Add function prologue/epilogue to conditionally add BTI landing pads
and/or PAC code generation & authentication instructions depending on
compilation flags.
This patch enables PACBTI for all relevant variants of strcmp:
* Newlib for armv8.1-m.main+pacbti
* Newlib for armv8.1-m.main+pacbti+mve
* Newlib-nano
ARM newlib has various strcmp implementations that use .cfi_*
directives to generate unwind information.
The effect of this is that the generated objects contain .eh_frame
sections. However, ARM uses its own unwind info format, not
.eh_frame, which is generated by ARM-specific directives, not .cfi_*.
The .eh_frame sections are useless, but also not removed by strip and
may be loaded into memory at runtime.
This patch fixes this by using .cfi_sections .debug_frame (as in
glibc) so that the directives generate .debug_frame instead.
.debug_frame is useful for the debugger, can be removed by strip, and
is not loaded into memory at runtime.
* libc/machine/arm/strcmp-arm-tiny.S: Use .cfi_sections
.debug_frame.
* libc/machine/arm/strcmp-armv4.S: Likewise.
* libc/machine/arm/strcmp-armv4t.S: Likewise.
* libc/machine/arm/strcmp-armv6.S: Likewise.
* libc/machine/arm/strcmp-armv6m.S: Likewise.
* libc/machine/arm/strcmp-armv7.S: Likewise.
* libc/machine/arm/strcmp-armv7m.S: Likewise.
* libc/machine/arm/strcmp-armv4.S: New file.
* libc/machine/arm/strcmp-armv4t.S: New file.
* libc/machine/arm/strcmp-armv6.S: New file.
* libc/machine/arm/strcmp-armv7.S: New file.
* libc/machine/arm/strcmp-armv7m.S: New file.
* libc/machine/arm/strcmp.S: Replace with wrapper for various
implementations.
* libc/machine/arm/Makefile.am (strcmp.o, strcmp.obj): Add
dependencies.
* libc/machine/arm/Makefile.in: Regenerated.
Victor L. Do Nascimento
Joseph Myers
Richard Earnshaw