Hi,
On 24.08.18 19:58, Julien Grall wrote:
From: Marc Zyngier <marc.zyng...@arm.com>
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: Stefano Stabellini <stefa...@xilinx.com>
Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
Reviewed-by: Volodymyr Babchuk <volodymr_babc...@epam.com>
---
xen/include/asm-arm/smccc.h | 30 ++++++++++++++++++++----------
1 file changed, 20 insertions(+), 10 deletions(-)
diff --git a/xen/include/asm-arm/smccc.h b/xen/include/asm-arm/smccc.h
index a31d67a1de..648bef28bd 100644
--- a/xen/include/asm-arm/smccc.h
+++ b/xen/include/asm-arm/smccc.h
@@ -125,41 +125,51 @@ struct arm_smccc_res {
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") = (uint32_t)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") = (uint32_t)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") = (uint32_t)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 unsigned long 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 typeof(a5) 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 typeof(a6) 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 typeof(a7) r7 asm("r7") = __a7
#define ___declare_args(count, ...) __declare_arg_ ## count(__VA_ARGS__)
#define __declare_args(count, ...) ___declare_args(count, __VA_ARGS__)
--
Volodymyr Babchuk
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