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4356e9f8 |
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09-Feb-2024 |
Linus Torvalds <torvalds@linux-foundation.org> |
work around gcc bugs with 'asm goto' with outputs We've had issues with gcc and 'asm goto' before, and we created a 'asm_volatile_goto()' macro for that in the past: see commits 3f0116c3238a ("compiler/gcc4: Add quirk for 'asm goto' miscompilation bug") and a9f180345f53 ("compiler/gcc4: Make quirk for asm_volatile_goto() unconditional"). Then, much later, we ended up removing the workaround in commit 43c249ea0b1e ("compiler-gcc.h: remove ancient workaround for gcc PR 58670") because we no longer supported building the kernel with the affected gcc versions, but we left the macro uses around. Now, Sean Christopherson reports a new version of a very similar problem, which is fixed by re-applying that ancient workaround. But the problem in question is limited to only the 'asm goto with outputs' cases, so instead of re-introducing the old workaround as-is, let's rename and limit the workaround to just that much less common case. It looks like there are at least two separate issues that all hit in this area: (a) some versions of gcc don't mark the asm goto as 'volatile' when it has outputs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98619 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110420 which is easy to work around by just adding the 'volatile' by hand. (b) Internal compiler errors: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110422 which are worked around by adding the extra empty 'asm' as a barrier, as in the original workaround. but the problem Sean sees may be a third thing since it involves bad code generation (not an ICE) even with the manually added 'volatile'. but the same old workaround works for this case, even if this feels a bit like voodoo programming and may only be hiding the issue. Reported-and-tested-by: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/ Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Uros Bizjak <ubizjak@gmail.com> Cc: Jakub Jelinek <jakub@redhat.com> Cc: Andrew Pinski <quic_apinski@quicinc.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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de66cb37 |
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16-Oct-2023 |
Mark Rutland <mark.rutland@arm.com> |
arm64: Add cpucap_is_possible() Many cpucaps can only be set when certain CONFIG_* options are selected, and we need to check the CONFIG_* option before the cap in order to avoid generating redundant code. Due to this, we have a growing number of helpers in <asm/cpufeature.h> of the form: | static __always_inline bool system_supports_foo(void) | { | return IS_ENABLED(CONFIG_ARM64_FOO) && | cpus_have_const_cap(ARM64_HAS_FOO); | } This is unfortunate as it forces us to use cpus_have_const_cap() unnecessarily, resulting in redundant code being generated by the compiler. In the vast majority of cases, we only require that feature checks indicate the presence of a feature after cpucaps have been finalized, and so it would be sufficient to use alternative_has_cap_*(). However some code needs to handle a feature before alternatives have been patched, and must test the system_cpucaps bitmap via cpus_have_const_cap(). In other cases we'd like to check for unintentional usage of a cpucap before alternatives are patched, and so it would be preferable to use cpus_have_final_cap(). Placing the IS_ENABLED() checks in each callsite is tedious and error-prone, and the same applies for writing wrappers for each comination of cpucap and alternative_has_cap_*() / cpus_have_cap() / cpus_have_final_cap(). It would be nicer if we could centralize the knowledge of which cpucaps are possible, and have alternative_has_cap_*(), cpus_have_cap(), and cpus_have_final_cap() handle this automatically. This patch adds a new cpucap_is_possible() function which will be responsible for checking the CONFIG_* option, and updates the low-level cpucap checks to use this. The existing CONFIG_* checks in <asm/cpufeature.h> are moved over to cpucap_is_possible(), but the (now trival) wrapper functions are retained for now. There should be no functional change as a result of this patch alone. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Mark Brown <broonie@kernel.org> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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#
5235c7e2 |
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07-Jun-2023 |
Mark Rutland <mark.rutland@arm.com> |
arm64: alternatives: use cpucap naming To more clearly align the various users of the cpucap enumeration, this patch changes the alternative code to use the term `cpucap` in favour of `feature`. The alternative_has_feature_{likely,unlikely}() functions are renamed to alternative_has_cap_<likely,unlikely}() to more clearly align with the cpus_have_{const_,}cap() helpers. At the same time remove the stale comment referring to the "ARM64_CB bit", which is evidently a typo for ARM64_CB_PATCH, which was removed in commit: 4c0bd995d73ed889 ("arm64: alternatives: have callbacks take a cap") There should be no functional change as a result of this patch; this is purely a renaming exercise. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Mark Brown <broonie@kernel.org> Cc: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20230607164846.3967305-3-mark.rutland@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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#
