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[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>
This commit is contained in:
David S. Miller 2005-04-17 18:03:11 -07:00 committed by Linus Torvalds
parent fb65b9619b
commit dadeafdfc8
2 changed files with 69 additions and 35 deletions
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82
arch/sparc64/kernel/ptrace.c
View File

@ -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);

22
include/asm-sparc64/cacheflush.h
View File

@ -49,16 +49,22 @@ extern void flush_dcache_page(struct page *page);
#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)