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[PATCH] x86_64: Save/restore CS in 64bit signal handlers and force __USER_CS for CS

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This allows to run 64bit signal handlers in 64bit processes that run small
code snippets in compat mode.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Bryan Ford 2005-11-05 17:25:54 +01:00 committed by Linus Torvalds
parent 420f8f68c9
commit e4e5d324b9
1 changed files with 17 additions and 0 deletions
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17
arch/x86_64/kernel/signal.c
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@ -110,6 +110,15 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, unsigned
COPY(r14);
COPY(r15);
/* Kernel saves and restores only the CS segment register on signals,
* which is the bare minimum needed to allow mixed 32/64-bit code.
* App's signal handler can save/restore other segments if needed. */
{
unsigned cs;
err |= __get_user(cs, &sc->cs);
regs->cs = cs | 3; /* Force into user mode */
}
{
unsigned int tmpflags;
err |= __get_user(tmpflags, &sc->eflags);
@ -187,6 +196,7 @@ setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, unsigned lo
{
int err = 0;
err |= __put_user(regs->cs, &sc->cs);
err |= __put_user(0, &sc->gs);
err |= __put_user(0, &sc->fs);
@ -318,7 +328,14 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
regs->rsp = (unsigned long)frame;
/* Set up the CS register to run signal handlers in 64-bit mode,
even if the handler happens to be interrupting 32-bit code. */
regs->cs = __USER_CS;
/* This, by contrast, has nothing to do with segment registers -
see include/asm-x86_64/uaccess.h for details. */
set_fs(USER_DS);
regs->eflags &= ~TF_MASK;
if (test_thread_flag(TIF_SINGLESTEP))
ptrace_notify(SIGTRAP);