sim/testsuite/bpf/ldabs.s

# mach: bpf
# sim: --skb-data-offset=0x20
# output: pass\nexit 0 (0x0)\n
;;; ldabs.s
;;; Tests for non-generic BPF load instructions in simulator.
;;; These instructions (ld{abs,ind}{b,h,w,dw}) are used to access
;;; kernel socket data from BPF programs for high performance filters.
;;;
;;; Register r6 is an implicit input holding a pointer to a struct sk_buff.
;;; Register r0 is an implicit output, holding the fetched data.
;;;
;;; e.g.
;;; ldabsw means:
;;; r0 = ntohl (*(u32 *) (((struct sk_buff *)r6)->data + imm32))
;;;
;;; ldindw means
;;; r0 = ntohl (*(u32 *) (((struct sk_buff *)r6)->data + src_reg + imm32))

    .include "testutils.inc"

    .text
    .global main
    .type main, @function
main:
    ;; R6 holds a pointer to a struct sk_buff, which we pretend
    ;; exists at 0x1000
    mov         %r6, 0x1000

    ;; We configure skb-data-offset=0x20
    ;; This specifies offsetof(struct sk_buff, data), where the field 'data'
    ;; is a pointer a data buffer, in this case at 0x2000
    stw         [%r6+0x20], 0x2000

    ;; Write the value 0x7eadbeef into memory at 0x2004
    ;; i.e. offset 4 within the data buffer pointed to by
    ;; ((struct sk_buff *)r6)->data
    stw         [%r6+0x1004], 0xdeadbeef

    ;; Now load data[4] into r0 using the ldabsw instruction
    ldabsw      0x4

    ;; ...and compare to what we expect
    fail_ne32   %r0, 0xdeadbeef

    ;; Repeat for a half-word (2-bytes)
    sth         [%r6+0x1008], 0x1234
    ldabsh      0x8
    fail_ne32   %r0, 0x1234

    ;; Repeat for a single byte
    stb         [%r6+0x1010], 0x5a
    ldabsb      0x10
    fail_ne32   %r0, 0x5a

    ;; Repeat for a double-word (8-byte)
    ;; (note: fail_ne macro uses r0, so copy to another r1 to compare)
    lddw        %r2, 0x1234deadbeef5678
    stxdw       [%r6+0x1018], %r2
    ldabsdw     0x18
    mov         %r1, %r0
    fail_ne     %r1, 0x1234deadbeef5678

    ;; Now, we do the same for the indirect loads
    mov         %r7, 0x100
    stw         [%r6+0x1100], 0xfeedbeef

    ldindw      %r7, 0x0
    fail_ne32   %r0, 0xfeedbeef

    ;; half-word
    sth         [%r6+0x1104], 0x6789
    ldindh      %r7, 0x4
    fail_ne32   %r0, 0x6789

    ;; byte
    stb         [%r6+0x1108], 0x5f
    ldindb      %r7, 0x8
    fail_ne32   %r0, 0x5f

    ;; double-word
    lddw        %r2, 0xcafe12345678d00d
    stxdw       [%r6+0x1110], %r2
    ldinddw     %r7, 0x10
    mov         %r1, %r0
    fail_ne     %r1, 0xcafe12345678d00d

    pass