Commit 1ca3b17b authored by Russell King's avatar Russell King Committed by Daniel Borkmann
Browse files

ARM: net: bpf: imm12 constant conversion 



Provide a version of the imm8m() function that the compiler can optimise
when used with a constant expression.

Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 96cced4e

arch/arm/net/bpf_jit_32.c

+49 −1
Original line number Diff line number Diff line
@@ -236,10 +236,56 @@ static inline void emit(u32 inst, struct jit_ctx *ctx) 
	_emit(ARM_COND_AL, inst, ctx);

}



/*

 * This is rather horrid, but necessary to convert an integer constant

 * to an immediate operand for the opcodes, and be able to detect at

 * build time whether the constant can't be converted (iow, usable in

 * BUILD_BUG_ON()).

 */

#define imm12val(v, s) (rol32(v, (s)) | (s) << 7)

#define const_imm8m(x)					\

	({ int r;					\

	   u32 v = (x);					\

	   if (!(v & ~0x000000ff))			\

		r = imm12val(v, 0);			\

	   else if (!(v & ~0xc000003f))			\

		r = imm12val(v, 2);			\

	   else if (!(v & ~0xf000000f))			\

		r = imm12val(v, 4);			\

	   else if (!(v & ~0xfc000003))			\

		r = imm12val(v, 6);			\

	   else if (!(v & ~0xff000000))			\

		r = imm12val(v, 8);			\

	   else if (!(v & ~0x3fc00000))			\

		r = imm12val(v, 10);			\

	   else if (!(v & ~0x0ff00000))			\

		r = imm12val(v, 12);			\

	   else if (!(v & ~0x03fc0000))			\

		r = imm12val(v, 14);			\

	   else if (!(v & ~0x00ff0000))			\

		r = imm12val(v, 16);			\

	   else if (!(v & ~0x003fc000))			\

		r = imm12val(v, 18);			\

	   else if (!(v & ~0x000ff000))			\

		r = imm12val(v, 20);			\

	   else if (!(v & ~0x0003fc00))			\

		r = imm12val(v, 22);			\

	   else if (!(v & ~0x0000ff00))			\

		r = imm12val(v, 24);			\

	   else if (!(v & ~0x00003fc0))			\

		r = imm12val(v, 26);			\

	   else if (!(v & ~0x00000ff0))			\

		r = imm12val(v, 28);			\

	   else if (!(v & ~0x000003fc))			\

		r = imm12val(v, 30);			\

	   else						\

		r = -1;					\

	   r; })



/*

 * Checks if immediate value can be converted to imm12(12 bits) value.

 */

static int16_t imm8m(u32 x)

static int imm8m(u32 x)

{

	u32 rot;
@@ -249,6 +295,8 @@ static int16_t imm8m(u32 x) 
	return -1;

}



#define imm8m(x) (__builtin_constant_p(x) ? const_imm8m(x) : imm8m(x))



static u32 arm_bpf_ldst_imm12(u32 op, u8 rt, u8 rn, s16 imm12)

{

	op |= rt << 12 | rn << 16;