Re: [PATCH v1 01/13] arm64: Do not enable uaccess for flush_icache_range
From: Mark Rutland <mark.rutland@arm.com>
Date: 2021-05-11 15:25:11
Hi Fuad, On Tue, May 11, 2021 at 03:42:40PM +0100, Fuad Tabba wrote:
__flush_icache_range works on the kernel linear map, and doesn't need uaccess. The existing code is a side-effect of its current implementation with __flush_cache_user_range fallthrough. Instead of fallthrough to share the code, use a common macro for the two where the caller can specify whether user-space access is needed.
FWIW, I agree that we should fix __flush_icache_range to not map fiddle with uaccess, and that we should split these.
No functional change intended.
There is a performance change here, since the existing `__flush_cache_user_range` takes IDC and DIC into account, whereas `invalidate_icache_by_line` does not. There's also an existing oversight where `__flush_cache_user_range` takes ARM64_WORKAROUND_CLEAN_CACHE into account, but `invalidate_icache_by_line` does not. I think that's a bug that we should fix first, so that we can backport something to stable. Arguably similar is true in `swsusp_arch_suspend_exit`, but for that we could add a comment and always use `DC CIVAC`. Thanks, Mark.
quoted hunk ↗ jump to hunk
Reported-by: Catalin Marinas <catalin.marinas@arm.com> Reported-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/linux-arch/20200511110014.lb9PEahJ4hVOYrbwIb_qUHXyNy9KQzNFdb_I3YlzY6A@z/ Signed-off-by: Fuad Tabba <redacted> --- arch/arm64/include/asm/assembler.h | 13 ++++-- arch/arm64/mm/cache.S | 64 +++++++++++++++++++++--------- 2 files changed, 54 insertions(+), 23 deletions(-)diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index 8418c1bd8f04..6ff7a3a3b238 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h@@ -426,16 +426,21 @@ alternative_endif * Macro to perform an instruction cache maintenance for the interval * [start, end) * - * start, end: virtual addresses describing the region - * label: A label to branch to on user fault. - * Corrupts: tmp1, tmp2 + * start, end: virtual addresses describing the region + * needs_uaccess: might access user space memory + * label: label to branch to on user fault (if needs_uaccess) + * Corrupts: tmp1, tmp2 */ - .macro invalidate_icache_by_line start, end, tmp1, tmp2, label + .macro invalidate_icache_by_line start, end, tmp1, tmp2, needs_uaccess, label icache_line_size \tmp1, \tmp2 sub \tmp2, \tmp1, #1 bic \tmp2, \start, \tmp2 9997: + .if \needs_uaccess USER(\label, ic ivau, \tmp2) // invalidate I line PoU + .else + ic ivau, \tmp2 + .endif add \tmp2, \tmp2, \tmp1 cmp \tmp2, \end b.lo 9997bdiff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S index 2d881f34dd9d..092f73acdf9a 100644 --- a/arch/arm64/mm/cache.S +++ b/arch/arm64/mm/cache.S@@ -15,30 +15,20 @@ #include <asm/asm-uaccess.h> /* - * flush_icache_range(start,end) + * __flush_cache_range(start,end) [needs_uaccess] * * Ensure that the I and D caches are coherent within specified region. * This is typically used when code has been written to a memory region, * and will be executed. * - * - start - virtual start address of region - * - end - virtual end address of region + * - start - virtual start address of region + * - end - virtual end address of region + * - needs_uaccess - (macro parameter) might access user space memory */ -SYM_FUNC_START(__flush_icache_range) - /* FALLTHROUGH */ - -/* - * __flush_cache_user_range(start,end) - * - * Ensure that the I and D caches are coherent within specified region. - * This is typically used when code has been written to a memory region, - * and will be executed. - * - * - start - virtual start address of region - * - end - virtual end address of region - */ -SYM_FUNC_START(__flush_cache_user_range) +.macro __flush_cache_range, needs_uaccess + .if \needs_uaccess uaccess_ttbr0_enable x2, x3, x4 + .endif alternative_if ARM64_HAS_CACHE_IDC dsb ishst b 7f@@ -47,7 +37,11 @@ alternative_else_nop_endif sub x3, x2, #1 bic x4, x0, x3 1: + .if \needs_uaccess user_alt 9f, "dc cvau, x4", "dc civac, x4", ARM64_WORKAROUND_CLEAN_CACHE + .else +alternative_insn "dc cvau, x4", "dc civac, x4", ARM64_WORKAROUND_CLEAN_CACHE + .endif add x4, x4, x2 cmp x4, x1 b.lo 1b@@ -58,15 +52,47 @@ alternative_if ARM64_HAS_CACHE_DIC isb b 8f alternative_else_nop_endif - invalidate_icache_by_line x0, x1, x2, x3, 9f + invalidate_icache_by_line x0, x1, x2, x3, \needs_uaccess, 9f 8: mov x0, #0 1: + .if \needs_uaccess uaccess_ttbr0_disable x1, x2 + .endif ret + + .if \needs_uaccess 9: mov x0, #-EFAULT b 1b + .endif +.endm + +/* + * flush_icache_range(start,end) + * + * Ensure that the I and D caches are coherent within specified region. + * This is typically used when code has been written to a memory region, + * and will be executed. + * + * - start - virtual start address of region + * - end - virtual end address of region + */ +SYM_FUNC_START(__flush_icache_range) + __flush_cache_range needs_uaccess=0 SYM_FUNC_END(__flush_icache_range) + +/* + * __flush_cache_user_range(start,end) + * + * Ensure that the I and D caches are coherent within specified region. + * This is typically used when code has been written to a memory region, + * and will be executed. + * + * - start - virtual start address of region + * - end - virtual end address of region + */ +SYM_FUNC_START(__flush_cache_user_range) + __flush_cache_range needs_uaccess=1 SYM_FUNC_END(__flush_cache_user_range) /*@@ -86,7 +112,7 @@ alternative_else_nop_endif uaccess_ttbr0_enable x2, x3, x4 - invalidate_icache_by_line x0, x1, x2, x3, 2f + invalidate_icache_by_line x0, x1, x2, x3, 1, 2f mov x0, xzr 1: uaccess_ttbr0_disable x1, x2-- 2.31.1.607.g51e8a6a459-goog
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