Thread (51 messages) 51 messages, 5 authors, 2021-09-01
STALE1763d REVIEWED: 3 (3M)
Revisions (9)
  1. v22 [diff vs current]
  2. v23 [diff vs current]
  3. v24 [diff vs current]
  4. v25 [diff vs current]
  5. v26 [diff vs current]
  6. v27 [diff vs current]
  7. v28 [diff vs current]
  8. v29 current
  9. v30 [diff vs current]

[PATCH v29 28/32] ELF: Introduce arch_setup_elf_property()

From: Yu-cheng Yu <hidden>
Date: 2021-08-20 18:22:17
Also in: linux-api, linux-arch, linux-mm, lkml
Subsystem: arm64 port (aarch64 architecture), exec & binfmt api, elf, filesystems (vfs and infrastructure), the rest, x86 architecture (32-bit and 64-bit) · Maintainers: Catalin Marinas, Will Deacon, Kees Cook, Alexander Viro, Christian Brauner, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen

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 <redacted>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: Kees Cook <redacted>
Cc: Mark Brown <broonie@kernel.org>
---
v27:
- Make X86_64 select ARCH_USE_GNU_PROPERTY and ARCH_BINFMT_ELF_STATE and
  remove #ifdef's.
- Add link to x86-64-psABI document.
---
 arch/arm64/include/asm/elf.h |  5 +++++
 arch/x86/Kconfig             |  2 ++
 arch/x86/include/asm/elf.h   | 11 +++++++++++
 arch/x86/kernel/process_64.c | 27 +++++++++++++++++++++++++++
 fs/binfmt_elf.c              |  4 ++++
 include/linux/elf.h          |  6 ++++++
 include/uapi/linux/elf.h     | 14 ++++++++++++++
 7 files changed, 69 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 cb0405ccf858..34692f02118c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -29,6 +29,7 @@ config X86_64
 	select ARCH_HAS_SHADOW_STACK
 	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_USE_GNU_PROPERTY
 	select HAVE_ARCH_SOFT_DIRTY
 	select MODULES_USE_ELF_RELA
 	select NEED_DMA_MAP_STATE
@@ -61,6 +62,7 @@ config X86
 	select ACPI_LEGACY_TABLES_LOOKUP	if ACPI
 	select ACPI_SYSTEM_POWER_STATES_SUPPORT	if ACPI
 	select ARCH_32BIT_OFF_T			if X86_32
+	select ARCH_BINFMT_ELF_STATE
 	select ARCH_CLOCKSOURCE_INIT
 	select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
 	select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 || (X86_32 && HIGHMEM)
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 29fea180a665..3281a3d01bd2 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -394,6 +394,17 @@ extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
 
 extern bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs);
 
+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)
+
 /* 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 ec0d836a13b1..4271963fdd8c 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -861,3 +861,30 @@ unsigned long KSTK_ESP(struct task_struct *task)
 {
 	return task_pt_regs(task)->sp;
 }
+
+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;
+
+#ifdef CONFIG_X86_SHADOW_STACK
+	memset(&current->thread.shstk, 0, sizeof(struct thread_shstk));
+
+	if (state->gnu_property & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
+		r = shstk_setup();
+#endif
+
+	return r;
+}
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 439ed81e755a..6a1936dab6b4 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 61bf4774b8f2..f50b3ce7bb75 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -456,4 +456,18 @@ typedef struct elf64_note {
 /* Bits for GNU_PROPERTY_AARCH64_FEATURE_1_BTI */
 #define GNU_PROPERTY_AARCH64_FEATURE_1_BTI	(1U << 0)
 
+/*
+ * See the x86 64 psABI at:
+ * https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/x86-64-psABI
+ * .note.gnu.property types for x86:
+ */
+/* 0xc0000000 and 0xc0000001 are reserved */
+#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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