Some ftrace features are broken since commit 714a8d02ca ("arm64: asm:
Override SYM_FUNC_START when building the kernel with BTI"). For example
the function_graph tracer:
$ echo function_graph > /sys/kernel/debug/tracing/current_tracer
[ 36.107016] WARNING: CPU: 0 PID: 115 at kernel/trace/ftrace.c:2691 ftrace_modify_all_code+0xc8/0x14c
When ftrace_modify_graph_caller() attempts to write a branch at
ftrace_graph_call, it finds the "BTI J" instruction inserted by
SYM_INNER_LABEL() instead of a NOP, and aborts.
It turns out we don't currently need the BTI landing pads inserted by
SYM_INNER_LABEL:
* ftrace_call and ftrace_graph_call are only used for runtime patching
of the active tracer. The patched code is not reached from a branch.
* install_el2_stub is reached from a CBZ instruction, which doesn't
change PSTATE.BTYPE.
* __guest_exit is reached from B instructions in the hyp-entry vectors,
which aren't subject to BTI checks either.
Remove the BTI annotation from SYM_INNER_LABEL.
Fixes: 714a8d02ca ("arm64: asm: Override SYM_FUNC_START when building the kernel with BTI")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20200624112253.1602786-1-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
For better or worse, GDB relies on the exact instruction sequence in the
VDSO sigreturn trampoline in order to unwind from signals correctly.
Commit c91db232da ("arm64: vdso: Convert to modern assembler annotations")
unfortunately added a BTI C instruction to the start of __kernel_rt_sigreturn,
which breaks this check. Thankfully, it's also not required, since the
trampoline is called from a RET instruction when returning from the signal
handler
Remove the unnecessary BTI C instruction from __kernel_rt_sigreturn,
and do the same for the 32-bit VDSO as well for good measure.
Cc: Daniel Kiss <daniel.kiss@arm.com>
Cc: Tamas Zsoldos <tamas.zsoldos@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Fixes: c91db232da ("arm64: vdso: Convert to modern assembler annotations")
Signed-off-by: Will Deacon <will@kernel.org>
When the kernel is built for BTI override SYM_FUNC_START and related macros
to add a BTI landing pad to the start of all global functions, ensuring that
they are BTI safe. The ; at the end of the BTI_x macros is for the
benefit of the macro-generated functions in xen-hypercall.S.
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20200506195138.22086-4-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
As part of an effort to make the annotations in assembly code clearer and
more consistent new macros have been introduced, including replacements
for ENTRY() and ENDPROC().
On arm64 we have ENDPIPROC(), a custom version of ENDPROC() which is
used for code that will need to run in position independent environments
like EFI, it creates an alias for the function with the prefix __pi_ and
then emits the standard ENDPROC. Add new-style macros to replace this
which expand to the standard SYM_FUNC_*() and SYM_FUNC_ALIAS_*(),
resulting in the same object code. These are added in linkage.h for
consistency with where the generic assembler code has its macros.
Signed-off-by: Mark Brown <broonie@kernel.org>
[will: Rename 'WEAK' macro, use ';' instead of ASM_NL, deprecate ENDPIPROC]
Signed-off-by: Will Deacon <will@kernel.org>
Aarch64 instructions must be word aligned. The current 16 byte
alignment is more than enough. Relax it into 4 byte alignment.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
An interesting effect of using the generic version of linkage.h
is that the padding is defined in terms of x86 NOPs, which can have
even more interesting effects when the assembly code looks like this:
ENTRY(func1)
mov x0, xzr
ENDPROC(func1)
// fall through
ENTRY(func2)
mov x0, #1
ret
ENDPROC(func2)
Admittedly, the code is not very nice. But having code from another
architecture doesn't look completely sane either.
The fix is to add arm64's version of linkage.h, which causes the insertion
of proper AArch64 NOPs.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
