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-rw-r--r--arch/x86_64/kernel/signal.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/arch/x86_64/kernel/signal.c b/arch/x86_64/kernel/signal.c
index d642fbf3da29..5876df116c92 100644
--- a/arch/x86_64/kernel/signal.c
+++ b/arch/x86_64/kernel/signal.c
@@ -110,6 +110,15 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, unsigned
110 COPY(r14); 110 COPY(r14);
111 COPY(r15); 111 COPY(r15);
112 112
113 /* Kernel saves and restores only the CS segment register on signals,
114 * which is the bare minimum needed to allow mixed 32/64-bit code.
115 * App's signal handler can save/restore other segments if needed. */
116 {
117 unsigned cs;
118 err |= __get_user(cs, &sc->cs);
119 regs->cs = cs | 3; /* Force into user mode */
120 }
121
113 { 122 {
114 unsigned int tmpflags; 123 unsigned int tmpflags;
115 err |= __get_user(tmpflags, &sc->eflags); 124 err |= __get_user(tmpflags, &sc->eflags);
@@ -187,6 +196,7 @@ setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, unsigned lo
187{ 196{
188 int err = 0; 197 int err = 0;
189 198
199 err |= __put_user(regs->cs, &sc->cs);
190 err |= __put_user(0, &sc->gs); 200 err |= __put_user(0, &sc->gs);
191 err |= __put_user(0, &sc->fs); 201 err |= __put_user(0, &sc->fs);
192 202
@@ -318,7 +328,14 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
318 328
319 regs->rsp = (unsigned long)frame; 329 regs->rsp = (unsigned long)frame;
320 330
331 /* Set up the CS register to run signal handlers in 64-bit mode,
332 even if the handler happens to be interrupting 32-bit code. */
333 regs->cs = __USER_CS;
334
335 /* This, by contrast, has nothing to do with segment registers -
336 see include/asm-x86_64/uaccess.h for details. */
321 set_fs(USER_DS); 337 set_fs(USER_DS);
338
322 regs->eflags &= ~TF_MASK; 339 regs->eflags &= ~TF_MASK;
323 if (test_thread_flag(TIF_SINGLESTEP)) 340 if (test_thread_flag(TIF_SINGLESTEP))
324 ptrace_notify(SIGTRAP); 341 ptrace_notify(SIGTRAP);