* [binutils-gdb] gas/ELF: allow "inheriting" section attributes and type
@ 2023-08-25 12:56 Jan Beulich
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From: Jan Beulich @ 2023-08-25 12:56 UTC (permalink / raw)
To: bfd-cvs
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=cefaa117f7675ce690c0ec38c353e7e4195dedcb
commit cefaa117f7675ce690c0ec38c353e7e4195dedcb
Author: Jan Beulich <jbeulich@suse.com>
Date: Fri Aug 25 14:55:12 2023 +0200
gas/ELF: allow "inheriting" section attributes and type
While --sectname-subst is nice, it isn't enough to e.g. mimic
-f{function,data}-sections in assembly code, when such use is to be
optional (e.g. dependent upon some configuration setting).
Assign meaning to '+' and '-' as section attribute letters, allowing
to inherit the prior section's attributes (and possibly type) along
with adding or removing some. Note that documenting the interaction
with '?' as undefined is a precautionary measure.
While touching the function invocation, stop using |= on the result of
obj_elf_parse_section_letters(): "attr" is firmly zero ahead of the
call.
Diff:
---
gas/config/obj-elf.c | 53 +++++++++++++++++++++++++++++--
gas/doc/as.texi | 12 +++++++
gas/testsuite/gas/elf/elf.exp | 5 +++
gas/testsuite/gas/elf/section30.d | 28 ++++++++++++++++
gas/testsuite/gas/elf/section30.s | 67 +++++++++++++++++++++++++++++++++++++++
5 files changed, 162 insertions(+), 3 deletions(-)
diff --git a/gas/config/obj-elf.c b/gas/config/obj-elf.c
index 142f004f0b6..a9258ce334c 100644
--- a/gas/config/obj-elf.c
+++ b/gas/config/obj-elf.c
@@ -822,10 +822,12 @@ obj_elf_change_section (const char *name,
static bfd_vma
obj_elf_parse_section_letters (char *str, size_t len,
- bool *is_clone, bfd_vma *gnu_attr)
+ bool *is_clone, int *inherit, bfd_vma *gnu_attr)
{
bfd_vma attr = 0;
+
*is_clone = false;
+ *inherit = 0;
while (len > 0)
{
@@ -923,6 +925,8 @@ obj_elf_parse_section_letters (char *str, size_t len,
len -= (end - str);
str = end;
}
+ else if (!attr && !*gnu_attr && (*str == '+' || *str == '-'))
+ *inherit = *str == '+' ? 1 : -1;
else
as_fatal ("%s", bad_msg);
}
@@ -1171,6 +1175,7 @@ obj_elf_section (int push)
if (*input_line_pointer == '"')
{
bool is_clone;
+ int inherit;
beg = demand_copy_C_string (&dummy);
if (beg == NULL)
@@ -1178,8 +1183,15 @@ obj_elf_section (int push)
ignore_rest_of_line ();
return;
}
- attr |= obj_elf_parse_section_letters (beg, strlen (beg),
- &is_clone, &gnu_attr);
+ attr = obj_elf_parse_section_letters (beg, strlen (beg), &is_clone,
+ &inherit, &gnu_attr);
+
+ if (inherit > 0)
+ attr |= elf_section_flags (now_seg);
+ else if (inherit < 0)
+ attr = elf_section_flags (now_seg) & ~attr;
+ if (inherit)
+ type = elf_section_type (now_seg);
SKIP_WHITESPACE ();
if (*input_line_pointer == ',')
@@ -1224,6 +1236,9 @@ obj_elf_section (int push)
{
++input_line_pointer;
SKIP_WHITESPACE ();
+ if (inherit && *input_line_pointer == ','
+ && (bfd_section_flags (now_seg) & SEC_MERGE) != 0)
+ goto fetch_entsize;
entsize = get_absolute_expression ();
SKIP_WHITESPACE ();
if (entsize < 0)
@@ -1233,6 +1248,12 @@ obj_elf_section (int push)
entsize = 0;
}
}
+ else if ((attr & SHF_MERGE) != 0 && inherit
+ && (bfd_section_flags (now_seg) & SEC_MERGE) != 0)
+ {
+ fetch_entsize:
+ entsize = now_seg->entsize;
+ }
else if ((attr & SHF_MERGE) != 0)
{
as_warn (_("entity size for SHF_MERGE not specified"));
@@ -1248,6 +1269,9 @@ obj_elf_section (int push)
{
linked_to_section_index = strtoul (input_line_pointer, & input_line_pointer, 0);
}
+ else if (inherit && *input_line_pointer == ','
+ && (elf_section_flags (now_seg) & SHF_LINK_ORDER) != 0)
+ goto fetch_linked_to;
else