b9024f87 |
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06-Oct-2022 |
Jisheng Zhang <jszhang@kernel.org> |
arm64: alternative: constify alternative_has_feature_* argument Inspired by x86 commit 864b435514b2("x86/jump_label: Mark arguments as const to satisfy asm constraints"), constify alternative_has_feature_* argument to satisfy asm constraints. And Steven in [1] also pointed out that "The "i" constraint needs to be a constant." Tested with building a simple external kernel module with "O0". Before the patch, got similar gcc warnings and errors as below: In file included from <command-line>: In function ‘alternative_has_feature_likely’, inlined from ‘system_capabilities_finalized’ at arch/arm64/include/asm/cpufeature.h:440:9, inlined from ‘arm64_preempt_schedule_irq’ at arch/arm64/kernel/entry-common.c:264:6: include/linux/compiler_types.h:285:33: warning: ‘asm’ operand 0 probably does not match constraints 285 | #define asm_volatile_goto(x...) asm goto(x) | ^~~ arch/arm64/include/asm/alternative-macros.h:232:9: note: in expansion of macro ‘asm_volatile_goto’ 232 | asm_volatile_goto( | ^~~~~~~~~~~~~~~~~ include/linux/compiler_types.h:285:33: error: impossible constraint in ‘asm’ 285 | #define asm_volatile_goto(x...) asm goto(x) | ^~~ arch/arm64/include/asm/alternative-macros.h:232:9: note: in expansion of macro ‘asm_volatile_goto’ 232 | asm_volatile_goto( | ^~~~~~~~~~~~~~~~~ After the patch, the simple external test kernel module is built fine with "-O0". [1]https://lore.kernel.org/all/20210212094059.5f8d05e8@gandalf.local.home/ Signed-off-by: Jisheng Zhang <jszhang@kernel.org> Link: https://lore.kernel.org/r/20221006075542.2658-3-jszhang@kernel.org Signed-off-by: Will Deacon <will@kernel.org>
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d2995249 |
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03-Oct-2022 |
Nathan Chancellor <nathan@kernel.org> |
arm64: alternatives: Use vdso/bits.h instead of linux/bits.h When building with CONFIG_LTO after commit ba00c2a04fa5 ("arm64: fix the build with binutils 2.27"), the following build error occurs: In file included from arch/arm64/kernel/module-plts.c:6: In file included from include/linux/elf.h:6: In file included from arch/arm64/include/asm/elf.h:8: In file included from arch/arm64/include/asm/hwcap.h:9: In file included from arch/arm64/include/asm/cpufeature.h:9: In file included from arch/arm64/include/asm/alternative-macros.h:5: In file included from include/linux/bits.h:22: In file included from include/linux/build_bug.h:5: In file included from include/linux/compiler.h:248: In file included from arch/arm64/include/asm/rwonce.h:71: include/asm-generic/rwonce.h:67:9: error: expected string literal in 'asm' return __READ_ONCE(*(unsigned long *)addr); ^ arch/arm64/include/asm/rwonce.h:43:16: note: expanded from macro '__READ_ONCE' asm volatile(__LOAD_RCPC(b, %w0, %1) \ ^ arch/arm64/include/asm/rwonce.h:17:2: note: expanded from macro '__LOAD_RCPC' ALTERNATIVE( \ ^ Similar to the issue resolved by commit 0072dc1b53c3 ("arm64: avoid BUILD_BUG_ON() in alternative-macros"), there is a circular include dependency through <linux/bits.h> when CONFIG_LTO is enabled due to <asm/rwonce.h> appearing in the include chain before the contents of <asm/alternative-macros.h>, which results in ALTERNATIVE() not getting expanded properly because it has not been defined yet. Avoid this issue by including <vdso/bits.h>, which includes the definition of the BIT() macro, instead of <linux/bits.h>, as BIT() is the only macro from bits.h that is relevant to this header. Fixes: ba00c2a04fa5 ("arm64: fix the build with binutils 2.27") Link: https://github.com/ClangBuiltLinux/linux/issues/1728 Signed-off-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20221003193759.1141709-1-nathan@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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#
ba00c2a0 |
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29-Sep-2022 |
Mark Rutland <mark.rutland@arm.com> |
