Re: [patch] Use mmap instead of obstack_alloc for dwarf debug sections.

Paul Pluzhnikov
2009-06-11T01:40:05Z

[-- Attachment #1: Type: text/plain, Size: 1186 bytes --]

On Sat, May 30, 2009 at 3:36 PM, Tom Tromey<tromey@redhat.com> wrote:

>>>>>> "Paul" == Paul Pluzhnikov <ppluzhnikov@google.com> writes:
>
> Tom> It has a number of minor formatting problems, mostly missing spaces
> Tom> before open parens.
>
> Paul> Sorry, these get me every time :-(
>
> Yeah. Whatever happened to running gdb_indent.sh?

Running gdb_indent.sh on these sources produces way too many incorrect
indentations :-(

I tried my best to have a space before parens this time.

> Paul> I would have used bfd_get_file_window(), but it's only compiled in
> Paul> when --use-mmap was given to bfd/configure.
> Paul> Is there a way to turn that on for GDB?
>
> Paul> Is it ok to do this in gdb/dwarf2read.c:
> Paul>   if (info->size > 4 * pagesize && (sectp->flags & SEC_RELOC) == 0
> Paul>       && (abfd->flags & BFD_IN_MEMORY) == 0)
>
> I don't know the answer to either of these.
> If nobody here knows, I suggest asking on the binutils list.
> If they aren't ok, maybe we could add a new BFD function for this.

bfd_mmap is now checking in; attached patch uses it.

Tested on Linux/x86_64 with no regressions.

Thanks,
--
Paul Pluzhnikov

[-- Attachment #2: bfd-mmap-patch-20090610.txt --]
[-- Type: text/plain, Size: 4922 bytes --]

Index: bfd-in2.h
===================================================================
RCS file: /cvs/src/src/bfd/bfd-in2.h,v
retrieving revision 1.482
diff -u -p -u -r1.482 bfd-in2.h
--- bfd-in2.h 1 Jun 2009 13:11:51 -0000 1.482
+++ bfd-in2.h 10 Jun 2009 17:01:28 -0000
@@ -463,6 +463,7 @@ extern int bfd_seek (bfd *, file_ptr, in
extern file_ptr bfd_tell (bfd *);
extern int bfd_flush (bfd *);
extern int bfd_stat (bfd *, struct stat *);
+extern void *bfd_mmap (bfd *, void *, bfd_size_type, int, int, file_ptr);

/* Deprecated old routines. */
#if __GNUC__
Index: bfdio.c
===================================================================
RCS file: /cvs/src/src/bfd/bfdio.c,v
retrieving revision 1.21
diff -u -p -u -r1.21 bfdio.c
--- bfdio.c 24 May 2009 11:47:27 -0000 1.21
+++ bfdio.c 10 Jun 2009 17:01:28 -0000
@@ -158,6 +158,8 @@ DESCRIPTION
. int (*bclose) (struct bfd *abfd);
. int (*bflush) (struct bfd *abfd);
. int (*bstat) (struct bfd *abfd, struct stat *sb);
+. void* (*bmmap) (struct bfd *abfd, void *addr, bfd_size_type len,
+. int prot, int flags, file_ptr offset);
.};

*/
@@ -511,3 +513,31 @@ bfd_get_size (bfd *abfd)

return buf.st_size;
}
+
+
+/*
+FUNCTION
+ bfd_mmap
+
+SYNOPSIS
+ void *bfd_mmap (bfd *abfd, void *addr, bfd_size_type len,
+ int prot, int flags, file_ptr offset);
+
+DESCRIPTION
+ Return mmap()ed region of the file, if possible and implemented.
+
+*/
+
+void *
+bfd_mmap (bfd *abfd, void *addr, bfd_size_type len,
+ int prot, int flags, file_ptr offset)
+{
+ void *ret = (void *)-1;
+ if ((abfd->flags & BFD_IN_MEMORY) != 0)
+ return ret;
+
+ if (abfd->iovec == NULL)
+ return ret;
+
+ return abfd->iovec->bmmap (abfd, addr, len, prot, flags, offset);
+}
Index: cache.c
===================================================================
RCS file: /cvs/src/src/bfd/cache.c,v
retrieving revision 1.34
diff -u -p -u -r1.34 cache.c
--- cache.c 30 Oct 2008 09:05:32 -0000 1.34
+++ cache.c 10 Jun 2009 17:01:28 -0000
@@ -46,6 +46,10 @@ SUBSECTION
#include "libbfd.h"
#include "libiberty.h"

