A klp relocation section is .klp.rela.<objname>.<secname>, where objname
is the object being patched.
klp-build wrongly derives objname from where the referenced symbol
lives, not where it's referenced. For a cross-module reference like
patched can_isotp code calling can.ko's can_rx_unregister(), that gives
.klp.rela.can..text rather than .klp.rela.can_isotp..text. Unless the
patch happens to patch can.ko as well, the relocation never gets applied
and the call goes off into the weeds.
Name the intermediate section __klp_relocs.<objname> so post-link can
read the patched object's name from there.
Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing
object files")
Reported-by: Joe Lawrence <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Josh Poimboeuf <[email protected]>
---
tools/objtool/include/objtool/klp.h | 10 ++++--
tools/objtool/klp-diff.c | 17 +++++++--
tools/objtool/klp-post-link.c | 53 +++++++++++++++++------------
3 files changed, 52 insertions(+), 28 deletions(-)
diff --git a/tools/objtool/include/objtool/klp.h
b/tools/objtool/include/objtool/klp.h
index 0118c2c170c3f..646d8e1f12eff 100644
--- a/tools/objtool/include/objtool/klp.h
+++ b/tools/objtool/include/objtool/klp.h
@@ -14,11 +14,15 @@
#define KLP_FUNCS_SEC ".init.klp_funcs"
/*
- * __klp_relocs is an intermediate section which are created by klp diff and
- * converted into KLP symbols/relas by "objtool klp post-link". This is needed
- * to work around the linker, which doesn't preserve SHN_LIVEPATCH or
+ * __klp_relocs.<objname> are intermediate sections which are created by klp
+ * diff and converted into KLP symbols/relas by "objtool klp post-link". This
+ * is needed to work around the linker, which doesn't preserve SHN_LIVEPATCH or
* SHF_RELA_LIVEPATCH, nor does it support having two RELA sections for a
* single PROGBITS section.
+ *
+ * "objname" is the name of the object being patched ("vmlinux" or a module
+ * name). post-link uses it to name the resulting
+ * .klp.rela.objname.section_name sections.
*/
#define KLP_RELOCS_SEC "__klp_relocs"
#define KLP_STRINGS_SEC ".rodata.klp.str1.1"
diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index 07cc8e2703260..91a9562c45a6e 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -1380,8 +1380,8 @@ static int clone_reloc_klp(struct elfs *e, struct reloc
*patched_reloc,
}
/*
- * Create the __klp_relocs entry. This will be converted to an actual
- * KLP rela by "objtool klp post-link".
+ * Create the __klp_relocs.<objname> entry. This will be converted to
+ * an actual KLP rela by "objtool klp post-link".
*
* This intermediate step is necessary to prevent corruption by the
* linker, which doesn't know how to properly handle two rela sections
@@ -1389,7 +1389,18 @@ static int clone_reloc_klp(struct elfs *e, struct reloc
*patched_reloc,
*/
if (!klp_relocs) {
- klp_relocs = elf_create_section(e->out, KLP_RELOCS_SEC, 0,
+ const char *objname = find_modname(e);
+ char sec_name[SEC_NAME_LEN];
+
+ if (!objname)
+ return -1;
+
+ /* section format: __klp_relocs.objname */
+ if (snprintf_check(sec_name, SEC_NAME_LEN,
+ KLP_RELOCS_SEC ".%s", objname))
+ return -1;
+
+ klp_relocs = elf_create_section(e->out, sec_name, 0,
0, SHT_PROGBITS, 8, SHF_ALLOC);
if (!klp_relocs)
return -1;
