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Commit da68d61f authored by David Brownell's avatar David Brownell Committed by Linus Torvalds
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[PATCH] remove modpost false warnings on ARM 



This patch stops "modpost" from issuing erroneous modpost warnings on ARM
builds, which it's been doing since 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 symbol **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
doesn't know should also include those "$d" mapping symbols, which are not
otherwise associated with "<name>_driver" symbols.

This patch prevents the modpost symbol lookup code from ever returning
those mapping symbols, so it will return a whitelisted symbol instead.
Then things work as expected.

Now to revert various code-bloating "fixes" that got merged because of this
modpost bug....

Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Roman Zippel <zippel@linux-m68k.org>
Acked-by: default avatarSam Ravnborg <sam@ravnborg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3deac046

scripts/mod/modpost.c

+28 −8
Original line number Diff line number Diff line
@@ -686,6 +686,30 @@ static Elf_Sym *find_elf_symbol(struct elf_info *elf, Elf_Addr addr, 
	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 merging __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.
@@ -714,15 +738,14 @@ static void find_symbols_between(struct elf_info *elf, Elf_Addr addr, 
		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;

			}

		}
@@ -733,9 +756,6 @@ static void find_symbols_between(struct elf_info *elf, Elf_Addr addr, 
				*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;

			}

		}