arm64: fix the build with binutils 2.27 Jon Hunter reports that for some toolchains the build has been broken since commit: 4c0bd995d73ed889 ("arm64: alternatives: have callbacks take a cap") ... with a stream of build-time splats of the form: | CC arch/arm64/kvm/hyp/vhe/debug-sr.o | /tmp/ccY3kbki.s: Assembler messages: | /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')' | /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')' | /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')' | /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')' | /tmp/ccY3kbki.s:1600: Error: junk at end of line, first unrecognized character | is `L' | /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')' | /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')' | /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')' | /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')' | /tmp/ccY3kbki.s:1723: Error: junk at end of line, first unrecognized character | is `L' | scripts/Makefile.build:249: recipe for target | 'arch/arm64/kvm/hyp/vhe/debug-sr.o' failed The issue here is that older versions of binutils (up to and including 2.27.0) don't like an 'L' suffix on constants. For plain assembly files, UL() avoids this suffix, but in C files this gets added, and so for inline assembly we can't directly use a constant defined with `UL()`. We could avoid this by passing the constant as an input parameter, but this isn't practical given the way we use the alternative macros. Instead, just open code the constant without the `UL` suffix, and for consistency do this for both the inline assembly macro and the regular assembly macro. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Fixes: 4c0bd995d73e ("arm64: alternatives: have callbacks take a cap") Reported-by: Jon Hunter <jonathanh@nvidia.com> Link: https://lore.kernel.org/linux-arm-kernel/3cecc3a5-30b0-f0bd-c3de-9e09bd21909b@nvidia.com/ Tested-by: Jon Hunter <jonathanh@nvidia.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20220929150227.1028556-1-mark.rutland@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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#
0072dc1b |
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20-Sep-2022 |
Mark Rutland <mark.rutland@arm.com> |
arm64: avoid BUILD_BUG_ON() in alternative-macros Nathan reports that the build fails when using clang and LTO: | In file included from kernel/bounds.c:10: | In file included from ./include/linux/page-flags.h:10: | In file included from ./include/linux/bug.h:5: | In file included from ./arch/arm64/include/asm/bug.h:26: | In file included from ./include/asm-generic/bug.h:5: | In file included from ./include/linux/compiler.h:248: | In file included from ./arch/arm64/include/asm/rwonce.h:11: | ./arch/arm64/include/asm/alternative-macros.h:224:2: error: call to undeclared function 'BUILD_BUG_ON'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] | BUILD_BUG_ON(feature >= ARM64_NCAPS); | ^ | ./arch/arm64/include/asm/alternative-macros.h:241:2: error: call to undeclared function 'BUILD_BUG_ON'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] | BUILD_BUG_ON(feature >= ARM64_NCAPS); | ^ | 2 errors generated. ... the problem being that when LTO is enabled, <asm/rwonce.h> includes <asm/alternative-macros.h>, and causes a circular include dependency through <linux/bug.h>. This manifests as BUILD_BUG_ON() not being defined when used within <asm/alternative-macros.h>. This patch avoids the problem and simplifies the include dependencies by using compiletime_assert() instead of BUILD_BUG_ON(). Signed-off-by: Mark Rutland <mark.rutland@arm.com> Fixes: 21fb26bfb01f ("arm64: alternatives: add alternative_has_feature_*()") Reported-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Link: http://lore.kernel.org/r/YyigTrxhE3IRPzjs@dev-arch.thelio-3990X Cc: Ard Biesheuvel <ardb@kernel.org> Cc: James Morse <james.morse@arm.com> Cc: Joey Gouly <joey.gouly@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Will Deacon <will@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220920140044.1709073-1-mark.rutland@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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#
d926079f |
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12-Sep-2022 |
Mark Rutland <mark.rutland@arm.com> |
arm64: alternatives: add shared NOP callback For each instance of an alternative, the compiler outputs a distinct copy of the alternative instructions into a subsection. As the compiler doesn't have special knowledge of alternatives, it cannot coalesce these to save space. In a defconfig kernel built with GCC 12.1.0, there are approximately 10,000 instances of alternative_has_feature_likely(), where the replacement instruction is always a NOP. As NOPs are position-independent, we don't need a unique copy per alternative sequence. This patch adds a callback to patch an alternative sequence with NOPs, and make use of this in alternative_has_feature_likely(). So that this can be used for other sites in future, this is written to patch multiple instructions up to the original sequence length. For NVHE, an alias is added to image-vars.h. For modules, the callback is exported. Note that as modules are loaded within 2GiB of the kernel, an alt_instr entry in a module can always refer directly to the callback, and no special handling is necessary. When building with GCC 12.1.0, the vmlinux is ~158KiB smaller, though the resulting Image size is unchanged due to alignment constraints and padding: | % ls -al vmlinux-* | -rwxr-xr-x 1 mark mark 134644592 Sep 1 14:52 vmlinux-after | -rwxr-xr-x 1 mark mark 134486232 Sep 1 14:50 vmlinux-before | % ls -al Image-* | -rw-r--r-- 1 mark mark 37108224 Sep 1 14:52 Image-after | -rw-r--r-- 1 mark mark 37108224 Sep 1 14:50 Image-before Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: James Morse <james.morse@arm.com> Cc: Joey Gouly <joey.gouly@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Will Deacon <will@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20220912162210.3626215-9-mark.rutland@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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#
