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Commit d449ceb1 authored by Russell King's avatar Russell King Committed by Daniel Borkmann
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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: default avatarRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent b103cbe0

arch/arm/net/bpf_jit_32.c

+42 −17
Original line number Diff line number Diff line
@@ -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)