Re: [PATCH v9 7/8] arm64: Store IMA log information in kimage used for kexec

[Lakshmi Ramasubramanian]

On 12/1/20 3:39 AM, Mimi Zohar wrote:
> On Fri, 2020-11-13 at 11:22 -0800, Lakshmi Ramasubramanian wrote:
> > Address and size of the buffer containing the IMA measurement log need
> > to be passed from the current kernel to the next kernel on kexec.
> >
> > Add address and size fields to "struct kimage_arch" for ARM64 platform
> > to hold the address and size of the IMA measurement log buffer.
> > Define an architecture specific function for ARM64 namely
> > arch_ima_add_kexec_buffer() that will set the address and size of
> > the current kernel's IMA buffer to be passed to the next kernel on kexec.
> >
> > Co-developed-by: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
> > Reviewed-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>
> > ---
> >   arch/arm64/include/asm/ima.h   | 18 ++++++++++++++++++
> >   arch/arm64/include/asm/kexec.h |  3 +++
> >   arch/arm64/kernel/Makefile     |  1 +
> >   arch/arm64/kernel/ima_kexec.c  | 34 ++++++++++++++++++++++++++++++++++
> >   4 files changed, 56 insertions(+)
> >   create mode 100644 arch/arm64/include/asm/ima.h
> >   create mode 100644 arch/arm64/kernel/ima_kexec.c
> >
> > diff --git a/arch/arm64/include/asm/ima.h b/arch/arm64/include/asm/ima.h
> > new file mode 100644
> > index 000000000000..507fc94ddaba
> > --- /dev/null
> > +++ b/arch/arm64/include/asm/ima.h
> > @@ -0,0 +1,18 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +/*
> > + * Copyright (C) 2019 Microsoft Corporation
> > + *
> > + * Author: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
> > + *
> > + */
> > +#ifndef _ASM_ARCH_IMA_H
> > +#define _ASM_ARCH_IMA_H
> > +
> > +struct kimage;
> > +
> > +#ifdef CONFIG_IMA_KEXEC
> > +int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
> > +			      size_t size);
> > +#endif /* CONFIG_IMA_KEXEC */
> > +
> > +#endif /* _ASM_ARCH_IMA_H */
> > diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
> > index d24b527e8c00..7bd60c185ad3 100644
> > --- a/arch/arm64/include/asm/kexec.h
> > +++ b/arch/arm64/include/asm/kexec.h
> > @@ -100,6 +100,9 @@ struct kimage_arch {
> >   	void *elf_headers;
> >   	unsigned long elf_headers_mem;
> >   	unsigned long elf_headers_sz;
> > +
> > +	phys_addr_t ima_buffer_addr;
> > +	size_t ima_buffer_size;
> >   };
>
> Any reason these definitions are not conditionally defined based on
> CONFIG_IMA_KEXEC, like on powerpc?

I'll define ima buffer related fields conditionally (CONFIG_IMA_KEXEC).

> > diff --git a/arch/arm64/kernel/ima_kexec.c b/arch/arm64/kernel/ima_kexec.c
> > new file mode 100644
> > index 000000000000..1847f1230710
> > --- /dev/null
> > +++ b/arch/arm64/kernel/ima_kexec.c
> > @@ -0,0 +1,34 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Copyright (C) 2019 Microsoft Corporation
> > + *
> > + * Author: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
> > + *
> > + * File: ima_kexec.c
> > + *       Defines IMA kexec functions.
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/kexec.h>
> > +#include <linux/types.h>
> > +#include <asm/ima.h>
> > +
> > +/**
> > + * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
> > + *
> > + * @image: kimage structure to set ima buffer information in for kexec
> > + * @load_addr: Start address of the IMA buffer
> > + * @size: size of the IMA buffer
> > + *
> > + * Architectures should use this function to pass on the IMA buffer
> > + * information to the next kernel.
> > + *
> > + * Return: 0 on success, negative errno on error.
> > + */
> > +int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
> > +			      size_t size)
> > +{
> > +	image->arch.ima_buffer_addr = load_addr;
> > +	image->arch.ima_buffer_size = size;
> > +	return 0;
> > +}
>
> This is exactly the same as the powerpc version.  Couldn't there be a
> common version of this as well?

I think it can be moved to a common version. I'll make that change.

thanks,
 -lakshmi