x86/usercopy: Remove .fixup usage

Typically usercopy does whole word copies followed by a number of byte
copies to finish the tail. This means that on exception it needs to
compute the remaining length as: words*sizeof(long) + bytes.

Create a new extable handler to do just this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20211110101326.081701085@infradead.org

diff --git a/arch/x86/include/asm/extable_fixup_types.h b/arch/x86/include/asm/extable_fixup_types.h
index 8278ed2..b5ab333 100644 (file)
--- a/arch/x86/include/asm/extable_fixup_types.h
+++ b/arch/x86/include/asm/extable_fixup_types.h
@@ -50,4 +50,9 @@
 
 #define        EX_TYPE_FAULT_SGX               18
 
+#define        EX_TYPE_UCOPY_LEN               19 /* cx := reg + imm*cx */
+#define        EX_TYPE_UCOPY_LEN1              (EX_TYPE_UCOPY_LEN | EX_DATA_IMM(1))
+#define        EX_TYPE_UCOPY_LEN4              (EX_TYPE_UCOPY_LEN | EX_DATA_IMM(4))
+#define        EX_TYPE_UCOPY_LEN8              (EX_TYPE_UCOPY_LEN | EX_DATA_IMM(8))
+
 #endif

diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c
index 1eb1506..422257c 100644 (file)
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -42,11 +42,7 @@ do {                                                                 \
                "       movl %2,%0\n"                                   \
                "1:     rep; stosb\n"                                   \
                "2: " ASM_CLAC "\n"                                     \
-               ".section .fixup,\"ax\"\n"                              \
-               "3:     lea 0(%2,%0,4),%0\n"                            \
-               "       jmp 2b\n"                                       \
-               ".previous\n"                                           \
-               _ASM_EXTABLE_UA(0b, 3b)                                 \
+               _ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UCOPY_LEN4, %2)   \
                _ASM_EXTABLE_UA(1b, 2b)                                 \
                : "=&c"(size), "=&D" (__d0)                             \
                : "r"(size & 3), "0"(size / 4), "1"(addr), "a"(0));     \
@@ -148,10 +144,6 @@ __copy_user_intel(void __user *to, const void *from, unsigned long size)
                       "36:    movl %%eax, %0\n"
                       "37:    rep; movsb\n"
                       "100:\n"
-                      ".section .fixup,\"ax\"\n"
-                      "101:   lea 0(%%eax,%0,4),%0\n"
-                      "       jmp 100b\n"
-                      ".previous\n"
                       _ASM_EXTABLE_UA(1b, 100b)
                       _ASM_EXTABLE_UA(2b, 100b)
                       _ASM_EXTABLE_UA(3b, 100b)
@@ -189,7 +181,7 @@ __copy_user_intel(void __user *to, const void *from, unsigned long size)
                       _ASM_EXTABLE_UA(35b, 100b)
                       _ASM_EXTABLE_UA(36b, 100b)
                       _ASM_EXTABLE_UA(37b, 100b)
-                      _ASM_EXTABLE_UA(99b, 101b)
+                      _ASM_EXTABLE_TYPE_REG(99b, 100b, EX_TYPE_UCOPY_LEN4, %%eax)
                       : "=&c"(size), "=&D" (d0), "=&S" (d1)
                       :  "1"(to), "2"(from), "0"(size)
                       : "eax", "edx", "memory");
@@ -254,10 +246,6 @@ static unsigned long __copy_user_intel_nocache(void *to,
               "        movl %%eax,%0\n"
               "7:      rep; movsb\n"
               "8:\n"
-              ".section .fixup,\"ax\"\n"
-              "9:      lea 0(%%eax,%0,4),%0\n"
-              "        jmp 8b\n"
-              ".previous\n"
               _ASM_EXTABLE_UA(0b, 8b)
               _ASM_EXTABLE_UA(1b, 8b)
               _ASM_EXTABLE_UA(2b, 8b)
@@ -276,7 +264,7 @@ static unsigned long __copy_user_intel_nocache(void *to,
               _ASM_EXTABLE_UA(81b, 8b)
               _ASM_EXTABLE_UA(14b, 8b)
               _ASM_EXTABLE_UA(91b, 8b)
-              _ASM_EXTABLE_UA(6b, 9b)
+              _ASM_EXTABLE_TYPE_REG(6b, 8b, EX_TYPE_UCOPY_LEN4, %%eax)
               _ASM_EXTABLE_UA(7b, 8b)
               : "=&c"(size), "=&D" (d0), "=&S" (d1)
               :  "1"(to), "2"(from), "0"(size)
@@ -314,14 +302,8 @@ do {                                                                       \
                "       movl %3,%0\n"                                   \
                "1:     rep; movsb\n"                                   \
                "2:\n"                                                  \
-               ".section .fixup,\"ax\"\n"                              \
-               "5:     addl %3,%0\n"                                   \
-               "       jmp 2b\n"                                       \
-               "3:     lea 0(%3,%0,4),%0\n"                            \
-               "       jmp 2b\n"                                       \
-               ".previous\n"                                           \
-               _ASM_EXTABLE_UA(4b, 5b)                                 \
-               _ASM_EXTABLE_UA(0b, 3b)                                 \
+               _ASM_EXTABLE_TYPE_REG(4b, 2b, EX_TYPE_UCOPY_LEN1, %3)   \
+               _ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UCOPY_LEN4, %3)   \
                _ASM_EXTABLE_UA(1b, 2b)                                 \
                : "=&c"(size), "=&D" (__d0), "=&S" (__d1), "=r"(__d2)   \
                : "3"(size), "0"(size), "1"(to), "2"(from)              \

diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index 508c81e..0402a74 100644 (file)
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -35,12 +35,10 @@ unsigned long __clear_user(void __user *addr, unsigned long size)
                "       incq   %[dst]\n"
                "       decl %%ecx ; jnz  1b\n"
                "2:\n"
-               ".section .fixup,\"ax\"\n"
-               "3:     lea 0(%[size1],%[size8],8),%[size8]\n"
-               "       jmp 2b\n"
-               ".previous\n"
-               _ASM_EXTABLE_UA(0b, 3b)
+
+               _ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UCOPY_LEN8, %[size1])
                _ASM_EXTABLE_UA(1b, 2b)
+
                : [size8] "=&c"(size), [dst] "=&D" (__d0)
                : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr));
        clac();

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index c869f43..41eaa64 100644 (file)
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -145,6 +145,13 @@ static bool ex_handler_imm_reg(const struct exception_table_entry *fixup,
        return ex_handler_default(fixup, regs);
 }
 
+static bool ex_handler_ucopy_len(const struct exception_table_entry *fixup,
+                                 struct pt_regs *regs, int trapnr, int reg, int imm)
+{
+       regs->cx = imm * regs->cx + *pt_regs_nr(regs, reg);
+       return ex_handler_uaccess(fixup, regs, trapnr);
+}
+
 int ex_get_fixup_type(unsigned long ip)
 {
        const struct exception_table_entry *e = search_exception_tables(ip);
@@ -217,6 +224,8 @@ int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,
                return ex_handler_imm_reg(e, regs, reg, imm);
        case EX_TYPE_FAULT_SGX:
                return ex_handler_sgx(e, regs, trapnr);
+       case EX_TYPE_UCOPY_LEN:
+               return ex_handler_ucopy_len(e, regs, trapnr, reg, imm);
        }
        BUG();
 }