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    Subject[tip: x86/core] x86/usercopy: Remove .fixup usage
    The following commit has been merged into the x86/core branch of tip:

    Commit-ID: d5d797dcbd781cb7c526ad32f31c7fd96babfdb2
    Gitweb: https://git.kernel.org/tip/d5d797dcbd781cb7c526ad32f31c7fd96babfdb2
    Author: Peter Zijlstra <peterz@infradead.org>
    AuthorDate: Wed, 10 Nov 2021 11:01:22 +01:00
    Committer: Peter Zijlstra <peterz@infradead.org>
    CommitterDate: Sat, 11 Dec 2021 09:09:50 +01:00

    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
    ---
    arch/x86/include/asm/extable_fixup_types.h | 5 ++++-
    arch/x86/lib/usercopy_32.c | 28 +++------------------
    arch/x86/lib/usercopy_64.c | 8 ++----
    arch/x86/mm/extable.c | 9 +++++++-
    4 files changed, 22 insertions(+), 28 deletions(-)

    diff --git a/arch/x86/include/asm/extable_fixup_types.h b/arch/x86/include/asm/extable_fixup_types.h
    index 8278ed2..b5ab333 100644
    --- 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
    --- 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
    --- 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
    --- 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();
    }
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