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| author |   weingart <weingart@openbsd.org> | 2008-11-12 21:42:43 +0000 |
|---|---|---|
| committer | weingart <weingart@openbsd.org> | 2008-11-12 21:42:43 +0000 |
| commit | 26be300f563a42fcda62bc8e04142279326e147e (patch) | |
| tree | 6815570ad1787f944fcd59f073b562c8133a4025 | |
| parent | when destroying the device, mark the mixer and the demultiplexer (diff) | |
| download | wireguard-openbsd-26be300f563a42fcda62bc8e04142279326e147e.tar.xz wireguard-openbsd-26be300f563a42fcda62bc8e04142279326e147e.zip | |
Add a comment to sigcode() to explain why the use of 'int $0x80' is
necessary, so that future hackers will not be mislead the same way I
was when looking at this code.
| -rw-r--r-- | sys/arch/amd64/amd64/locore.S | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/sys/arch/amd64/amd64/locore.S b/sys/arch/amd64/amd64/locore.S index e554a9d8440..bd569f17cf4 100644 --- a/sys/arch/amd64/amd64/locore.S +++ b/sys/arch/amd64/amd64/locore.S @@ -1,4 +1,4 @@ -/* $OpenBSD: locore.S,v 1.29 2008/10/24 06:32:17 deraadt Exp $ */ +/* $OpenBSD: locore.S,v 1.30 2008/11/12 21:42:43 weingart Exp $ */ /* $NetBSD: locore.S,v 1.13 2004/03/25 18:33:17 drochner Exp $ */ /* @@ -637,6 +637,12 @@ longmode_hi: /* * Signal trampoline; copied to top of user stack. + * + * Note, the "system call" to sigreturn() needs to be an 'int $0x80' one + * so that the kernel returns using 'iretq' method. This way if a process + * was interrupted (by tick) as opposed to in the kernel when a signal was + * being delivered, the process will be completely restored, including the + * userland %rcx register, which the 'sysret' instruction can not restore. */ NENTRY(sigcode) call *%rax |