+#ifdef HAVE_MMAP
+#include <sys/mman.h>
+#endif
+
/* In some cases we can optimize cache operation when reopening files.
For instance, a flush is entirely unnecessary if the file is already
closed, so a flush would use CACHE_NO_OPEN. Similarly, a seek using
@@ -388,10 +392,38 @@ cache_bstat (struct bfd *abfd, struct st
return sts;
}

+static void *
+cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
+ void *addr ATTRIBUTE_UNUSED,
+ bfd_size_type len ATTRIBUTE_UNUSED,
+ int prot ATTRIBUTE_UNUSED,
+ int flags ATTRIBUTE_UNUSED,
+ file_ptr offset ATTRIBUTE_UNUSED)
+{
+ void *ret = (void *) -1;
+
+ if ((abfd->flags & BFD_IN_MEMORY) != 0)
+ abort ();
+#ifdef HAVE_MMAP
+ else
+ {
+ FILE *f = bfd_cache_lookup (abfd, CACHE_NO_SEEK_ERROR);
+ if (f == NULL)
+ return ret;
+
+ ret = mmap (addr, len, prot, flags, fileno (f), offset);
+ if (ret == (void *) -1)
+ bfd_set_error (bfd_error_system_call);
+ }
+#endif
+
+ return ret;
+}
+
static const struct bfd_iovec cache_iovec =
{
&cache_bread, &cache_bwrite, &cache_btell, &cache_bseek,
- &cache_bclose, &cache_bflush, &cache_bstat
+ &cache_bclose, &cache_bflush, &cache_bstat, &cache_bmmap
};

/*
Index: libbfd.h
===================================================================
RCS file: /cvs/src/src/bfd/libbfd.h,v
retrieving revision 1.216
diff -u -p -u -r1.216 libbfd.h
--- libbfd.h 1 Jun 2009 13:11:52 -0000 1.216
+++ libbfd.h 10 Jun 2009 17:01:28 -0000
@@ -773,6 +773,9 @@ struct bfd_iovec
int (*bclose) (struct bfd *abfd);
int (*bflush) (struct bfd *abfd);
int (*bstat) (struct bfd *abfd, struct stat *sb);
+ /* Just like mmap: (void*)-1 on failure, mmapped address on success. */
+ void *(*bmmap) (struct bfd *abfd, void *addr, bfd_size_type len,
+ int prot, int flags, file_ptr offset);
};
/* Extracted from bfdwin.c. */
struct _bfd_window_internal {
Index: opncls.c
===================================================================
RCS file: /cvs/src/src/bfd/opncls.c,v
retrieving revision 1.53
diff -u -p -u -r1.53 opncls.c
--- opncls.c 23 Aug 2008 08:08:58 -0000 1.53
+++ opncls.c 10 Jun 2009 17:01:28 -0000
@@ -505,9 +505,20 @@ opncls_bstat (struct bfd *abfd, struct s
return (vec->stat) (abfd, vec->stream, sb);
}

+static void *
+opncls_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
+ void *addr ATTRIBUTE_UNUSED,
+ bfd_size_type len ATTRIBUTE_UNUSED,
+ int prot ATTRIBUTE_UNUSED,
+ int flags ATTRIBUTE_UNUSED,
+ file_ptr offset ATTRIBUTE_UNUSED)
+{
+ return (void *) -1;
+}
+
static const struct bfd_iovec opncls_iovec = {
&opncls_bread, &opncls_bwrite, &opncls_btell, &opncls_bseek,
- &opncls_bclose, &opncls_bflush, &opncls_bstat
+ &opncls_bclose, &opncls_bflush, &opncls_bstat, &opncls_bmmap
};

bfd *