Christophe Leroy wrote:
Le 13/12/2022 à 11:23, Naveen N. Rao a écrit :
Christophe Leroy wrote:
BPF core calls the jit compiler again for an extra pass in order
to properly set subprog addresses.
Unlike other architectures, powerpc only updates the addresses
during that extra pass. It means that holes must have been left
in the code in order to enable the maximum possible instruction
size.
In order avoid waste of space, and waste of CPU time on powerpc
processors on which the NOP instruction is not 0-cycle, perform
two real additional passes.
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
arch/powerpc/net/bpf_jit_comp.c | 85 ---------------------------------
1 file changed, 85 deletions(-)
diff --git a/arch/powerpc/net/bpf_jit_comp.c
b/arch/powerpc/net/bpf_jit_comp.c
index 43e634126514..8833bf23f5aa 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -23,74 +23,6 @@ static void bpf_jit_fill_ill_insns(void *area,
unsigned int size)
memset32(area, BREAKPOINT_INSTRUCTION, size / 4);
}
-/* Fix updated addresses (for subprog calls, ldimm64, et al) during
extra pass */
-static int bpf_jit_fixup_addresses(struct bpf_prog *fp, u32 *image,
- struct codegen_context *ctx, u32 *addrs)
-{
- const struct bpf_insn *insn = fp->insnsi;
- bool func_addr_fixed;
- u64 func_addr;
- u32 tmp_idx;
- int i, j, ret;
-
- for (i = 0; i < fp->len; i++) {
- /*
- * During the extra pass, only the branch target addresses for
- * the subprog calls need to be fixed. All other instructions
- * can left untouched.
- *
- * The JITed image length does not change because we already
- * ensure that the JITed instruction sequence for these calls
- * are of fixed length by padding them with NOPs.
- */
- if (insn[i].code == (BPF_JMP | BPF_CALL) &&
- insn[i].src_reg == BPF_PSEUDO_CALL) {
- ret = bpf_jit_get_func_addr(fp, &insn[i], true,
- &func_addr,
- &func_addr_fixed);
I don't see you updating calls to bpf_jit_get_func_addr() in
bpf_jit_build_body() to set extra_pass to true. Afaics, that's required
to get the correct address to be branched to for subprogs.
I don't understand what you mean.
I am referring to the third parameter we pass to
bpf_jit_get_func_addr().
In bpf_jit_build_body(), we do:
case BPF_JMP | BPF_CALL:
ctx->seen |= SEEN_FUNC;
ret = bpf_jit_get_func_addr(fp, &insn[i], false,
&func_addr, &func_addr_fixed);
The third parameter (extra_pass) to bpf_jit_get_func_addr() is set to
false. In bpf_jit_get_func_addr(), we have:
*func_addr_fixed = insn->src_reg != BPF_PSEUDO_CALL;
if (!*func_addr_fixed) {
/* Place-holder address till the last pass has collected
* all addresses for JITed subprograms in which case we
* can pick them up from prog->aux.
*/
if (!extra_pass)
addr = NULL;
Before this patch series, in bpf_jit_fixup_addresses(), we were calling
bpf_jit_get_func_addr() with the third parameter set to true.
- Naveen
