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Peter Anvin" , Thomas Gleixner , Ingo Molnar , kernel list , linux-doc@vger.kernel.org, Linux-MM , linux-arch , Linux API , Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 733C418038E67 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Aug 25, 2020 at 2:30 AM Yu-cheng Yu wrote: > Add REGSET_CET64/REGSET_CET32 to get/set CET MSRs: > > IA32_U_CET (user-mode CET settings) and > IA32_PL3_SSP (user-mode Shadow Stack) [...] > diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c [...] > +int cetregs_get(struct task_struct *target, const struct user_regset *regset, > + struct membuf to) > +{ > + struct fpu *fpu = &target->thread.fpu; > + struct cet_user_state *cetregs; > + > + if (!boot_cpu_has(X86_FEATURE_SHSTK)) > + return -ENODEV; > + > + fpu__prepare_read(fpu); > + cetregs = get_xsave_addr(&fpu->state.xsave, XFEATURE_CET_USER); > + if (!cetregs) > + return -EFAULT; Can this branch ever be hit without a kernel bug? If yes, I think -EFAULT is probably a weird error code to choose here. If no, this should probably use WARN_ON(). Same thing in cetregs_set(). > + return membuf_write(&to, cetregs, sizeof(struct cet_user_state)); > +} [...] > diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c [...] > @@ -52,7 +52,9 @@ enum x86_regset { > REGSET_IOPERM64 = REGSET_XFP, > REGSET_XSTATE, > REGSET_TLS, > + REGSET_CET64 = REGSET_TLS, > REGSET_IOPERM32, > + REGSET_CET32, > }; [...] > @@ -1229,6 +1231,13 @@ static struct user_regset x86_64_regsets[] __ro_after_init = { [...] > + [REGSET_CET64] = { > + .core_note_type = NT_X86_CET, > + .n = sizeof(struct cet_user_state) / sizeof(u64), > + .size = sizeof(u64), .align = sizeof(u64), > + .active = cetregs_active, .regset_get = cetregs_get, > + .set = cetregs_set > + }, > }; [...] > @@ -1284,6 +1293,13 @@ static struct user_regset x86_32_regsets[] __ro_after_init = { [...] > + [REGSET_CET32] = { > + .core_note_type = NT_X86_CET, > + .n = sizeof(struct cet_user_state) / sizeof(u64), > + .size = sizeof(u64), .align = sizeof(u64), > + .active = cetregs_active, .regset_get = cetregs_get, > + .set = cetregs_set > + }, > }; Why are there different identifiers for 32-bit CET and 64-bit CET when they operate on the same structs and have the same handlers? If there's a good reason for that, the commit message should probably point that out.