kernel/kexec_file.c: remove mis-use of sh_offset field during purgatory load
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 misuse and store the offset of the section in
pugaroty_info->purgatory_buf in sh_offset.
Link: http://lkml.kernel.org/r/20180321112751.22196-10-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo <prudo@linux.vnet.ibm.com>
Acked-by: Dave Young <dyoung@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 63dea30..a5e55d8 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -417,13 +417,15 @@ 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 7b63de8..269116fd 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -790,6 +790,10 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
Elf_Shdr *sechdrs;
int i;
+ /*
+ * The section headers in kexec_purgatory are read-only. In order to
+ * have them modifiable make a temporary copy.
+ */
sechdrs = vzalloc(pi->ehdr->e_shnum * sizeof(Elf_Shdr));
if (!sechdrs)
return -ENOMEM;
@@ -797,28 +801,6 @@ 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.
- *
- * 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;
@@ -847,17 +829,12 @@ 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;
}
@@ -1067,7 +1044,7 @@ 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);