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([172.25.112.68]) by orsmga007.jf.intel.com with ESMTP; 19 Dec 2022 23:01:19 -0800 From: Xin Li To: linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org, andrew.cooper3@citrix.com, seanjc@google.com, pbonzini@redhat.com, ravi.v.shankar@intel.com Subject: [RFC PATCH 28/32] x86/fred: fixup fault on ERETU by jumping to fred_entrypoint_user Date: Mon, 19 Dec 2022 22:36:54 -0800 Message-Id: <20221220063658.19271-29-xin3.li@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221220063658.19271-1-xin3.li@intel.com> References: <20221220063658.19271-1-xin3.li@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If the stack frame contains an invalid user context (e.g. due to invalid SS, a non-canonical RIP, etc.) the ERETU instruction will trap (#SS or #GP). >From a Linux point of view, this really should be considered a user space failure, so use the standard fault fixup mechanism to intercept the fault, fix up the exception frame, and redirect execution to fred_entrypoint_user. The end result is that it appears just as if the hardware had taken the exception immediately after completing the transition to user space. Suggested-by: H. Peter Anvin (Intel) Signed-off-by: Xin Li --- arch/x86/entry/entry_64_fred.S | 8 +++++-- arch/x86/include/asm/extable_fixup_types.h | 4 ++++ arch/x86/mm/extable.c | 28 ++++++++++++++++++++++ 3 files changed, 38 insertions(+), 2 deletions(-) diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S index 1fb765fd3871..027ef8f1e600 100644 --- a/arch/x86/entry/entry_64_fred.S +++ b/arch/x86/entry/entry_64_fred.S @@ -5,8 +5,10 @@ * The actual FRED entry points. */ #include -#include +#include #include +#include +#include #include #include "calling.h" @@ -38,7 +40,9 @@ SYM_CODE_START_NOALIGN(fred_entrypoint_user) call fred_entry_from_user SYM_INNER_LABEL(fred_exit_user, SYM_L_GLOBAL) FRED_EXIT - ERETU +1: ERETU + + _ASM_EXTABLE_TYPE(1b, fred_entrypoint_user, EX_TYPE_ERETU) SYM_CODE_END(fred_entrypoint_user) /* diff --git a/arch/x86/include/asm/extable_fixup_types.h b/arch/x86/include/asm/extable_fixup_types.h index 991e31cfde94..ddebd5b8b340 100644 --- a/arch/x86/include/asm/extable_fixup_types.h +++ b/arch/x86/include/asm/extable_fixup_types.h @@ -66,4 +66,8 @@ #define EX_TYPE_ZEROPAD 20 /* longword load with zeropad on fault */ +#ifdef CONFIG_X86_FRED +#define EX_TYPE_ERETU 21 +#endif + #endif diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c index 60814e110a54..be9d75358f50 100644 --- a/arch/x86/mm/extable.c +++ b/arch/x86/mm/extable.c @@ -6,6 +6,7 @@ #include #include +#include #include #include #include @@ -195,6 +196,29 @@ static bool ex_handler_ucopy_len(const struct exception_table_entry *fixup, return ex_handler_uaccess(fixup, regs, trapnr); } +#ifdef CONFIG_X86_FRED +static bool ex_handler_eretu(const struct exception_table_entry *fixup, + struct pt_regs *regs, unsigned long error_code) +{ + struct pt_regs *uregs = (struct pt_regs *)(regs->sp - offsetof(struct pt_regs, ip)); + unsigned short ss = uregs->ss; + unsigned short cs = uregs->cs; + + fred_info(uregs)->edata = fred_event_data(regs); + uregs->ssl = regs->ssl; + uregs->ss = ss; + uregs->csl = regs->csl; + uregs->current_stack_level = 0; + uregs->cs = cs; + uregs->orig_ax = error_code; + + /* drop error code */ + regs->sp -= 8; + + return ex_handler_default(fixup, regs); +} +#endif + int ex_get_fixup_type(unsigned long ip) { const struct exception_table_entry *e = search_exception_tables(ip); @@ -272,6 +296,10 @@ int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code, return ex_handler_ucopy_len(e, regs, trapnr, reg, imm); case EX_TYPE_ZEROPAD: return ex_handler_zeropad(e, regs, fault_addr); +#ifdef CONFIG_X86_FRED + case EX_TYPE_ERETU: + return ex_handler_eretu(e, regs, error_code); +#endif } BUG(); } -- 2.34.1