Morello vDSO fixes#27
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Map the purecap vDSO into userspace application address space, therefore providing purecap userspace applications a purecap vDSO to use, and provide a capability to it in AT_SYSINFO_EHDR by updating ARCH_DLINFO. Redefine the aarch64 vDSO as the compat vDSO, therefore allowing both regular arm64 and purecap binaries to use a vDSO under PCuABI. Now that the purecap vDSO is mapped in purecap processes, instead of the standard aarch64 vDSO one, we also need to ensure that setup_return() uses the right offset for the sigret trampoline. This is done by including only the appropriate offsets header (which is possible as signal.c is built twice, once for purecap and once for compat64). The bootstrap Morello kselftest is also amended to expect AT_SYSINFO_EHDR to be a valid capability, not a null one. -- CHERI-Linux (Hesham): cherry-picked 21ed9c7 and fixed merge conflits: * Removed VVAR * Aligned with the current purecap-vdso paths and builds -- Signed-off-by: Aditya Deshpande <aditya.deshpande@arm.com> Co-developed-by: Kevin Brodsky <kevin.brodsky@arm.com> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com> Signed-off-by: Hesham Almatary <hesham.almatary@cl.cam.ac.uk>
vdso_u_time_data and vdso_u_rng_data were added after the original Morello port and purecap vDSO support. As a result, purecap users currently fall back to the generic accessors. However, the generic helpers return invalid capabilities because they derive capabilities from zero-sized linker-defined symbols. Implement purecap-specific accessors for these symbols, similar to __arch_get_vdso_data(), so tagged capabilities are returned to purecap userspace by deriving them from the valid vDSO mapping capability (PCC). Signed-off-by: Hesham Almatary <hesham.almatary@cl.cam.ac.uk>
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Jun 1, 2026
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The commit order should be swapped, otherwise the first commit will result in a broken vDSO being mapped.
| extern int purecap_setup_additional_pages(struct linux_binprm *bprm, | ||
| int uses_interp); | ||
| #define arch_setup_additional_pages purecap_setup_additional_pages | ||
| #define ARCH_DLINFO SETUP_DLINFO(current->mm->context.vdso) |
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Would be better to leave a tab between ARCH_DLINFO and SETUP_DLINFO to avoid polluting the diff, like in the original commit.
| #include <generated/vdso-offsets.h> | ||
| #ifdef CONFIG_COMPAT_VDSO | ||
| #include <generated/vdso32-offsets.h> | ||
| #endif |
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Why are we doing this?
| mmap_write_unlock(mm); | ||
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| return ret; | ||
| } |
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All of this was basically a copy/paste of the AA64 handlers below. Let's update it accordingly, now that vvar is gone this can be a lot simpler.
enum aarch64_map below should also be removed.
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This PR brings an original Morello commit that was missed in CHERI-Linux which is required for purecap Morello userspace. Furthermore, it adds a couple of accessors for new vDSO pointers that got introduced after the original Morello port and purecap vDSO was done.