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authorRussell King <rmk@dyn-67.arm.linux.org.uk>2008-09-07 16:16:54 (GMT)
committerRussell King <rmk+kernel@arm.linux.org.uk>2008-10-01 15:41:10 (GMT)
commit8ec53663d2698076468b3e1edc4e1b418bd54de3 (patch)
treed98f0ac21ec96be15aab1b05d3d6e2f60a657815 /arch/arm/kernel
parent5ec9407dd1196daaf12b427b351e2cd62d2a16a7 (diff)
downloadlinux-8ec53663d2698076468b3e1edc4e1b418bd54de3.tar.xz
[ARM] Improve non-executable support
Add support for detecting non-executable stack binaries, and adjust permissions to prevent execution from data and stack areas. Also, ensure that READ_IMPLIES_EXEC is enabled for older CPUs where that is true, and for any executable-stack binary. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel')
-rw-r--r--arch/arm/kernel/Makefile2
-rw-r--r--arch/arm/kernel/elf.c79
-rw-r--r--arch/arm/kernel/module.c2
3 files changed, 81 insertions, 2 deletions
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 1d296fc..4305345 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -10,7 +10,7 @@ endif
# Object file lists.
-obj-y := compat.o entry-armv.o entry-common.o irq.o \
+obj-y := compat.o elf.o entry-armv.o entry-common.o irq.o \
process.o ptrace.o setup.o signal.o \
sys_arm.o stacktrace.o time.o traps.o
diff --git a/arch/arm/kernel/elf.c b/arch/arm/kernel/elf.c
new file mode 100644
index 0000000..513f332
--- /dev/null
+++ b/arch/arm/kernel/elf.c
@@ -0,0 +1,79 @@
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/personality.h>
+#include <linux/binfmts.h>
+#include <linux/elf.h>
+
+int elf_check_arch(const struct elf32_hdr *x)
+{
+ unsigned int eflags;
+
+ /* Make sure it's an ARM executable */
+ if (x->e_machine != EM_ARM)
+ return 0;
+
+ /* Make sure the entry address is reasonable */
+ if (x->e_entry & 1) {
+ if (!(elf_hwcap & HWCAP_THUMB))
+ return 0;
+ } else if (x->e_entry & 3)
+ return 0;
+
+ eflags = x->e_flags;
+ if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
+ /* APCS26 is only allowed if the CPU supports it */
+ if ((eflags & EF_ARM_APCS_26) && !(elf_hwcap & HWCAP_26BIT))
+ return 0;
+
+ /* VFP requires the supporting code */
+ if ((eflags & EF_ARM_VFP_FLOAT) && !(elf_hwcap & HWCAP_VFP))
+ return 0;
+ }
+ return 1;
+}
+EXPORT_SYMBOL(elf_check_arch);
+
+void elf_set_personality(const struct elf32_hdr *x)
+{
+ unsigned int eflags = x->e_flags;
+ unsigned int personality = PER_LINUX_32BIT;
+
+ /*
+ * APCS-26 is only valid for OABI executables
+ */
+ if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
+ if (eflags & EF_ARM_APCS_26)
+ personality = PER_LINUX;
+ }
+
+ set_personality(personality);
+
+ /*
+ * Since the FPA coprocessor uses CP1 and CP2, and iWMMXt uses CP0
+ * and CP1, we only enable access to the iWMMXt coprocessor if the
+ * binary is EABI or softfloat (and thus, guaranteed not to use
+ * FPA instructions.)
+ */
+ if (elf_hwcap & HWCAP_IWMMXT &&
+ eflags & (EF_ARM_EABI_MASK | EF_ARM_SOFT_FLOAT)) {
+ set_thread_flag(TIF_USING_IWMMXT);
+ } else {
+ clear_thread_flag(TIF_USING_IWMMXT);
+ }
+}
+EXPORT_SYMBOL(elf_set_personality);
+
+/*
+ * Set READ_IMPLIES_EXEC if:
+ * - the binary requires an executable stack
+ * - we're running on a CPU which doesn't support NX.
+ */
+int arm_elf_read_implies_exec(const struct elf32_hdr *x, int executable_stack)
+{
+ if (executable_stack != EXSTACK_ENABLE_X)
+ return 1;
+ if (cpu_architecture() <= CPU_ARCH_ARMv6)
+ return 1;
+ return 0;
+}
+EXPORT_SYMBOL(arm_elf_read_implies_exec);
diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index a68259a..9203ba7 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -47,7 +47,7 @@ void *module_alloc(unsigned long size)
if (!area)
return NULL;
- return __vmalloc_area(area, GFP_KERNEL, PAGE_KERNEL);
+ return __vmalloc_area(area, GFP_KERNEL, PAGE_KERNEL_EXEC);
}
#else /* CONFIG_MMU */
void *module_alloc(unsigned long size)