MIPS: Move signal trampolines off of the stack.

This is a follow on to the vdso patch.

Since all processes now have signal trampolines permanently mapped, we
can use those instead of putting the trampoline on the stack and
invalidating the corresponding icache across all CPUs.  We also get rid
of a bunch of ICACHE_REFILLS_WORKAROUND_WAR code.

[Ralf: GDB 7.1 which has the necessary modifications to allow backtracing
over signal frames will supposedly be released tomorrow.  The old signal
frame format obsoleted by this patch exists in two variations, for sane
processors and for those requiring ICACHE_REFILLS_WORKAROUND_WAR.  So
there was never a GDB which did support backtracing over signal frames
on all MIPS systems.  This convinved me this series should be applied and
pushed upstream as soon as possible.]

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/974/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 19 insertions, 67 deletions

diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index d0c68b5d717..2099d5a4c4b 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -32,6 +32,7 @@
 #include <asm/ucontext.h>
 #include <asm/cpu-features.h>
 #include <asm/war.h>
+#include <asm/vdso.h>
 
 #include "signal-common.h"
 
@@ -44,47 +45,20 @@ extern asmlinkage int _restore_fp_context(struct sigcontext __user *sc);
 extern asmlinkage int fpu_emulator_save_context(struct sigcontext __user *sc);
 extern asmlinkage int fpu_emulator_restore_context(struct sigcontext __user *sc);
 
-/*
- * Horribly complicated - with the bloody RM9000 workarounds enabled
- * the signal trampolines is moving to the end of the structure so we can
- * increase the alignment without breaking software compatibility.
- */
-#if ICACHE_REFILLS_WORKAROUND_WAR == 0
-
 struct sigframe {
 	u32 sf_ass[4];		/* argument save space for o32 */
-	u32 sf_code[2];		/* signal trampoline */
+	u32 sf_pad[2];		/* Was: signal trampoline */
 	struct sigcontext sf_sc;
 	sigset_t sf_mask;
 };
 
 struct rt_sigframe {
 	u32 rs_ass[4];		/* argument save space for o32 */
-	u32 rs_code[2];		/* signal trampoline */
+	u32 rs_pad[2];		/* Was: signal trampoline */
 	struct siginfo rs_info;
 	struct ucontext rs_uc;
 };
 
-#else
-
-struct sigframe {
-	u32 sf_ass[4];			/* argument save space for o32 */
-	u32 sf_pad[2];
-	struct sigcontext sf_sc;	/* hw context */
-	sigset_t sf_mask;
-	u32 sf_code[8] ____cacheline_aligned;	/* signal trampoline */
-};
-
-struct rt_sigframe {
-	u32 rs_ass[4];			/* argument save space for o32 */
-	u32 rs_pad[2];
-	struct siginfo rs_info;
-	struct ucontext rs_uc;
-	u32 rs_code[8] ____cacheline_aligned;	/* signal trampoline */
-};
-
-#endif
-
 /*
  * Helper routines
  */
@@ -266,32 +240,6 @@ void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
 	return (void __user *)((sp - frame_size) & (ICACHE_REFILLS_WORKAROUND_WAR ? ~(cpu_icache_line_size()-1) : ALMASK));
 }
 
-int install_sigtramp(unsigned int __user *tramp, unsigned int syscall)
-{
-	int err;
-
-	/*
-	 * Set up the return code ...
-	 *
-	 *         li      v0, __NR__foo_sigreturn
-	 *         syscall
-	 */
-
-	err = __put_user(0x24020000 + syscall, tramp + 0);
-	err |= __put_user(0x0000000c         , tramp + 1);
-	if (ICACHE_REFILLS_WORKAROUND_WAR) {
-		err |= __put_user(0, tramp + 2);
-		err |= __put_user(0, tramp + 3);
-		err |= __put_user(0, tramp + 4);
-		err |= __put_user(0, tramp + 5);
-		err |= __put_user(0, tramp + 6);
-		err |= __put_user(0, tramp + 7);
-	}
-	flush_cache_sigtramp((unsigned long) tramp);
-
-	return err;
-}
-
 /*
  * Atomically swap in the new signal mask, and wait for a signal.
  */
@@ -484,8 +432,8 @@ badframe:
 }
 
