Introduce a macro, SYMBOL, which is a simple wrapper around RELOC_HIDE to be used everywhere symbols such as _stext and _etext are used in the code.
RELOC_HIDE is needed when accessing symbols such as _stext and _etext because the C standard forbids for both comparisons and substraction (see C Standard, 6.5.6 [ISO/IEC 9899:2011] and ). forbids comparisons between pointers pointing to different objects. _stext, _etext, etc. are all pointers to different objects from ANCI C point of view. To work around potential C compiler issues (which have actually been found, see the comment on top of RELOC_HIDE in Linux), and to help with certifications, let's introduce some syntactic sugar to be used in following patches.  https://wiki.sei.cmu.edu/confluence/display/c/ARR36-C.+Do+not+subtract+or+compare+two+pointers+that+do+not+refer+to+the+same+array Signed-off-by: Stefano Stabellini <stefa...@xilinx.com> CC: jbeul...@suse.com CC: andrew.coop...@citrix.com CC: wei.l...@citrix.com --- Changes in v3: - improve commit message - rename __symbol to SYMBOL to avoid name space violations Changes in v2: - do not cast return to char* - move to common header --- xen/include/xen/compiler.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h index ff6c0f5..b3375f6 100644 --- a/xen/include/xen/compiler.h +++ b/xen/include/xen/compiler.h @@ -99,6 +99,12 @@ __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \ (typeof(ptr)) (__ptr + (off)); }) +/* + * Use RELOC_HIDE with symbols such as _stext and _etext to avoid errors + * on comparing pointers to different objects + */ +#define SYMBOL(x) (RELOC_HIDE((unsigned long)(x), 0)) + #ifdef __GCC_ASM_FLAG_OUTPUTS__ # define ASM_FLAG_OUT(yes, no) yes #else -- 1.9.1 _______________________________________________ Xen-devel mailing list Xenfirstname.lastname@example.org https://lists.xenproject.org/mailman/listinfo/xen-devel