{
char c;
@@ -1260,6 +1284,17 @@ obj_elf_section (int push)
match.linked_to_symbol_name = xmemdup0 (beg, length);
}
}
+ else if ((attr & SHF_LINK_ORDER) != 0 && inherit
+ && (elf_section_flags (now_seg) & SHF_LINK_ORDER) != 0)
+ {
+ fetch_linked_to:
+ if (now_seg->map_head.linked_to_symbol_name)
+ match.linked_to_symbol_name =
+ now_seg->map_head.linked_to_symbol_name;
+ else
+ linked_to_section_index =
+ elf_section_data (now_seg)->this_hdr.sh_link;
+ }
if ((attr & SHF_GROUP) != 0 && is_clone)
{
@@ -1270,6 +1305,10 @@ obj_elf_section (int push)
if ((attr & SHF_GROUP) != 0 && *input_line_pointer == ',')
{
++input_line_pointer;
+ SKIP_WHITESPACE ();
+ if (inherit && *input_line_pointer == ','
+ && (elf_section_flags (now_seg) & SHF_GROUP) != 0)
+ goto fetch_group;
match.group_name = obj_elf_section_name ();
if (match.group_name == NULL)
attr &= ~SHF_GROUP;
@@ -1286,6 +1325,14 @@ obj_elf_section (int push)
else if (startswith (name, ".gnu.linkonce"))
linkonce = 1;
}
+ else if ((attr & SHF_GROUP) != 0 && inherit
+ && (elf_section_flags (now_seg) & SHF_GROUP) != 0)
+ {
+ fetch_group:
+ match.group_name = elf_group_name (now_seg);
+ linkonce =
+ (bfd_section_flags (now_seg) & SEC_LINK_ONCE) != 0;
+ }
else if ((attr & SHF_GROUP) != 0)
{
as_warn (_("group name for SHF_GROUP not specified"));
diff --git a/gas/doc/as.texi b/gas/doc/as.texi
index 15867dfcb5e..6a3e5eed39f 100644
--- a/gas/doc/as.texi
+++ b/gas/doc/as.texi
@@ -6818,6 +6818,12 @@ section is a member of a section group
section is used for thread-local-storage
@item ?
section is a member of the previously-current section's group, if any
+@item +
+section inherits attributes and (unless explicitly specified) type from the
+previously-current section, adding other attributes as specified
+@item -
+section inherits attributes and (unless explicitly specified) type from the
+previously-current section, removing other attributes as specified
@item R
retained section (apply SHF_GNU_RETAIN to prevent linker garbage
collection, GNU ELF extension)
@@ -6839,6 +6845,12 @@ section may have the executable (@code{x}) flag added. Also note that the
@code{.attach_to_group} directive can be used to add a section to a group even
if the section was not originally declared to be part of that group.
+Note further that @code{+} and @code{-} need to come first and can only take
+the effect described here unless overridden by a target. The attributes
+inherited are those in effect at the time the directive is processed.
+Attributes added later (see above) will not be inherited. Using either
+together with @code{?} is undefined at this point.
+
The optional @var{type} argument may contain one of the following constants:
@table @code
diff --git a/gas/testsuite/gas/elf/elf.exp b/gas/testsuite/gas/elf/elf.exp
index 00eadc8c372..854c78aebd3 100644
--- a/gas/testsuite/gas/elf/elf.exp
+++ b/gas/testsuite/gas/elf/elf.exp
@@ -280,6 +280,11 @@ if { [is_elf_format] } then {
run_dump_test "section27"
run_dump_test "section28"
run_dump_test "section29"
+ if { ![istarget "rx-*-*"] } then {
+ run_dump_test "section30"
+ } else {
+ run_dump_test "section30" {{as -muse-conventional-section-names}}
+ }
run_dump_test "sh-link-zero"
run_dump_test "size"
run_dump_test "dwarf2-1" $dump_opts
diff --git a/gas/testsuite/gas/elf/section30.d b/gas/testsuite/gas/elf/section30.d
new file mode 100644
index 00000000000..821af1e2cd5
--- /dev/null
+++ b/gas/testsuite/gas/elf/section30.d
@@ -0,0 +1,28 @@
+#as: --sectname-subst
+#readelf: -SW
+#name: --sectname-subst plus section attr/type inherting
+# Targets setting NO_PSEUDO_DOT don't allow macros of certain names.
