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Date: Thu, 1 Apr 2021 15:11:00 -0700
From: Yu-cheng Yu <yu-cheng.yu@...el.com>
To: x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-mm@...ck.org,
linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
Arnd Bergmann <arnd@...db.de>,
Andy Lutomirski <luto@...nel.org>,
Balbir Singh <bsingharora@...il.com>,
Borislav Petkov <bp@...en8.de>,
Cyrill Gorcunov <gorcunov@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Eugene Syromiatnikov <esyr@...hat.com>,
Florian Weimer <fweimer@...hat.com>,
"H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
Jonathan Corbet <corbet@....net>,
Kees Cook <keescook@...omium.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Nadav Amit <nadav.amit@...il.com>,
Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
Peter Zijlstra <peterz@...radead.org>,
Randy Dunlap <rdunlap@...radead.org>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
Dave Martin <Dave.Martin@....com>,
Weijiang Yang <weijiang.yang@...el.com>,
Pengfei Xu <pengfei.xu@...el.com>,
Haitao Huang <haitao.huang@...el.com>
Cc: Yu-cheng Yu <yu-cheng.yu@...el.com>,
Mark Brown <broonie@...nel.org>,
Catalin Marinas <catalin.marinas@....com>
Subject: [PATCH v24 26/30] ELF: Introduce arch_setup_elf_property()
An ELF file's .note.gnu.property indicates arch features supported by the
file. These features are extracted by arch_parse_elf_property() and stored
in 'arch_elf_state'.
Introduce x86 feature definitions and arch_setup_elf_property(), which
enables such features. The first use-case of this function is Shadow
Stack.
ARM64 is the other arch that has ARCH_USE_GNU_PROPERTY and arch_parse_elf_
property(). Add arch_setup_elf_property() for it.
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Cc: Mark Brown <broonie@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Dave Martin <Dave.Martin@....com>
---
v24:
- Change cet_setup_shstk() to shstk_setup() to reflect function name changes
relating to the splitting of shadow stack and ibt.
arch/arm64/include/asm/elf.h | 5 +++++
arch/x86/Kconfig | 2 ++
arch/x86/include/asm/elf.h | 13 +++++++++++++
arch/x86/kernel/process_64.c | 32 ++++++++++++++++++++++++++++++++
fs/binfmt_elf.c | 4 ++++
include/linux/elf.h | 6 ++++++
include/uapi/linux/elf.h | 9 +++++++++
7 files changed, 71 insertions(+)
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 8d1c8dcb87fd..d37bc7915935 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -281,6 +281,11 @@ static inline int arch_parse_elf_property(u32 type, const void *data,
return 0;
}
+static inline int arch_setup_elf_property(struct arch_elf_state *arch)
+{
+ return 0;
+}
+
static inline int arch_elf_pt_proc(void *ehdr, void *phdr,
struct file *f, bool is_interp,
struct arch_elf_state *state)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f42560b220ef..a69e351e7386 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1955,6 +1955,8 @@ config X86_SHADOW_STACK
depends on ARCH_HAS_SHADOW_STACK
select ARCH_USES_HIGH_VMA_FLAGS
select X86_CET
+ select ARCH_USE_GNU_PROPERTY
+ select ARCH_BINFMT_ELF_STATE
help
Shadow Stack protection is a hardware feature that detects function
return address corruption. This helps mitigate ROP attacks.
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 9224d40cdefe..6a131047be8a 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -390,6 +390,19 @@ extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
extern bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs);
+#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 d08307df69ad..892d8e742e3b 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -835,3 +835,35 @@ unsigned long KSTK_ESP(struct task_struct *task)
{
return task_pt_regs(task)->sp;
}
+
+#ifdef CONFIG_ARCH_USE_GNU_PROPERTY
+int arch_parse_elf_property(u32 type, const void *data, size_t datasz,
+ bool compat, struct arch_elf_state *state)
+{
+ if (type != GNU_PROPERTY_X86_FEATURE_1_AND)
+ return 0;
+
+ if (datasz != sizeof(unsigned int))
+ return -ENOEXEC;
+
+ state->gnu_property = *(unsigned int *)data;
+ return 0;
+}
+
+int arch_setup_elf_property(struct arch_elf_state *state)
+{
+ int r = 0;
+
+ if (!IS_ENABLED(CONFIG_X86_CET))
+ return r;
+
+ memset(¤t->thread.cet, 0, sizeof(struct cet_status));
+
+ if (static_cpu_has(X86_FEATURE_SHSTK)) {
+ if (state->gnu_property & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
+ r = shstk_setup();
+ }
+
+ return r;
+}
+#endif
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index b12ba98ae9f5..fa665eceba04 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1248,6 +1248,10 @@ static int load_elf_binary(struct linux_binprm *bprm)
set_binfmt(&elf_format);
+ retval = arch_setup_elf_property(&arch_state);
+ if (retval < 0)
+ goto out;
+
#ifdef ARCH_HAS_SETUP_ADDITIONAL_PAGES
retval = ARCH_SETUP_ADDITIONAL_PAGES(bprm, elf_ex, !!interpreter);
if (retval < 0)
diff --git a/include/linux/elf.h b/include/linux/elf.h
index c9a46c4e183b..be04d15e937f 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -92,9 +92,15 @@ static inline int arch_parse_elf_property(u32 type, const void *data,
{
return 0;
}
+
+static inline int arch_setup_elf_property(struct arch_elf_state *arch)
+{
+ return 0;
+}
#else
extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz,
bool compat, struct arch_elf_state *arch);
+extern int arch_setup_elf_property(struct arch_elf_state *arch);
#endif
#ifdef CONFIG_ARCH_HAVE_ELF_PROT
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 30f68b42eeb5..24ba55ba8278 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -455,4 +455,13 @@ typedef struct elf64_note {
/* Bits for GNU_PROPERTY_AARCH64_FEATURE_1_BTI */
#define GNU_PROPERTY_AARCH64_FEATURE_1_BTI (1U << 0)
+/* .note.gnu.property types for x86: */
+#define GNU_PROPERTY_X86_FEATURE_1_AND 0xc0000002
+
+/* Bits for GNU_PROPERTY_X86_FEATURE_1_AND */
+#define GNU_PROPERTY_X86_FEATURE_1_IBT 0x00000001
+#define GNU_PROPERTY_X86_FEATURE_1_SHSTK 0x00000002
+#define GNU_PROPERTY_X86_FEATURE_1_VALID (GNU_PROPERTY_X86_FEATURE_1_IBT | \
+ GNU_PROPERTY_X86_FEATURE_1_SHSTK)
+
#endif /* _UAPI_LINUX_ELF_H */
--
2.21.0
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