Re: [PATCH v5 8/8] remoteproc: Adapt coredump to generate correct elf type

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Mon 09 Mar 13:32 PDT 2020, Mathieu Poirier wrote:

> On Mon, Mar 02, 2020 at 10:39:02AM +0100, Clement Leger wrote:
> > Now that remoteproc can load an elf64, coredump elf class should be
> > the same as the loaded elf class. In order to do that, add a
> > elf_class field to rproc with default values. If an elf is loaded
> > successfully, this field will be updated with the loaded elf class.
> > Then, the coredump core code has been modified to use the generic elf
> > macro in order to create an elf file with correct class.
> > 
> > Signed-off-by: Clement Leger <cleger@kalray.eu>
> > ---
> >  drivers/remoteproc/remoteproc_core.c       | 67 ++++++++++++++++--------------
> >  drivers/remoteproc/remoteproc_elf_loader.c |  3 ++
> >  include/linux/remoteproc.h                 |  1 +
> >  3 files changed, 39 insertions(+), 32 deletions(-)
> > 
> > diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> > index b932a64a2be2..f923355aa3f9 100644
> > --- a/drivers/remoteproc/remoteproc_core.c
> > +++ b/drivers/remoteproc/remoteproc_core.c
> > @@ -38,6 +38,7 @@
> >  #include <linux/platform_device.h>
> >  
> >  #include "remoteproc_internal.h"
> > +#include "remoteproc_elf_helpers.h"
> >  
> >  #define HIGH_BITS_MASK 0xFFFFFFFF00000000ULL
> >  
> > @@ -1566,20 +1567,21 @@ EXPORT_SYMBOL(rproc_coredump_add_custom_segment);
> >  static void rproc_coredump(struct rproc *rproc)
> >  {
> >  	struct rproc_dump_segment *segment;
> > -	struct elf32_phdr *phdr;
> > -	struct elf32_hdr *ehdr;
> > +	void *phdr;
> > +	void *ehdr;
> >  	size_t data_size;
> >  	size_t offset;
> >  	void *data;
> >  	void *ptr;
> > +	u8 class = rproc->elf_class;
> >  	int phnum = 0;
> >  
> >  	if (list_empty(&rproc->dump_segments))
> >  		return;
> >  
> > -	data_size = sizeof(*ehdr);
> > +	data_size = elf_size_of_hdr(class);
> >  	list_for_each_entry(segment, &rproc->dump_segments, node) {
> > -		data_size += sizeof(*phdr) + segment->size;
> > +		data_size += elf_size_of_phdr(class) + segment->size;
> >  
> >  		phnum++;
> >  	}
> > @@ -1590,33 +1592,33 @@ static void rproc_coredump(struct rproc *rproc)
> >  
> >  	ehdr = data;
> >  
> > -	memset(ehdr, 0, sizeof(*ehdr));
> > -	memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
> > -	ehdr->e_ident[EI_CLASS] = ELFCLASS32;
> > -	ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
> > -	ehdr->e_ident[EI_VERSION] = EV_CURRENT;
> > -	ehdr->e_ident[EI_OSABI] = ELFOSABI_NONE;
> > -	ehdr->e_type = ET_CORE;
> > -	ehdr->e_machine = EM_NONE;
> > -	ehdr->e_version = EV_CURRENT;
> > -	ehdr->e_entry = rproc->bootaddr;
> > -	ehdr->e_phoff = sizeof(*ehdr);
> > -	ehdr->e_ehsize = sizeof(*ehdr);
> > -	ehdr->e_phentsize = sizeof(*phdr);
> > -	ehdr->e_phnum = phnum;
> > -
> > -	phdr = data + ehdr->e_phoff;
> > -	offset = ehdr->e_phoff + sizeof(*phdr) * ehdr->e_phnum;
> > +	memset(ehdr, 0, elf_size_of_hdr(class));
> > +	/* e_ident field is common for both elf32 and elf64 */
> > +	elf_hdr_init_ident(ehdr, class);
> > +
> > +	elf_hdr_set_e_type(class, ehdr, ET_CORE);
> > +	elf_hdr_set_e_machine(class, ehdr, EM_NONE);
> > +	elf_hdr_set_e_version(class, ehdr, EV_CURRENT);
> > +	elf_hdr_set_e_entry(class, ehdr, rproc->bootaddr);
> > +	elf_hdr_set_e_phoff(class, ehdr, elf_size_of_hdr(class));
> > +	elf_hdr_set_e_ehsize(class, ehdr, elf_size_of_hdr(class));
> > +	elf_hdr_set_e_phentsize(class, ehdr, elf_size_of_phdr(class));
> > +	elf_hdr_set_e_phnum(class, ehdr, phnum);
> > +
> > +	phdr = data + elf_hdr_get_e_phoff(class, ehdr);
> > +	offset = elf_hdr_get_e_phoff(class, ehdr);
> > +	offset += elf_size_of_phdr(class) * elf_hdr_get_e_phnum(class, ehdr);
> > +
> >  	list_for_each_entry(segment, &rproc->dump_segments, node) {
> > -		memset(phdr, 0, sizeof(*phdr));
> > -		phdr->p_type = PT_LOAD;
> > -		phdr->p_offset = offset;
> > -		phdr->p_vaddr = segment->da;
> > -		phdr->p_paddr = segment->da;
> > -		phdr->p_filesz = segment->size;
> > -		phdr->p_memsz = segment->size;
> > -		phdr->p_flags = PF_R | PF_W | PF_X;
> > -		phdr->p_align = 0;
> > +		memset(phdr, 0, elf_size_of_phdr(class));
> > +		elf_phdr_set_p_type(class, phdr, PT_LOAD);
> > +		elf_phdr_set_p_offset(class, phdr, offset);
> > +		elf_phdr_set_p_vaddr(class, phdr, segment->da);
> > +		elf_phdr_set_p_paddr(class, phdr, segment->da);
> > +		elf_phdr_set_p_filesz(class, phdr, segment->size);
> > +		elf_phdr_set_p_memsz(class, phdr, segment->size);
> > +		elf_phdr_set_p_flags(class, phdr, PF_R | PF_W | PF_X);
> > +		elf_phdr_set_p_align(class, phdr, 0);
> >  
> >  		if (segment->dump) {
> >  			segment->dump(rproc, segment, data + offset);
> > @@ -1632,8 +1634,8 @@ static void rproc_coredump(struct rproc *rproc)
> >  			}
> >  		}
> >  
> > -		offset += phdr->p_filesz;
> > -		phdr++;
> > +		offset += elf_phdr_get_p_filesz(class, phdr);
> > +		phdr += elf_size_of_phdr(class);
> >  	}
> >  
> >  	dev_coredumpv(&rproc->dev, data, data_size, GFP_KERNEL);
> > @@ -2031,6 +2033,7 @@ struct rproc *rproc_alloc(struct device *dev, const char *name,
> >  	rproc->name = name;
> >  	rproc->priv = &rproc[1];
> >  	rproc->auto_boot = true;
> > +	rproc->elf_class = ELFCLASS32;
> 
> I would initialise this to ELFCLASSNONE to make sure that if a platform driver
> overwrites rproc_elf_load_segments or doesn't provide one, we don't falsely
> deduce the elf type.  It goes without saying that if elf_class == ELFCLASSNONE,
> a coredump is not generated. 
> 

