From 5aa5ce53bcb23e1c31362bae317725ea0cce175a Mon Sep 17 00:00:00 2001 From: Cristian-Bogdan SIRB Date: Thu, 27 Feb 2020 11:36:53 +0200 Subject: [PATCH] Kernel: Fix the gettid syscall syscall_handler was not actually updating the value in regs->eax, so the gettid() was always returning 85: the value of regs->eax was not actually updated, and it remained the one from Userland (the value of SC_gettid). The syscall_handler was modified to actually get a pointer to RegisterState, so any changes to it will actually be saved. NOTE: This was actually more of a compiler optimization: On the SC_gettid flow, we saved in regs.eax the return value of sys$gettid(), but the compiler discarded it, since it followed a return. On a normal flow, the value of regs.eax was reused in tracer->did_syscall, so the compiler actually updated the value. --- Kernel/Syscall.cpp | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/Kernel/Syscall.cpp b/Kernel/Syscall.cpp index f1f19617f4..e40af90bdc 100644 --- a/Kernel/Syscall.cpp +++ b/Kernel/Syscall.cpp @@ -33,7 +33,7 @@ namespace Kernel { -extern "C" void syscall_handler(RegisterState); +extern "C" void syscall_handler(RegisterState&); extern "C" void syscall_asm_entry(); asm( @@ -52,8 +52,9 @@ asm( " cld\n" " xor %esi, %esi\n" " xor %edi, %edi\n" + " push %esp\n" " call syscall_handler\n" - " add $0x4, %esp\n" + " add $0x8, %esp\n" " popl %gs\n" " popl %fs\n" " popl %es\n" @@ -121,7 +122,7 @@ int handle(RegisterState& regs, u32 function, u32 arg1, u32 arg2, u32 arg3) } -void syscall_handler(RegisterState regs) +void syscall_handler(RegisterState& regs) { // Special handling of the "gettid" syscall since it's extremely hot. // FIXME: Remove this hack once userspace locks stop calling it so damn much.