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Commit 35607b02 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
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sparc: bpf_jit: fix loads from negative offsets 



- fix BPF_LD|ABS|IND from negative offsets:
  make sure to sign extend lower 32 bits in 64-bit register
  before calling C helpers from JITed code, otherwise 'int k'
  argument of bpf_internal_load_pointer_neg_helper() function
  will be added as large unsigned integer, causing packet size
  check to trigger and abort the program.

  It's worth noting that JITed code for 'A = A op K' will affect
  upper 32 bits differently depending whether K is simm13 or not.
  Since small constants are sign extended, whereas large constants
  are stored in temp register and zero extended.
  That is ok and we don't have to pay a penalty of sign extension
  for every sethi, since all classic BPF instructions have 32-bit
  semantics and we only need to set correct upper bits when
  transitioning from JITed code into C.

- though instructions 'A &= 0' and 'A *= 0' are odd, JIT compiler
  should not optimize them out

Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 543a2dff

arch/sparc/net/bpf_jit_asm.S

+3 −0
Original line number Diff line number Diff line
@@ -6,10 +6,12 @@ 
#define SAVE_SZ		176

#define SCRATCH_OFF	STACK_BIAS + 128

#define BE_PTR(label)	be,pn %xcc, label

#define SIGN_EXTEND(reg)	sra reg, 0, reg

#else

#define SAVE_SZ		96

#define SCRATCH_OFF	72

#define BE_PTR(label)	be label

#define SIGN_EXTEND(reg)

#endif



#define SKF_MAX_NEG_OFF	(-0x200000) /* SKF_LL_OFF from filter.h */
@@ -135,6 +137,7 @@ bpf_slow_path_byte_msh: 
	save	%sp, -SAVE_SZ, %sp;			\

	mov	%i0, %o0;				\

	mov	r_OFF, %o1;				\

	SIGN_EXTEND(%o1);				\

	call	bpf_internal_load_pointer_neg_helper;	\

	 mov	(LEN), %o2;				\

	mov	%o0, r_TMP;				\

arch/sparc/net/bpf_jit_comp.c

+1 −1
Original line number Diff line number Diff line
@@ -184,7 +184,7 @@ do { \ 
	 */

#define emit_alu_K(OPCODE, K)					\

do {								\

	if (K) {						\

	if (K || OPCODE == AND || OPCODE == MUL) {		\

		unsigned int _insn = OPCODE;			\

		_insn |= RS1(r_A) | RD(r_A);			\

		if (is_simm13(K)) {				\