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powerpc/bpf: Always reallocate BPF_REG_5, BPF_REG_AX and TMP_REG when possible

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BPF_REG_5, BPF_REG_AX and TMP_REG are mapped on non volatile registers
because there are not enough volatile registers, but they don't need
to be preserved on function calls.

So when some volatile registers become available, those registers can
always be reallocated regardless of whether SEEN_FUNC is set or not.

Suggested-by: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b04c246874b716911139c04bc004b3b14eed07ef.1641817763.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2022-01-10 12:29:42 +00:00 committed by Michael Ellerman
parent f222ab83df
commit a8936569a0
2 changed files with 12 additions and 7 deletions
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3
arch/powerpc/net/bpf_jit.h
View File

@ -127,9 +127,6 @@
#define SEEN_FUNC 0x20000000 /* might call external helpers */
#define SEEN_TAILCALL 0x40000000 /* uses tail calls */
#define SEEN_VREG_MASK 0x1ff80000 /* Volatile registers r3-r12 */
#define SEEN_NVREG_MASK 0x0003ffff /* Non volatile registers r14-r31 */
#ifdef CONFIG_PPC64
extern const int b2p[MAX_BPF_JIT_REG + 2];
#else

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

@ -77,14 +77,22 @@ static int bpf_jit_stack_offsetof(struct codegen_context *ctx, int reg)
return BPF_PPC_STACKFRAME(ctx) - 4;
}
#define SEEN_VREG_MASK 0x1ff80000 /* Volatile registers r3-r12 */
#define SEEN_NVREG_FULL_MASK 0x0003ffff /* Non volatile registers r14-r31 */
#define SEEN_NVREG_TEMP_MASK 0x00001e01 /* BPF_REG_5, BPF_REG_AX, TMP_REG */
void bpf_jit_realloc_regs(struct codegen_context *ctx)
{
if (ctx->seen & SEEN_FUNC)
return;
unsigned int nvreg_mask;
while (ctx->seen & SEEN_NVREG_MASK &&
if (ctx->seen & SEEN_FUNC)
nvreg_mask = SEEN_NVREG_TEMP_MASK;
else
nvreg_mask = SEEN_NVREG_FULL_MASK;
while (ctx->seen & nvreg_mask &&
(ctx->seen & SEEN_VREG_MASK) != SEEN_VREG_MASK) {
int old = 32 - fls(ctx->seen & (SEEN_NVREG_MASK & 0xaaaaaaab));
int old = 32 - fls(ctx->seen & (nvreg_mask & 0xaaaaaaab));
int new = 32 - fls(~ctx->seen & (SEEN_VREG_MASK & 0xaaaaaaaa));
int i;