[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>
diff --git a/arch/sparc64/kernel/ptrace.c b/arch/sparc64/kernel/ptrace.c
index 08bac53..5f080cf 100644
--- a/arch/sparc64/kernel/ptrace.c
+++ b/arch/sparc64/kernel/ptrace.c
@@ -103,6 +103,55 @@
/* 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 @@
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 @@
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 @@
(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 @@
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 @@
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);
diff --git a/include/asm-sparc64/cacheflush.h b/include/asm-sparc64/cacheflush.h
index 86f0293..51b26e81 100644
--- a/include/asm-sparc64/cacheflush.h
+++ b/include/asm-sparc64/cacheflush.h
@@ -49,16 +49,22 @@
#define flush_icache_page(vma, pg) do { } while(0)
#define flush_icache_user_range(vma,pg,adr,len) do { } while (0)
-#define copy_to_user_page(vma, page, vaddr, dst, src, len) \
- do { \
- flush_cache_page(vma, vaddr, page_to_pfn(page));\
- memcpy(dst, src, len); \
+extern void flush_ptrace_access(struct vm_area_struct *, struct page *,
+ unsigned long uaddr, void *kaddr,
+ unsigned long len, int write);
+
+#define copy_to_user_page(vma, page, vaddr, dst, src, len) \
+ do { \
+ flush_cache_page(vma, vaddr, page_to_pfn(page)); \
+ memcpy(dst, src, len); \
+ flush_ptrace_access(vma, page, vaddr, src, len, 0); \
} while (0)
-#define copy_from_user_page(vma, page, vaddr, dst, src, len) \
- do { \
- flush_cache_page(vma, vaddr, page_to_pfn(page));\
- memcpy(dst, src, len); \
+#define copy_from_user_page(vma, page, vaddr, dst, src, len) \
+ do { \
+ flush_cache_page(vma, vaddr, page_to_pfn(page)); \
+ memcpy(dst, src, len); \
+ flush_ptrace_access(vma, page, vaddr, dst, len, 1); \
} while (0)
#define flush_dcache_mmap_lock(mapping) do { } while (0)