Commit 9cb7f1e4 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Greg Kroah-Hartman

sparc: bpf_jit: fix loads from negative offsets

[ Upstream commit 35607b02 ]

- 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>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6e2d91c6
......@@ -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; \
......
......@@ -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)) { \
......
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