Re: [PATCHv5 06/12] kexec: Integrate with the introduced bpf kfuncs

[Pingfan Liu <piliu@redhat.com>]

On Mon, Sep 01, 2025 at 04:30:42PM +0200, Philipp Rudo wrote:
> Hi Pingfan,
> 
> 
> On Tue, 19 Aug 2025 09:24:22 +0800
> Pingfan Liu <piliu@redhat.com> wrote:
> 
> > This patch does two things:
> > First, register as a listener on bpf_copy_to_kernel()
> > Second, in order that the hooked bpf-prog can call the sleepable kfuncs,
> > bpf_handle_pefile and bpf_post_handle_pefile are marked as
> > KF_SLEEPABLE.
> > 
> > Signed-off-by: Pingfan Liu <piliu@redhat.com>
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > Cc: Philipp Rudo <prudo@redhat.com>
> > Cc: Baoquan He <bhe@redhat.com>
> > Cc: Dave Young <dyoung@redhat.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: bpf@vger.kernel.org
> > To: kexec@lists.infradead.org
> > ---
> >  kernel/kexec_pe_image.c | 67 +++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 67 insertions(+)
> > 
> > diff --git a/kernel/kexec_pe_image.c b/kernel/kexec_pe_image.c
> > index b0cf9942e68d2..f8debcde6b516 100644
> > --- a/kernel/kexec_pe_image.c
> > +++ b/kernel/kexec_pe_image.c
> > @@ -38,6 +38,51 @@ static struct kexec_res parsed_resource[3] = {
> >  	{ KEXEC_RES_CMDLINE_NAME, },
> >  };
> >  
> > +/*
> > + * @name should be one of : kernel, initrd, cmdline
> > + */
> > +static int bpf_kexec_carrier(const char *name, struct mem_range_result *r)
> > +{
> > +	struct kexec_res *res;
> > +	int i;
> > +
> > +	if (!r || !name)
> > +		return -EINVAL;
> > +
> > +	for (i = 0; i < 3; i++) {
> > +		if (!strcmp(parsed_resource[i].name, name))
> > +			break;
> > +	}
> > +	if (i >= 3)
> > +		return -EINVAL;
> 
> Can you please replace the magic '3' by ARRAY_SIZE, just like you did
> below when (un-)registering the listener.
> 

Yes, I will introduce a macro KEXEC_RES_ARRAY_SIZE to unify all of them.

Thanks,

Pingfan

> Thanks
> Philipp
> 
> > +
> > +	res = &parsed_resource[i];
> > +	/*
> > +	 * Replace the intermediate resource generated by the previous step.
> > +	 */
> > +	if (!!res->r)
> > +		mem_range_result_put(res->r);
> > +	mem_range_result_get(r);
> > +	res->r = r;
> > +	return 0;
> > +}
> > +
> > +static struct carrier_listener kexec_res_listener[3] = {
> > +	{ .name = KEXEC_RES_KERNEL_NAME,
> > +	  .alloc_type = 1,
> > +	  .handler = bpf_kexec_carrier,
> > +	},
> > +	{ .name = KEXEC_RES_INITRD_NAME,
> > +	  .alloc_type = 1,
> > +	  .handler = bpf_kexec_carrier,
> > +	},
> > +	{ .name = KEXEC_RES_CMDLINE_NAME,
> > +	  /* kmalloc-ed */
> > +	  .alloc_type = 0,
> > +	  .handler = bpf_kexec_carrier,
> > +	},
> > +};
> > +
> >  static bool pe_has_bpf_section(const char *file_buf, unsigned long pe_sz);
> >  
> >  static bool is_valid_pe(const char *kernel_buf, unsigned long kernel_len)
> > @@ -159,6 +204,22 @@ __attribute__((used, optimize("O0"))) void bpf_post_handle_pefile(struct kexec_c
> >  	dummy += 2;
> >  }
> >  
> > +BTF_KFUNCS_START(kexec_modify_return_ids)
> > +BTF_ID_FLAGS(func, bpf_handle_pefile, KF_SLEEPABLE)
> > +BTF_ID_FLAGS(func, bpf_post_handle_pefile, KF_SLEEPABLE)
> > +BTF_KFUNCS_END(kexec_modify_return_ids)
> > +
> > +static const struct btf_kfunc_id_set kexec_modify_return_set = {
> > +	.owner = THIS_MODULE,
> > +	.set = &kexec_modify_return_ids,
> > +};
> > +
> > +static int __init kexec_bpf_prog_run_init(void)
> > +{
> > +	return register_btf_fmodret_id_set(&kexec_modify_return_set);
> > +}
> > +late_initcall(kexec_bpf_prog_run_init);
> > +
> >  /*
> >   * PE file may be nested and should be unfold one by one.
> >   * Query 'kernel', 'initrd', 'cmdline' in cur_phase, as they are inputs for the
> > @@ -213,6 +274,9 @@ static void *pe_image_load(struct kimage *image,
> >  	cmdline_start = cmdline;
> >  	cmdline_sz = cmdline_len;
> >  
> > +	for (int i = 0; i < ARRAY_SIZE(kexec_res_listener); i++)
> > +		register_carrier_listener(&kexec_res_listener[i]);
> > +
> >  	while (is_valid_format(linux_start, linux_sz) &&
> >  	       pe_has_bpf_section(linux_start, linux_sz)) {
> >  		struct kexec_context context;
> > @@ -250,6 +314,9 @@ static void *pe_image_load(struct kimage *image,
> >  		disarm_bpf_prog();
> >  	}
> >  
> > +	for (int i = 0; i < ARRAY_SIZE(kexec_res_listener); i++)
> > +		unregister_carrier_listener(kexec_res_listener[i].name);
> > +
> >  	/*
> >  	 * image's kernel_buf, initrd_buf, cmdline_buf are set. Now they should
> >  	 * be updated to the new content.
>