diff --git a/tools/objtool/klp-post-link.c b/tools/objtool/klp-post-link.c
index c013e39957b11..350d20495897b 100644
--- a/tools/objtool/klp-post-link.c
+++ b/tools/objtool/klp-post-link.c
@@ -19,19 +19,11 @@
#include <objtool/util.h>
#include <linux/livepatch_external.h>
-static int fix_klp_relocs(struct elf *elf)
+static int fix_klp_reloc_sec(struct elf *elf, struct section *symtab,
+ struct section *klp_relocs)
{
- struct section *symtab, *klp_relocs;
-
- klp_relocs = find_section_by_name(elf, KLP_RELOCS_SEC);
- if (!klp_relocs)
- return 0;
-
- symtab = find_section_by_name(elf, ".symtab");
- if (!symtab) {
- ERROR("missing .symtab");
- return -1;
- }
+ /* section format: __klp_relocs.sec_objname */
+ const char *sec_objname = klp_relocs->name + strlen(KLP_RELOCS_SEC ".");
for (int i = 0; i < sec_size(klp_relocs) / sizeof(struct klp_reloc);
i++) {
struct klp_reloc *klp_reloc;
@@ -39,7 +31,6 @@ static int fix_klp_relocs(struct elf *elf)
struct section *sec, *tmp, *klp_rsec;
unsigned long offset;
struct reloc *reloc;
- char sym_modname[64];
char rsec_name[SEC_NAME_LEN];
u64 addend;
struct symbol *sym, *klp_sym;
@@ -55,7 +46,7 @@ static int fix_klp_relocs(struct elf *elf)
reloc = find_reloc_by_dest(elf, klp_relocs,
klp_reloc_off + offsetof(struct
klp_reloc, offset));
if (!reloc) {
- ERROR("malformed " KLP_RELOCS_SEC " section");
+ ERROR("malformed %s section", klp_relocs->name);
return -1;
}
@@ -66,17 +57,13 @@ static int fix_klp_relocs(struct elf *elf)
reloc = find_reloc_by_dest(elf, klp_relocs,
klp_reloc_off + offsetof(struct
klp_reloc, sym));
if (!reloc) {
- ERROR("malformed " KLP_RELOCS_SEC " section");
+ ERROR("malformed %s section", klp_relocs->name);
return -1;
}
klp_sym = reloc->sym;
addend = reloc_addend(reloc);
- /* symbol format: .klp.sym.modname.sym_name,sympos */
- if (sscanf(klp_sym->name + strlen(KLP_SYM_PREFIX), "%55[^.]",
sym_modname) != 1)
- ERROR("can't find modname in klp symbol '%s'",
klp_sym->name);
-
/*
* Create the KLP rela:
*/
@@ -84,7 +71,7 @@ static int fix_klp_relocs(struct elf *elf)
/* section format: .klp.rela.sec_objname.section_name */
if (snprintf_check(rsec_name, SEC_NAME_LEN,
KLP_RELOC_SEC_PREFIX "%s.%s",
- sym_modname, sec->name))
+ sec_objname, sec->name))
return -1;
klp_rsec = find_section_by_name(elf, rsec_name);
@@ -134,10 +121,32 @@ static int fix_klp_relocs(struct elf *elf)
return 0;
}
+static int fix_klp_relocs(struct elf *elf)
+{
+ struct section *symtab, *sec;
+
+ symtab = find_section_by_name(elf, ".symtab");
+ if (!symtab) {
+ ERROR("missing .symtab");
+ return -1;
+ }
+
+ for_each_sec(elf, sec) {
+ if (strncmp(sec->name, KLP_RELOCS_SEC ".",
+ strlen(KLP_RELOCS_SEC ".")))
+ continue;
+
+ if (fix_klp_reloc_sec(elf, symtab, sec))
+ return -1;
+ }
+
+ return 0;
+}
+
/*
* This runs on the livepatch module after all other linking has been done. It
- * converts the intermediate __klp_relocs section into proper KLP relocs to be
- * processed by livepatch. This needs to run last to avoid linker wreckage.
+ * converts the intermediate __klp_relocs.* sections into proper KLP relocs to
+ * be processed by livepatch. This needs to run last to avoid linker wreckage.
* Linkers don't tend to handle the "two rela sections for a single base
* section" case very well, nor do they appreciate SHN_LIVEPATCH.
*/
--
2.54.0
