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Provide a gcc-safe zero pointer 

zeroptr is a linker object pointing at 0 that can be used to thwart
GCC's (and other compilers') "dereferencing NULL is undefined"
optimization strategy when it gets in the way.

Change-Id: I6aa6f28283281ebae73d6349811e290bf1b99483
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: https://review.coreboot.org/12294
Tested-by: Raptor Engineering Automated Test Stand <noreply@raptorengineeringinc.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
This commit is contained in:
Patrick Georgi 2016-01-27 08:18:16 +01:00 committed by Martin Roth
parent cc728f0284
commit ff8076d75a
2 changed files with 12 additions and 0 deletions
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8
src/include/stddef.h
View File

@ -34,4 +34,12 @@ typedef unsigned int wint_t;
#define MAYBE_STATIC static #define MAYBE_STATIC static
#endif #endif
#ifndef __ROMCC__
/* Provide a pointer to address 0 that thwarts any "accessing this is
* undefined behaviour and do whatever" trickery in compilers.
* Use when you _really_ need to read32(zeroptr) (ie. read address 0).
*/
extern void *zeroptr;
#endif
#endif /* STDDEF_H */ #endif /* STDDEF_H */

4
src/lib/program.ld
View File

@ -133,6 +133,10 @@ _eprogram = .;
/* Discard the sections we don't need/want */ /* Discard the sections we don't need/want */
.zeroptr 0 (NOLOAD) : {
zeroptr = .;
}
/DISCARD/ : { /DISCARD/ : {
*(.comment) *(.comment)
*(.comment.*) *(.comment.*)