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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
2 changed files with 49 additions and 21 deletions
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31
Architecture/amd64/SystemCalls.cpp
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@ -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()