Re: [PATCH v2] remoteproc: Add elf64 support in elf loader

From: Mathieu Poirier
Date: Fri Jan 24 2020 - 16:58:49 EST

On Fri, Jan 24, 2020 at 09:24:16AM +0100, Clément Leger wrote:
> Hi Mathieu,
>
> ----- On 24 Jan, 2020, at 01:53, Mathieu Poirier mathieu.poirier@xxxxxxxxxx wrote:
>
> > Hi Clement,
> >
> > On Fri, Oct 04, 2019 at 08:42:20PM +0200, Clement Leger wrote:
> >> elf32 and elf64 mainly differ by their types. In order to avoid
> >> copy/pasting the whole loader code, generate static inline functions
> >> which will access values according to the elf class. It allows to keep a
> >> common loader basis.
> >> In order to accomodate both elf types sizes, the maximum size for a
> >> elf header member is chosen using the maximum value of both elf class.
> >>
> >> Signed-off-by: Clement Leger <cleger@xxxxxxxxx>
> >> Tested-by: Arnaud POULIQUEN <arnaud.pouliquen@xxxxxx>
> >> ---
> >> Changes in v2:
> >> - Add ELF64 support in documentation
> >>
> >
> > First and foremost please address the complaints from checkpatch.
>
> I fixed one typo in accommodate. The other checkpatch complaint is
> about missing parenthesis for macros with complex values which is
> unfortunately not possible since I'm generating inline functions.
>
> Did you have any other one ?
>
> >
> >> ---
> >> Documentation/remoteproc.txt | 2 +-
> >> drivers/remoteproc/remoteproc_elf_loader.c | 135 ++++++++++++++++++-----------
> >> drivers/remoteproc/remoteproc_elf_loader.h | 69 +++++++++++++++
> >> drivers/remoteproc/remoteproc_internal.h | 2 +-
> >> drivers/remoteproc/st_remoteproc.c | 2 +-
> >> include/linux/remoteproc.h | 4 +-
> >> 6 files changed, 157 insertions(+), 57 deletions(-)
> >> create mode 100644 drivers/remoteproc/remoteproc_elf_loader.h
> >>
> >> diff --git a/Documentation/remoteproc.txt b/Documentation/remoteproc.txt
> >> index 77fb03acdbb4..bf4f0c41ec4e 100644
> >> --- a/Documentation/remoteproc.txt
> >> +++ b/Documentation/remoteproc.txt
> >> @@ -230,7 +230,7 @@ in the used rings.
> >> Binary Firmware Structure
> >> =========================
> >>
> >> -At this point remoteproc only supports ELF32 firmware binaries. However,
> >> +At this point remoteproc supports ELF32 and ELF64 firmware binaries. However,
> >> it is quite expected that other platforms/devices which we'd want to
> >> support with this framework will be based on different binary formats.
> >>
> >> diff --git a/drivers/remoteproc/remoteproc_elf_loader.c
> >> b/drivers/remoteproc/remoteproc_elf_loader.c
> >> index b17d72ec8603..6a2d31d6092c 100644
> >> --- a/drivers/remoteproc/remoteproc_elf_loader.c
> >> +++ b/drivers/remoteproc/remoteproc_elf_loader.c
> >> @@ -31,6 +31,7 @@
> >> #include <linux/elf.h>
> >>
> >> #include "remoteproc_internal.h"
> >> +#include "remoteproc_elf_loader.h"
> >>
> >> /**
> >> * rproc_elf_sanity_check() - Sanity Check ELF firmware image
> >> @@ -43,8 +44,16 @@ int rproc_elf_sanity_check(struct rproc *rproc, const struct
> >> firmware *fw)
> >> {
> >> const char *name = rproc->firmware;
> >> struct device *dev = &rproc->dev;
> >> + /*
> >> + * Elf files are beginning with the same structure. Thus, to simplify
> >> + * header parsing, we can use the elf32_hdr one for both elf64 and
> >> + * elf32.
> >> + */
> >> struct elf32_hdr *ehdr;
> >> + u32 elf_shdr_size;
> >> + u64 phoff, shoff;
> >> char class;
> >> + u16 phnum;
> >>
> >> if (!fw) {
> >> dev_err(dev, "failed to load %s\n", name);
> >> @@ -58,9 +67,13 @@ int rproc_elf_sanity_check(struct rproc *rproc, const struct
> >> firmware *fw)
> >
> > In the current code [1] fw->size is compared against the size of an elf32_hdr.
