_STAR[63:48] + 8
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// From this we get:
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// - Entry CS = KERNEL_CODE_SELECTOR
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// - Entry SS = KERNEL_CODE_SELECTOR + 8 = KERNEL_DATA_SELECTOR
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// - Return CS = USER32_CODE_SELECTOR + 16 = USER_CODE_SELECTOR
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// - Return SS = USER32_CODE_SELECTOR + 8 = USER_DATA_SELECTOR
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x86_write_msr(IA32_MSR_STAR, ((uint64)(USER32_CODE_SELECTOR) << 48)
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| ((uint64)(KERNEL_CODE_SELECTOR) << 32));
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}
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// #pragma mark -
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void
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x86_initialize_syscall(void)
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{
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// SYSCALL/SYSRET are always available on x86_64 so we just use them, no
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// need to use the commpage. Tell all CPUs to initialize the SYSCALL MSRs.
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call_all_cpus_sync(&init_syscall_registers, NULL);
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}
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#ifdef _COMPAT_MODE
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static void
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set_intel_syscall_stack(addr_t stackTop)
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{
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x86_write_msr(IA32_MSR_SYSENTER_ESP, stackTop);
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}
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static void
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init_intel_syscall_registers(void* dummy, int cpuNum)
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{
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x86_write_msr(IA32_MSR_SYSENTER_CS, KERNEL_CODE_SELECTOR);
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x86_write_msr(IA32_MSR_SYSENTER_ESP, 0);
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x86_write_msr(IA32_MSR_SYSENTER_EIP, (addr_t)x86_64_sysenter32_entry);
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gX86SetSyscallStack = &set_intel_syscall_stack;
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}
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void
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x86_compat_initialize_syscall(void)
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{
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// for 32-bit syscalls, fill the commpage with the right mechanism
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call_all_cpus_sync(&init_intel_syscall_registers, NULL);
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void* syscallCode = (void *)&x86_user_syscall_sysenter;
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void* syscallCodeEnd = &x86_user_syscall_sysenter_end;
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// TODO check AMD for sysenter
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// fill in the table entry
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size_t len = (size_t)((addr_t)syscallCodeEnd - (addr_t)syscallCode);
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addr_t position = fill_commpage_compat_entry(COMMPAGE_ENTRY_X86_SYSCALL,
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syscallCode, len);
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image_id image = get_commpage_compat_image();
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elf_add_memory_image_symbol(image, "commpage_compat_syscall", position,
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len, B_SYMBOL_TYPE_TEXT);
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void* threadExitCode = (void *)&x86_sysenter32_userspace_thread_exit;
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void* threadExitCodeEnd = &x86_sysenter32_userspace_thread_exit_end;
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len = (size_t)((addr_t)threadExitCodeEnd - (addr_t)threadExitCode);
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position = fill_commpage_compat_entry(COMMPAGE_ENTRY_X86_THREAD_EXIT,
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threadExitCode, len);
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elf_add_memory_image_symbol(image, "commpage_compat_thread_exit",
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position, len, B_SYMBOL_TYPE_TEXT);
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}
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#endif // _COMPAT_MODE
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