From d19f5e41b344a057bb2450024a807476f30978d2 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Sat, 25 Mar 2017 11:59:15 +0100 Subject: [PATCH] parisc: Clean up fixup routines for get_user()/put_user() Al Viro noticed that userspace accesses via get_user()/put_user() can be simplified a lot with regard to usage of the exception handling. This patch implements a fixup routine for get_user() and put_user() in such that the exception handler will automatically load -EFAULT into the register %r8 (the error value) in case on a fault on userspace. Additionally the fixup routine will zero the target register on fault in case of a get_user() call. The target register is extracted out of the faulting assembly instruction. This patch brings a few benefits over the old implementation: 1. Exception handling gets much cleaner, easier and smaller in size. 2. Helper functions like fixup_get_user_skip_1 (all of fixup.S) can be dropped. 3. No need to hardcode %r9 as target register for get_user() any longer. This helps the compiler register allocator and thus creates less assembler statements. 4. No dependency on the exception_data contents any longer. 5. Nested faults will be handled cleanly. Reported-by: Al Viro Cc: # v4.9+ Signed-off-by: Helge Deller --- arch/parisc/include/asm/uaccess.h | 59 +++++++++++-------- arch/parisc/kernel/parisc_ksyms.c | 10 ---- arch/parisc/lib/Makefile | 2 +- arch/parisc/lib/fixup.S | 98 ------------------------------- arch/parisc/mm/fault.c | 17 ++++++ 5 files changed, 52 insertions(+), 134 deletions(-) delete mode 100644 arch/parisc/lib/fixup.S diff --git a/arch/parisc/include/asm/uaccess.h b/arch/parisc/include/asm/uaccess.h index edfbf9d6a6dd..8442727f28d2 100644 --- a/arch/parisc/include/asm/uaccess.h +++ b/arch/parisc/include/asm/uaccess.h @@ -64,6 +64,15 @@ struct exception_table_entry { ".word (" #fault_addr " - .), (" #except_addr " - .)\n\t" \ ".previous\n" +/* + * ASM_EXCEPTIONTABLE_ENTRY_EFAULT() creates a special exception table entry + * (with lowest bit set) for which the fault handler in fixup_exception() will + * load -EFAULT into %r8 for a read or write fault, and zeroes the target + * register in case of a read fault in get_user(). + */ +#define ASM_EXCEPTIONTABLE_ENTRY_EFAULT( fault_addr, except_addr )\ + ASM_EXCEPTIONTABLE_ENTRY( fault_addr, except_addr + 1) + /* * The page fault handler stores, in a per-cpu area, the following information * if a fixup routine is available. @@ -91,7 +100,7 @@ struct exception_data { #define __get_user(x, ptr) \ ({ \ register long __gu_err __asm__ ("r8") = 0; \ - register long __gu_val __asm__ ("r9") = 0; \ + register long __gu_val; \ \ load_sr2(); \ switch (sizeof(*(ptr))) { \ @@ -107,22 +116,23 @@ struct exception_data { }) #define __get_user_asm(ldx, ptr) \ - __asm__("\n1:\t" ldx "\t0(%%sr2,%2),%0\n\t" \ - ASM_EXCEPTIONTABLE_ENTRY(1b, fixup_get_user_skip_1)\ + __asm__("1: " ldx " 0(%%sr2,%2),%0\n" \ + "9:\n" \ + ASM_EXCEPTIONTABLE_ENTRY_EFAULT(1b, 9b) \ : "=r"(__gu_val), "=r"(__gu_err) \ - : "r"(ptr), "1"(__gu_err) \ - : "r1"); + : "r"(ptr), "1"(__gu_err)); #if !defined(CONFIG_64BIT) #define __get_user_asm64(ptr) \ - __asm__("\n1:\tldw 