> > If support for elf64 is added that code needs to be modified to check for the
> > right header size using fw_elf_get_class().
>
> Actually, the elf32 header is smaller than the elf64 one so this check is
> there to ensure that we have at least a minimal elf header (elf32).
> And since the class is derived from the header, you better have to check the
> header size before accessing it.
>
> To be more clear, I could compare it to min(sizeof(struct elf32_hdr),
> sizeof(struct elf64_hdr)) or add a comment at least stating that since
> elf header contains the same fields for identification, we can use the
> elf32 one.
>
> >
> > [1]
> > https://elixir.bootlin.com/linux/v5.5-rc6/source/drivers/remoteproc/remoteproc_elf_loader.c#L46
> >
> >>
> >> ehdr = (struct elf32_hdr *)fw->data;
> >>
> >> - /* We only support ELF32 at this point */
> >> + if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG)) {
> >> + dev_err(dev, "Image is corrupted (bad magic)\n");
> >> + return -EINVAL;
> >> + }
> >> +
> >
> > Is there a reason to move this check up where? If not please bring it back to
> > its original location, that is below:
> >
> > "if (fw->size < ehdr->e_shoff + sizeof(structelf32_shdr))"
> >
>
> This is because the new check for size uses elf_shdr_size which is derived from
> the class. And since the class is extracted from the elf header, we need to check
> the header to be correct first.
>
> >> class = ehdr->e_ident[EI_CLASS];
> >> - if (class != ELFCLASS32) {
> >> + if (class != ELFCLASS32 && class != ELFCLASS64) {
> >> dev_err(dev, "Unsupported class: %d\n", class);
> >> return -EINVAL;
> >> }
> >> @@ -75,26 +88,29 @@ int rproc_elf_sanity_check(struct rproc *rproc, const struct
> >> firmware *fw)
> >> return -EINVAL;
> >> }
> >>
> >> - if (fw->size < ehdr->e_shoff + sizeof(struct elf32_shdr)) {
> >> - dev_err(dev, "Image is too small\n");
> >> - return -EINVAL;
> >> - }
> >> + phoff = elf_hdr_e_phoff(class, fw->data);
> >> + shoff = elf_hdr_e_shoff(class, fw->data);
> >> + phnum = elf_hdr_e_phnum(class, fw->data);
> >> + elf_shdr_size = elf_size_of_shdr(class);
> >>
> >> - if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG)) {
> >> - dev_err(dev, "Image is corrupted (bad magic)\n");
> >> + if (fw->size < shoff + elf_shdr_size) {
> >> + dev_err(dev, "Image is too small\n");
> >> return -EINVAL;
> >> }
> >>
> >> - if (ehdr->e_phnum == 0) {
> >> + if (phnum == 0) {
> >> dev_err(dev, "No loadable segments\n");
> >> return -EINVAL;
> >> }
> >>
> >> - if (ehdr->e_phoff > fw->size) {
> >> + if (phoff > fw->size) {
> >> dev_err(dev, "Firmware size is too small\n");
> >> return -EINVAL;
> >> }
> >>
> >> + dev_dbg(dev, "Firmware is an elf%d file\n",
> >> + class == ELFCLASS32 ? 32 : 64);
> >> +
> >
> > Yes, this is useful.
> >
> >> return 0;
> >> }
> >> EXPORT_SYMBOL(rproc_elf_sanity_check);
> >> @@ -110,11 +126,9 @@ EXPORT_SYMBOL(rproc_elf_sanity_check);
> >> * Note that the boot address is not a configurable property of all remote
> >> * processors. Some will always boot at a specific hard-coded address.
