Date: Tue, 24 Nov 2009 10:29:38 -0800 From: Navdeep Parhar <nparhar@gmail.com> To: freebsd-hackers@freebsd.org Subject: zero size set_pcpu linker sets Message-ID: <d04e16b70911241029q41fb4f8au12574763d9a8eb99@mail.gmail.com>
next in thread | raw e-mail | index | archive | help
objdump -h shows that most, but not all, KLDs on amd64 have a "set_pcpu"
section of size 0. Why? What is the difference between having a 0
sized set_pcpu vs. not having it at all?
The kernel linker considers the alignment requirements of these empty
sections and advances mapsize/mapbase. This bothers my kgdb (which is
slightly modified to deal with amd64 KLDs).
I'm using the patch shown here as a stopgap measure. I think the correct
fix is to not have these empty sections in the KLD to begin with.
Regards,
Navdeep
diff -r 09b877bb00f2 sys/kern/link_elf_obj.c
--- a/sys/kern/link_elf_obj.c Mon Nov 23 12:42:09 2009 -0800
+++ b/sys/kern/link_elf_obj.c Tue Nov 24 10:13:02 2009 -0800
@@ -680,10 +680,12 @@
switch (shdr[i].sh_type) {
case SHT_PROGBITS:
case SHT_NOBITS:
- alignmask = shdr[i].sh_addralign - 1;
- mapsize += alignmask;
- mapsize &= ~alignmask;
- mapsize += shdr[i].sh_size;
+ if (shdr[i].sh_size) {
+ alignmask = shdr[i].sh_addralign - 1;
+ mapsize += alignmask;
+ mapsize &= ~alignmask;
+ mapsize += shdr[i].sh_size;
+ }
break;
}
}
@@ -740,9 +742,15 @@
switch (shdr[i].sh_type) {
case SHT_PROGBITS:
case SHT_NOBITS:
- alignmask = shdr[i].sh_addralign - 1;
- mapbase += alignmask;
- mapbase &= ~alignmask;
+ if (shdr[i].sh_size) {
+ alignmask = shdr[i].sh_addralign - 1;
+ mapbase += alignmask;
+ mapbase &= ~alignmask;
+ }
if (ef->shstrtab && shdr[i].sh_name != 0)
ef->progtab[pb].name =
ef->shstrtab + shdr[i].sh_name;
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?d04e16b70911241029q41fb4f8au12574763d9a8eb99>