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, 14 insertions, 41 deletions

diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
index 03abaf048f09..a0ed0e052b2e 100644
--- a/arch/mips/kernel/signal32.c
+++ b/arch/mips/kernel/signal32.c
@@ -32,6 +32,7 @@
 #include <asm/system.h>
 #include <asm/fpu.h>
 #include <asm/war.h>
+#include <asm/vdso.h>
 
 #include "signal-common.h"
 
@@ -47,8 +48,6 @@ extern asmlinkage int fpu_emulator_restore_context32(struct sigcontext32 __user
 /*
  * Including <asm/unistd.h> would give use the 64-bit syscall numbers ...
  */
-#define __NR_O32_sigreturn              4119
-#define __NR_O32_rt_sigreturn           4193
 #define __NR_O32_restart_syscall        4253
 
 /* 32-bit compatibility types */
@@ -77,47 +76,20 @@ struct ucontext32 {
         compat_sigset_t     uc_sigmask;   /* mask last for extensibility */
 };
 
-/*
- * 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 sigframe32 {
         u32 sf_ass[4];          /* argument save space for o32 */
-        u32 sf_code[2];         /* signal trampoline */
+        u32 sf_pad[2];          /* Was: signal trampoline */
         struct sigcontext32 sf_sc;
         compat_sigset_t sf_mask;
 };
 
 struct rt_sigframe32 {
         u32 rs_ass[4];                  /* argument save space for o32 */
-        u32 rs_code[2];                 /* signal trampoline */
+        u32 rs_pad[2];                  /* Was: signal trampoline */
         compat_siginfo_t rs_info;
         struct ucontext32 rs_uc;
 };
 
-#else  /* ICACHE_REFILLS_WORKAROUND_WAR */
-
-struct sigframe32 {
-        u32 sf_ass[4];                  /* argument save space for o32 */
-        u32 sf_pad[2];
-        struct sigcontext32 sf_sc;      /* hw context */
-        compat_sigset_t sf_mask;
-        u32 sf_code[8] ____cacheline_aligned;   /* signal trampoline */
-};
-
-struct rt_sigframe32 {
-        u32 rs_ass[4];                  /* argument save space for o32 */
-        u32 rs_pad[2];
-        compat_siginfo_t rs_info;
-        struct ucontext32 rs_uc;
-        u32 rs_code[8] __attribute__((aligned(32)));    /* signal trampoline */
-};
-
-#endif  /* !ICACHE_REFILLS_WORKAROUND_WAR */
-
 /*
  * sigcontext handlers
  */
@@ -598,8 +570,8 @@ badframe:
         force_sig(SIGSEGV, current);
 }
 
-static int setup_frame_32(struct k_sigaction * ka, struct pt_regs *regs,
-        int signr, sigset_t *set)
+static int setup_frame_32(void *sig_return, struct k_sigaction *ka,
+                          struct pt_regs *regs, int signr, sigset_t *set)
 {
         struct sigframe32 __user *frame;
         int err = 0;
@@ -608,8 +580,6 @@ static int setup_frame_32(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_O32_sigreturn);
-
         err |= setup_sigcontext32(regs, &frame->sf_sc);
         err |= __copy_conv_sigset_to_user(&frame->sf_mask, set);
 
@@ -630,7 +600,7 @@ static int setup_frame_32(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",
@@ -644,8 +614,9 @@ give_sigsegv:
         return -EFAULT;
 }
 
-static int setup_rt_frame_32(struct k_sigaction * ka, struct pt_regs *regs,
-        int signr, sigset_t *set, siginfo_t *info)
+static int setup_rt_frame_32(void *sig_return, struct k_sigaction *ka,
+                             struct pt_regs *regs, int signr, sigset_t *set,
+                             siginfo_t *info)
 {
         struct rt_sigframe32 __user *frame;
         int err = 0;
@@ -655,8 +626,6 @@ static int setup_rt_frame_32(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_O32_rt_sigreturn);
-
         /* Convert (siginfo_t -> compat_siginfo_t) and copy to user. */
         err |= copy_siginfo_to_user32(&frame->rs_info, info);
 
@@ -690,7 +659,7 @@ static int setup_rt_frame_32(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",
@@ -709,7 +678,11 @@ give_sigsegv:
  */
 struct mips_abi mips_abi_32 = {
         .setup_frame    = setup_frame_32,
+        .signal_return_offset =
+                offsetof(struct mips_vdso, o32_signal_trampoline),
         .setup_rt_frame = setup_rt_frame_32,
+        .rt_signal_return_offset =
+                offsetof(struct mips_vdso, o32_rt_signal_trampoline),
         .restart        = __NR_O32_restart_syscall
 };