On Friday 12 January 2007 8:38 am, Russell King wrote:
> A more correct test would be that found in kallsyms.c:
Good point. Updated patch appended.
- Dave
=============== CUT HERE
This patch stops "modpost" from issuing erroneous modpost warnings on ARM
builds, which it's been doing simce since maybe last summer. A canonical
example would be driver method table entries:
WARNING: <path> - Section mismatch: reference to .exit.text:<name>_remove
from .data after '$d' (at offset 0x4)
That "$d" symbol is generated by tools conformant with ARM ABI specs; in
this case, it's a relocation in the middle of a "<name>_driver" struct.
The erroneous warnings appear to be issued because "modpost" whitelists
references from "<name>_driver" data into init and exit sections ... but
does NOT whitelist them from "$d" (and can't).
This patch prevents the modpost symbol lookup code from ever returning
those symbols, so it will return a whitelisted symbol instead.
Now to revert various code-bloating "fixes" that got merged because of
this modpost bug....
Signed-off-by: David Brownell <[email protected]>
---
Likely this patch can be improved on, but there's another issue.
It seems to me that these modpost checks are wrong:
* Lingering pointers that point into sections modprobe removes are
*always* unsafe ... including probe() methods marked "__init"
on hotpluggable busses. Trivial fix: use __devinit instead;
or maybe platform_driver_probe().
* Lingering pointers that point into sections that aren't removed
are *never* unsafe ... including this remove() method case, since
module unloading is configured and the __exit stuff must stay.
Whitelisting the former means not reporting potential oopsing cases;
dangerous. Whereas even *checking* the latter is a waste of effort.
Index: at91/scripts/mod/modpost.c
===================================================================
--- at91.orig/scripts/mod/modpost.c 2006-12-15 10:08:57.000000000 -0800
+++ at91/scripts/mod/modpost.c 2007-01-12 12:09:29.000000000 -0800
@@ -655,6 +655,30 @@ static Elf_Sym *find_elf_symbol(struct e
return NULL;
}
+static inline int is_arm_mapping_symbol(const char *str)
+{
+ return str[0] == '$' && strchr("atd", str[1])
+ && (str[2] == '\0' || str[2] == '.');
+}
+
+/*
+ * If there's no name there, ignore it; likewise, ignore it if it's
+ * one of the magic symbols emitted used by current ARM tools.
+ *
+ * Otherwise if find_symbols_between() returns those symbols, they'll
+ * fail the whitelist tests and cause lots of false alarms ... fixable
+ * only by shrinking __exit and __init sections into __text, bloating
+ * the kernel (which is especially evil on embedded platforms).
+ */
+static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym)
+{
+ const char *name = elf->strtab + sym->st_name;
+
+ if (!name || !strlen(name))
+ return 0;
+ return !is_arm_mapping_symbol(name);
+}
+
/*
* Find symbols before or equal addr and after addr - in the section sec.
* If we find two symbols with equal offset prefer one with a valid name.
@@ -683,16 +707,15 @@ static void find_symbols_between(struct
symsec = secstrings + elf->sechdrs[sym->st_shndx].sh_name;
if (strcmp(symsec, sec) != 0)
continue;
+ if (!is_valid_name(elf, sym))
+ continue;
if (sym->st_value <= addr) {
if ((addr - sym->st_value) < beforediff) {
beforediff = addr - sym->st_value;
*before = sym;
}
else if ((addr - sym->st_value) == beforediff) {
- /* equal offset, valid name? */
- const char *name = elf->strtab + sym->st_name;
- if (name && strlen(name))
- *before = sym;
+ *before = sym;
}
}
else
@@ -702,10 +725,7 @@ static void find_symbols_between(struct
*after = sym;
}
else if ((sym->st_value - addr) == afterdiff) {
- /* equal offset, valid name? */
- const char *name = elf->strtab + sym->st_name;
- if (name && strlen(name))
- *after = sym;
+ *after = sym;
}
}
}
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
