On Tue, May 10, 2011 at 13:40, Martin Schwidefsky <schwidefsky@xxxxxxxxxx> wrote: > That leaves arm as the last remaining architecture with a non trivial > ftrace_call_adjust function. There the least significant bit is removed > from the address with an and operation. The comment says this is done > for Thumb-2. This implies that for Thumb-1 the offset is 0 and for > Thumb-2 the offset is -1, correct? ARM supports building the kernel using either the ARM instruction set or the Thumb-2 instruction set. The kernel cannot be built with the "Thumb-1" instruction set (btw usually referred to as just Thumb). Thumb-2 via recordmcount.pl needs the clearing of the lsb because the relocation (R_ARM_ABS32) that gets used for the assembly file that recordmcount.pl generates and assembles dictates that the lsb be set if the target symbol is Thumb/Thumb-2 function. mcount_adjust would not help here since the ORing is done later, when the relocation is applied. Thumb-2 via recordmcount.c does not need the clearing of the lsb in ftrace_call_adjust. Building with the ARM instruction set also does not need the clearing of the lsb. > Thumb-2 the offset is -1, correct? If there is a way to distinguish > the two targets in recordmcount at compile time we could convert arm > as well. Which would allow us to remove the ftrace_call_adjust function. To remove ftrace_call_adjust, we could either deprecate the recordmcount.pl usage for ARM (you already have to edit the Kconfig to use it) or modify it to generate specific relocations explicitly instead of using the assembler data directives. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
