SORT_BY_INIT_PRIORITY
I was looking at the implementation of this script keyword today and couldn't remember why we do what we do in get_init_priority, because the comments explain how the init_priority is encoded but don't say why it is necessary to extract the priority and sort on that. So after figuring out why (again), I wrote some more comments. Then I simplified get_init_priority a little, adding some sanity checking on the strtoul result. This actually makes get_init_priority support sorting by numerical suffix more generally, but I figure this feature would be better as a new keyword (without the .ctors/.dtors special case), so haven't documented the extension. * ld.texi (SORT_BY_ALIGNMENT): Reword slightly. (SORT_BY_INIT_PRIORITY): Elucidate. * ldlang.c: Include limits.h. (get_init_priority): Comment. Change param to a section, return an int. Sanity check priority digits. Support sorting more sections with trailing digits. Return -1 on error. (compare_section): Adjust.
This commit is contained in:
Alan Modra
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commit
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10
ld/ChangeLog
10
ld/ChangeLog
@ -1,3 +1,13 @@
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2019-09-25 Alan Modra <amodra@gmail.com>
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* ld.texi (SORT_BY_ALIGNMENT): Reword slightly.
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(SORT_BY_INIT_PRIORITY): Elucidate.
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* ldlang.c: Include limits.h.
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(get_init_priority): Comment. Change param to a section,
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return an int. Sanity check priority digits. Support sorting
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more sections with trailing digits. Return -1 on error.
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(compare_section): Adjust.
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2019-09-25 Nick Clifton <nickc@redhat.com>
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* emultempl/avrelf.em (_before_allocation): Silence build warning
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21
ld/ld.texi
21
ld/ld.texi
@ -4630,17 +4630,20 @@ pattern in parentheses (e.g., @code{SORT_BY_NAME(.text*)}). When the
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into ascending order by name before placing them in the output file.
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@cindex SORT_BY_ALIGNMENT
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@code{SORT_BY_ALIGNMENT} is very similar to @code{SORT_BY_NAME}. The
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difference is @code{SORT_BY_ALIGNMENT} will sort sections into
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descending order by alignment before placing them in the output file.
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Larger alignments are placed before smaller alignments in order to
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reduce the amount of padding necessary.
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@code{SORT_BY_ALIGNMENT} is similar to @code{SORT_BY_NAME}.
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@code{SORT_BY_ALIGNMENT} will sort sections into descending order of
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alignment before placing them in the output file. Placing larger
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alignments before smaller alignments can reduce the amount of padding
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needed.
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@cindex SORT_BY_INIT_PRIORITY
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@code{SORT_BY_INIT_PRIORITY} is very similar to @code{SORT_BY_NAME}. The
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difference is @code{SORT_BY_INIT_PRIORITY} will sort sections into
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ascending order by numerical value of the GCC init_priority attribute
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encoded in the section name before placing them in the output file.
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@code{SORT_BY_INIT_PRIORITY} is also similar to @code{SORT_BY_NAME}.
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@code{SORT_BY_INIT_PRIORITY} will sort sections into ascending
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numerical order of the GCC init_priority attribute encoded in the
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section name before placing them in the output file. In
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@code{.init_array.NNNNN} and @code{.fini_array.NNNNN}, @code{NNNNN} is
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the init_priority. In @code{.ctors.NNNNN} and @code{.dtors.NNNNN},
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@code{NNNNN} is 65535 minus the init_priority.
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@cindex SORT
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@code{SORT} is an alias for @code{SORT_BY_NAME}.
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64
ld/ldlang.c
64
ld/ldlang.c
@ -19,6 +19,7 @@
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MA 02110-1301, USA. */
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#include "sysdep.h"
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#include <limits.h>
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#include "bfd.h"
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#include "libiberty.h"
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#include "filenames.h"
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@ -403,39 +404,50 @@ match_simple_wild (const char *pattern, const char *name)
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/* Return the numerical value of the init_priority attribute from
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section name NAME. */
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static unsigned long
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get_init_priority (const char *name)
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static int
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get_init_priority (const asection *sec)
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{
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char *end;
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unsigned long init_priority;
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const char *name = bfd_section_name (sec);
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const char *dot;
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/* GCC uses the following section names for the init_priority
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attribute with numerical values 101 and 65535 inclusive. A
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attribute with numerical values 101 to 65535 inclusive. A
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lower value means a higher priority.
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1: .init_array.NNNN/.fini_array.NNNN: Where NNNN is the
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1: .init_array.NNNNN/.fini_array.NNNNN: Where NNNNN is the
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decimal numerical value of the init_priority attribute.
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The order of execution in .init_array is forward and
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.fini_array is backward.
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2: .ctors.NNNN/.dtors.NNNN: Where NNNN is 65535 minus the
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2: .ctors.NNNNN/.dtors.NNNNN: Where NNNNN is 65535 minus the
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decimal numerical value of the init_priority attribute.
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The order of execution in .ctors is backward and .dtors
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is forward.
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*/
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if (strncmp (name, ".init_array.", 12) == 0
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|| strncmp (name, ".fini_array.", 12) == 0)
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{
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init_priority = strtoul (name + 12, &end, 10);
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return *end ? 0 : init_priority;
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}
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else if (strncmp (name, ".ctors.", 7) == 0
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|| strncmp (name, ".dtors.", 7) == 0)
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{
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init_priority = strtoul (name + 7, &end, 10);
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return *end ? 0 : 65535 - init_priority;
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}
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return 0;
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.init_array.NNNNN sections would normally be placed in an output
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.init_array section, .fini_array.NNNNN in .fini_array,
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.ctors.NNNNN in .ctors, and .dtors.NNNNN in .dtors. This means
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we should sort by increasing number (and could just use
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SORT_BY_NAME in scripts). However if .ctors.NNNNN sections are
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being placed in .init_array (which may also contain
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.init_array.NNNNN sections) or .dtors.NNNNN sections are being
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placed in .fini_array then we need to extract the init_priority
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attribute and sort on that. */
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dot = strrchr (name, '.');
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if (dot != NULL && ISDIGIT (dot[1]))
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{
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char *end;
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unsigned long init_priority = strtoul (dot + 1, &end, 10);
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if (*end == 0)
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{
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if (dot == name + 6
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&& (strncmp (name, ".ctors", 6) == 0
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|| strncmp (name, ".dtors", 6) == 0))
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init_priority = 65535 - init_priority;
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if (init_priority <= INT_MAX)
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return init_priority;
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}
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}
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return -1;
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}
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/* Compare sections ASEC and BSEC according to SORT. */
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@ -444,7 +456,7 @@ static int
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compare_section (sort_type sort, asection *asec, asection *bsec)
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{
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int ret;
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unsigned long ainit_priority, binit_priority;
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int a_priority, b_priority;
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switch (sort)
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{
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@ -452,11 +464,11 @@ compare_section (sort_type sort, asection *asec, asection *bsec)
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abort ();
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case by_init_priority:
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ainit_priority = get_init_priority (bfd_section_name (asec));
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binit_priority = get_init_priority (bfd_section_name (bsec));
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if (ainit_priority == 0 || binit_priority == 0)
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a_priority = get_init_priority (asec);
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b_priority = get_init_priority (bsec);
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if (a_priority < 0 || b_priority < 0)
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goto sort_by_name;
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ret = ainit_priority - binit_priority;
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ret = a_priority - b_priority;
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if (ret)
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break;
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else
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