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Kernel: Stop hardcoding syscall in signal trampoline.

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We now no longer hardcode the sigreturn syscall in
the signal trampoline. Because of the way inline asm inputs
work, I've had to enclose the trampoline in the function
signal_trampoline_dummy.
This commit is contained in:
Drew Stratford 2019-09-18 01:41:42 +12:00 • committed by Andreas Kling
parent 224fbb7910
commit 6e51ebad8c
1 changed files with 23 additions and 20 deletions
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43
Kernel/Process.cpp
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@ -793,26 +793,29 @@ void Process::sys$exit(int status)
ASSERT_NOT_REACHED(); ASSERT_NOT_REACHED();
} }
// The trampoline preserves the current eax, pushes the signal code and void signal_trampoline_dummy(void)
// then calls the signal handler. We do this because, when interrupting a {
// blocking syscall, that syscall may return some special error code in eax; // The trampoline preserves the current eax, pushes the signal code and
// This error code would likely be overwritten by the signal handler, so it's // then calls the signal handler. We do this because, when interrupting a
// neccessary to preserve it here. // blocking syscall, that syscall may return some special error code in eax;
asm( // This error code would likely be overwritten by the signal handler, so it's
".intel_syntax noprefix\n" // neccessary to preserve it here.
"asm_signal_trampoline:\n" asm(
"push ebp\n" ".intel_syntax noprefix\n"
"mov ebp, esp\n" "asm_signal_trampoline:\n"
"push eax\n" // we have to store eax 'cause it might be the return value from a syscall "push ebp\n"
"sub esp, 4\n" // align the stack to 16 bytes "mov ebp, esp\n"
"mov eax, [ebp+12]\n" // push the signal code "push eax\n" // we have to store eax 'cause it might be the return value from a syscall
"push eax\n" "sub esp, 4\n" // align the stack to 16 bytes
"call [ebp+8]\n" // call the signal handler "mov eax, [ebp+12]\n" // push the signal code
"add esp, 8\n" "push eax\n"
"mov eax, 0x2d\n" // FIXME: We shouldn't be hardcoding this. "call [ebp+8]\n" // call the signal handler
"int 0x82\n" // sigreturn syscall "add esp, 8\n"
"asm_signal_trampoline_end:\n" "mov eax, %P0\n"
".att_syntax"); "int 0x82\n" // sigreturn syscall
"asm_signal_trampoline_end:\n"
".att_syntax" ::"i"(Syscall::SC_sigreturn));
}
extern "C" void asm_signal_trampoline(void); extern "C" void asm_signal_trampoline(void);
extern "C" void asm_signal_trampoline_end(void); extern "C" void asm_signal_trampoline_end(void);