[PATCH] sparc64: Reduce ptrace cache flushing

We were flushing the D-cache excessively for ptrace() processing
and this makes debugging threads so slow as to be totally unusable.

All process page accesses via ptrace() go via access_process_vm().
This routine, for each process page, uses get_user_pages().  That
in turn does a flush_dcache_page() on the child pages before we
copy in/out the ptrace request data.

Therefore, all we need to do after the data movement is:

1) Flush the D-cache pages if the kernel maps the page to a different
   color than userspace does.
2) If we wrote to the page, we need to flush the I-cache on older cpus.

Previously we just flushed the entire cache at the end of a ptrace()
request, and that was beyond stupid.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 55 insertions, 27 deletions

diff --git a/arch/sparc64/kernel/ptrace.c b/arch/sparc64/kernel/ptrace.c
index 08bac537262a..5f080cf04b33 100644
--- a/arch/sparc64/kernel/ptrace.c
+++ b/arch/sparc64/kernel/ptrace.c
@@ -103,6 +103,55 @@ void ptrace_disable(struct task_struct *child)
         /* nothing to do */
 }
 
+/* To get the necessary page struct, access_process_vm() first calls
+ * get_user_pages().  This has done a flush_dcache_page() on the
+ * accessed page.  Then our caller (copy_{to,from}_user_page()) did
+ * to memcpy to read/write the data from that page.
+ *
+ * Now, the only thing we have to do is:
+ * 1) flush the D-cache if it's possible than an illegal alias
+ *    has been created
+ * 2) flush the I-cache if this is pre-cheetah and we did a write
+ */
+void flush_ptrace_access(struct vm_area_struct *vma, struct page *page,
+                         unsigned long uaddr, void *kaddr,
+                         unsigned long len, int write)
+{
+        BUG_ON(len > PAGE_SIZE);
+
+#ifdef DCACHE_ALIASING_POSSIBLE
+        /* If bit 13 of the kernel address we used to access the
+         * user page is the same as the virtual address that page
+         * is mapped to in the user's address space, we can skip the
+         * D-cache flush.
+         */
+        if ((uaddr ^ kaddr) & (1UL << 13)) {
+                unsigned long start = __pa(kaddr);
+                unsigned long end = start + len;
+
+                if (tlb_type == spitfire) {
+                        for (; start < end; start += 32)
+                                spitfire_put_dcache_tag(va & 0x3fe0, 0x0);
+                } else {
+                        for (; start < end; start += 32)
+                                __asm__ __volatile__(
+                                        "stxa %%g0, [%0] %1\n\t"
+                                        "membar #Sync"
+                                        : /* no outputs */
+                                        : "r" (va),
+                                        "i" (ASI_DCACHE_INVALIDATE));
+                }
+        }
+#endif
+        if (write && tlb_type == spitfire) {
+                unsigned long start = (unsigned long) kaddr;
+                unsigned long end = start + len;
+
+                for (; start < end; start += 32)
+                        flushi(start);
+        }
+}
+
 asmlinkage void do_ptrace(struct pt_regs *regs)
 {
         int request = regs->u_regs[UREG_I0];
@@ -227,7 +276,7 @@ asmlinkage void do_ptrace(struct pt_regs *regs)
                         pt_error_return(regs, -res);
                 else
                         pt_os_succ_return(regs, tmp64, (void __user *) data);
-                goto flush_and_out;
+                goto out_tsk;
         }
 
         case PTRACE_POKETEXT: /* write the word at location addr. */
@@ -253,7 +302,7 @@ asmlinkage void do_ptrace(struct pt_regs *regs)
                         pt_error_return(regs, -res);
                 else
                         pt_succ_return(regs, res);
-                goto flush_and_out;
+                goto out_tsk;
         }
 
         case PTRACE_GETREGS: {
@@ -485,12 +534,12 @@ asmlinkage void do_ptrace(struct pt_regs *regs)
                                           (char __user *)addr2, data);
                 if (res == data) {
                         pt_succ_return(regs, 0);
-                        goto flush_and_out;
+                        goto out_tsk;
                 }
                 if (res >= 0)
                         res = -EIO;
                 pt_error_return(regs, -res);
-                goto flush_and_out;
+                goto out_tsk;
         }
 
         case PTRACE_WRITETEXT:
@@ -499,12 +548,12 @@ asmlinkage void do_ptrace(struct pt_regs *regs)
                                            addr, data);
                 if (res == data) {
                         pt_succ_return(regs, 0);
-                        goto flush_and_out;
+                        goto out_tsk;
                 }
                 if (res >= 0)
                         res = -EIO;
                 pt_error_return(regs, -res);
-                goto flush_and_out;
+                goto out_tsk;
         }
         case PTRACE_SYSCALL: /* continue and stop at (return from) syscall */
                 addr = 1;
@@ -571,27 +620,6 @@ asmlinkage void do_ptrace(struct pt_regs *regs)
                 goto out_tsk;
         }
         }
-flush_and_out:
-        {
-                unsigned long va;
-
-                if (tlb_type == cheetah || tlb_type == cheetah_plus) {
-                        for (va = 0; va < (1 << 16); va += (1 << 5))
-                                spitfire_put_dcache_tag(va, 0x0);
-                        /* No need to mess with I-cache on Cheetah. */
-                } else {
-                        for (va =  0; va < L1DCACHE_SIZE; va += 32)
-                                spitfire_put_dcache_tag(va, 0x0);
-                        if (request == PTRACE_PEEKTEXT ||
-                            request == PTRACE_POKETEXT ||
-                            request == PTRACE_READTEXT ||
-                            request == PTRACE_WRITETEXT) {
-                                for (va =  0; va < (PAGE_SIZE << 1); va += 32)
-                                        spitfire_put_icache_tag(va, 0x0);
-                                __asm__ __volatile__("flush %g6");
-                        }
-                }
-        }
 out_tsk:
         if (child)
                 put_task_struct(child);