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gcc-plugins: arm_ssp_per_task_plugin: fix for GCC 9+ 

GCC 9 reworks the way the references to the stack canary are
emitted, to prevent the value from being spilled to the stack
before the final comparison in the epilogue, defeating the
purpose, given that the spill slot is under control of the
attacker that we are protecting ourselves from.

Since our canary value address is obtained without accessing
memory (as opposed to pre-v7 code that will obtain it from a
literal pool), it is unlikely (although not guaranteed) that
the compiler will spill the canary value in the same way, so
let's just disable this improvement when building with GCC9+.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Ard Biesheuvel 2019-01-18 11:58:07 +01:00 committed by Kees Cook
parent 560706d5d2
commit 2c88c742d0
1 changed files with 18 additions and 0 deletions
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18
scripts/gcc-plugins/arm_ssp_per_task_plugin.c
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@ -53,6 +53,19 @@ static unsigned int arm_pertask_ssp_rtl_execute(void)
#define NO_GATE
#include "gcc-generate-rtl-pass.h"
#if BUILDING_GCC_VERSION >= 9000
static bool no(void)
{
return false;
}
static void arm_pertask_ssp_start_unit(void *gcc_data, void *user_data)
{
targetm.have_stack_protect_combined_set = no;
targetm.have_stack_protect_combined_test = no;
}
#endif
__visible int plugin_init(struct plugin_name_args *plugin_info,
struct plugin_gcc_version *version)
{
@ -100,5 +113,10 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
register_callback(plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP,
NULL, &arm_pertask_ssp_rtl_pass_info);
#if BUILDING_GCC_VERSION >= 9000
register_callback(plugin_info->base_name, PLUGIN_START_UNIT,
arm_pertask_ssp_start_unit, NULL);
#endif
return 0;
}