On Fri, Mar 02, 2018 at 01:39:45PM +0800, Dave Young wrote:
> On 02/27/18 at 01:48pm, AKASHI Takahiro wrote:
> > removing bufp variable in prepare_elf64_headers() makes the code simpler
> > and more understandable.
> >
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
> > Cc: Dave Young <dyoung@xxxxxxxxxx>
> > Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
> > Cc: Baoquan He <bhe@xxxxxxxxxx>
> > ---
> > arch/x86/kernel/crash.c | 18 +++++++-----------
> > 1 file changed, 7 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> > index bfc37ad20d4a..a842fd847684 100644
> > --- a/arch/x86/kernel/crash.c
> > +++ b/arch/x86/kernel/crash.c
> > @@ -334,7 +334,7 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> > Elf64_Ehdr *ehdr;
> > Elf64_Phdr *phdr;
> > unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
> > - unsigned char *buf, *bufp;
> > + unsigned char *buf;
> > unsigned int cpu, i;
> > unsigned long long notes_addr;
> > unsigned long mstart, mend;
> > @@ -359,9 +359,8 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> > if (!buf)
> > return -ENOMEM;
> >
> > - bufp = buf;
> > - ehdr = (Elf64_Ehdr *)bufp;
> > - bufp += sizeof(Elf64_Ehdr);
> > + ehdr = (Elf64_Ehdr *)buf;
> > + phdr = (Elf64_Phdr *)(ehdr + 1);
>
> phdr should start with ehdr + sizeof(Elf64_Ehdr);
Well, it's a matter of rhetoric :)
The values from both expressions are the same.
Or do you mean my expression is confusing?
-Takahiro AKASHI
> > memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
> > ehdr->e_ident[EI_CLASS] = ELFCLASS64;
> > ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
> > @@ -377,33 +376,30 @@ static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> >
> > /* Prepare one phdr of type PT_NOTE for each present cpu */
> > for_each_present_cpu(cpu) {
> > - phdr = (Elf64_Phdr *)bufp;
> > - bufp += sizeof(Elf64_Phdr);
> > phdr->p_type = PT_NOTE;
> > notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
> > phdr->p_offset = phdr->p_paddr = notes_addr;
> > phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
> > (ehdr->e_phnum)++;
> > + phdr++;
> > }
> >
> > /* Prepare one PT_NOTE header for vmcoreinfo */
> > - phdr = (Elf64_Phdr *)bufp;
> > - bufp += sizeof(Elf64_Phdr);
> > phdr->p_type = PT_NOTE;
> > phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
> > phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
> > (ehdr->e_phnum)++;
> > + phdr++;
> >
> > /* Prepare PT_LOAD type program header for kernel text region */
> > if (kernel_map) {
> > - phdr = (Elf64_Phdr *)bufp;
> > - bufp += sizeof(Elf64_Phdr);
> > phdr->p_type = PT_LOAD;
> > phdr->p_flags = PF_R|PF_W|PF_X;
> > phdr->p_vaddr = (Elf64_Addr)_text;
> > phdr->p_filesz = phdr->p_memsz = _end - _text;
> > phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
> > - (ehdr->e_phnum)++;
> > + ehdr->e_phnum++;
> > + phdr++;
> > }
> >
> > /* Go through all the ranges in cmem->ranges[] and prepare phdr */
> > --
> > 2.16.2
> >
>
> Thanks
> Dave
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