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

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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>
This commit is contained in:
Russell King 2018-07-11 10:31:31 +01:00 committed by Daniel Borkmann
parent b103cbe0d7
commit d449ceb11b
1 changed files with 42 additions and 17 deletions
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59
arch/arm/net/bpf_jit_32.c
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@ -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)