21fb26bf |
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12-Sep-2022 |
Mark Rutland <mark.rutland@arm.com> |
arm64: alternatives: add alternative_has_feature_*() Currrently we use a mixture of alternative sequences and static branches to handle features detected at boot time. For ease of maintenance we generally prefer to use static branches in C code, but this has a few downsides: * Each static branch has metadata in the __jump_table section, which is not discarded after features are finalized. This wastes some space, and slows down the patching of other static branches. * The static branches are patched at a different point in time from the alternatives, so changes are not atomic. This leaves a transient period where there could be a mismatch between the behaviour of alternatives and static branches, which could be problematic for some features (e.g. pseudo-NMI). * More (instrumentable) kernel code is executed to patch each static branch, which can be risky when patching certain features (e.g. irqflags management for pseudo-NMI). * When CONFIG_JUMP_LABEL=n, static branches are turned into a load of a flag and a conditional branch. This means it isn't safe to use such static branches in an alternative address space (e.g. the NVHE/PKVM hyp code), where the generated address isn't safe to acccess. To deal with these issues, this patch introduces new alternative_has_feature_*() helpers, which work like static branches but are patched using alternatives. This ensures the patching is performed at the same time as other alternative patching, allows the metadata to be freed after patching, and is safe for use in alternative address spaces. Note that all supported toolchains have asm goto support, and since commit: a0a12c3ed057af57 ("asm goto: eradicate CC_HAS_ASM_GOTO)" ... the CC_HAS_ASM_GOTO Kconfig symbol has been removed, so no feature check is necessary, and we can always make use of asm goto. Additionally, note that: * This has no impact on cpus_have_cap(), which is a dynamic check. * This has no functional impact on cpus_have_const_cap(). The branches are patched slightly later than before this patch, but these branches are not reachable until caps have been finalised. * It is now invalid to use cpus_have_final_cap() in the window between feature detection and patching. All existing uses are only expected after patching anyway, so this should not be a problem. * The LSE atomics will now be enabled during alternatives patching rather than immediately before. As the LL/SC an LSE atomics are functionally equivalent this should not be problematic. When building defconfig with GCC 12.1.0, the resulting Image is 64KiB smaller: | % ls -al Image-* | -rw-r--r-- 1 mark mark 37108224 Aug 23 09:56 Image-after | -rw-r--r-- 1 mark mark 37173760 Aug 23 09:54 Image-before According to bloat-o-meter.pl: | add/remove: 44/34 grow/shrink: 602/1294 up/down: 39692/-61108 (-21416) | Function old new delta | [...] | Total: Before=16618336, After=16596920, chg -0.13% | add/remove: 0/2 grow/shrink: 0/0 up/down: 0/-1296 (-1296) | Data old new delta | arm64_const_caps_ready 16 - -16 | cpu_hwcap_keys 1280 - -1280 | Total: Before=8987120, After=8985824, chg -0.01% | add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0) | RO Data old new delta | Total: Before=18408, After=18408, chg +0.00% Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: James Morse <james.morse@arm.com> Cc: Joey Gouly <joey.gouly@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Will Deacon <will@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20220912162210.3626215-8-mark.rutland@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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#
4c0bd995 |
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12-Sep-2022 |
Mark Rutland <mark.rutland@arm.com> |
arm64: alternatives: have callbacks take a cap Today, callback alternatives are special-cased within __apply_alternatives(), and are applied alongside patching for system capabilities as ARM64_NCAPS is not part of the boot_capabilities feature mask. This special-casing is less than ideal. Giving special meaning to ARM64_NCAPS for this requires some structures and loops to use ARM64_NCAPS + 1 (AKA ARM64_NPATCHABLE), while others use ARM64_NCAPS. It's also not immediately clear callback alternatives are only applied when applying alternatives for system-wide features. To make this a bit clearer, changes the way that callback alternatives are identified to remove the special-casing of ARM64_NCAPS, and to allow callback alternatives to be associated with a cpucap as with all other alternatives. New cpucaps, ARM64_ALWAYS_BOOT and ARM64_ALWAYS_SYSTEM are added which are always detected alongside boot cpu capabilities and system capabilities respectively. All existing callback alternatives are made to use ARM64_ALWAYS_SYSTEM, and so will be patched at the same point during the boot flow as before. Subsequent patches will make more use of these new cpucaps. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: James Morse <james.morse@arm.com> Cc: Joey Gouly <joey.gouly@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Will Deacon <will@kernel.org> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20220912162210.3626215-7-mark.rutland@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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69bb0585 |
