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powerpc/ebpf32: Use standard function call for functions within 32M distance

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If the target of a function call is within 32 Mbytes distance, use a
standard function call with 'bl' instead of the 'lis/ori/mtlr/blrl'
sequence.

In the first pass, no memory has been allocated yet and the code
position is not known yet (image pointer is NULL). This pass is there
to calculate the amount of memory to allocate for the EBPF code, so
assume the 4 instructions sequence is required, so that enough memory
is allocated.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/74944a1e3e5cfecc141e440a6ccd37920e186b70.1618227846.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2021-04-12 11:44:18 +00:00 committed by Michael Ellerman
parent e7de0023e1
commit ee7c3ec3b4
3 changed files with 15 additions and 5 deletions
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1
arch/powerpc/include/asm/ppc-opcode.h
View File

@ -265,6 +265,7 @@
#define PPC_INST_ORI 0x60000000
#define PPC_INST_ORIS 0x64000000
#define PPC_INST_BRANCH 0x48000000
#define PPC_INST_BL 0x48000001
#define PPC_INST_BRANCH_COND 0x40800000
/* Prefixes */

3
arch/powerpc/net/bpf_jit.h
View File

@ -26,6 +26,9 @@
/* Long jump; (unconditional 'branch') */
#define PPC_JMP(dest) EMIT(PPC_INST_BRANCH | \
(((dest) - (ctx->idx * 4)) & 0x03fffffc))
/* blr; (unconditional 'branch' with link) to absolute address */
#define PPC_BL_ABS(dest) EMIT(PPC_INST_BL | \
(((dest) - (unsigned long)(image + ctx->idx)) & 0x03fffffc))
/* "cond" here covers BO:BI fields. */
#define PPC_BCC_SHORT(cond, dest) EMIT(PPC_INST_BRANCH_COND | \
(((cond) & 0x3ff) << 16) | \

16
arch/powerpc/net/bpf_jit_comp32.c
View File

@ -187,11 +187,17 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, u64 func)
{
/* Load function address into r0 */
EMIT(PPC_RAW_LIS(__REG_R0, IMM_H(func)));
EMIT(PPC_RAW_ORI(__REG_R0, __REG_R0, IMM_L(func)));
EMIT(PPC_RAW_MTLR(__REG_R0));
EMIT(PPC_RAW_BLRL());
s32 rel = (s32)func - (s32)(image + ctx->idx);
if (image && rel < 0x2000000 && rel >= -0x2000000) {
PPC_BL_ABS(func);
} else {
/* Load function address into r0 */
EMIT(PPC_RAW_LIS(__REG_R0, IMM_H(func)));
EMIT(PPC_RAW_ORI(__REG_R0, __REG_R0, IMM_L(func)));
EMIT(PPC_RAW_MTLR(__REG_R0));
EMIT(PPC_RAW_BLRL());
}
}
static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out)