lkml.org 
[lkml]   [2018]   [Sep]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH AUTOSEL 4.9 13/14] arm/arm64: smccc-1.1: Handle function result as parameters
    Date
    From: Marc Zyngier <marc.zyngier@arm.com>

    [ Upstream commit 755a8bf5579d22eb5636685c516d8dede799e27b ]

    If someone has the silly idea to write something along those lines:

    extern u64 foo(void);

    void bar(struct arm_smccc_res *res)
    {
    arm_smccc_1_1_smc(0xbad, foo(), res);
    }

    they are in for a surprise, as this gets compiled as:

    0000000000000588 <bar>:
    588: a9be7bfd stp x29, x30, [sp, #-32]!
    58c: 910003fd mov x29, sp
    590: f9000bf3 str x19, [sp, #16]
    594: aa0003f3 mov x19, x0
    598: aa1e03e0 mov x0, x30
    59c: 94000000 bl 0 <_mcount>
    5a0: 94000000 bl 0 <foo>
    5a4: aa0003e1 mov x1, x0
    5a8: d4000003 smc #0x0
    5ac: b4000073 cbz x19, 5b8 <bar+0x30>
    5b0: a9000660 stp x0, x1, [x19]
    5b4: a9010e62 stp x2, x3, [x19, #16]
    5b8: f9400bf3 ldr x19, [sp, #16]
    5bc: a8c27bfd ldp x29, x30, [sp], #32
    5c0: d65f03c0 ret
    5c4: d503201f nop

    The call to foo "overwrites" the x0 register for the return value,
    and we end up calling the wrong secure service.

    A solution is to evaluate all the parameters before assigning
    anything to specific registers, leading to the expected result:

    0000000000000588 <bar>:
    588: a9be7bfd stp x29, x30, [sp, #-32]!
    58c: 910003fd mov x29, sp
    590: f9000bf3 str x19, [sp, #16]
    594: aa0003f3 mov x19, x0
    598: aa1e03e0 mov x0, x30
    59c: 94000000 bl 0 <_mcount>
    5a0: 94000000 bl 0 <foo>
    5a4: aa0003e1 mov x1, x0
    5a8: d28175a0 mov x0, #0xbad
    5ac: d4000003 smc #0x0
    5b0: b4000073 cbz x19, 5bc <bar+0x34>
    5b4: a9000660 stp x0, x1, [x19]
    5b8: a9010e62 stp x2, x3, [x19, #16]
    5bc: f9400bf3 ldr x19, [sp, #16]
    5c0: a8c27bfd ldp x29, x30, [sp], #32
    5c4: d65f03c0 ret

    Reported-by: Julien Grall <julien.grall@arm.com>
    Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    include/linux/arm-smccc.h | 30 ++++++++++++++++++++----------
    1 file changed, 20 insertions(+), 10 deletions(-)

    diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
    index 5a91ff33720b..18863d56273c 100644
    --- a/include/linux/arm-smccc.h
    +++ b/include/linux/arm-smccc.h
    @@ -205,41 +205,51 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
    register unsigned long r3 asm("r3")

    #define __declare_arg_1(a0, a1, res) \
    + typeof(a1) __a1 = a1; \
    struct arm_smccc_res *___res = res; \
    register unsigned long r0 asm("r0") = (u32)a0; \
    - register unsigned long r1 asm("r1") = a1; \
    + register unsigned long r1 asm("r1") = __a1; \
    register unsigned long r2 asm("r2"); \
    register unsigned long r3 asm("r3")

    #define __declare_arg_2(a0, a1, a2, res) \
    + typeof(a1) __a1 = a1; \
    + typeof(a2) __a2 = a2; \
    struct arm_smccc_res *___res = res; \
    register unsigned long r0 asm("r0") = (u32)a0; \
    - register unsigned long r1 asm("r1") = a1; \
    - register unsigned long r2 asm("r2") = a2; \
    + register unsigned long r1 asm("r1") = __a1; \
    + register unsigned long r2 asm("r2") = __a2; \
    register unsigned long r3 asm("r3")

    #define __declare_arg_3(a0, a1, a2, a3, res) \
    + typeof(a1) __a1 = a1; \
    + typeof(a2) __a2 = a2; \
    + typeof(a3) __a3 = a3; \
    struct arm_smccc_res *___res = res; \
    register unsigned long r0 asm("r0") = (u32)a0; \
    - register unsigned long r1 asm("r1") = a1; \
    - register unsigned long r2 asm("r2") = a2; \
    - register unsigned long r3 asm("r3") = a3
    + register unsigned long r1 asm("r1") = __a1; \
    + register unsigned long r2 asm("r2") = __a2; \
    + register unsigned long r3 asm("r3") = __a3

    #define __declare_arg_4(a0, a1, a2, a3, a4, res) \
    + typeof(a4) __a4 = a4; \
    __declare_arg_3(a0, a1, a2, a3, res); \
    - register typeof(a4) r4 asm("r4") = a4
    + register unsigned long r4 asm("r4") = __a4

    #define __declare_arg_5(a0, a1, a2, a3, a4, a5, res) \
    + typeof(a5) __a5 = a5; \
    __declare_arg_4(a0, a1, a2, a3, a4, res); \
    - register typeof(a5) r5 asm("r5") = a5
    + register unsigned long r5 asm("r5") = __a5

    #define __declare_arg_6(a0, a1, a2, a3, a4, a5, a6, res) \
    + typeof(a6) __a6 = a6; \
    __declare_arg_5(a0, a1, a2, a3, a4, a5, res); \
    - register typeof(a6) r6 asm("r6") = a6
    + register unsigned long r6 asm("r6") = __a6

    #define __declare_arg_7(a0, a1, a2, a3, a4, a5, a6, a7, res) \
    + typeof(a7) __a7 = a7; \
    __declare_arg_6(a0, a1, a2, a3, a4, a5, a6, res); \
    - register typeof(a7) r7 asm("r7") = a7
    + register unsigned long r7 asm("r7") = __a7

    #define ___declare_args(count, ...) __declare_arg_ ## count(__VA_ARGS__)
    #define __declare_args(count, ...) ___declare_args(count, __VA_ARGS__)
    --
    2.17.1
    \
     
     \ /
      Last update: 2018-09-20 05:19    [W:2.974 / U:0.368 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site