ARM: net: bpf: enumerate the JIT scratch stack layout

Enumerate the contents of the JIT scratch stack layout used for storing
some of the JITs 64-bit registers, tail call counter and AX register.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index f6a62ae..f2e6ffe 100644 (file)
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -72,7 +72,38 @@
 #define CALLEE_PUSH_MASK (CALLEE_MASK | 1 << ARM_LR)
 #define CALLEE_POP_MASK  (CALLEE_MASK | 1 << ARM_PC)
 
-#define STACK_OFFSET(k)        (k)
+enum {
+       /* Stack layout - these are offsets from (top of stack - 4) */
+       BPF_R2_HI,
+       BPF_R2_LO,
+       BPF_R3_HI,
+       BPF_R3_LO,
+       BPF_R4_HI,
+       BPF_R4_LO,
+       BPF_R5_HI,
+       BPF_R5_LO,
+       BPF_R7_HI,
+       BPF_R7_LO,
+       BPF_R8_HI,
+       BPF_R8_LO,
+       BPF_R9_HI,
+       BPF_R9_LO,
+       BPF_FP_HI,
+       BPF_FP_LO,
+       BPF_TC_HI,
+       BPF_TC_LO,
+       BPF_AX_HI,
+       BPF_AX_LO,
+       /* Stack space for BPF_REG_2, BPF_REG_3, BPF_REG_4,
+        * BPF_REG_5, BPF_REG_7, BPF_REG_8, BPF_REG_9,
+        * BPF_REG_FP and Tail call counts.
+        */
+       BPF_JIT_SCRATCH_REGS,
+};
+
+#define STACK_OFFSET(k)        ((k) * 4)
+#define SCRATCH_SIZE   (BPF_JIT_SCRATCH_REGS * 4)
+
 #define TMP_REG_1      (MAX_BPF_JIT_REG + 0)   /* TEMP Register 1 */
 #define TMP_REG_2      (MAX_BPF_JIT_REG + 1)   /* TEMP Register 2 */
 #define TCALL_CNT      (MAX_BPF_JIT_REG + 2)   /* Tail Call Count */
@@ -100,29 +131,29 @@ static const u8 bpf2a32[][2] = {
        /* arguments from eBPF program to in-kernel function */
        [BPF_REG_1] = {ARM_R3, ARM_R2},
        /* Stored on stack scratch space */
-       [BPF_REG_2] = {STACK_OFFSET(0), STACK_OFFSET(4)},
-       [BPF_REG_3] = {STACK_OFFSET(8), STACK_OFFSET(12)},
-       [BPF_REG_4] = {STACK_OFFSET(16), STACK_OFFSET(20)},
-       [BPF_REG_5] = {STACK_OFFSET(24), STACK_OFFSET(28)},
+       [BPF_REG_2] = {STACK_OFFSET(BPF_R2_HI), STACK_OFFSET(BPF_R2_LO)},
+       [BPF_REG_3] = {STACK_OFFSET(BPF_R3_HI), STACK_OFFSET(BPF_R3_LO)},
+       [BPF_REG_4] = {STACK_OFFSET(BPF_R4_HI), STACK_OFFSET(BPF_R4_LO)},
+       [BPF_REG_5] = {STACK_OFFSET(BPF_R5_HI), STACK_OFFSET(BPF_R5_LO)},
        /* callee saved registers that in-kernel function will preserve */
        [BPF_REG_6] = {ARM_R5, ARM_R4},
        /* Stored on stack scratch space */
-       [BPF_REG_7] = {STACK_OFFSET(32), STACK_OFFSET(36)},
-       [BPF_REG_8] = {STACK_OFFSET(40), STACK_OFFSET(44)},
-       [BPF_REG_9] = {STACK_OFFSET(48), STACK_OFFSET(52)},
+       [BPF_REG_7] = {STACK_OFFSET(BPF_R7_HI), STACK_OFFSET(BPF_R7_LO)},
+       [BPF_REG_8] = {STACK_OFFSET(BPF_R8_HI), STACK_OFFSET(BPF_R8_LO)},
+       [BPF_REG_9] = {STACK_OFFSET(BPF_R9_HI), STACK_OFFSET(BPF_R9_LO)},
        /* Read only Frame Pointer to access Stack */
-       [BPF_REG_FP] = {STACK_OFFSET(56), STACK_OFFSET(60)},
+       [BPF_REG_FP] = {STACK_OFFSET(BPF_FP_HI), STACK_OFFSET(BPF_FP_LO)},
        /* Temporary Register for internal BPF JIT, can be used
         * for constant blindings and others.
         */
        [TMP_REG_1] = {ARM_R7, ARM_R6},
        [TMP_REG_2] = {ARM_R10, ARM_R8},
        /* Tail call count. Stored on stack scratch space. */
-       [TCALL_CNT] = {STACK_OFFSET(64), STACK_OFFSET(68)},
+       [TCALL_CNT] = {STACK_OFFSET(BPF_TC_HI), STACK_OFFSET(BPF_TC_LO)},
        /* temporary register for blinding constants.
         * Stored on stack scratch space.
         */
-       [BPF_REG_AX] = {STACK_OFFSET(72), STACK_OFFSET(76)},
+       [BPF_REG_AX] = {STACK_OFFSET(BPF_AX_HI), STACK_OFFSET(BPF_AX_LO)},
 };
 
 #define        dst_lo  dst[1]
@@ -227,12 +258,6 @@ static void jit_fill_hole(void *area, unsigned int size)
 #define STACK_ALIGNMENT        4
 #endif
 
-/* Stack space for BPF_REG_2, BPF_REG_3, BPF_REG_4,
- * BPF_REG_5, BPF_REG_7, BPF_REG_8, BPF_REG_9,
- * BPF_REG_FP and Tail call counts.
- */
-#define SCRATCH_SIZE 80
-
 /* total stack size used in JITed code */
 #define _STACK_SIZE    (ctx->prog->aux->stack_depth + SCRATCH_SIZE)
 #define STACK_SIZE     ALIGN(_STACK_SIZE, STACK_ALIGNMENT)