> >> */
> >> -u32 rproc_elf_get_boot_addr(struct rproc *rproc, const struct firmware *fw)
> >> +u64 rproc_elf_get_boot_addr(struct rproc *rproc, const struct firmware *fw)
> >> {
> >> - struct elf32_hdr *ehdr = (struct elf32_hdr *)fw->data;
> >> -
> >> - return ehdr->e_entry;
> >> + return elf_hdr_e_entry(fw_elf_get_class(fw), fw->data);
> >> }
> >> EXPORT_SYMBOL(rproc_elf_get_boot_addr);
> >>
> >> @@ -145,37 +159,41 @@ EXPORT_SYMBOL(rproc_elf_get_boot_addr);
> >> int rproc_elf_load_segments(struct rproc *rproc, const struct firmware *fw)
> >> {
> >> struct device *dev = &rproc->dev;
> >> - struct elf32_hdr *ehdr;
> >> - struct elf32_phdr *phdr;
> >> + const void *ehdr, *phdr;
> >> int i, ret = 0;
> >> + u16 phnum;
> >> const u8 *elf_data = fw->data;
> >> + u8 class = fw_elf_get_class(fw);
> >> + u32 elf_phdr_size = elf_size_of_phdr(class);
> >>
> >> - ehdr = (struct elf32_hdr *)elf_data;
> >> - phdr = (struct elf32_phdr *)(elf_data + ehdr->e_phoff);
> >> + ehdr = elf_data;
> >> + phnum = elf_hdr_e_phnum(class, ehdr);
> >> + phdr = elf_data + elf_hdr_e_phoff(class, ehdr);
> >>
> >> /* go through the available ELF segments */
> >> - for (i = 0; i < ehdr->e_phnum; i++, phdr++) {
> >> - u32 da = phdr->p_paddr;
> >> - u32 memsz = phdr->p_memsz;
> >> - u32 filesz = phdr->p_filesz;
> >> - u32 offset = phdr->p_offset;
> >> + for (i = 0; i < phnum; i++, phdr += elf_phdr_size) {
> >> + u64 da = elf_phdr_p_paddr(class, phdr);
> >> + u64 memsz = elf_phdr_p_memsz(class, phdr);
> >> + u64 filesz = elf_phdr_p_filesz(class, phdr);
> >> + u64 offset = elf_phdr_p_offset(class, phdr);
> >> + u32 type = elf_phdr_p_type(class, phdr);
> >> void *ptr;
> >>
> >> - if (phdr->p_type != PT_LOAD)
> >> + if (type != PT_LOAD)
> >> continue;
> >>
> >> - dev_dbg(dev, "phdr: type %d da 0x%x memsz 0x%x filesz 0x%x\n",
> >> - phdr->p_type, da, memsz, filesz);
> >> + dev_dbg(dev, "phdr: type %d da 0x%llx memsz 0x%llx filesz 0x%llx\n",
> >> + type, da, memsz, filesz);
> >>
> >> if (filesz > memsz) {
> >> - dev_err(dev, "bad phdr filesz 0x%x memsz 0x%x\n",
> >> + dev_err(dev, "bad phdr filesz 0x%llx memsz 0x%llx\n",
> >> filesz, memsz);
> >> ret = -EINVAL;
> >> break;
> >> }
> >>
> >> if (offset + filesz > fw->size) {
> >> - dev_err(dev, "truncated fw: need 0x%x avail 0x%zx\n",
> >> + dev_err(dev, "truncated fw: need 0x%llx avail 0x%zx\n",
> >> offset + filesz, fw->size);
> >> ret = -EINVAL;
> >> break;
> >> @@ -184,14 +202,15 @@ int rproc_elf_load_segments(struct rproc *rproc, const
> >> struct firmware *fw)
> >> /* grab the kernel address for this device address */
> >> ptr = rproc_da_to_va(rproc, da, memsz);
> >> if (!ptr) {
> >> - dev_err(dev, "bad phdr da 0x%x mem 0x%x\n", da, memsz);
> >> + dev_err(dev, "bad phdr da 0x%llx mem 0x%llx\n", da,
> >> + memsz);
> >> ret = -EINVAL;
> >> break;
> >> }
> >>
> >> /* put the segment where the remote processor expects it */
> >> - if (phdr->p_filesz)
> >> - memcpy(ptr, elf_data + phdr->p_offset, filesz);
> >> + if (filesz)
> >> + memcpy(ptr, elf_data + offset, filesz);
> >>
> >> /*
> >> * Zero out remaining memory for this segment.
> >> @@ -208,24 +227,32 @@ int rproc_elf_load_segments(struct rproc *rproc, const
> >> struct firmware *fw)
> >> }
> >> EXPORT_SYMBOL(rproc_elf_load_segments);
> >>
> >> -static struct elf32_shdr *
> >> -find_table(struct device *dev, struct elf32_hdr *ehdr, size_t fw_size)
> >> +static const void *
> >
> > Not sure I understand the "const" - was the compiler complaining?
>
> It's actually caused by the fact I used a const void* shdr in the caller.
