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| author |   Kees Cook <keescook@chromium.org> | 2021-04-01 16:23:46 -0700 |
|---|---|---|
| committer |   Thomas Gleixner <tglx@linutronix.de> | 2021-04-08 14:12:19 +0200 |
| commit | 70918779aec9bd01d16f4e6e800ffe423d196021 (patch) | |
| tree | 55ba55366efd83242e4ddfe44dcc6f48fe8d78d8 /arch/arm64/kernel/Makefile | |
| parent | lkdtm: Add REPORT_STACK for checking stack offsets (diff) | |
| download | linux-dev-70918779aec9bd01d16f4e6e800ffe423d196021.tar.xz linux-dev-70918779aec9bd01d16f4e6e800ffe423d196021.zip | |
arm64: entry: Enable random_kstack_offset support
Allow for a randomized stack offset on a per-syscall basis, with roughly
5 bits of entropy. (And include AAPCS rationale AAPCS thanks to Mark
Rutland.)
In order to avoid unconditional stack canaries on syscall entry (due to
the use of alloca()), also disable stack protector to avoid triggering
needless checks and slowing down the entry path. As there is no general
way to control stack protector coverage with a function attribute[1],
this must be disabled at the compilation unit level. This isn't a problem
here, though, since stack protector was not triggered before: examining
the resulting syscall.o, there are no changes in canary coverage (none
before, none now).
[1] a working __attribute__((no_stack_protector)) has been added to GCC
and Clang but has not been released in any version yet:
https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=346b302d09c1e6db56d9fe69048acb32fbb97845
https://reviews.llvm.org/rG4fbf84c1732fca596ad1d6e96015e19760eb8a9b
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210401232347.2791257-6-keescook@chromium.org
Diffstat (limited to 'arch/arm64/kernel/Makefile')
| -rw-r--r-- | arch/arm64/kernel/Makefile | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index ed65576ce710..6cc97730790e 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -9,6 +9,11 @@ CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_insn.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_return_address.o = $(CC_FLAGS_FTRACE) +# Remove stack protector to avoid triggering unneeded stack canary +# checks due to randomize_kstack_offset. +CFLAGS_REMOVE_syscall.o = -fstack-protector -fstack-protector-strong +CFLAGS_syscall.o += -fno-stack-protector + # Object file lists. obj-y := debug-monitors.o entry.o irq.o fpsimd.o \ entry-common.o entry-fpsimd.o process.o ptrace.o \ |