> In any case, unless you have any information that suggests that GCC in > Thumb2 mode can be coerced into managing the frame pointer in a way > that allows us to do something similar in EDK2, I am going to stick > with my assertion that this is not currently possible on ARM.
I think it's not possible because they enable ARM_UNWIND when compiling a THUMB2_KERNEL. porting libunwind would be hard because of UEFI's architecture. every *.efi would need a section with unwind information, and I don't even know if the spec allows additional sections. Thanks Michael On Fri, Sep 9, 2016 at 3:08 PM, Ard Biesheuvel <ard.biesheu...@linaro.org> wrote: > On 7 September 2016 at 12:32, Ard Biesheuvel <ard.biesheu...@linaro.org> > wrote: > > On 7 September 2016 at 12:25, Michael Zimmermann > > <sigmaepsilo...@gmail.com> wrote: > >>> However, looking at this > >>> code, this is still not sufficient to find the *next* frame pointer on > >>> the stack. > >> are you sure about that? this code looks like it does just that: > >> https://github.com/torvalds/linux/blob/master/arch/arm/ > kernel/stacktrace.c > >> > > > > First of all, that comment makes little sense: > > > > * With framepointer enabled, a simple function prologue looks like this: > > * mov ip, sp > > * stmdb sp!, {fp, ip, lr, pc} > > > > I assume this should be > > > > stmdb sp!, {fp, ip, lr} > > > > * sub fp, ip, #4 > > * > > * A simple function epilogue looks like this: > > * ldm sp, {fp, sp, pc} > > > > OK, I spoke a bit too soon. The 'pop' does not actually increment the > stack pointer, so while the push does make sense (and pushing the pc > in addition is just informational), the pop should actually be > implemented as > > ldm sp, {fp, sp, lr} > > ... do other stuff including incrementing the sp to its original value ... > > bx lr > > In any case, unless you have any information that suggests that GCC in > Thumb2 mode can be coerced into managing the frame pointer in a way > that allows us to do something similar in EDK2, I am going to stick > with my assertion that this is not currently possible on ARM. > > Thanks, > Ard. > _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
