[PATCH v8 23/27] x86/cet/shstk: ELF header parsing of Shadow Stack

Yu-cheng Yu
2019-08-13T21:03:06Z

Look in .note.gnu.property of an ELF file and check if Shadow Stack needs
to be enabled for the task.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
arch/x86/Kconfig | 2 ++
arch/x86/include/asm/elf.h | 13 +++++++++++++
arch/x86/kernel/process_64.c | 34 ++++++++++++++++++++++++++++++++++
3 files changed, 49 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index eaf86ef13348..7d13ba326962 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1947,6 +1947,8 @@ config X86_INTEL_SHADOW_STACK_USER
select ARCH_USES_HIGH_VMA_FLAGS
select X86_INTEL_CET
select ARCH_HAS_SHSTK
+ select ARCH_USE_GNU_PROPERTY
+ select ARCH_BINFMT_ELF_STATE
---help---
Shadow stack provides hardware protection against program stack
corruption. Only when all the following are true will an application
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 69c0f892e310..fac79b621e0a 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -367,6 +367,19 @@ extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
int uses_interp);
#define compat_arch_setup_additional_pages compat_arch_setup_additional_pages

+#ifdef CONFIG_ARCH_BINFMT_ELF_STATE
+struct arch_elf_state {
+ unsigned int gnu_property;
+};
+
+#define INIT_ARCH_ELF_STATE { \
+ .gnu_property = 0, \
+}
+
+#define arch_elf_pt_proc(ehdr, phdr, elf, interp, state) (0)
+#define arch_check_elf(ehdr, interp, interp_ehdr, state) (0)
+#endif
+
/* Do not change the values. See get_align_mask() */
enum align_flags {
ALIGN_VA_32 = BIT(0),
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index af64519b2695..1232f7a6c023 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -818,3 +818,37 @@ unsigned long KSTK_ESP(struct task_struct *task)
{
return task_pt_regs(task)->sp;
}
+
+#ifdef CONFIG_ARCH_USE_GNU_PROPERTY
+int arch_parse_property(void *ehdr, void *phdr, struct file *f, bool inter,
+ struct arch_elf_state *state)
+{
+ int r = 0;
+ unsigned int property = 0;
+
+ r = get_gnu_property(ehdr, phdr, f, GNU_PROPERTY_X86_FEATURE_1_AND,
+ &property);
+
+ if (r)
+ return r;
+
+ state->gnu_property = property;
+ return 0;
+}
+
+int arch_setup_property(struct arch_elf_state *state)
+{
+ int r = 0;
+
+ memset(&current->thread.cet, 0, sizeof(struct cet_status));
+
+ if (cpu_feature_enabled(X86_FEATURE_SHSTK)) {
+ if (state->gnu_property & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
+ r = cet_setup_shstk();
+ if (r < 0)
+ return r;
+ }
+
+ return r;
+}
+#endif
--
2.17.1