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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();
}
// The trampoline preserves the current eax, pushes the signal code and
// then calls the signal handler. We do this because, when interrupting a
// blocking syscall, that syscall may return some special error code in eax;
// This error code would likely be overwritten by the signal handler, so it's
// neccessary to preserve it here.
asm(
".intel_syntax noprefix\n"
"asm_signal_trampoline:\n"
"push ebp\n"
"mov ebp, esp\n"
"push eax\n" // we have to store eax 'cause it might be the return value from a syscall
"sub esp, 4\n" // align the stack to 16 bytes
"mov eax, [ebp+12]\n" // push the signal code
"push eax\n"
"call [ebp+8]\n" // call the signal handler
"add esp, 8\n"
"mov eax, 0x2d\n" // FIXME: We shouldn't be hardcoding this.
"int 0x82\n" // sigreturn syscall
"asm_signal_trampoline_end:\n"
".att_syntax");
void signal_trampoline_dummy(void)
{
// The trampoline preserves the current eax, pushes the signal code and
// then calls the signal handler. We do this because, when interrupting a
// blocking syscall, that syscall may return some special error code in eax;
// This error code would likely be overwritten by the signal handler, so it's
// neccessary to preserve it here.
asm(
".intel_syntax noprefix\n"
"asm_signal_trampoline:\n"
"push ebp\n"
"mov ebp, esp\n"
"push eax\n" // we have to store eax 'cause it might be the return value from a syscall
"sub esp, 4\n" // align the stack to 16 bytes
"mov eax, [ebp+12]\n" // push the signal code
"push eax\n"
"call [ebp+8]\n" // call the signal handler
"add esp, 8\n"
"mov eax, %P0\n"
"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_end(void);