From: Heiko Carstens Date: Tue, 11 Feb 2025 19:19:26 +0000 (+0100) Subject: s390/uaccess: Shorten raw_copy_from_user() / raw_copy_to_user() inline assemblies X-Git-Tag: v6.15-rc1~113^2~67 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c488f5187a24969b40fd08c3e9ead377c0cfb9b3;p=thirdparty%2Fkernel%2Flinux.git s390/uaccess: Shorten raw_copy_from_user() / raw_copy_to_user() inline assemblies Add specific exception handler for copy_to_user() / copy_from_user() mvcos fault handling, which allows to shorten the inline assemblies to three instructions. On fault the exception handler adjusts the length used by the mvcos instruction in a way that the instruction completes with condition code zero, indicating the number of bytes copied with the input/output operand 'size'. This allows to calculate and return the number of bytes not copied, if any, like required. Loop and return value handling is changed to C so that the compiler may optimize the code. Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- diff --git a/arch/s390/include/asm/asm-extable.h b/arch/s390/include/asm/asm-extable.h index 2e829c16fd8ad..d23ea0c94e4ea 100644 --- a/arch/s390/include/asm/asm-extable.h +++ b/arch/s390/include/asm/asm-extable.h @@ -14,6 +14,8 @@ #define EX_TYPE_UA_LOAD_REGPAIR 6 #define EX_TYPE_ZEROPAD 7 #define EX_TYPE_FPC 8 +#define EX_TYPE_UA_MVCOS_TO 9 +#define EX_TYPE_UA_MVCOS_FROM 10 #define EX_DATA_REG_ERR_SHIFT 0 #define EX_DATA_REG_ERR GENMASK(3, 0) @@ -84,4 +86,10 @@ #define EX_TABLE_FPC(_fault, _target) \ __EX_TABLE(__ex_table, _fault, _target, EX_TYPE_FPC, __stringify(%%r0), __stringify(%%r0), 0) +#define EX_TABLE_UA_MVCOS_TO(_fault, _target) \ + __EX_TABLE(__ex_table, _fault, _target, EX_TYPE_UA_MVCOS_TO, __stringify(%%r0), __stringify(%%r0), 0) + +#define EX_TABLE_UA_MVCOS_FROM(_fault, _target) \ + __EX_TABLE(__ex_table, _fault, _target, EX_TYPE_UA_MVCOS_FROM, __stringify(%%r0), __stringify(%%r0), 0) + #endif /* __ASM_EXTABLE_H */ diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h index f5920163ee974..f9ace938743ca 100644 --- a/arch/s390/include/asm/uaccess.h +++ b/arch/s390/include/asm/uaccess.h @@ -44,43 +44,42 @@ union oac { }; }; -static __always_inline __must_check unsigned long +#ifdef CONFIG_KMSAN +#define uaccess_kmsan_or_inline noinline __maybe_unused __no_sanitize_memory +#else +#define uaccess_kmsan_or_inline __always_inline +#endif + +static uaccess_kmsan_or_inline __must_check unsigned long raw_copy_from_user_key(void *to, const void __user *from, unsigned long size, unsigned long key) { - unsigned long rem; + unsigned long osize; union oac spec = { .oac2.key = key, .oac2.as = PSW_BITS_AS_SECONDARY, .oac2.k = 1, .oac2.a = 1, }; - - asm_inline volatile( - " lr %%r0,%[spec]\n" - "0: mvcos 0(%[to]),0(%[from]),%[size]\n" - "1: jz 5f\n" - " algr %[size],%[val]\n" - " slgr %[from],%[val]\n" - " slgr %[to],%[val]\n" - " j 0b\n" - "2: la %[rem],4095(%[from])\n" /* rem = from + 4095 */ - " nr %[rem],%[val]\n" /* rem = (from + 4095) & -4096 */ - " slgr %[rem],%[from]\n" - " clgr %[size],%[rem]\n" /* copy crosses next page boundary? */ - " jnh 6f\n" - "3: mvcos 0(%[to]),0(%[from]),%[rem]\n" - "4: slgr %[size],%[rem]\n" - " j 6f\n" - "5: lghi %[size],0\n" - "6:\n" - EX_TABLE(0b, 2b) - EX_TABLE(1b, 2b) - EX_TABLE(3b, 6b) - EX_TABLE(4b, 6b) - : [size] "+&a" (size), [from] "+&a" (from), [to] "+&a" (to), [rem] "=&a" (rem) - : [val] "a" (-4096UL), [spec] "d" (spec.val) - : "cc", "memory", "0"); - return size; + int cc; + + while (1) { + osize = size; + asm_inline volatile( + " lr %%r0,%[spec]\n" + "0: mvcos %[to],%[from],%[size]\n" + "1: nopr %%r7\n" + CC_IPM(cc) + EX_TABLE_UA_MVCOS_FROM(0b, 0b) + EX_TABLE_UA_MVCOS_FROM(1b, 0b) + : CC_OUT(cc, cc), [size] "+d" (size), [to] "=Q" (*(char *)to) + : [spec] "d" (spec.val), [from] "Q" (*(const char __user *)from) + : CC_CLOBBER_LIST("memory", "0")); + if (likely(CC_TRANSFORM(cc) == 0)) + return osize - size; + size -= 4096; + to += 4096; + from += 4096; + } } static __always_inline __must_check unsigned long @@ -89,43 +88,36 @@ raw_copy_from_user(void *to, const void __user *from, unsigned long n) return raw_copy_from_user_key(to, from, n, 0); } -static __always_inline __must_check unsigned long +static uaccess_kmsan_or_inline __must_check unsigned long raw_copy_to_user_key(void __user *to, const void *from, unsigned long size, unsigned long key) { - unsigned long rem; + unsigned long osize; union oac spec = { .oac1.key = key, .oac1.as = PSW_BITS_AS_SECONDARY, .oac1.k = 1, .oac1.a = 1, }; - - asm_inline volatile( - " lr %%r0,%[spec]\n" - "0: mvcos 0(%[to]),0(%[from]),%[size]\n" - "1: jz 5f\n" - " algr %[size],%[val]\n" - " slgr %[to],%[val]\n" - " slgr %[from],%[val]\n" - " j 0b\n" - "2: la %[rem],4095(%[to])\n" /* rem = to + 4095 */ - " nr %[rem],%[val]\n" /* rem = (to + 4095) & -4096 */ - " slgr %[rem],%[to]\n" - " clgr %[size],%[rem]\n" /* copy crosses next page boundary? */ - " jnh 6f\n" - "3: mvcos 0(%[to]),0(%[from]),%[rem]\n" - "4: slgr %[size],%[rem]\n" - " j 6f\n" - "5: lghi %[size],0\n" - "6:\n" - EX_TABLE(0b, 2b) - EX_TABLE(1b, 2b) - EX_TABLE(3b, 6b) - EX_TABLE(4b, 6b) - : [size] "+&a" (size), [to] "+&a" (to), [from] "+&a" (from), [rem] "=&a" (rem) - : [val] "a" (-4096UL), [spec] "d" (spec.val) - : "cc", "memory", "0"); - return size; + int cc; + + while (1) { + osize = size; + asm_inline volatile( + " lr %%r0,%[spec]\n" + "0: mvcos %[to],%[from],%[size]\n" + "1: nopr %%r7\n" + CC_IPM(cc) + EX_TABLE_UA_MVCOS_TO(0b, 0b) + EX_TABLE_UA_MVCOS_TO(1b, 0b) + : CC_OUT(cc, cc), [size] "+d" (size), [to] "=Q" (*(char __user *)to) + : [spec] "d" (spec.val), [from] "Q" (*(const char *)from) + : CC_CLOBBER_LIST("memory", "0")); + if (likely(CC_TRANSFORM(cc) == 0)) + return osize - size; + size -= 4096; + to += 4096; + from += 4096; + } } static __always_inline __must_check unsigned long @@ -158,12 +150,6 @@ copy_to_user_key(void __user *to, const void *from, unsigned long n, unsigned lo int __noreturn __put_user_bad(void); -#ifdef CONFIG_KMSAN -#define uaccess_kmsan_or_inline noinline __maybe_unused __no_sanitize_memory -#else -#define uaccess_kmsan_or_inline __always_inline -#endif - #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT #define DEFINE_PUT_USER_NOINSTR(type) \ diff --git a/arch/s390/mm/extable.c b/arch/s390/mm/extable.c index a046be1715cf0..7498e858c4019 100644 --- a/arch/s390/mm/extable.c +++ b/arch/s390/mm/extable.c @@ -73,6 +73,49 @@ static bool ex_handler_fpc(const struct exception_table_entry *ex, struct pt_reg return true; } +struct insn_ssf { + u64 opc1 : 8; + u64 r3 : 4; + u64 opc2 : 4; + u64 b1 : 4; + u64 d1 : 12; + u64 b2 : 4; + u64 d2 : 12; +} __packed; + +static bool ex_handler_ua_mvcos(const struct exception_table_entry *ex, + bool from, struct pt_regs *regs) +{ + unsigned long uaddr, remainder; + struct insn_ssf *insn; + + /* + * If the faulting user space access crossed a page boundary retry by + * limiting the access to the first page (adjust length accordingly). + * Then the mvcos instruction will either complete with condition code + * zero, or generate another fault where the user space access did not + * cross a page boundary. + * If the faulting user space access did not cross a page boundary set + * length to zero and retry. In this case no user space access will + * happen, and the mvcos instruction will complete with condition code + * zero. + * In both cases the instruction will complete with condition code + * zero (copying finished), and the register which contains the + * length, indicates the number of bytes copied. + */ + regs->psw.addr = extable_fixup(ex); + insn = (struct insn_ssf *)regs->psw.addr; + if (from) + uaddr = regs->gprs[insn->b2] + insn->d2; + else + uaddr = regs->gprs[insn->b1] + insn->d1; + remainder = PAGE_SIZE - (uaddr & (PAGE_SIZE - 1)); + if (regs->gprs[insn->r3] <= remainder) + remainder = 0; + regs->gprs[insn->r3] = remainder; + return true; +} + bool fixup_exception(struct pt_regs *regs) { const struct exception_table_entry *ex; @@ -95,6 +138,10 @@ bool fixup_exception(struct pt_regs *regs) return ex_handler_zeropad(ex, regs); case EX_TYPE_FPC: return ex_handler_fpc(ex, regs); + case EX_TYPE_UA_MVCOS_TO: + return ex_handler_ua_mvcos(ex, false, regs); + case EX_TYPE_UA_MVCOS_FROM: + return ex_handler_ua_mvcos(ex, true, regs); } panic("invalid exception table entry"); }