diff options
| author | Patrick Georgi <patrick@georgi-clan.de> | 2016-01-27 08:18:16 +0100 |
|---|---|---|
| committer | Martin Roth <martinroth@google.com> | 2016-01-28 23:25:53 +0100 |
| commit | ff8076d75ace8da247b927f7de37f3ed5081b55e (patch) | |
| tree | 239a0d035ffc5fd4d46e3cfb8b3b88191fbe08e7 | |
| parent | cc728f02846a1752215503dc7897caf6fc5a1fc1 (diff) | |
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>
| -rw-r--r-- | src/include/stddef.h | 8 | ||||
| -rw-r--r-- | src/lib/program.ld | 4 |
2 files changed, 12 insertions, 0 deletions
diff --git a/src/include/stddef.h b/src/include/stddef.h index b58f645a3b..35326ed6c6 100644 --- a/src/include/stddef.h +++ b/src/include/stddef.h @@ -34,4 +34,12 @@ typedef unsigned int wint_t; #define MAYBE_STATIC static #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 */ diff --git a/src/lib/program.ld b/src/lib/program.ld index 865b5f6aa7..9b8c7c9ec1 100644 --- a/src/lib/program.ld +++ b/src/lib/program.ld @@ -133,6 +133,10 @@ _eprogram = .; /* Discard the sections we don't need/want */ +.zeroptr 0 (NOLOAD) : { + zeroptr = .; +} + /DISCARD/ : { *(.comment) *(.comment.*) |