 #ifdef CONFIG_TRAD_SIGNALS
-static int setup_frame(struct k_sigaction * ka, struct pt_regs *regs,
-	int signr, sigset_t *set)
+static int setup_frame(void *sig_return, struct k_sigaction *ka,
+		       struct pt_regs *regs, int signr, sigset_t *set)
 {
 	struct sigframe __user *frame;
 	int err = 0;
@@ -494,8 +442,6 @@ static int setup_frame(struct k_sigaction * ka, struct pt_regs *regs,
 	if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
 		goto give_sigsegv;
 
-	err |= install_sigtramp(frame->sf_code, __NR_sigreturn);
-
 	err |= setup_sigcontext(regs, &frame->sf_sc);
 	err |= __copy_to_user(&frame->sf_mask, set, sizeof(*set));
 	if (err)
@@ -515,7 +461,7 @@ static int setup_frame(struct k_sigaction * ka, struct pt_regs *regs,
 	regs->regs[ 5] = 0;
 	regs->regs[ 6] = (unsigned long) &frame->sf_sc;
 	regs->regs[29] = (unsigned long) frame;
-	regs->regs[31] = (unsigned long) frame->sf_code;
+	regs->regs[31] = (unsigned long) sig_return;
 	regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;
 
 	DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n",
@@ -529,8 +475,9 @@ give_sigsegv:
 }
 #endif
 
-static int setup_rt_frame(struct k_sigaction * ka, struct pt_regs *regs,
-	int signr, sigset_t *set, siginfo_t *info)
+static int setup_rt_frame(void *sig_return, struct k_sigaction *ka,
+			  struct pt_regs *regs,	int signr, sigset_t *set,
+			  siginfo_t *info)
 {
 	struct rt_sigframe __user *frame;
 	int err = 0;
@@ -539,8 +486,6 @@ static int setup_rt_frame(struct k_sigaction * ka, struct pt_regs *regs,
 	if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
 		goto give_sigsegv;
 
-	err |= install_sigtramp(frame->rs_code, __NR_rt_sigreturn);
-
 	/* Create siginfo.  */
 	err |= copy_siginfo_to_user(&frame->rs_info, info);
 
@@ -573,7 +518,7 @@ static int setup_rt_frame(struct k_sigaction * ka, struct pt_regs *regs,
 	regs->regs[ 5] = (unsigned long) &frame->rs_info;
 	regs->regs[ 6] = (unsigned long) &frame->rs_uc;
 	regs->regs[29] = (unsigned long) frame;
-	regs->regs[31] = (unsigned long) frame->rs_code;
+	regs->regs[31] = (unsigned long) sig_return;
 	regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;
 
 	DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n",
@@ -590,8 +535,11 @@ give_sigsegv:
 struct mips_abi mips_abi = {
 #ifdef CONFIG_TRAD_SIGNALS
 	.setup_frame	= setup_frame,
+	.signal_return_offset = offsetof(struct mips_vdso, signal_trampoline),
 #endif
 	.setup_rt_frame	= setup_rt_frame,
+	.rt_signal_return_offset =
+		offsetof(struct mips_vdso, rt_signal_trampoline),
 	.restart	= __NR_restart_syscall
 };
 
@@ -599,6 +547,8 @@ static int handle_signal(unsigned long sig, siginfo_t *info,
 	struct k_sigaction *ka, sigset_t *oldset, struct pt_regs *regs)
 {
 	int ret;
+	struct mips_abi *abi = current->thread.abi;
+	void *vdso = current->mm->context.vdso;
 
 	switch(regs->regs[0]) {
 	case ERESTART_RESTARTBLOCK:
@@ -619,9 +569,11 @@ static int handle_signal(unsigned long sig, siginfo_t *info,
 	regs->regs[0] = 0;		/* Don't deal with this again.  */
 
 	if (sig_uses_siginfo(ka))
-		ret = current->thread.abi->setup_rt_frame(ka, regs, sig, oldset, info);
+		ret = abi->setup_rt_frame(vdso + abi->rt_signal_return_offset,
+					  ka, regs, sig, oldset, info);
 	else
-		ret = current->thread.abi->setup_frame(ka, regs, sig, oldset);
+		ret = abi->setup_frame(vdso + abi->signal_return_offset,
+				       ka, regs, sig, oldset);
 
 	spin_lock_irq(&current->sighand->siglock);
 	sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);