Re: [PATCH 08/11] kexec_file: Simplify kexec_purgatory_setup_sechdrs 2

From: Philipp Rudo
Date: Fri Mar 09 2018 - 04:54:20 EST


Hi Dave,

On Fri, 9 Mar 2018 11:18:05 +0800
Dave Young <dyoung@xxxxxxxxxx> wrote:

> Hi,
>
> On 02/26/18 at 04:16pm, Philipp Rudo wrote:
> > The main loop currently uses quite a lot of variables to update the section
> > headers. Some of them are unnecessary. So clean them up a little.
> >
>
> It looks better to use some patch subject eg below:
> "Remove unnecessary variables in kexec_purgatory_setup_sechdrs"

ok, done. I also renamed the patch before and after. The subjects now
are

kexec_file: Remove mis-use of sh_offset field during purgatory load
kexec_file: Remove unneeded variables in kexec_purgatory_setup_sechdrs
kexec_file: Remove unneeded for-loop in kexec_purgatory_setup_sechdrs

Thanks
Philipp


> > Signed-off-by: Philipp Rudo <prudo@xxxxxxxxxxxxxxxxxx>
> > ---
> > kernel/kexec_file.c | 34 ++++++++++++----------------------
> > 1 file changed, 12 insertions(+), 22 deletions(-)
> >
> > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> > index bb31a3b627c2..746b91e46e34 100644
> > --- a/kernel/kexec_file.c
> > +++ b/kernel/kexec_file.c
> > @@ -724,12 +724,8 @@ static int kexec_purgatory_setup_kbuf(struct purgatory_info *pi,
> > static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
> > struct kexec_buf *kbuf)
> > {
> > - unsigned long curr_load_addr;
> > - unsigned long load_addr;
> > unsigned long bss_addr;
> > unsigned long offset;
> > - unsigned char *buf_addr;
> > - unsigned char *src;
> > Elf_Shdr *sechdrs;
> > int i;
> >
> > @@ -762,20 +758,18 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
> > sechdrs[i].sh_offset;
> > }
> >
> > - /* Load SHF_ALLOC sections */
> > - buf_addr = kbuf->buffer;
> > - load_addr = curr_load_addr = kbuf->mem;
> > - bss_addr = load_addr + kbuf->bufsz;
> > + offset = 0;
> > + bss_addr = kbuf->mem + kbuf->bufsz;
> > kbuf->image->start = pi->ehdr->e_entry;
> >
> > for (i = 0; i < pi->ehdr->e_shnum; i++) {
> > unsigned long align;
> > + void *src, *dst;
> >
> > if (!(sechdrs[i].sh_flags & SHF_ALLOC))
> > continue;
> >
> > align = sechdrs[i].sh_addralign;
> > -
> > if (sechdrs[i].sh_type == SHT_NOBITS) {
> > bss_addr = ALIGN(bss_addr, align);
> > sechdrs[i].sh_addr = bss_addr;
> > @@ -783,31 +777,27 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
> > continue;
> > }
> >
> > - curr_load_addr = ALIGN(curr_load_addr, align);
> > - offset = curr_load_addr - load_addr;
> > - /* We already modifed ->sh_offset to keep src addr */
> > - src = (char *)sechdrs[i].sh_offset;
> > - memcpy(buf_addr + offset, src, sechdrs[i].sh_size);
> > -
> > + offset = ALIGN(offset, align);
> > if (sechdrs[i].sh_flags & SHF_EXECINSTR &&
> > pi->ehdr->e_entry >= sechdrs[i].sh_addr &&
> > pi->ehdr->e_entry < (sechdrs[i].sh_addr
> > + sechdrs[i].sh_size)) {
> > kbuf->image->start -= sechdrs[i].sh_addr;
> > - kbuf->image->start += curr_load_addr
> > + kbuf->image->start += kbuf->mem + offset;
> > }
> >
> > - /* Store load address and source address of section */
> > - sechdrs[i].sh_addr = curr_load_addr;
> > + src = (void *)sechdrs[i].sh_offset;
> > + dst = pi->purgatory_buf + offset;
> > + memcpy(dst, src, sechdrs[i].sh_size);
> > +
> > + sechdrs[i].sh_addr = kbuf->mem + offset;
> >
> > /*
> > * This section got copied to temporary buffer. Update
> > * ->sh_offset accordingly.
> > */
> > - sechdrs[i].sh_offset = (unsigned long)(buf_addr + offset);
> > -
> > - /* Advance to the next address */
> > - curr_load_addr += sechdrs[i].sh_size;
> > + sechdrs[i].sh_offset = (unsigned long)dst;
> > + offset += sechdrs[i].sh_size;
> > }
> >
> > return 0;
> > --
> > 2.13.5
> >
>
> Thanks
> Dave
>