The runtime only exposes the following information about the kernarg segment:
HSA_CODE_SYMBOL_INFO_KERNEL_KERNARG_SEGMENT_SIZE - Size of kernarg segment memory that is required to hold the values of the kernel arguments, in bytes. The value of this attribute is undefined if the symbol is not a kernel. The type of this attribute is uint32_t.
HSA_CODE_SYMBOL_INFO_KERNEL_KERNARG_SEGMENT_ALIGNMENT - Alignment (in bytes) of the buffer used to pass arguments to the kernel, which is the maximum of 16 and the maximum alignment of any of the kernel arguments. The value of this attribute is undefined if the symbol is not a kernel. The type of this attribute is uint32_t.
Specific information regarding the kernarg segment and the alignment of the kernel argument list are described in section 4.21 of the HSA Programmer's Reference Manual, located here.