On Tue, 8 May 2018, Jan Hubicka wrote:
> Hi,
> for incremental linking of LTO objects we need to copy debug sections from
> source object files into destination without renaming them from .gnu.debuglto
> into the standard debug section (because they will again be LTO debug section
> in the resulting object file).
>
> I have discussed this with Richard on IRC and I hope it is fine to change the
> API here becuase lto-wrapper is the only user of this function. I will send
> lto-wrapper support in separate patch.
>
> I have lto-bootstrapped/regtested the whole incremental linking patchet on
> x86-64-linux with libbackend being incrementaly linked and also experimented
> with extra testcases and tested that debugging works on resulting cc1 binary.
> OK?
Works for me.
Richard.
> Honza
>
> * simple-object.h (simple_object_copy_lto_debug_sections): Add rename
> parameter.
> * simple-object.c (handle_lto_debug_sections): Add rename parameter.
> (handle_lto_debug_sections_rename): New function.
> (handle_lto_debug_sections_norename): New function.
> (simple_object_copy_lto_debug_sections): Add rename parameter.
> Index: include/simple-object.h
> ===================================================================
> --- include/simple-object.h (revision 260042)
> +++ include/simple-object.h (working copy)
> @@ -198,12 +198,15 @@
> simple_object_release_write (simple_object_write *);
>
> /* Copy LTO debug sections from SRC_OBJECT to DEST.
> + If RENAME is true, rename LTO debug section into debug section (i.e.
> + when producing final binary) and if it is false, keep the sections with
> + original names (when incrementally linking).
> If an error occurs, return the errno value in ERR and an error string. */
>
> extern const char *
> simple_object_copy_lto_debug_sections (simple_object_read *src_object,
> const char *dest,
> - int *err);
> + int *err, int rename);
>
> #ifdef __cplusplus
> }
> Index: libiberty/simple-object.c
> ===================================================================
> --- libiberty/simple-object.c (revision 260042)
> +++ libiberty/simple-object.c (working copy)
> @@ -251,12 +251,15 @@
> }
>
> /* Callback to identify and rename LTO debug sections by name.
> - Returns 1 if NAME is a LTO debug section, 0 if not. */
> + Returns non-NULL if NAME is a LTO debug section, NULL if not.
> + If RENAME is true it will rename LTO debug sections to non-LTO
> + ones. */
>
> static char *
> -handle_lto_debug_sections (const char *name)
> +handle_lto_debug_sections (const char *name, int rename)
> {
> - char *newname = XCNEWVEC (char, strlen (name) + 1);
> + char *newname = rename ? XCNEWVEC (char, strlen (name) + 1)
> + : xstrdup (name);
>
> /* ??? So we can't use .gnu.lto_ prefixed sections as the assembler
> complains about bogus section flags. Which means we need to arrange
> @@ -265,12 +268,14 @@
> /* Also include corresponding reloc sections. */
> if (strncmp (name, ".rela", sizeof (".rela") - 1) == 0)
> {
> - strncpy (newname, name, sizeof (".rela") - 1);
> + if (rename)
> + strncpy (newname, name, sizeof (".rela") - 1);
> name += sizeof (".rela") - 1;
> }
> else if (strncmp (name, ".rel", sizeof (".rel") - 1) == 0)
> {
> - strncpy (newname, name, sizeof (".rel") - 1);
> + if (rename)
> + strncpy (newname, name, sizeof (".rel") - 1);
> name += sizeof (".rel") - 1;
> }
> /* ??? For now this handles both .gnu.lto_ and .gnu.debuglto_ prefixed
> @@ -277,10 +282,10 @@
> sections. */
> /* Copy LTO debug sections and rename them to their non-LTO name. */
> if (strncmp (name, ".gnu.debuglto_", sizeof (".gnu.debuglto_") - 1) == 0)
> - return strcat (newname, name + sizeof (".gnu.debuglto_") - 1);
> + return rename ? strcat (newname, name + sizeof (".gnu.debuglto_") - 1) :
> newname;
> else if (strncmp (name, ".gnu.lto_.debug_",
> sizeof (".gnu.lto_.debug_") -1) == 0)
> - return strcat (newname, name + sizeof (".gnu.lto_") - 1);
> + return rename ? strcat (newname, name + sizeof (".gnu.lto_") - 1) :
> newname;
> /* Copy over .note.GNU-stack section under the same name if present. */
> else if (strcmp (name, ".note.GNU-stack") == 0)
> return strcpy (newname, name);
> @@ -289,14 +294,31 @@
> COMDAT sections in objects produced by GCC. */
> else if (strcmp (name, ".comment") == 0)
> return strcpy (newname, name);
> + free (newname);
> return NULL;
> }
>
> +/* Wrapper for handle_lto_debug_sections. */
> +
> +static char *
> +handle_lto_debug_sections_rename (const char *name)
> +{
> + return handle_lto_debug_sections (name, 1);
> +}
> +
> +/* Wrapper for handle_lto_debug_sections. */
> +
> +static char *
> +handle_lto_debug_sections_norename (const char *name)
> +{
> + return handle_lto_debug_sections (name, 0);
> +}
> +
> /* Copy LTO debug sections. */
>
> const char *
> simple_object_copy_lto_debug_sections (simple_object_read *sobj,
> - const char *dest, int *err)
> + const char *dest, int *err, int rename)
> {
> const char *errmsg;
> simple_object_write *dest_sobj;
> @@ -317,9 +339,10 @@
> if (! dest_sobj)
> return errmsg;
>
> - errmsg = sobj->functions->copy_lto_debug_sections (sobj, dest_sobj,
> - handle_lto_debug_sections,
> - err);
> + errmsg = sobj->functions->copy_lto_debug_sections
> + (sobj, dest_sobj,
> + rename ? handle_lto_debug_sections_rename
> + : handle_lto_debug_sections_norename, err);
> if (errmsg)
> {
> simple_object_release_write (dest_sobj);
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
