From: ndesaulniers@xxxxxxxxxx <ndesaulniers@xxxxxxxxxx>
commit 514ca14ed5444b911de59ed3381dfd195d99fe4b upstream.
Back during the discussion of
commit a9a3ed1eff36 ("x86: Fix early boot crash on gcc-10, third try")
we discussed the need for a function attribute to control the omission
of stack protectors on a per-function basis; at the time Clang had
support for no_stack_protector but GCC did not. This was fixed in
gcc-11. Now that the function attribute is available, let's start using
it.
Callers of boot_init_stack_canary need to use this function attribute
unless they're compiled with -fno-stack-protector, otherwise the canary
stored in the stack slot of the caller will differ upon the call to
boot_init_stack_canary. This will lead to a call to __stack_chk_fail()
then panic.
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94722
Link: https://lore.kernel.org/all/20200316130414.GC12561@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Acked-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> (powerpc)
Acked-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230412-no_stackp-v2-1-116f9fe4bbe7@xxxxxxxxxx
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: ndesaulniers@xxxxxxxxxx <ndesaulniers@xxxxxxxxxx>
---
arch/powerpc/kernel/smp.c | 1 +
include/linux/compiler_attributes.h | 12 ++++++++++++
init/main.c | 3 ++-
3 files changed, 15 insertions(+), 1 deletion(-)
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -1605,6 +1605,7 @@ static void add_cpu_to_masks(int cpu)
}
/* Activate a secondary processor. */
+__no_stack_protector
void start_secondary(void *unused)
{
unsigned int cpu = raw_smp_processor_id();
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -256,6 +256,18 @@
#define __noreturn __attribute__((__noreturn__))
/*
+ * Optional: only supported since GCC >= 11.1, clang >= 7.0.
+ *
+ * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-no_005fstack_005fprotector-function-attribute
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#no-stack-protector-safebuffers
+ */
+#if __has_attribute(__no_stack_protector__)
+# define __no_stack_protector __attribute__((__no_stack_protector__))
+#else
+# define __no_stack_protector
+#endif
+
+/*
* Optional: not supported by gcc.
*
* clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
--- a/init/main.c
+++ b/init/main.c
@@ -877,7 +877,8 @@ static void __init print_unknown_bootopt
memblock_free(unknown_options, len);
}
-asmlinkage __visible void __init __no_sanitize_address __noreturn start_kernel(void)
+asmlinkage __visible __init __no_sanitize_address __noreturn __no_stack_protector
+void start_kernel(void)
{
char *command_line;
char *after_dashes;
