diff options
| -rw-r--r-- | arch/arm/kernel/entry-armv.S | 3 | ||||
| -rw-r--r-- | arch/arm/kernel/traps.c | 23 | ||||
| -rw-r--r-- | arch/arm/mm/Kconfig | 34 |
3 files changed, 51 insertions, 9 deletions
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 94caefb550bf..d40d0ef389db 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -753,6 +753,7 @@ ENDPROC(__switch_to) .endr .endm +#ifdef CONFIG_KUSER_HELPERS .align 5 .globl __kuser_helper_start __kuser_helper_start: @@ -939,6 +940,8 @@ __kuser_helper_version: @ 0xffff0ffc .globl __kuser_helper_end __kuser_helper_end: +#endif + THUMB( .thumb ) /* diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index 2c8c7fa78b8c..e3ca35ccd38e 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -800,15 +800,26 @@ void __init trap_init(void) return; } -static void __init kuser_get_tls_init(unsigned long vectors) +#ifdef CONFIG_KUSER_HELPERS +static void __init kuser_init(void *vectors) { + extern char __kuser_helper_start[], __kuser_helper_end[]; + int kuser_sz = __kuser_helper_end - __kuser_helper_start; + + memcpy(vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz); + /* * vectors + 0xfe0 = __kuser_get_tls * vectors + 0xfe8 = hardware TLS instruction at 0xffff0fe8 */ if (tls_emu || has_tls_reg) - memcpy((void *)vectors + 0xfe0, (void *)vectors + 0xfe8, 4); + memcpy(vectors + 0xfe0, vectors + 0xfe8, 4); +} +#else +static void __init kuser_init(void *vectors) +{ } +#endif void __init early_trap_init(void *vectors_base) { @@ -816,8 +827,6 @@ void __init early_trap_init(void *vectors_base) unsigned long vectors = (unsigned long)vectors_base; extern char __stubs_start[], __stubs_end[]; extern char __vectors_start[], __vectors_end[]; - extern char __kuser_helper_start[], __kuser_helper_end[]; - int kuser_sz = __kuser_helper_end - __kuser_helper_start; unsigned i; vectors_page = vectors_base; @@ -838,12 +847,8 @@ void __init early_trap_init(void *vectors_base) */ memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start); memcpy((void *)vectors + 0x1000, __stubs_start, __stubs_end - __stubs_start); - memcpy((void *)vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz); - /* - * Do processor specific fixups for the kuser helpers - */ - kuser_get_tls_init(vectors); + kuser_init(vectors_base); /* * Copy signal return handlers into the vector page, and diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index 6cacdc8dd654..db5c2cab8fda 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -421,24 +421,28 @@ config CPU_32v3 select CPU_USE_DOMAINS if MMU select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select TLS_REG_EMUL if SMP || !MMU + select NEED_KUSER_HELPERS config CPU_32v4 bool select CPU_USE_DOMAINS if MMU select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select TLS_REG_EMUL if SMP || !MMU + select NEED_KUSER_HELPERS config CPU_32v4T bool select CPU_USE_DOMAINS if MMU select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select TLS_REG_EMUL if SMP || !MMU + select NEED_KUSER_HELPERS config CPU_32v5 bool select CPU_USE_DOMAINS if MMU select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select TLS_REG_EMUL if SMP || !MMU + select NEED_KUSER_HELPERS config CPU_32v6 bool @@ -776,6 +780,7 @@ config CPU_BPREDICT_DISABLE config TLS_REG_EMUL bool + select NEED_KUSER_HELPERS help An SMP system using a pre-ARMv6 processor (there are apparently a few prototypes like that in existence) and therefore access to @@ -783,11 +788,40 @@ config TLS_REG_EMUL config NEEDS_SYSCALL_FOR_CMPXCHG bool + select NEED_KUSER_HELPERS help SMP on a pre-ARMv6 processor? Well OK then. Forget about fast user space cmpxchg support. It is just not possible. +config NEED_KUSER_HELPERS + bool + +config KUSER_HELPERS + bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS + default y + help + Warning: disabling this option may break user programs. + + Provide kuser helpers in the vector page. The kernel provides + helper code to userspace in read only form at a fixed location + in the high vector page to allow userspace to be independent of + the CPU type fitted to the system. This permits binaries to be + run on ARMv4 through to ARMv7 without modification. + + However, the fixed address nature of these helpers can be used + by ROP (return orientated programming) authors when creating + exploits. + + If all of the binaries and libraries which run on your platform + are built specifically for your platform, and make no use of + these helpers, then you can turn this option off. However, + when such an binary or library is run, it will receive a SIGILL + signal, which will terminate the program. + + Say N here only if you are absolutely certain that you do not + need these helpers; otherwise, the safe option is to say Y. + config DMA_CACHE_RWFO bool "Enable read/write for ownership DMA cache maintenance" depends on CPU_V6K && SMP |