I like the idea of making the choice explicit, perhaps even more
explicit than the assumption that the coredumps should be of the same
type as the ELF loaded. Note that it's different consumers of the two
ELF files.

> Unless you think this is a seriously bad idea or Bjorn over rules me,
> 
> Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> 

Not sure if it count as "over ruling", I accept your suggestion but used
your R-b to merge the patch as is, no need to hold this up any longer.

Clement, can you please follow up with a patch implementing this (don't
forget that the qcom drivers doesn't use rproc_elf_load_segments())

Thanks Clement and thanks for the reviews Mathieu.

Regards,
Bjorn

> Thanks,
> Mathieu
> 
> >  
> >  	device_initialize(&rproc->dev);
> >  	rproc->dev.parent = dev;
> > diff --git a/drivers/remoteproc/remoteproc_elf_loader.c b/drivers/remoteproc/remoteproc_elf_loader.c
> > index 4869fb7d8fe4..16e2c496fd45 100644
> > --- a/drivers/remoteproc/remoteproc_elf_loader.c
> > +++ b/drivers/remoteproc/remoteproc_elf_loader.c
> > @@ -248,6 +248,9 @@ int rproc_elf_load_segments(struct rproc *rproc, const struct firmware *fw)
> >  			memset(ptr + filesz, 0, memsz - filesz);
> >  	}
> >  
> > +	if (ret == 0)
> > +		rproc->elf_class = class;
> > +
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL(rproc_elf_load_segments);
> > diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> > index 1683d6c386a6..ed127b2d35ca 100644
> > --- a/include/linux/remoteproc.h
> > +++ b/include/linux/remoteproc.h
> > @@ -514,6 +514,7 @@ struct rproc {
> >  	bool auto_boot;
> >  	struct list_head dump_segments;
> >  	int nb_vdev;
> > +	u8 elf_class;
> >  };
> >  
> >  /**
> > -- 
> > 2.15.0.276.g89ea799
> >