On Thu, Apr 23, 2020 at 12:59:05PM +0100, Catalin Marinas wrote: > On Thu, Apr 23, 2020 at 12:18:03PM +0100, Mark Brown wrote: > > On Wed, Apr 22, 2020 at 07:00:28PM +0100, Catalin Marinas wrote: > > > Forcing .S files to armv8.5 would not cause any problems with > > > the base armv8.0 that the kernel image support since it shouldn't change > > > the opcodes gas generates. The .S files would use alternatives anyway > > > (or simply have code not called). > > > > We do loose the checking that the assembler does that nobody used a > > newer feature by mistake but yeah, shouldn't affect the output. > > We may need some push/pop_arch macros to contain the supported features. > > The gas documentation says that .arch_extension may be used multiple > times to add or remove extensions. However, I couldn't find a way to > remove memtag after adding it (tried -memtag, !memtag, empty string). So > I may go with a '.arch armv8.0-a' as a base, followed by temporary > setting of '.arch armv8.5-a+memtag' (and hope we don't need combinations > of such extensions). Quick attempt at this on top of the MTE patches: diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index e7338e129dfd..6180ac605406 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -24,10 +24,18 @@ #include <asm/sysreg.h> #include <asm/thread_info.h> -#ifdef CONFIG_ARM64_MTE - .arch armv8.5-a - .arch_extension memtag -#endif + /* Base architecture version for the .S files */ + .arch armv8-a + + .macro arm64_set_arch, arch, enable = 1 + .if \enable + .arch \arch + .endif + .endm + + .macro arm64_reset_arch + .arch armv8-a + .endm .macro save_and_disable_daif, flags mrs \flags, daif diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index e4ab82e543cf..df2037fc431b 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -148,6 +148,7 @@ alternative_cb_end /* Check for MTE asynchronous tag check faults */ .macro check_mte_async_tcf, flgs, tmp #ifdef CONFIG_ARM64_MTE + arm64_set_arch armv8.5-a+memtag alternative_if_not ARM64_MTE b 1f alternative_else_nop_endif @@ -158,16 +159,19 @@ alternative_else_nop_endif str \flgs, [tsk, #TSK_TI_FLAGS] msr_s SYS_TFSRE0_EL1, xzr 1: + arm64_reset_arch #endif .endm /* Clear the MTE asynchronous tag check faults */ .macro clear_mte_async_tcf #ifdef CONFIG_ARM64_MTE + arm64_set_arch armv8.5-a+memtag alternative_if ARM64_MTE dsb ish msr_s SYS_TFSRE0_EL1, xzr alternative_else_nop_endif + arm64_reset_arch #endif .endm diff --git a/arch/arm64/lib/clear_page.S b/arch/arm64/lib/clear_page.S index 9f85a4cf9568..a8e26f232502 100644 --- a/arch/arm64/lib/clear_page.S +++ b/arch/arm64/lib/clear_page.S @@ -22,8 +22,10 @@ SYM_FUNC_START(clear_page) mov x2, #4 lsl x1, x2, x1 1: + arm64_set_arch armv8.5-a+memtag, IS_ENABLED(CONFIG_ARM64_MTE) alternative_insn "dc zva, x0", "stzgm xzr, [x0]", \ ARM64_MTE, IS_ENABLED(CONFIG_ARM64_MTE), 1 + arm64_reset_arch add x0, x0, x1 tst x0, #(PAGE_SIZE - 1) b.ne 1b diff --git a/arch/arm64/lib/copy_page.S b/arch/arm64/lib/copy_page.S index c3234175efe0..8322043e75e6 100644 --- a/arch/arm64/lib/copy_page.S +++ b/arch/arm64/lib/copy_page.S @@ -26,6 +26,7 @@ alternative_if ARM64_HAS_NO_HW_PREFETCH alternative_else_nop_endif #ifdef CONFIG_ARM64_MTE + arm64_set_arch armv8.5-a+memtag alternative_if_not ARM64_MTE b 2f alternative_else_nop_endif @@ -46,6 +47,7 @@ alternative_else_nop_endif tst x2, #(PAGE_SIZE - 1) b.ne 1b 2: + arm64_reset_arch #endif ldp x2, x3, [x1] diff --git a/arch/arm64/lib/mte.S b/arch/arm64/lib/mte.S index 45be04a8c73c..8f824fc62ad4 100644 --- a/arch/arm64/lib/mte.S +++ b/arch/arm64/lib/mte.S @@ -7,6 +7,8 @@ #include <asm/assembler.h> #include <asm/mte.h> + arm64_set_arch armv8.5-a+memtag + /* * Compare tags of two pages * x0 - page1 address -- Catalin
