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AJvYcCW//rki2OGkVliVcShSCvH6Afjw5suPblOLWUNwTawwNTyGyQbg0VmAWSbuNWBDVR9RsSX/IiaEqXU=@lists.xenproject.org X-Gm-Message-State: AOJu0YxWahdq/ia5a6ky5ArlkgxQ8sxukynaLc6NE9CFvLWqpb3nJoUZ T6cnDYs3NUfeubQ32J88xOfch71LDpUTgszmQ4qNdHfLfhLyGd1SE3nskYCim50= X-Google-Smtp-Source: AGHT+IFQyAfe4VcuzRBKzDf3RvzDjdCIN/JVY5KA0hmrikio3IhdfPZ1TuGaq6F46X5YB7HhWPyNPw== X-Received: by 2002:a17:907:940f:b0:a9a:597:8cca with SMTP id a640c23a62f3a-a9de615f959mr1257000866b.45.1730214565871; Tue, 29 Oct 2024 08:09:25 -0700 (PDT) Message-ID: <6fed0353-d9eb-4e48-af49-15841bbfaacf@citrix.com> Date: Tue, 29 Oct 2024 15:09:23 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 1/5] x86/boot: Rework how 32bit C is linked/included for early boot To: Frediano Ziglio , xen-devel@lists.xenproject.org Cc: Jan Beulich , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Julien Grall , Stefano Stabellini , Anthony PERARD References: <20241029102942.162912-1-frediano.ziglio@cloud.com> <20241029102942.162912-2-frediano.ziglio@cloud.com> Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 29/10/2024 10:29 am, Frediano Ziglio wrote: > Right now, the two functions which were really too complicated to write > in asm are compiled as 32bit PIC, linked to a blob and included > directly, using global asm() to arrange for them to have function semantics. > > This is limiting and fragile; the use of data relocations will compile > fine but malfunction when used, creating hard-to-debug bugs. > > Furthermore, we would like to increase the amount of C, to > deduplicate/unify Xen's boot logic, as well as making it easier to > follow. Therefore, rework how the 32bit objects are included. > > Link all 32bit objects together first. This allows for sharing of logic > between translation units. Use differential linking and explicit > imports/exports to confirm that we only have the expected relocations, > and write the object back out as an assembly file so it can be linked > again as if it were 64bit, to integrate with the rest of Xen. > > This allows for the use of external references (e.g. access to global > variables) with reasonable assurance of doing so safely. > > No functional change. > > Signed-off-by: Frediano Ziglio > Reviewed-by: Anthony PERARD Acked-by: Andrew Cooper