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[109.42.51.207]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43d1ffbcf12sm23837335e9.12.2025.03.14.11.01.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Mar 2025 11:01:47 -0700 (PDT) Message-ID: <71188823-2a9e-4565-8ace-03a682d8d0da@redhat.com> Date: Fri, 14 Mar 2025 19:01:45 +0100 Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 08/41] arm64: Replace __ASSEMBLY__ with __ASSEMBLER__ in uapi headers To: Will Deacon , Arnd Bergmann Cc: linux-kernel@vger.kernel.org, Linux-Arch , Catalin Marinas References: <20250314071013.1575167-1-thuth@redhat.com> <20250314071013.1575167-9-thuth@redhat.com> <20250314115554.GA8986@willie-the-truck> <20250314134215.GA9171@willie-the-truck> Content-Language: en-US From: Thomas Huth Autocrypt: addr=thuth@redhat.com; keydata= xsFNBFH7eUwBEACzyOXKU+5Pcs6wNpKzrlJwzRl3VGZt95VCdb+FgoU9g11m7FWcOafrVRwU yYkTm9+7zBUc0sW5AuPGR/dp3pSLX/yFWsA/UB4nJsHqgDvDU7BImSeiTrnpMOTXb7Arw2a2 4CflIyFqjCpfDM4MuTmzTjXq4Uov1giGE9X6viNo1pxyEpd7PanlKNnf4PqEQp06X4IgUacW tSGj6Gcns1bCuHV8OPWLkf4hkRnu8hdL6i60Yxz4E6TqlrpxsfYwLXgEeswPHOA6Mn4Cso9O 0lewVYfFfsmokfAVMKWzOl1Sr0KGI5T9CpmRfAiSHpthhHWnECcJFwl72NTi6kUcUzG4se81 O6n9d/kTj7pzTmBdfwuOZ0YUSqcqs0W+l1NcASSYZQaDoD3/SLk+nqVeCBB4OnYOGhgmIHNW 0CwMRO/GK+20alxzk//V9GmIM2ACElbfF8+Uug3pqiHkVnKqM7W9/S1NH2qmxB6zMiJUHlTH gnVeZX0dgH27mzstcF786uPcdEqS0KJuxh2kk5IvUSL3Qn3ZgmgdxBMyCPciD/1cb7/Ahazr 3ThHQXSHXkH/aDXdfLsKVuwDzHLVSkdSnZdt5HHh75/NFHxwaTlydgfHmFFwodK8y/TjyiGZ zg2Kje38xnz8zKn9iesFBCcONXS7txENTzX0z80WKBhK+XSFJwARAQABzR5UaG9tYXMgSHV0 aCA8dGh1dGhAcmVkaGF0LmNvbT7CwXgEEwECACIFAlVgX6oCGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAAoJEC7Z13T+cC21EbIP/ii9cvT2HHGbFRl8HqGT6+7Wkb+XLMqJBMAIGiQK QIP3xk1HPTsLfVG0ao4hy/oYkGNOP8+ubLnZen6Yq3zAFiMhQ44lvgigDYJo3Ve59gfe99KX EbtB+X95ODARkq0McR6OAsPNJ7gpEUzfkQUUJTXRDQXfG/FX303Gvk+YU0spm2tsIKPl6AmV 1CegDljzjycyfJbk418MQmMu2T82kjrkEofUO2a24ed3VGC0/Uz//XCR2ZTo+vBoBUQl41BD eFFtoCSrzo3yPFS+w5fkH9NT8ChdpSlbNS32NhYQhJtr9zjWyFRf0Zk+T/1P7ECn6gTEkp5k ofFIA4MFBc/fXbaDRtBmPB0N9pqTFApIUI4vuFPPO0JDrII9dLwZ6lO9EKiwuVlvr1wwzsgq zJTPBU3qHaUO4d/8G+gD7AL/6T4zi8Jo/GmjBsnYaTzbm94lf0CjXjsOX3seMhaE6WAZOQQG tZHAO1kAPWpaxne+wtgMKthyPLNwelLf+xzGvrIKvLX6QuLoWMnWldu22z2ICVnLQChlR9d6 WW8QFEpo/FK7omuS8KvvopFcOOdlbFMM8Y/8vBgVMSsK6fsYUhruny/PahprPbYGiNIhKqz7 UvgyZVl4pBFjTaz/SbimTk210vIlkDyy1WuS8Zsn0htv4+jQPgo9rqFE4mipJjy/iboDzsFN BFH7eUwBEAC2nzfUeeI8dv0C4qrfCPze6NkryUflEut9WwHhfXCLjtvCjnoGqFelH/PE9NF4 4VPSCdvD1SSmFVzu6T9qWdcwMSaC+e7G/z0/AhBfqTeosAF5XvKQlAb9ZPkdDr7YN0a1XDfa +NgA+JZB4ROyBZFFAwNHT+HCnyzy0v9Sh3BgJJwfpXHH2l3LfncvV8rgFv0bvdr70U+On2XH 5bApOyW1WpIG5KPJlDdzcQTyptOJ1dnEHfwnABEfzI3dNf63rlxsGouX/NFRRRNqkdClQR3K gCwciaXfZ7ir7fF0u1N2UuLsWA8Ei1JrNypk+MRxhbvdQC4tyZCZ8mVDk+QOK6pyK2f4rMf/ WmqxNTtAVmNuZIwnJdjRMMSs4W4w6N/bRvpqtykSqx7VXcgqtv6eqoDZrNuhGbekQA0sAnCJ VPArerAZGArm63o39me/bRUQeQVSxEBmg66yshF9HkcUPGVeC4B0TPwz+HFcVhheo6hoJjLq knFOPLRj+0h+ZL+D0GenyqD3CyuyeTT5dGcNU9qT74bdSr20k/CklvI7S9yoQje8BeQAHtdV cvO8XCLrpGuw9SgOS7OP5oI26a0548M4KldAY+kqX6XVphEw3/6U1KTf7WxW5zYLTtadjISB X9xsRWSU+Yqs3C7oN5TIPSoj9tXMoxZkCIHWvnqGwZ7JhwARAQABwsFfBBgBAgAJBQJR+3lM AhsMAAoJEC7Z13T+cC21hPAQAIsBL9MdGpdEpvXs9CYrBkd6tS9mbaSWj6XBDfA1AEdQkBOn ZH1Qt7HJesk+qNSnLv6+jP4VwqK5AFMrKJ6IjE7jqgzGxtcZnvSjeDGPF1h2CKZQPpTw890k