+#notarget: m681*-*-* m68hc1*-*-* s12z-*-* spu-*-* xgate-*-* z80-*-*
+
+#...
+ \[..\] \.group +GROUP +[0-9a-f]+ [0-9a-f]+ 0+c 04 +[1-9][0-9]* +[1-9][0-9]* +4
+ \[..\] \.text +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+0 00 AX 0 0 +[1-9][0-9]*
+ \[..\] \.data +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+0 00 WA 0 0 +[1-9][0-9]*
+ \[..\] \.bss +NOBITS +[0-9a-f]+ [0-9a-f]+ 0+0 00 WA 0 0 +[1-9][0-9]*
+#...
+ \[..\] \.text\.func1 +PROGBITS +[0-9a-f]+ [0-9a-f]+ [0-9a-f]+ 00 AX 0 0 +[1-9][0-9]*
+ \[..\] \.text\.func2 +PROGBITS +[0-9a-f]+ [0-9a-f]+ [0-9a-f]+ 00 AX 0 0 +[1-9][0-9]*
+ \[..\] \.data\.data1 +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+1 00 WA 0 0 1
+#...
+ \[..\] \.bss\.data2 +NOBITS +[0-9a-f]+ [0-9a-f]+ 0+2 00 WA 0 0 1
+ \[..\] \.rodata +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+0 00 A 0 0 1
+ \[..\] \.rodata\.data3 +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+3 00 A 0 0 1
+ \[..\] \.rodata\.str1\.1 +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+0 01 AMS 0 0 1
+ \[..\] \.rodata\.str1\.1\.str1 +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+8 01 AMS 0 0 1
+ \[..\] \.rodata\.2 +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+0 00 AL [1-9] 0 1
+ \[..\] \.rodata\.2\.data4 +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+4 00 AL [1-9] 0 1
+ \[..\] \.bss\.data5 +NOBITS +[0-9a-f]+ [0-9a-f]+ 0+5 00 WA 0 0 1
+ \[..\] \.rodata\.3 +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+0 00 AG 0 0 1
+ \[..\] \.rodata\.3\.data6 +PROGBITS +[0-9a-f]+ [0-9a-f]+ 0+6 00 AG 0 0 1
+ \[..\] \.bss\.data7 +NOBITS +[0-9a-f]+ [0-9a-f]+ 0+7 00 WA 0 0 1
+#pass
diff --git a/gas/testsuite/gas/elf/section30.s b/gas/testsuite/gas/elf/section30.s
new file mode 100644
index 00000000000..aeda04c6514
--- /dev/null
+++ b/gas/testsuite/gas/elf/section30.s
@@ -0,0 +1,67 @@
+ .macro func name:req
+ .pushsection %S.\name, "+"
+ .type \name, %function
+ .global \name
+ .hidden \name
+\name:
+ .endm
+
+ .macro data name:req
+ .pushsection %S.\name, "+"
+ .type \name, %object
+\name:
+ .endm
+
+ .macro end name:req
+ .size \name, . - \name
+ .popsection
+ .endm
+
+
+ .text
+ func func1
+ .nop
+ end func1
+
+ func func2
+ .nop
+ .nop
+ end func2
+
+ .data
+ data data1
+ .byte 1
+ end data1
+
+ .section .bss
+ data data2
+ .skip 2
+ end data2
+
+ .section .rodata, "a", %progbits
+ data data3
+ .byte 3, 3, 3
+ end data3
+
+ .section .rodata.str1.1, "aMS", %progbits, 1
+ data str1
+ .asciz "string1"
+ end str1
+
+ .section .rodata.2, "ao", %progbits, func1
+ data data4
+ .byte 4, 4, 4, 4
+ end data4
+ .pushsection .bss.data5, "-o", %nobits
+ .type data5, %object
+data5: .fill 5
+ end data5
+
+ .section .rodata.3, "aG", %progbits, sig1, comdat
+ data data6
+ .byte 6, 6, 6, 6, 6, 6
+ end data6
+ .pushsection .bss.data7, "-G", %nobits
+ .type data7, %object
+data7: .skip 7
+ end data7
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