0(%%sr2,%2),%0" \ - "\n2:\tldw 4(%%sr2,%2),%R0\n\t" \ - ASM_EXCEPTIONTABLE_ENTRY(1b, fixup_get_user_skip_2)\ - ASM_EXCEPTIONTABLE_ENTRY(2b, fixup_get_user_skip_1)\ + __asm__(" copy %%r0,%R0\n" \ + "1: ldw 0(%%sr2,%2),%0\n" \ + "2: ldw 4(%%sr2,%2),%R0\n" \ + "9:\n" \ + ASM_EXCEPTIONTABLE_ENTRY_EFAULT(1b, 9b) \ + ASM_EXCEPTIONTABLE_ENTRY_EFAULT(2b, 9b) \ : "=r"(__gu_val), "=r"(__gu_err) \ - : "r"(ptr), "1"(__gu_err) \ - : "r1"); + : "r"(ptr), "1"(__gu_err)); #endif /* !defined(CONFIG_64BIT) */ @@ -148,32 +158,31 @@ struct exception_data { * The "__put_user/kernel_asm()" macros tell gcc they read from memory * instead of writing. This is because they do not write to any memory * gcc knows about, so there are no aliasing issues. These macros must - * also be aware that "fixup_put_user_skip_[12]" are executed in the - * context of the fault, and any registers used there must be listed - * as clobbers. In this case only "r1" is used by the current routines. - * r8/r9 are already listed as err/val. + * also be aware that fixups are executed in the context of the fault, + * and any registers used there must be listed as clobbers. + * r8 is already listed as err. */ #define __put_user_asm(stx, x, ptr) \ __asm__ __volatile__ ( \ - "\n1:\t" stx "\t%2,0(%%sr2,%1)\n\t" \ - ASM_EXCEPTIONTABLE_ENTRY(1b, fixup_put_user_skip_1)\ + "1: " stx " %2,0(%%sr2,%1)\n" \ + "9:\n" \ + ASM_EXCEPTIONTABLE_ENTRY_EFAULT(1b, 9b) \ : "=r"(__pu_err) \ - : "r"(ptr), "r"(x), "0"(__pu_err) \ - : "r1") + : "r"(ptr), "r"(x), "0"(__pu_err)) #if !defined(CONFIG_64BIT) #define __put_user_asm64(__val, ptr) do { \ __asm__ __volatile__ ( \ - "\n1:\tstw %2,0(%%sr2,%1)" \ - "\n2:\tstw %R2,4(%%sr2,%1)\n\t" \ - ASM_EXCEPTIONTABLE_ENTRY(1b, fixup_put_user_skip_2)\ - ASM_EXCEPTIONTABLE_ENTRY(2b, fixup_put_user_skip_1)\ + "1: stw %2,0(%%sr2,%1)\n" \ + "2: stw %R2,4(%%sr2,%1)\n" \ + "9:\n" \ + ASM_EXCEPTIONTABLE_ENTRY_EFAULT(1b, 9b) \ + ASM_EXCEPTIONTABLE_ENTRY_EFAULT(2b, 9b) \ : "=r"(__pu_err) \ - : "r"(ptr), "r"(__val), "0"(__pu_err) \ - : "r1"); \ + : "r"(ptr), "r"(__val), "0"(__pu_err)); \ } while (0) #endif /* !defined(CONFIG_64BIT) */ diff --git a/arch/parisc/kernel/parisc_ksyms.c b/arch/parisc/kernel/parisc_ksyms.c index 7484b3d11e0d..c6d6272a934f 100644 --- a/arch/parisc/kernel/parisc_ksyms.c +++ b/arch/parisc/kernel/parisc_ksyms.c @@ -47,16 +47,6 @@ EXPORT_SYMBOL(__cmpxchg_u64); EXPORT_SYMBOL(lclear_user); EXPORT_SYMBOL(lstrnlen_user); -/* Global fixups - defined as int to avoid creation of function pointers */ -extern int fixup_get_user_skip_1; -extern int fixup_get_user_skip_2; -extern int fixup_put_user_skip_1; -extern int fixup_put_user_skip_2; -EXPORT_SYMBOL(fixup_get_user_skip_1); -EXPORT_SYMBOL(fixup_get_user_skip_2); -EXPORT_SYMBOL(fixup_put_user_skip_1); -EXPORT_SYMBOL(fixup_put_user_skip_2); - #ifndef CONFIG_64BIT /* Needed so insmod can set dp value */ extern int $global$; diff --git a/arch/parisc/lib/Makefile b/arch/parisc/lib/Makefile index 8fa92b8d839a..f2dac4d73b1b 100644 --- a/arch/parisc/lib/Makefile +++ b/arch/parisc/lib/Makefile @@ -2,7 +2,7 @@ # Makefile for parisc-specific library files # -lib-y := lusercopy.o bitops.o