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Shutemov" To: Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Ard Biesheuvel , "Paul E. McKenney" , Josh Poimboeuf , Xiongwei Song , Xin Li , "Mike Rapoport (IBM)" , Brijesh Singh , Michael Roth , Tony Luck , Alexey Kardashevskiy , Alexander Shishkin Cc: Jonathan Corbet , Sohil Mehta , Ingo Molnar , Pawan Gupta , Daniel Sneddon , Kai Huang , Sandipan Das , Breno Leitao , Rick Edgecombe , Alexei Starovoitov , Hou Tao , Juergen Gross , Vegard Nossum , Kees Cook , Eric Biggers , Jason Gunthorpe , "Masami Hiramatsu (Google)" , Andrew Morton , Luis Chamberlain , Yuntao Wang , Rasmus Villemoes , Christophe Leroy , Tejun Heo , Changbin Du , Huang Shijie , Geert Uytterhoeven , Namhyung Kim , Arnaldo Carvalho de Melo , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, linux-mm@kvack.org, "Kirill A. Shutemov" Subject: [PATCHv9 13/16] x86/traps: Handle LASS thrown #SS Date: Mon, 7 Jul 2025 11:03:13 +0300 Message-ID: <20250707080317.3791624-14-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250707080317.3791624-1-kirill.shutemov@linux.intel.com> References: <20250707080317.3791624-1-kirill.shutemov@linux.intel.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit LASS throws a #GP for any violations except for stack register accesses, in which case it throws a #SS instead. Handle this similarly to how other LASS violations are handled. In case of FRED, before handling #SS as LASS violation, kernel has to check if there's a fixup for the exception. It can address #SS due to invalid user context on ERETU. See 5105e7687ad3 ("x86/fred: Fixup fault on ERETU by jumping to fred_entrypoint_user") for more details. Co-developed-by: Alexander Shishkin Signed-off-by: Alexander Shishkin Signed-off-by: Kirill A. Shutemov --- arch/x86/kernel/traps.c | 41 +++++++++++++++++++++++++++++++++++------ 1 file changed, 35 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index f75d6a8dcf20..0f6f187b1a9e 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -418,12 +418,6 @@ DEFINE_IDTENTRY_ERRORCODE(exc_segment_not_present) SIGBUS, 0, NULL); } -DEFINE_IDTENTRY_ERRORCODE(exc_stack_segment) -{ - do_error_trap(regs, error_code, "stack segment", X86_TRAP_SS, SIGBUS, - 0, NULL); -} - DEFINE_IDTENTRY_ERRORCODE(exc_alignment_check) { char *str = "alignment check"; @@ -869,6 +863,41 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) cond_local_irq_disable(regs); } +#define SSFSTR "stack segment" + +DEFINE_IDTENTRY_ERRORCODE(exc_stack_segment) +{ + enum kernel_exc_hint hint; + unsigned long exc_addr; + + if (user_mode(regs)) + goto error_trap; + + if (cpu_feature_enabled(X86_FEATURE_FRED) && + fixup_exception(regs, X86_TRAP_SS, error_code, 0)) + return; + + if (!cpu_feature_enabled(X86_FEATURE_LASS)) + goto error_trap; + + if (notify_die(DIE_TRAP, SSFSTR, regs, error_code, + X86_TRAP_SS, SIGBUS) == NOTIFY_STOP) + return; + + hint = get_kernel_exc_address(regs, &exc_addr); + if (hint != EXC_NO_HINT) + printk(SSFSTR ", %s 0x%lx", kernel_exc_hint_help[hint], exc_addr); + + if (hint != EXC_NON_CANONICAL) + exc_addr = 0; + + die_addr(SSFSTR, regs, error_code, exc_addr); + return; + +error_trap: + do_error_trap(regs, error_code, SSFSTR, X86_TRAP_SS, SIGBUS, 0, NULL); +} + static bool do_int3(struct pt_regs *regs) { int res; -- 2.47.2