> I will check if this is mandatory.
>
> >
> >> +find_table(struct device *dev, const struct firmware *fw)
> >> {
> >> - struct elf32_shdr *shdr;
> >> + const void *shdr, *name_table_shdr;
> >> int i;
> >> const char *name_table;
> >> struct resource_table *table = NULL;
> >> - const u8 *elf_data = (void *)ehdr;
> >> + const u8 *elf_data = (void *)fw->data;
> >> + u8 class = fw_elf_get_class(fw);
> >> + size_t fw_size = fw->size;
> >> + const void *ehdr = elf_data;
> >> + u16 shnum = elf_hdr_e_shnum(class, ehdr);
> >> + u32 elf_shdr_size = elf_size_of_shdr(class);
> >> + u16 shstrndx = elf_hdr_e_shstrndx(class, ehdr);
> >>
> >> /* look for the resource table and handle it */
> >> - shdr = (struct elf32_shdr *)(elf_data + ehdr->e_shoff);
> >> - name_table = elf_data + shdr[ehdr->e_shstrndx].sh_offset;
> >> + shdr = elf_data + elf_hdr_e_shoff(class, ehdr);
> >> + name_table_shdr = shdr + (shstrndx * elf_shdr_size);
> >> + name_table = elf_data + elf_shdr_sh_offset(class, name_table_shdr);
> >
> > It took me a while but I figured out what is happening here. To save me (and
> > other people) from going through the same mental process every time I look at
> > this code, please add a comment for each of the above 3 lines.
>
> Indeed.
>
> >
> >>
> >> - for (i = 0; i < ehdr->e_shnum; i++, shdr++) {
> >> - u32 size = shdr->sh_size;
> >> - u32 offset = shdr->sh_offset;
> >> + for (i = 0; i < shnum; i++, shdr += elf_shdr_size) {
> >> + u64 size = elf_shdr_sh_size(class, shdr);
> >> + u64 offset = elf_shdr_sh_offset(class, shdr);
> >> + u32 name = elf_shdr_sh_name(class, shdr);
> >>
> >> - if (strcmp(name_table + shdr->sh_name, ".resource_table"))
> >> + if (strcmp(name_table + name, ".resource_table"))
> >> continue;
> >>
> >> table = (struct resource_table *)(elf_data + offset);
> >> @@ -279,21 +306,21 @@ find_table(struct device *dev, struct elf32_hdr *ehdr,
> >> size_t fw_size)
> >> */
> >> int rproc_elf_load_rsc_table(struct rproc *rproc, const struct firmware *fw)
> >> {
> >> - struct elf32_hdr *ehdr;
> >> - struct elf32_shdr *shdr;
> >> + const void *shdr;
> >> struct device *dev = &rproc->dev;
> >> struct resource_table *table = NULL;
> >> const u8 *elf_data = fw->data;
> >> size_t tablesz;
> >> + u8 class = fw_elf_get_class(fw);
> >> + u64 sh_offset;
> >>
> >> - ehdr = (struct elf32_hdr *)elf_data;
> >> -
> >> - shdr = find_table(dev, ehdr, fw->size);
> >> + shdr = find_table(dev, fw);
> >> if (!shdr)
> >> return -EINVAL;
> >>
> >> - table = (struct resource_table *)(elf_data + shdr->sh_offset);
> >> - tablesz = shdr->sh_size;
> >> + sh_offset = elf_shdr_sh_offset(class, shdr);
> >> + table = (struct resource_table *)(elf_data + sh_offset);
> >> + tablesz = elf_shdr_sh_size(class, shdr);
> >>
> >> /*
> >> * Create a copy of the resource table. When a virtio device starts
> >> @@ -326,13 +353,17 @@ EXPORT_SYMBOL(rproc_elf_load_rsc_table);
> >> struct resource_table *rproc_elf_find_loaded_rsc_table(struct rproc *rproc,
> >> const struct firmware *fw)
> >> {
> >> - struct elf32_hdr *ehdr = (struct elf32_hdr *)fw->data;
> >> - struct elf32_shdr *shdr;
> >> + const void *shdr;
> >> + u64 sh_addr, sh_size;
> >> + u8 class = fw_elf_get_class(fw);
> >>
> >> - shdr = find_table(&rproc->dev, ehdr, fw->size);
> >> + shdr = find_table(&rproc->dev, fw);
> >> if (!shdr)
> >> return NULL;
> >>
> >> - return rproc_da_to_va(rproc, shdr->sh_addr, shdr->sh_size);
> >> + sh_addr = elf_shdr_sh_addr(class, shdr);
> >> + sh_size = elf_shdr_sh_size(class, shdr);
> >> +
> >> + return rproc_da_to_va(rproc, sh_addr, sh_size);
> >
> > The prototype for the above is as follow:
> >
> > void *rproc_da_to_va(struct rproc *rproc, u64 da, int len)
> >
> > But sh_size is a u64, which will cause problem that are hard to debug. I think
> > it is better to move 'len' to an 8 byte type along with the refactoring of the
> > existing code that is implied. I suggest to split this work in a preparatory
> > patch (that will still be part of this set).