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18-Jun-2021 |
Mark Rutland <mark.rutland@arm.com> |
arm64: insn: avoid circular include dependency Nathan reports that when building with CONFIG_LTO_CLANG_THIN=y, the build fails due to BUILD_BUG_ON() not being defined before its uss in <asm/insn.h>. The problem is that with LTO, we patch READ_ONCE(), and <asm/rwonce.h> includes <asm/insn.h>, creating a circular include chain: <linux/build_bug.h> <linux/compiler.h> <asm/rwonce.h> <asm/alternative-macros.h> <asm/insn.h> <linux/build-bug.h> ... and so when <asm/insn.h> includes <linux/build_bug.h>, none of the BUILD_BUG* definitions have happened yet. To avoid this, let's move AARCH64_INSN_SIZE into a header without any dependencies, such that it can always be safely included. At the same time, avoid including <asm/alternative.h> in <asm/insn.h>, which should no longer be necessary (and doesn't make sense when insn.h is consumed by userspace). Reported-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20210621080830.GA37068@C02TD0UTHF1T.local Fixes: 3e00e39d9dad ("arm64: insn: move AARCH64_INSN_SIZE into <asm/insn.h>") Signed-off-by: Will Deacon <will@kernel.org>
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#
3e00e39d |
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09-Jun-2021 |
Mark Rutland <mark.rutland@arm.com> |
arm64: insn: move AARCH64_INSN_SIZE into <asm/insn.h> For histroical reasons, we define AARCH64_INSN_SIZE in <asm/alternative-macros.h>, but it would make more sense to do so in <asm/insn.h>. Let's move it into <asm/insn.h>, and add the necessary include directives for this. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/r/20210609102301.17332-3-mark.rutland@arm.com Signed-off-by: Will Deacon <will@kernel.org>
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55272ecc |
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24-May-2021 |
Fuad Tabba <tabba@google.com> |
arm64: assembler: remove user_alt user_alt isn't being used anymore. It's also simpler and clearer to directly use alternative_insn and _cond_extable in-line when needed. Reported-by: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/linux-arm-kernel/20210520125735.GF17233@C02TD0UTHF1T.local/ Signed-off-by: Fuad Tabba <tabba@google.com> Acked-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20210524083001.2586635-8-tabba@google.com Signed-off-by: Will Deacon <will@kernel.org>
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22315a22 |
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13-Apr-2021 |
Nathan Chancellor <nathan@kernel.org> |
arm64: alternatives: Move length validation in alternative_{insn, endif} After commit 2decad92f473 ("arm64: mte: Ensure TIF_MTE_ASYNC_FAULT is set atomically"), LLVM's integrated assembler fails to build entry.S: <instantiation>:5:7: error: expected assembly-time absolute expression .org . - (664b-663b) + (662b-661b) ^ <instantiation>:6:7: error: expected assembly-time absolute expression .org . - (662b-661b) + (664b-663b) ^ The root cause is LLVM's assembler has a one-pass design, meaning it cannot figure out these instruction lengths when the .org directive is outside of the subsection that they are in, which was changed by the .arch_extension directive added in the above commit. Apply the same fix from commit 966a0acce2fc ("arm64/alternatives: move length validation inside the subsection") to the alternative_endif macro, shuffling the .org directives so that the length validation happen will always happen in the same subsections. alternative_insn has not shown any issue yet but it appears that it could have the same issue in the future so just preemptively change it. Fixes: f7b93d42945c ("arm64/alternatives: use subsections for replacement sequences") Cc: <stable@vger.kernel.org> # 5.8.x Link: https://github.com/ClangBuiltLinux/linux/issues/1347 Signed-off-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Link: https://lore.kernel.org/r/20210414000803.662534-1-nathan@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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7cda23da |
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30-Jun-2020 |
Will Deacon <will@kernel.org> |
arm64: alternatives: Split up alternative.h asm/alternative.h contains both the macros needed to use alternatives, as well the type definitions and function prototypes for applying them. Split the header in two, so that alternatives can be used from core header files such as linux/compiler.h without the risk of circular includes Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will@kernel.org>
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