checksum.o io.o memset.o fixup.o memcpy.o \ +lib-y := lusercopy.o bitops.o checksum.o io.o memset.o memcpy.o \ ucmpdi2.o delay.o obj-y := iomap.o diff --git a/arch/parisc/lib/fixup.S b/arch/parisc/lib/fixup.S deleted file mode 100644 index a5b72f22c7a6..000000000000 --- a/arch/parisc/lib/fixup.S +++ /dev/null @@ -1,98 +0,0 @@ -/* - * Linux/PA-RISC Project (http://www.parisc-linux.org/) - * - * Copyright (C) 2004 Randolph Chung - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2, or (at your option) - * any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. - * - * Fixup routines for kernel exception handling. - */ -#include -#include -#include -#include - -#ifdef CONFIG_SMP - .macro get_fault_ip t1 t2 - loadgp - addil LT%__per_cpu_offset,%r27 - LDREG RT%__per_cpu_offset(%r1),\t1 - /* t2 = smp_processor_id() */ - mfctl 30,\t2 - ldw TI_CPU(\t2),\t2 -#ifdef CONFIG_64BIT - extrd,u \t2,63,32,\t2 -#endif - /* t2 = &__per_cpu_offset[smp_processor_id()]; */ - LDREGX \t2(\t1),\t2 - addil LT%exception_data,%r27 - LDREG RT%exception_data(%r1),\t1 - /* t1 = this_cpu_ptr(&exception_data) */ - add,l \t1,\t2,\t1 - /* %r27 = t1->fault_gp - restore gp */ - LDREG EXCDATA_GP(\t1), %r27 - /* t1 = t1->fault_ip */ - LDREG EXCDATA_IP(\t1), \t1 - .endm -#else - .macro get_fault_ip t1 t2 - loadgp - /* t1 = this_cpu_ptr(&exception_data) */ - addil LT%exception_data,%r27 - LDREG RT%exception_data(%r1),\t2 - /* %r27 = t2->fault_gp - restore gp */ - LDREG EXCDATA_GP(\t2), %r27 - /* t1 = t2->fault_ip */ - LDREG EXCDATA_IP(\t2), \t1 - .endm -#endif - - .level LEVEL - - .text - .section .fixup, "ax" - - /* get_user() fixups, store -EFAULT in r8, and 0 in r9 */ -ENTRY_CFI(fixup_get_user_skip_1) - get_fault_ip %r1,%r8 - ldo 4(%r1), %r1 - ldi -EFAULT, %r8 - bv %r0(%r1) - copy %r0, %r9 -ENDPROC_CFI(fixup_get_user_skip_1) - -ENTRY_CFI(fixup_get_user_skip_2) - get_fault_ip %r1,%r8 - ldo 8(%r1), %r1 - ldi -EFAULT, %r8 - bv %r0(%r1) - copy %r0, %r9 -ENDPROC_CFI(fixup_get_user_skip_2) - - /* put_user() fixups, store -EFAULT in r8 */ -ENTRY_CFI(fixup_put_user_skip_1) - get_fault_ip %r1,%r8 - ldo 4(%r1), %r1 - bv %r0(%r1) - ldi -EFAULT, %r8 -ENDPROC_CFI(fixup_put_user_skip_1) - -ENTRY_CFI(fixup_put_user_skip_2) - get_fault_ip %r1,%r8 - ldo 8(%r1), %r1 - bv %r0(%r1) - ldi -EFAULT, %r8 -ENDPROC_CFI(fixup_put_user_skip_2) - diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c index deab89a8915a..32ec22146141 100644 --- a/arch/parisc/mm/fault.c +++ b/arch/parisc/mm/fault.c @@ -150,6 +150,23 @@ int fixup_exception(struct pt_regs *regs) d->fault_space = regs->isr; d->fault_addr = regs->ior; + /* + * Fix up get_user() and put_user(). + * ASM_EXCEPTIONTABLE_ENTRY_EFAULT() sets the least-significant + * bit in the relative address of the fixup routine to indicate + * that %r8 should be loaded with -EFAULT to report a userspace + * access error. + */ + if (fix->fixup & 1) { + regs->gr[8] = -EFAULT; + + /* zero target register for get_user() */ + if (parisc_acctyp(0, regs->iir) == VM_READ) { + int treg = regs->iir & 0x1f; + regs->gr[treg] = 0; + } + } + regs->iaoq[0] = (unsigned long)&fix->fixup + fix->fixup; regs->iaoq[0] &= ~3; /* -- 2.20.1