>
> Nice catch ! I will do that.
>
> >
> >> }
> >> EXPORT_SYMBOL(rproc_elf_find_loaded_rsc_table);
> >> diff --git a/drivers/remoteproc/remoteproc_elf_loader.h
> >> b/drivers/remoteproc/remoteproc_elf_loader.h
> >> new file mode 100644
> >> index 000000000000..fac3565734f9
> >> --- /dev/null
> >> +++ b/drivers/remoteproc/remoteproc_elf_loader.h
> >> @@ -0,0 +1,69 @@
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> >> +/*
> >> + * Remote processor elf loader defines
> >> + *
> >> + * Copyright (C) 2019 Kalray, Inc.
> >> + */
> >> +
> >> +#ifndef REMOTEPROC_ELF_LOADER_H
> >> +#define REMOTEPROC_ELF_LOADER_H
> >> +
> >> +#include <linux/elf.h>
> >> +#include <linux/types.h>
> >> +
> >> +/**
> >> + * fw_elf_get_class - Get elf class
> >> + * @fw: the ELF firmware image
> >> + *
> >> + * Note that we use and elf32_hdr to access the class since the start of the
> >> + * struct is the same for both elf class
> >> + *
> >> + * Return: elf class of the firmware
> >> + */
> >> +static inline u8 fw_elf_get_class(const struct firmware *fw)
> >> +{
> >> + struct elf32_hdr *ehdr = (struct elf32_hdr *)fw->data;
> >> +
> >> + return ehdr->e_ident[EI_CLASS];
> >> +}
> >> +
> >> +#define ELF_GET_FIELD(__s, __field, __type) \
> >> +static inline __type elf_##__s##_##__field(u8 class, const void *arg) \
> >> +{ \
> >> + if (class == ELFCLASS32) \
> >> + return (__type) ((const struct elf32_##__s *) arg)->__field; \
> >> + else \
> >> + return (__type) ((const struct elf64_##__s *) arg)->__field; \
> >> +}
> >> +
> >> +ELF_GET_FIELD(hdr, e_entry, u64)
> >> +ELF_GET_FIELD(hdr, e_phnum, u16)
> >> +ELF_GET_FIELD(hdr, e_shnum, u16)
> >> +ELF_GET_FIELD(hdr, e_phoff, u64)
> >> +ELF_GET_FIELD(hdr, e_shoff, u64)
> >> +ELF_GET_FIELD(hdr, e_shstrndx, u16)
> >> +
> >> +ELF_GET_FIELD(phdr, p_paddr, u64)
> >> +ELF_GET_FIELD(phdr, p_filesz, u64)
> >> +ELF_GET_FIELD(phdr, p_memsz, u64)
> >> +ELF_GET_FIELD(phdr, p_type, u32)
> >> +ELF_GET_FIELD(phdr, p_offset, u64)
> >> +
> >> +ELF_GET_FIELD(shdr, sh_size, u64)
> >> +ELF_GET_FIELD(shdr, sh_offset, u64)
> >> +ELF_GET_FIELD(shdr, sh_name, u32)
> >> +ELF_GET_FIELD(shdr, sh_addr, u64)
> >
> > I like how you did this.
