On Mon, 12 Mar 2018 15:42:18 +0800 Dave Young <dyoung@xxxxxxxxxx> wrote: > Hi Philipp, > On 03/09/18 at 11:02am, Philipp Rudo wrote: > > Hi Dave, > > > > > > On Fri, 9 Mar 2018 11:14:20 +0800 > > Dave Young <dyoung@xxxxxxxxxx> wrote: > > > > > On 02/26/18 at 04:16pm, Philipp Rudo wrote: > > > > The current code uses the sh_offset field in purgatory_info->sechdrs to > > > > store a pointer to the current load address of the section. Depending > > > > whether the section will be loaded or not this is either a pointer into > > > > purgatory_info->purgatory_buf or kexec_purgatory. This is not only a > > > > violation of the ELF standard but also makes the code very hard to > > > > understand as you cannot tell if the memory you are using is read-only or > > > > not. > > > > > > > > Remove this mis-use and store the offset of the section in > > > > pugaroty_info->purgatory_buf in sh_offset. > > > > > > > > Signed-off-by: Philipp Rudo <prudo@xxxxxxxxxxxxxxxxxx> > > > > --- > > > > arch/x86/kernel/machine_kexec_64.c | 10 ++++++---- > > > > kernel/kexec_file.c | 33 +++------------------------------ > > > > 2 files changed, 9 insertions(+), 34 deletions(-) > > > > > > > > diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c > > > > index 51667c8b5c9b..41db74bdc88b 100644 > > > > --- a/arch/x86/kernel/machine_kexec_64.c > > > > +++ b/arch/x86/kernel/machine_kexec_64.c > > > > @@ -457,13 +457,15 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi, > > > > * rel[i].r_offset contains byte offset from beginning > > > > * of section to the storage unit affected. > > > > * > > > > - * This is location to update (->sh_offset). This is temporary > > > > - * buffer where section is currently loaded. This will finally > > > > - * be loaded to a different address later, pointed to by > > > > + * This is location to update. This is temporary buffer > > > > + * where section is currently loaded. This will finally be > > > > + * loaded to a different address later, pointed to by > > > > * ->sh_addr. kexec takes care of moving it > > > > * (kexec_load_segment()). > > > > */ > > > > - location = (void *)(section->sh_offset + rel[i].r_offset); > > > > + location = pi->purgatory_buf; > > > > + location += section->sh_offset; > > > > + location += rel[i].r_offset; > > > > > > > > /* Final address of the location */ > > > > address = section->sh_addr + rel[i].r_offset; > > > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > > > > index 746b91e46e34..25b44d1a664a 100644 > > > > --- a/kernel/kexec_file.c > > > > +++ b/kernel/kexec_file.c > > > > @@ -736,28 +736,6 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, > > > > pi->ehdr->e_shnum * sizeof(Elf_Shdr)); > > > > pi->sechdrs = sechdrs; > > > > > > > > - /* > > > > - * We seem to have multiple copies of sections. First copy is which > > > > - * is embedded in kernel in read only section. Some of these sections > > > > - * will be copied to a temporary buffer and relocated. And these > > > > - * sections will finally be copied to their final destination at > > > > - * segment load time. > > > > > > It would be good to keep above part comment somewhere.. > > > > there is a comment in include/linux/kexec.h for the purgatory_info->sechdrs > > field saying > > > > Temporary, modifiable buffer for sechdrs used for relocation. > > This memory can be freed post image load > > > > When you think this is not enough i can add a comment here like > > > > The section headers in kexec_purgatory are read-only. In order to have them > > modifiable make a temporary copy. > > Looks better to add above comment here. Ok, it's added. I'll wait what Ingo says about the string.c issue befor sending around v2. Thanks Philipp > > > > What do you think. > > > > Thanks > > Philipp > > > > > > - * > > > > - * Use ->sh_offset to reflect section address in memory. It will > > > > - * point to original read only copy if section is not allocatable. > > > > - * Otherwise it will point to temporary copy which will be relocated. > > > > - * > > > > - * Use ->sh_addr to contain final address of the section where it > > > > - * will go during execution time. > > > > - */ > > > > - for (i = 0; i < pi->ehdr->e_shnum; i++) { > > > > - if (sechdrs[i].sh_type == SHT_NOBITS) > > > > - continue; > > > > - > > > > - sechdrs[i].sh_offset = (unsigned long)pi->ehdr + > > > > - sechdrs[i].sh_offset; > > > > - } > > > > - > > > > offset = 0; > > > > bss_addr = kbuf->mem + kbuf->bufsz; > > > > kbuf->image->start = pi->ehdr->e_entry; > > > > @@ -786,17 +764,12 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, > > > > kbuf->image->start += kbuf->mem + offset; > > > > } > > > > > > > > - src = (void *)sechdrs[i].sh_offset; > > > > + src = (void *)pi->ehdr + 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)dst; > > > > + sechdrs[i].sh_offset = offset; > > > > offset += sechdrs[i].sh_size; > > > > } > > > > > > > > @@ -1006,7 +979,7 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name, > > > > return -EINVAL; > > > > } > > > > > > > > - sym_buf = (char *)sec->sh_offset + sym->st_value; > > > > + sym_buf = (char *)pi->purgatory_buf + sec->sh_offset + sym->st_value; > > > > > > > > if (get_value) > > > > memcpy((void *)buf, sym_buf, size); > > > > -- > > > > 2.13.5 > > > > > > > > > > Thanks > > > Dave > > > > > > > Thanks > Dave > -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html