diff options
| author | James Morse <james.morse@arm.com> | 2016-02-05 14:58:48 +0000 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2016-02-18 17:27:04 +0000 |
| commit | 57f4959bad0a154aeca125b7d38d1d9471a12422 (patch) | |
| tree | 6d75f86840bb0bd2d3f4928993f696c44e2033c0 /arch/arm64/include/asm/alternative.h | |
| parent | 406e308770a92bd33995b2e5b681e86358328bb0 (diff) | |
arm64: kernel: Add support for User Access Override
'User Access Override' is a new ARMv8.2 feature which allows the
unprivileged load and store instructions to be overridden to behave in
the normal way.
This patch converts {get,put}_user() and friends to use ldtr*/sttr*
instructions - so that they can only access EL0 memory, then enables
UAO when fs==KERNEL_DS so that these functions can access kernel memory.
This allows user space's read/write permissions to be checked against the
page tables, instead of testing addr<USER_DS, then using the kernel's
read/write permissions.
Signed-off-by: James Morse <james.morse@arm.com>
[catalin.marinas@arm.com: move uao_thread_switch() above dsb()]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/alternative.h')
| -rw-r--r-- | arch/arm64/include/asm/alternative.h | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h index e4962f04201e..a9fc24ec1aa9 100644 --- a/arch/arm64/include/asm/alternative.h +++ b/arch/arm64/include/asm/alternative.h @@ -1,6 +1,8 @@ #ifndef __ASM_ALTERNATIVE_H #define __ASM_ALTERNATIVE_H +#include <asm/cpufeature.h> + #ifndef __ASSEMBLY__ #include <linux/init.h> @@ -63,6 +65,8 @@ void apply_alternatives(void *start, size_t length); #else +#include <asm/assembler.h> + .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len .word \orig_offset - . .word \alt_offset - . @@ -136,6 +140,74 @@ void apply_alternatives(void *start, size_t length); alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) +/* + * Generate the assembly for UAO alternatives with exception table entries. + * This is complicated as there is no post-increment or pair versions of the + * unprivileged instructions, and USER() only works for single instructions. + */ +#ifdef CONFIG_ARM64_UAO + .macro uao_ldp l, reg1, reg2, addr, post_inc + alternative_if_not ARM64_HAS_UAO +8888: ldp \reg1, \reg2, [\addr], \post_inc; +8889: nop; + nop; + alternative_else + ldtr \reg1, [\addr]; + ldtr \reg2, [\addr, #8]; + add \addr, \addr, \post_inc; + alternative_endif + + .section __ex_table,"a"; + .align 3; + .quad 8888b,\l; + .quad 8889b,\l; + .previous; + .endm + + .macro uao_stp l, reg1, reg2, addr, post_inc + alternative_if_not ARM64_HAS_UAO +8888: stp \reg1, \reg2, [\addr], \post_inc; +8889: nop; + nop; + alternative_else + sttr \reg1, [\addr]; + sttr \reg2, [\addr, #8]; + add \addr, \addr, \post_inc; + alternative_endif + + .section __ex_table,"a"; + .align 3; + .quad 8888b,\l; + .quad 8889b,\l; + .previous + .endm + + .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc + alternative_if_not ARM64_HAS_UAO +8888: \inst \reg, [\addr], \post_inc; + nop; + alternative_else + \alt_inst \reg, [\addr]; + add \addr, \addr, \post_inc; + alternative_endif + + .section __ex_table,"a"; + .align 3; + .quad 8888b,\l; + .previous + .endm +#else + .macro uao_ldp l, reg1, reg2, addr, post_inc + USER(\l, ldp \reg1, \reg2, [\addr], \post_inc) + .endm + .macro uao_stp l, reg1, reg2, addr, post_inc + USER(\l, stp \reg1, \reg2, [\addr], \post_inc) + .endm + .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc + USER(\l, \inst \reg, [\addr], \post_inc) + .endm +#endif + #endif /* __ASSEMBLY__ */ /* |