Le 25/08/2023 à 17:18, Hari Bathini a écrit :
> bpf_arch_text_copy is used to dump JITed binary to RX page, allowing
> multiple BPF programs to share the same page. Use patch_instruction()
> to implement it.
By using patch_instruction() for doing that you are mapping and
unmapping the same page for each instruction you copy. You should
implement something to map a page, copy all instruction going into that
page, unmap the page and map next page, etc ....
And then perform the icache flush at the end.
>
> Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxx>
> ---
> arch/powerpc/net/bpf_jit_comp.c | 40 ++++++++++++++++++++++++++++++++-
> 1 file changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index 37043dfc1add..170ebf8ac0f2 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c
> @@ -13,9 +13,12 @@
> #include <linux/netdevice.h>
> #include <linux/filter.h>
> #include <linux/if_vlan.h>
> -#include <asm/kprobes.h>
> +#include <linux/memory.h>
> #include <linux/bpf.h>
>
> +#include <asm/kprobes.h>
> +#include <asm/code-patching.h>
> +
> #include "bpf_jit.h"
>
> static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
> @@ -23,6 +26,27 @@ static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
> memset32(area, BREAKPOINT_INSTRUCTION, size / 4);
> }
>
> +/*
> + * Patch 'len' bytes of instructions from opcode to addr, one instruction
> + * at a time. Returns addr on success. ERR_PTR(-EINVAL), otherwise.
> + */
> +static void *bpf_patch_instructions(void *addr, void *opcode, size_t len)
> +{
> + while (len > 0) {
> + ppc_inst_t insn = ppc_inst_read(opcode);
> + int ilen = ppc_inst_len(insn);
> +
> + if (patch_instruction(addr, insn))
> + return ERR_PTR(-EINVAL);
> +
> + len -= ilen;
> + addr = addr + ilen;
> + opcode = opcode + ilen;
> + }
> +
> + return addr;
> +}
> +
> int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr)
> {
> if (!exit_addr || is_offset_in_branch_range(exit_addr - (ctx->idx * 4))) {
> @@ -274,3 +298,17 @@ int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct code
> ctx->exentry_idx++;
> return 0;
> }
> +
> +void *bpf_arch_text_copy(void *dst, void *src, size_t len)
> +{
> + void *ret;
> +
> + if (WARN_ON_ONCE(core_kernel_text((unsigned long)dst)))
> + return ERR_PTR(-EINVAL);
> +
> + mutex_lock(&text_mutex);
> + ret = bpf_patch_instructions(dst, src, len);
> + mutex_unlock(&text_mutex);
> +
> + return ret;
> +}
