Auditing of external function calls and their return values relies on
lazy binding with PLT. When external functions are called indirectly
via GOT without using PLT, auditing stops working.
Here is a proposal to support auditing of external function called
indirectly via GOT:
1. Add optional dynamic tags:
#define DT_GNU_PLT 0x6ffffef4 /* Address of PLT section */
#define DT_GNU_PLTSZ 0x6ffffdf1 /* Size of PLT section */
#define DT_GNU_PLTENT 0x6ffffdf2 /* Size of one PLT entry */
#define DT_GNU_PLT0SZ 0x6ffffdf3 /* Size of the first PLT entry */
#define DT_GNU_PLTGOTSZ 0x6ffffdf4 /* Size of PLTGOT section */
and update DT_FLAGS_1 with:
#define DF_1_JMPRELIGN 0x10000000 /* DT_JMPREL can be ignored */
2. Linker creates PLT entries for auditing external function calls via
GOT and sets DT_GNU_PLT, DT_GNU_PLTSZ, DT_GNU_PLTENT, DT_GNU_PLT0SZ and
DT_GNU_PLTGOTSZ. If PLT isn't required for lazy binding, set the
DF_1_JMPRELIGN bit in DT_FLAGS_1.