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Rewrite syscall stub and SyscallsFrame structure

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This commit is contained in:
Alex 2023-05-05 17:33:33 +03:00
parent 2b44ad7d75
commit 72918cdc18
Signed by untrusted user who does not match committer: enderice2
GPG Key ID: EACC3AD603BAB4DD
2 changed files with 49 additions and 21 deletions
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31
Architecture/amd64/SystemCalls.cpp
View File

@ -31,17 +31,16 @@ extern "C" void SystemCallHandlerStub();
extern "C" __naked __used __no_stack_protector __aligned(16) void SystemCallHandlerStub()
{
asmv("swapgs\n");
asmv("swapgs\n"); /* Swap GS to get the CPUData */
asmv("mov %rsp, %gs:0x8\n"); /* We save the current rsp to CPUData->TempStack */
asmv("mov %gs:0x0, %rsp\n"); /* Get CPUData->SystemCallStack and set it as rsp */
asmv("push $0x1b\n"); /* Push user data segment for SyscallsFrame */
asmv("push %gs:0x8\n"); /* Push CPUData->TempStack (old rsp) for SyscallsFrame */
asmv("push %r11\n"); /* Push the flags for SyscallsFrame */
asmv("push $0x23\n"); /* Push user code segment for SyscallsFrame */
asmv("push %rcx\n"); /* Push the return address for SyscallsFrame + sysretq (https://www.felixcloutier.com/x86/sysret) */
asmv("mov %rsp, %gs:0x8\n"); // CPUData->TempStack
asmv("mov %gs:0x0, %rsp\n"); // CPUData->SystemCallStack
asmv("push $0x1b\n"); // user data segment
asmv("push %gs:0x8\n"); // saved stack
asmv("push %r11\n"); // saved rflags
asmv("push $0x23\n"); // user code segment
asmv("push %rcx\n"); // Current RIP
asmv("push %rax\n"
asmv("push %rax\n" /* Push registers */
"push %rbx\n"
"push %rcx\n"
"push %rdx\n"
@ -57,11 +56,11 @@ extern "C" __naked __used __no_stack_protector __aligned(16) void SystemCallHand
"push %r14\n"
"push %r15\n");
asmv("mov %rsp, %rdi\n");
asmv("mov %rsp, %rdi\n"); /* Set the first argument to the SyscallsFrame pointer */
asmv("mov $0, %rbp\n");
asmv("call SystemCallsHandler\n");
asmv("pop %r15\n"
asmv("pop %r15\n" /* Pop registers except rax */
"pop %r14\n"
"pop %r13\n"
"pop %r12\n"
@ -76,14 +75,14 @@ extern "C" __naked __used __no_stack_protector __aligned(16) void SystemCallHand
"pop %rcx\n"
"pop %rbx\n");
asmv("mov %gs:0x8, %rsp\n"); // CPUData->TempStack
asmv("mov %gs:0x8, %rsp\n"); // Restore rsp from CPUData->TempStack
#ifdef DEBUG
asmv("movq $0, %gs:0x8\n"); // Easier to debug stacks // FIXME: Can't use xor
#endif
asmv("swapgs\n");
asmv("sti\n");
asmv("sysretq\n");
asmv("swapgs\n"); // Swap GS back to the user GS
asmv("sti\n"); // Enable interrupts
asmv("sysretq\n"); // Return to rcx address in user mode
}
void InitializeSystemCalls()

39
include/syscalls.hpp
View File

@ -23,12 +23,41 @@
typedef struct SyscallsFrame
{
#if defined(a64)
uint64_t r15, r14, r13, r12, r11, r10, r9, r8;
uint64_t rbp, rdi, rsi, rdx, rcx, rbx, rax;
uint64_t InterruptNumber, ErrorCode, rip, cs, rflags, rsp, ss;
uint64_t r15;
uint64_t r14;
uint64_t r13;
uint64_t r12;
uint64_t r11;
uint64_t r10;
uint64_t r9;
uint64_t r8;
uint64_t rbp;
uint64_t rdi;
uint64_t rsi;
uint64_t rdx;
uint64_t rcx;
uint64_t rbx;
uint64_t rax;
uint64_t ReturnAddress;
uint64_t CodeSegment;
uint64_t Flags;
uint64_t StackPointer;
uint64_t StackSegment;
#elif defined(a32)
uint32_t ebp, edi, esi, edx, ecx, ebx, eax;
uint32_t InterruptNumber, ErrorCode, eip, cs, eflags, esp, ss;
uint32_t ebp;
uint32_t edi;
uint32_t esi;
uint32_t edx;
uint32_t ecx;
uint32_t ebx;
uint32_t eax;
uint32_t ReturnAddress;
uint32_t CodeSegment;
uint32_t Flags;
uint32_t StackPointer;
uint32_t StackSegment;
#elif defined(aa64)
#endif
} SyscallsFrame;