> >
> >> +
> >> +#define ELF_STRUCT_SIZE(__s) \
> >> +static inline unsigned long elf_size_of_##__s(u8 class) \
> >> +{ \
> >> + if (class == ELFCLASS32)\
> >> + return sizeof(struct elf32_##__s); \
> >> + else \
> >> + return sizeof(struct elf64_##__s); \
> >> +}
> >> +
> >> +ELF_STRUCT_SIZE(shdr)
> >> +ELF_STRUCT_SIZE(phdr)
> >> +
> >> +#endif /* REMOTEPROC_ELF_LOADER_H */
> >> diff --git a/drivers/remoteproc/remoteproc_internal.h
> >> b/drivers/remoteproc/remoteproc_internal.h
> >> index 45ff76a06c72..4ef745e3a1bc 100644
> >> --- a/drivers/remoteproc/remoteproc_internal.h
> >> +++ b/drivers/remoteproc/remoteproc_internal.h
> >> @@ -63,7 +63,7 @@ phys_addr_t rproc_va_to_pa(void *cpu_addr);
> >> int rproc_trigger_recovery(struct rproc *rproc);
> >>
> >> int rproc_elf_sanity_check(struct rproc *rproc, const struct firmware *fw);
> >> -u32 rproc_elf_get_boot_addr(struct rproc *rproc, const struct firmware *fw);
> >> +u64 rproc_elf_get_boot_addr(struct rproc *rproc, const struct firmware *fw);
> >> int rproc_elf_load_segments(struct rproc *rproc, const struct firmware *fw);
> >> int rproc_elf_load_rsc_table(struct rproc *rproc, const struct firmware *fw);
> >> struct resource_table *rproc_elf_find_loaded_rsc_table(struct rproc *rproc,
> >> diff --git a/drivers/remoteproc/st_remoteproc.c
> >> b/drivers/remoteproc/st_remoteproc.c
> >> index 51049d17b1e5..e23abd8a96b0 100644
> >> --- a/drivers/remoteproc/st_remoteproc.c
> >> +++ b/drivers/remoteproc/st_remoteproc.c
> >> @@ -193,7 +193,7 @@ static int st_rproc_start(struct rproc *rproc)
> >> }
> >> }
> >>
> >> - dev_info(&rproc->dev, "Started from 0x%x\n", rproc->bootaddr);
> >> + dev_info(&rproc->dev, "Started from 0x%llx\n", rproc->bootaddr);
> >>
> >> return 0;
> >>
> >> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> >> index 04d04709f2bd..512de9a2590c 100644
> >> --- a/include/linux/remoteproc.h
> >> +++ b/include/linux/remoteproc.h
> >> @@ -362,7 +362,7 @@ struct rproc_ops {
> >> struct rproc *rproc, const struct firmware *fw);
> >> int (*load)(struct rproc *rproc, const struct firmware *fw);
> >> int (*sanity_check)(struct rproc *rproc, const struct firmware *fw);
> >> - u32 (*get_boot_addr)(struct rproc *rproc, const struct firmware *fw);
> >> + u64 (*get_boot_addr)(struct rproc *rproc, const struct firmware *fw);
> >> };
> >>
> >> /**
> >> @@ -478,7 +478,7 @@ struct rproc {
> >> int num_traces;
> >> struct list_head carveouts;
> >> struct list_head mappings;
> >> - u32 bootaddr;
> >> + u64 bootaddr;
> >> struct list_head rvdevs;
> >> struct list_head subdevs;
> >> struct idr notifyids;
> >
> > Please hold off before doing another respin of this patch. While doing
> > something completely different I noticed TI also did some work in this area.
> > I'd like to take some time to look at their implementation and see if they carry
> > features that haven't been included here. I intend to do this tomorrow.
>
> Ok,
>
> Thanks for your review,

As promised I looked at what Suman had done on his side [1] to support 64-bit ELF
files. His approach to offer the same functionality but for 64 bit in a new file
is quick, simple and flexible. On the flip side it introduces code duplication,
something that is seriously frowned upon upstream.

I did some soul searching in the kernel code and found very little in terms of
implementation that deals with both 32 and 64 bit ELF format. The most
convincing approach was set forth by the MIPS guys [2]. They too have decided
to support both types in the same functions, but I don't see us adding an if()
statement (and the code duplication that comes with it) every time we need to
deal with file types.

Given the above I'm in favour of moving forward with your approach. One could
rightly argue the macros make the code harder to read but given the
alternatives, it seems to be the best solution.

Mathieu

[1]. https://bit.ly/2Rpmb4E
[2]. https://elixir.bootlin.com/linux/v5.5-rc6/source/arch/mips/kernel/elf.c#L75
>
> Clément
>
> >
> > Thanks,
> > Mathieu
> >
> >> --
> >> 2.15.0.276.g89ea799