diff mbox series

[v5,06/12] arm64: elf: Enable BTI at exec based on ELF program properties

Message ID 20200122212144.6409-7-broonie@kernel.org (mailing list archive)
State New, archived
Headers show
Series arm64: ARMv8.5-A: Branch Target Identification support | expand

Commit Message

Mark Brown Jan. 22, 2020, 9:21 p.m. UTC 
From: Dave Martin <Dave.Martin@arm.com>

For BTI protection to be as comprehensive as possible, it is
desirable to have BTI enabled from process startup.  If this is not
done, the process must use mprotect() to enable BTI for each of its
executable mappings, but this is painful to do in the libc startup
code.  It's simpler and more sound to have the kernel do it
instead.

To this end, detect BTI support in the executable (or ELF
interpreter, as appropriate), via the
NT_GNU_PROGRAM_PROPERTY_TYPE_0 note, and tweak the initial prot
flags for the process' executable pages to include PROT_BTI as
appropriate.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/Kconfig           |  3 +++
 arch/arm64/include/asm/elf.h | 50 ++++++++++++++++++++++++++++++++++++
 arch/arm64/kernel/process.c  | 19 ++++++++++++++
 include/linux/elf.h          |  6 ++++-
 include/uapi/linux/elf.h     |  6 +++++
 5 files changed, 83 insertions(+), 1 deletion(-)

Comments

kernel test robot Jan. 24, 2020, 7:12 p.m. UTC | #1 
Hi Mark,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on asm-generic/master]
[also build test ERROR on kvmarm/next linus/master v5.5-rc7]
[cannot apply to arm64/for-next/core arm-perf/for-next/perf next-20200124]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Mark-Brown/arm64-ARMv8-5-A-Branch-Target-Identification-support/20200124-203746
base:   https://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git master
config: arm64-allnoconfig (attached as .config)
compiler: aarch64-linux-gcc (GCC) 7.5.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.5.0 make.cross ARCH=arm64 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from include/linux/module.h:18:0,
                    from include/linux/kallsyms.h:13,
                    from include/linux/ftrace.h:11,
                    from include/linux/perf_event.h:49,
                    from include/kvm/arm_pmu.h:10,
                    from arch/arm64/include/asm/kvm_host.h:37,
                    from include/linux/kvm_host.h:36,
                    from arch/arm64/kernel/asm-offsets.c:14:
>> include/linux/elf.h:79:19: error: redefinition of 'arch_parse_elf_property'
    static inline int arch_parse_elf_property(u32 type, const void *data,
                      ^~~~~~~~~~~~~~~~~~~~~~~
   In file included from include/linux/elf.h:6:0,
                    from include/linux/module.h:18,
                    from include/linux/kallsyms.h:13,
                    from include/linux/ftrace.h:11,
                    from include/linux/perf_event.h:49,
                    from include/kvm/arm_pmu.h:10,
                    from arch/arm64/include/asm/kvm_host.h:37,
                    from include/linux/kvm_host.h:36,
                    from arch/arm64/kernel/asm-offsets.c:14:
   arch/arm64/include/asm/elf.h:241:19: note: previous definition of 'arch_parse_elf_property' was here
    static inline int arch_parse_elf_property(u32 type, const void *data,
                      ^~~~~~~~~~~~~~~~~~~~~~~
   make[2]: *** [arch/arm64/kernel/asm-offsets.s] Error 1
   make[2]: Target '__build' not remade because of errors.
   make[1]: *** [prepare0] Error 2
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [sub-make] Error 2
   115 real  3 user  4 sys  7.44% cpu 	make prepare

vim +/arch_parse_elf_property +79 include/linux/elf.h

efb25e29b815dd Dave Martin 2020-01-22  77  
efb25e29b815dd Dave Martin 2020-01-22  78  #ifndef CONFIG_ARCH_USE_GNU_PROPERTY
efb25e29b815dd Dave Martin 2020-01-22 @79  static inline int arch_parse_elf_property(u32 type, const void *data,
efb25e29b815dd Dave Martin 2020-01-22  80  					  size_t datasz, bool compat,
efb25e29b815dd Dave Martin 2020-01-22  81  					  struct arch_elf_state *arch)
efb25e29b815dd Dave Martin 2020-01-22  82  {
efb25e29b815dd Dave Martin 2020-01-22  83  	return 0;
efb25e29b815dd Dave Martin 2020-01-22  84  }
efb25e29b815dd Dave Martin 2020-01-22  85  #else
efb25e29b815dd Dave Martin 2020-01-22  86  extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz,
efb25e29b815dd Dave Martin 2020-01-22  87  				   bool compat, struct arch_elf_state *arch);
efb25e29b815dd Dave Martin 2020-01-22  88  #endif
efb25e29b815dd Dave Martin 2020-01-22  89  

:::::: The code at line 79 was first introduced by commit
:::::: efb25e29b815ddf0dd1bbe3728659da08c80fa14 ELF: Add ELF program property parsing support

:::::: TO: Dave Martin <Dave.Martin@arm.com>
:::::: CC: 0day robot <lkp@intel.com>

---
0-DAY kernel test infrastructure                 Open Source Technology Center
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org Intel Corporation
diff mbox series

