Hi,
aja@ shows me some problems with x11/gnome/librsvg update (the port is
Rust based), and I finally tracked the problem inside nm(1).
I will not speak of Rust anymore, and will use only C for the example.
When an object is compiled using -ffunction-sections, the
compiler/linker will use one section per function (if I correctly
understood the usual purpose, it is to be able to easily discard
unused sections/functions at linking time).
$ cat test.c
#include <stdio.h>
void
test_fn(void)
{
printf("test_fn()\n");
}
$ cc -Wall -c test.c -ffunction-sections
$ readelf --sections test.o | grep -A1 test_fn
[ 3] .text.test_fn PROGBITS 0000000000000000 00000040
0000000000000040 0000000000000000 AX 0 0 16
$ readelf -s test.o
Symbol table '.symtab' contains 8 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 FILE LOCAL DEFAULT ABS test.c
2: 0000000000000000 11 OBJECT LOCAL DEFAULT 7 .L.str
3: 0000000000000000 0 SECTION LOCAL DEFAULT 3
4: 0000000000000000 24 FUNC WEAK HIDDEN 6 __llvm_retpoline_r11
5: 0000000000000000 8 OBJECT WEAK HIDDEN 9 __retguard_759
6: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND printf
7: 0000000000000000 64 FUNC GLOBAL DEFAULT 3 test_fn
The problem is nm(1) doesn't recognize the test_fn type as a TEXT function:
$ nm test.o
00000000 d .L.str
00000000 W __llvm_retpoline_r11
00000000 W __retguard_759
U printf
00000000 F test.c
00000000 ? test_fn
test_fn symbol should be 'T', but it is reported as '?'.
llvm-nm(1) is working correctly (but we don't have it in base):
$ llvm-nm test.o
0000000000000000 r .L.str
0000000000000000 W __llvm_retpoline_r11
0000000000000000 V __retguard_759
U printf
0000000000000000 T test_fn
The following diff makes nm(1) to properly mark the function 'T', by
recognize ".text.*" sections:
diff cecccd4b3c548875286ca2b010c95cbce6c0e359 /home/semarie/repos/openbsd/src
blob - 5aeef7a01a7cbff029299cfc5562cfcec085347f
file + usr.bin/nm/elf.c
--- usr.bin/nm/elf.c
+++ usr.bin/nm/elf.c
@@ -274,6 +274,8 @@ elf_shn2type(Elf_Ehdr *eh, u_int shn, const char *sn)
return (-1);
else if (!strcmp(sn, ELF_TEXT))
return (N_TEXT);
+ else if (!strncmp(sn, ".text.", 6))
+ return (N_TEXT);
else if (!strcmp(sn, ELF_RODATA))
return (N_SIZE);
else if (!strcmp(sn, ELF_OPENBSDRANDOMDATA))
@@ -355,6 +357,7 @@ elf2nlist(Elf_Sym *sym, Elf_Ehdr *eh, Elf_Shdr *shdr,
} else if (sn != NULL && *sn != 0 &&
strcmp(sn, ELF_INIT) &&
strcmp(sn, ELF_TEXT) &&
+ strncmp(sn, ".text.", 6) &&
strcmp(sn, ELF_FINI)) /* XXX GNU compat */
np->nl.n_other = '?';
break;
The change on elf_shn2type() isn't strictly necessary for my use-case,
but it (should) makes .text.* support better (recognize N_TEXT for
STT_NOTYPE, STT_OBJECT, STT_TLS).
After, nm(1) properly recognize the symbol:
$ /usr/obj/usr.bin/nm/nm test.o
00000000 d .L.str
00000000 W __llvm_retpoline_r11
00000000 W __retguard_759
U printf
00000000 F test.c
00000000 T test_fn
and it makes libtool(1) happy (LT/Archive.pm: get_symbollist
function), and it makes librsvg build happy (which is playing with
symbols at build time), and it should makes aja@ happy too.
Comments or OK ?
--
Sebastien Marie