fy18AvgFHkVk2Oylyexw3aOBsXg6ukN44vIFqPoc+YSU0+0QIdYJp/XFsgWxnFIMYwDpxSHS 5fdDxUjsk3UBHZx+IhFjs2siVZi5wnHIqM7eK9abr2cK2weInTBwXwqVWjsXZ4tq5+jQrwDK cvxIcwXdUTLGxc4/Z/VRH1PZSvfQxdxMGmNTGaXVNfdFZjm4fz0mz+OUi6AHC4CZpwnsliGV ODqwX8Y1zic9viSTbKS01ZNp175POyWViUk9qisPZB7ypfSIVSEULrL347qY/hm9ahhqmn17 Ng255syASv3ehvX7iwWDfzXbA0/TVaqwa1YIkec+/8miicV0zMP9siRcYQkyTqSzaTFBBmqD oiT+z+/E59qj/EKfyce3sbC9XLjXv3mHMrq1tKX4G7IJGnS989E/fg6crv6NHae9Ckm7+lSs IQu4bBP2GxiRQ+NV3iV/KU3ebMRzqIC//DCOxzQNFNJAKldPe/bKZMCxEqtVoRkuJtNdp/5a yXFZ6TfE1hGKrDBYAm4vrnZ4CXFSBDllL59cFFOJCkn4Xboj/aVxxJxF30bn In-Reply-To: <20250314134215.GA9171@willie-the-truck> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 14/03/2025 14.42, Will Deacon wrote: > On Fri, Mar 14, 2025 at 01:05:15PM +0100, Arnd Bergmann wrote: >> On Fri, Mar 14, 2025, at 12:55, Will Deacon wrote: >>> On Fri, Mar 14, 2025 at 08:09:39AM +0100, Thomas Huth wrote: >>>> __ASSEMBLY__ is only defined by the Makefile of the kernel, so >>>> this is not really useful for uapi headers (unless the userspace >>>> Makefile defines it, too). Let's switch to __ASSEMBLER__ which >>>> gets set automatically by the compiler when compiling assembly >>>> code. >>>> >>>> Cc: Catalin Marinas >>>> Cc: Will Deacon >>>> Signed-off-by: Thomas Huth >>>> --- >>>> arch/arm64/include/uapi/asm/kvm.h | 2 +- >>>> arch/arm64/include/uapi/asm/ptrace.h | 4 ++-- >>>> arch/arm64/include/uapi/asm/sigcontext.h | 4 ++-- >>>> 3 files changed, 5 insertions(+), 5 deletions(-) >>> >>> Is there a risk of breaking userspace with this? I wonder if it would >>> be more conservative to do something like: >>> >>> #if !defined(__ASSEMBLY__) && !defined(__ASSEMBLER__) >>> >>> so that if somebody is doing '#define __ASSEMBLY__' then they get the >>> same behaviour as today. >>> >>> Or maybe we don't care? >> >> I think the main risk we would have is user applications relying >> on the __ASSEMBLER__ checks in new kernel headers and not defining >> __ASSEMBLY__. This would result in the application not building >> against old kernel headers that only check against __ASSEMBLY__. > > Hmm. I hadn't thought about the case of old headers :/ > > A quick Debian codesearch shows that glibc might #define __ASSEMBLY__ > for some arch-specific headers: > > https://codesearch.debian.net/search?q=%23define+__ASSEMBLY__&literal=1 > > which is what I was more worried about. Since both, GCC and Clang, define __ASSEMBLER__ since a long time (Arnd checked GCC 2.95, and I checked that at least Clang 7.0 still has it), I think the only problem might be other compiler toolchains that might not set __ASSEMBLER__ automatically. I just checked Tiny-C 0.9.27, and that also sets __ASSEMBLER__ already. And according to https://github.com/IanHarvey/pcc/blob/master/cc/cc/cc.1#L405 it is also set in PCC. I haven't spotted it in LCC though (which seems to be an old C89 compiler if I got it right). So if we are worried about such exotic old compilers, it's maybe better to check both, __ASSEMBLY__ and __ASSEMBLER__ in the uapi files? Or would it be ok to force those few people to set __ASSEMBLER__ manually in their Makefiles (just like they had to do before with __ASSEMBLY__) in case they want to compile assembler code with such exotic compilers and new kernel headers? Thomas