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Peter Anvin (Intel)" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/entry] x86/entry: Use int everywhere for system call numbers Cc: "H. Peter Anvin (Intel)" , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210518191303.4135296-7-hpa@zytor.com> References: <20210518191303.4135296-7-hpa@zytor.com> MIME-Version: 1.0 Message-ID: <162193039683.29796.7156654843953588379.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/entry branch of tip: Commit-ID: 2978996f620001f4e748c79af0fe89be729ef58d Gitweb: https://git.kernel.org/tip/2978996f620001f4e748c79af0fe89be729ef58d Author: H. Peter Anvin (Intel) AuthorDate: Tue, 18 May 2021 12:13:03 -07:00 Committer: Thomas Gleixner CommitterDate: Tue, 25 May 2021 10:07:00 +02:00 x86/entry: Use int everywhere for system call numbers System call numbers are defined as int, so use int everywhere for system call numbers. This is strictly a cleanup; it should not change anything user visible; all ABI changes have been done in the preceeding patches. [ tglx: Replaced the unsigned long cast ] Signed-off-by: H. Peter Anvin (Intel) Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210518191303.4135296-7-hpa@zytor.com --- arch/x86/entry/common.c | 87 ++++++++++++++++++++++----------- arch/x86/include/asm/syscall.h | 2 +- 2 files changed, 60 insertions(+), 29 deletions(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index f51bc17..ee95fe3 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -36,49 +36,81 @@ #include #ifdef CONFIG_X86_64 -__visible noinstr void do_syscall_64(struct pt_regs *regs, unsigned long nr) + +static __always_inline bool do_syscall_x64(struct pt_regs *regs, int nr) +{ + /* + * Convert negative numbers to very high and thus out of range + * numbers for comparisons. + */ + unsigned int unr = nr; + + if (likely(unr < NR_syscalls)) { + unr = array_index_nospec(unr, NR_syscalls); + regs->ax = sys_call_table[unr](regs); + return true; + } + return false; +} + +static __always_inline bool do_syscall_x32(struct pt_regs *regs, int nr) +{ + /* + * Adjust the starting offset of the table, and convert numbers + * < __X32_SYSCALL_BIT to very high and thus out of range + * numbers for comparisons. + */ + unsigned int xnr = nr - __X32_SYSCALL_BIT; + + if (IS_ENABLED(CONFIG_X86_X32_ABI) && likely(xnr < X32_NR_syscalls)) { + xnr = array_index_nospec(xnr, X32_NR_syscalls); + regs->ax = x32_sys_call_table[xnr](regs); + return true; + } + return false; +} + +__visible noinstr void do_syscall_64(struct pt_regs *regs, int nr) { add_random_kstack_offset(); nr = syscall_enter_from_user_mode(regs, nr); instrumentation_begin(); - if (likely(nr < NR_syscalls)) { - nr = array_index_nospec(nr, NR_syscalls); - regs->ax = sys_call_table[nr](regs); -#ifdef CONFIG_X86_X32_ABI - } else if (likely((nr & __X32_SYSCALL_BIT) && - (nr & ~__X32_SYSCALL_BIT) < X32_NR_syscalls)) { - nr = array_index_nospec(nr & ~__X32_SYSCALL_BIT, - X32_NR_syscalls); - regs->ax = x32_sys_call_table[nr](regs); -#endif - } else if (unlikely((int)nr != -1)) { + + if (!do_syscall_x64(regs, nr) && !do_syscall_x32(regs, nr) && nr != -1) { + /* Invalid system call, but still a system call. */ regs->ax = __x64_sys_ni_syscall(regs); } + instrumentation_end(); syscall_exit_to_user_mode(regs); } #endif #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) -static __always_inline unsigned int syscall_32_enter(struct pt_regs *regs) +static __always_inline int syscall_32_enter(struct pt_regs *regs) { if (IS_ENABLED(CONFIG_IA32_EMULATION)) current_thread_info()->status |= TS_COMPAT; - return (unsigned int)regs->orig_ax; + return (int)regs->orig_ax; } /* * Invoke a 32-bit syscall. Called with IRQs on in CONTEXT_KERNEL. */ -static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, - unsigned int nr) +static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, int nr) { - if (likely(nr < IA32_NR_syscalls)) { - nr = array_index_nospec(nr, IA32_NR_syscalls); - regs->ax = ia32_sys_call_table[nr](regs); - } else if (unlikely((int)nr != -1)) { + /* + * Convert negative numbers to very high and thus out of range + * numbers for comparisons. + */ + unsigned int unr = nr; + + if (likely(unr < IA32_NR_syscalls)) { + unr = array_index_nospec(unr, IA32_NR_syscalls); + regs->ax = ia32_sys_call_table[unr](regs); + } else if (nr != -1) { regs->ax = __ia32_sys_ni_syscall(regs); } } @@ -86,15 +118,15 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, /* Handles int $0x80 */ __visible noinstr void do_int80_syscall_32(struct pt_regs *regs) { - unsigned int nr = syscall_32_enter(regs); + int nr = syscall_32_enter(regs); add_random_kstack_offset(); /* - * Subtlety here: if ptrace pokes something larger than 2^32-1 into - * orig_ax, the unsigned int return value truncates it. This may - * or may not be necessary, but it matches the old asm behavior. + * Subtlety here: if ptrace pokes something larger than 2^31-1 into + * orig_ax, the int return value truncates it. This matches + * the semantics of syscall_get_nr(). */ - nr = (unsigned int)syscall_enter_from_user_mode(regs, nr); + nr = syscall_enter_from_user_mode(regs, nr); instrumentation_begin(); do_syscall_32_irqs_on(regs, nr); @@ -105,7 +137,7 @@ __visible noinstr void do_int80_syscall_32(struct pt_regs *regs) static noinstr bool __do_fast_syscall_32(struct pt_regs *regs) { - unsigned int nr = syscall_32_enter(regs); + int nr = syscall_32_enter(regs); int res; add_random_kstack_offset(); @@ -140,8 +172,7 @@ static noinstr bool __do_fast_syscall_32(struct pt_regs *regs) return false; } - /* The case truncates any ptrace induced syscall nr > 2^32 -1 */ - nr = (unsigned int)syscall_enter_from_user_mode_work(regs, nr); + nr = syscall_enter_from_user_mode_work(regs, nr); /* Now this is just like a normal syscall. */ do_syscall_32_irqs_on(regs, nr); diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h index f6593ca..f7e2d82 100644 --- a/arch/x86/include/asm/syscall.h +++ b/arch/x86/include/asm/syscall.h @@ -159,7 +159,7 @@ static inline int syscall_get_arch(struct task_struct *task) ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64; } -void do_syscall_64(struct pt_regs *regs, unsigned long nr); +void do_syscall_64(struct pt_regs *regs, int nr); void do_int80_syscall_32(struct pt_regs *regs); long do_fast_syscall_32(struct pt_regs *regs);