netdev - Re: [PATCH bpf-next v3 06/10] tools: bpftool: resolve calls without using imm field

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Message-ID: <20180522123643.5ed1e391@cakuba>
Date:   Tue, 22 May 2018 12:36:43 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Sandipan Das <sandipan@...ux.vnet.ibm.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, mpe@...erman.id.au,
        naveen.n.rao@...ux.vnet.ibm.com
Subject: Re: [PATCH bpf-next v3 06/10] tools: bpftool: resolve calls without
 using imm field

On Tue, 22 May 2018 22:46:09 +0530, Sandipan Das wrote:
> Currently, we resolve the callee's address for a JITed function
> call by using the imm field of the call instruction as an offset
> from __bpf_call_base. If bpf_jit_kallsyms is enabled, we further
> use this address to get the callee's kernel symbol's name.
> 
> For some architectures, such as powerpc64, the imm field is not
> large enough to hold this offset. So, instead of assigning this
> offset to the imm field, the verifier now assigns the subprog
> id. Also, a list of kernel symbol addresses for all the JITed
> functions is provided in the program info. We now use the imm
> field as an index for this list to lookup a callee's symbol's
> address and resolve its name.
> 
> Suggested-by: Daniel Borkmann <daniel@...earbox.net>
> Signed-off-by: Sandipan Das <sandipan@...ux.vnet.ibm.com>

Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>