Patch

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 39292a0fc603..ea3a5150f5f6 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -9,6 +9,7 @@  config ARM64
 	select ACPI_MCFG if (ACPI && PCI)
 	select ACPI_SPCR_TABLE if ACPI
 	select ACPI_PPTT if ACPI
+	select ARCH_BINFMT_ELF_STATE
 	select ARCH_CLOCKSOURCE_DATA
 	select ARCH_HAS_DEBUG_VIRTUAL
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
@@ -33,6 +34,7 @@  config ARM64
 	select ARCH_HAS_SYSCALL_WRAPPER
 	select ARCH_HAS_TEARDOWN_DMA_OPS if IOMMU_SUPPORT
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
+	select ARCH_HAVE_ELF_PROT
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_INLINE_READ_LOCK if !PREEMPT
 	select ARCH_INLINE_READ_LOCK_BH if !PREEMPT
@@ -62,6 +64,7 @@  config ARM64
 	select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPT
 	select ARCH_KEEP_MEMBLOCK
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_USE_GNU_PROPERTY if BINFMT_ELF
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
 	select ARCH_SUPPORTS_MEMORY_FAILURE
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index b618017205a3..fca3a48e9db5 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -114,7 +114,11 @@ 
 
 #ifndef __ASSEMBLY__
 
+#include <uapi/linux/elf.h>
 #include <linux/bug.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/types.h>
 #include <asm/processor.h> /* for signal_minsigstksz, used by ARCH_DLINFO */
 
 typedef unsigned long elf_greg_t;
@@ -224,6 +228,52 @@  extern int aarch32_setup_additional_pages(struct linux_binprm *bprm,
 
 #endif /* CONFIG_COMPAT */
 
+struct arch_elf_state {
+	int flags;
+};
+
+#define ARM64_ELF_BTI		(1 << 0)
+
+#define INIT_ARCH_ELF_STATE {			\
+	.flags = 0,				\
+}
+
+static inline int arch_parse_elf_property(u32 type, const void *data,
+					  size_t datasz, bool compat,
+					  struct arch_elf_state *arch)
+{
+	/* No known properties for AArch32 yet */
+	if (IS_ENABLED(CONFIG_COMPAT) && compat)
+		return 0;
+
+	if (type == GNU_PROPERTY_AARCH64_FEATURE_1_AND) {
+		const u32 *p = data;
+
+		if (datasz != sizeof(*p))
+			return -ENOEXEC;
+
+		if (IS_ENABLED(CONFIG_ARM64_BTI) &&
+		    (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
+			arch->flags |= ARM64_ELF_BTI;
+	}
+
+	return 0;
+}
+
+static inline int arch_elf_pt_proc(void *ehdr, void *phdr,
+				   struct file *f, bool is_interp,
+				   struct arch_elf_state *state)
+{
+	return 0;
+}
+
+static inline int arch_check_elf(void *ehdr, bool has_interp,
+				 void *interp_ehdr,
+				 struct arch_elf_state *state)
+{
+	return 0;
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #endif
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 71f788cd2b18..37c508f409ac 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -11,6 +11,7 @@ 
 
 #include <linux/compat.h>
 #include <linux/efi.h>
+#include <linux/elf.h>
 #include <linux/export.h>
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
@@ -18,6 +19,7 @@ 
 #include <linux/sched/task_stack.h>
 #include <linux/kernel.h>
 #include <linux/lockdep.h>
+#include <linux/mman.h>
 #include <linux/mm.h>
 #include <linux/stddef.h>
 #include <linux/sysctl.h>
@@ -649,3 +651,20 @@  asmlinkage void __sched arm64_preempt_schedule_irq(void)
 	if (static_branch_likely(&arm64_const_caps_ready))
 		preempt_schedule_irq();
 }
+
+#ifdef CONFIG_BINFMT_ELF
+int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state,
+			 bool has_interp, bool is_interp)
+{
+	if (is_interp != has_interp)
+		return prot;
+
+	if (!(state->flags & ARM64_ELF_BTI))
+		return prot;
+
+	if (prot & PROT_EXEC)
+		prot |= PROT_BTI;
+
+	return prot;
+}
+#endif
diff --git a/include/linux/elf.h b/include/linux/elf.h
index 1b6e8955c597..5d5b0321da0b 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -63,7 +63,11 @@  extern int elf_coredump_extra_notes_size(void);
 extern int elf_coredump_extra_notes_write(struct coredump_params *cprm);
 #endif
 
-/* NT_GNU_PROPERTY_TYPE_0 header */
+/*
+ * NT_GNU_PROPERTY_TYPE_0 header:
+ * Keep this internal until/unless there is an agreed UAPI definition.
+ * pr_type values (GNU_PROPERTY_*) are public and defined in the UAPI header.
+ */
 struct gnu_property {
 	u32 pr_type;
 	u32 pr_datasz;
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 20900f4496b7..c6dd0215482e 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -448,4 +448,10 @@  typedef struct elf64_note {
   Elf64_Word n_type;	/* Content type */
 } Elf64_Nhdr;
 
+/* .note.gnu.property types for EM_AARCH64: */
+#define GNU_PROPERTY_AARCH64_FEATURE_1_AND	0xc0000000
+
+/* Bits for GNU_PROPERTY_AARCH64_FEATURE_1_BTI */
+#define GNU_PROPERTY_AARCH64_FEATURE_1_BTI	(1U << 0)
+
 #endif /* _UAPI_LINUX_ELF_H */