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, 6 insertions, 20 deletions

diff --git a/arch/mips/kernel/signal_n32.c b/arch/mips/kernel/signal_n32.c
index bb277e82d421..2c5df818c65a 100644
--- a/arch/mips/kernel/signal_n32.c
+++ b/arch/mips/kernel/signal_n32.c
@@ -39,13 +39,13 @@
 #include <asm/fpu.h>
 #include <asm/cpu-features.h>
 #include <asm/war.h>
+#include <asm/vdso.h>
 
 #include "signal-common.h"
 
 /*
  * Including <asm/unistd.h> would give use the 64-bit syscall numbers ...
  */
-#define __NR_N32_rt_sigreturn           6211
 #define __NR_N32_restart_syscall        6214
 
 extern int setup_sigcontext(struct pt_regs *, struct sigcontext __user *);
@@ -67,27 +67,13 @@ struct ucontextn32 {
         compat_sigset_t     uc_sigmask;   /* mask last for extensibility */
 };
 
-#if ICACHE_REFILLS_WORKAROUND_WAR == 0
-
-struct rt_sigframe_n32 {
-        u32 rs_ass[4];                  /* argument save space for o32 */
-        u32 rs_code[2];                 /* signal trampoline */
-        struct compat_siginfo rs_info;
-        struct ucontextn32 rs_uc;
-};
-
-#else  /* ICACHE_REFILLS_WORKAROUND_WAR */
-
 struct rt_sigframe_n32 {
         u32 rs_ass[4];                  /* argument save space for o32 */
-        u32 rs_pad[2];
+        u32 rs_pad[2];                  /* Was: signal trampoline */
         struct compat_siginfo rs_info;
         struct ucontextn32 rs_uc;
-        u32 rs_code[8] ____cacheline_aligned;           /* signal trampoline */
 };
 
-#endif  /* !ICACHE_REFILLS_WORKAROUND_WAR */
-
 extern void sigset_from_compat(sigset_t *set, compat_sigset_t *compat);
 
 asmlinkage int sysn32_rt_sigsuspend(nabi_no_regargs struct pt_regs regs)
@@ -173,7 +159,7 @@ badframe:
         force_sig(SIGSEGV, current);
 }
 
-static int setup_rt_frame_n32(struct k_sigaction * ka,
+static int setup_rt_frame_n32(void *sig_return, struct k_sigaction *ka,
         struct pt_regs *regs, int signr, sigset_t *set, siginfo_t *info)
 {
         struct rt_sigframe_n32 __user *frame;
@@ -184,8 +170,6 @@ static int setup_rt_frame_n32(struct k_sigaction * ka,
         if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
                 goto give_sigsegv;
 
-        install_sigtramp(frame->rs_code, __NR_N32_rt_sigreturn);
-
         /* Create siginfo.  */
         err |= copy_siginfo_to_user32(&frame->rs_info, info);
 
@@ -219,7 +203,7 @@ static int setup_rt_frame_n32(struct k_sigaction * ka,
         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",
@@ -235,5 +219,7 @@ give_sigsegv:
 
 struct mips_abi mips_abi_n32 = {
         .setup_rt_frame = setup_rt_frame_n32,
+        .rt_signal_return_offset =
+                offsetof(struct mips_vdso, n32_rt_signal_trampoline),
         .restart        = __NR_N32_restart_syscall
 };