boot: Add support for -fstack-protector

meson.build

@@ -397,7 +397,14 @@ possible_common_cc_flags = [
         '-Wno-error=#warnings',  # clang
         '-Wno-string-plus-int',  # clang
 
+        '-fstack-protector',
+        '-fstack-protector-strong',
         '-fstrict-flex-arrays',
+        '--param=ssp-buffer-size=4',
+]
+
+possible_common_link_flags = [
+        '-fstack-protector',
 ]
 
 c_args = get_option('c_args')
@@ -432,7 +439,6 @@ possible_link_flags = [
         '-Wl,--fatal-warnings',
         '-Wl,-z,now',
         '-Wl,-z,relro',
-        '-fstack-protector',
 ]
 
 if get_option('b_sanitize') == 'none'
@@ -459,11 +465,8 @@ possible_cc_flags = [
         '-fdiagnostics-show-option',
         '-fno-common',
         '-fno-strict-aliasing',
-        '-fstack-protector',
-        '-fstack-protector-strong',
         '-fstrict-flex-arrays=1',
         '-fvisibility=hidden',
-        '--param=ssp-buffer-size=4',
 ]
 
 if get_option('buildtype') != 'debug'
@@ -486,6 +489,10 @@ add_project_arguments(
         ),
         language : 'c')
 
+add_project_link_arguments(
+        cc.get_supported_link_arguments(possible_common_link_flags),
+        language : 'c')
+
 userspace_c_args += cc.get_supported_arguments(possible_cc_flags)
 userspace_c_ld_args += cc.get_supported_link_arguments(possible_link_flags)
 

src/boot/efi/log.c

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
 #include "log.h"
+#include "proto/rng.h"
 #include "proto/simple-text-io.h"
 
 static unsigned log_count = 0;
@@ -59,6 +60,27 @@ void log_wait(void) {
         log_count = 0;
 }
 
+_used_ intptr_t __stack_chk_guard = (intptr_t) 0x70f6967de78acae3;
+
+/* We can only set a random stack canary if this function attribute is available,
+ * otherwise this may create a stack check fail. */
+#if STACK_PROTECTOR_RANDOM
+void __stack_chk_guard_init(void) {
+        EFI_RNG_PROTOCOL *rng;
+        if (BS->LocateProtocol(MAKE_GUID_PTR(EFI_RNG_PROTOCOL), NULL, (void **) &rng) == EFI_SUCCESS)
+                (void) rng->GetRNG(rng, NULL, sizeof(__stack_chk_guard), (void *) &__stack_chk_guard);
+}
+#endif
+
+_used_ _noreturn_ void __stack_chk_fail(void);
+_used_ _noreturn_ void __stack_chk_fail_local(void);
+void __stack_chk_fail(void) {
+        panic(u"systemd-boot: Stack check failed, halting.");
+}
+void __stack_chk_fail_local(void) {
+        __stack_chk_fail();
+}
+
 #if defined(__ARM_EABI__)
 /* These override the (weak) div0 handlers from libgcc as they would otherwise call raise() instead. */
 

src/boot/efi/log.h

@@ -3,6 +3,22 @@
 
 #include "efi-string.h"
 
+#if defined __has_attribute
+#  if __has_attribute(no_stack_protector)
+#    define HAVE_NO_STACK_PROTECTOR_ATTRIBUTE
+#  endif
+#endif
+
+#if defined(HAVE_NO_STACK_PROTECTOR_ATTRIBUTE) && \
+    (defined(__SSP__) || defined(__SSP_ALL__) || \
+    defined(__SSP_STRONG__) || defined(__SSP_EXPLICIT__))
+#  define STACK_PROTECTOR_RANDOM 1
+__attribute__((no_stack_protector, noinline)) void __stack_chk_guard_init(void);
+#else
+#  define STACK_PROTECTOR_RANDOM 0
+#  define __stack_chk_guard_init()
+#endif
+
 void log_wait(void);
 _gnu_printf_(2, 3) EFI_STATUS log_internal(EFI_STATUS status, const char *format, ...);
 #define log_error_status(status, ...) log_internal(status, __VA_ARGS__)

src/boot/efi/meson.build

@@ -139,6 +139,7 @@ efi_c_args += cc.get_supported_arguments(
         '-fwide-exec-charset=UCS2',
         # gcc docs says this is required for ms_abi to work correctly.
         '-maccumulate-outgoing-args',
+        '-mstack-protector-guard=global',
 )
 
 # Debug information has little value in release builds as no normal human being knows
@@ -180,8 +181,6 @@ efi_disabled_c_args = cc.get_supported_arguments(
         '-fno-exceptions',
         '-fno-trapv',
         '-fno-sanitize=all',
-        '-fno-stack-clash-protection',
-        '-fno-stack-protector',
         '-fno-unwind-tables',
 )
 efi_c_args += efi_disabled_c_args

src/boot/efi/util.h

@@ -176,6 +176,7 @@ void hexdump(const char16_t *prefix, const void *data, size_t size);
                 ST = system_table;                                                     \
                 BS = system_table->BootServices;                                       \
                 RT = system_table->RuntimeServices;                                    \
+                __stack_chk_guard_init();                                              \
                 notify_debugger((identity), (wait_for_debugger));                      \
                 EFI_STATUS err = func(image);                                          \
                 log_wait();                                                            \