Occasionally objtool encounters symbol (as opposed to section)
relocations in .altinstructions. Typically they are the alternatives
written by elf_add_alternative() as encountered on a noinstr
validation run on vmlinux after having already ran objtool on the
individual .o files.
Basically this is the counterpart of commit 44f6a7c0755d ("objtool:
Fix seg fault with Clang non-section symbols"), because when these new
assemblers (binutils now also does this) strip the section symbols,
elf_add_reloc_to_insn() is forced to emit symbol based relocations.
As such, teach get_alt_entry() about different relocation types.
Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls")
Reported-by: Stephen Rothwell <[email protected]>
Reported-by: Borislav Petkov <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
---
tools/objtool/special.c | 32 +++++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 7 deletions(-)
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -58,6 +58,24 @@ void __weak arch_handle_alternative(unsi
{
}
+static bool reloc2sec_off(struct reloc *reloc, struct section **sec, unsigned long *off)
+{
+ switch (reloc->sym->type) {
+ case STT_FUNC:
+ *sec = reloc->sym->sec;
+ *off = reloc->sym->offset + reloc->addend;
+ return true;
+
+ case STT_SECTION:
+ *sec = reloc->sym->sec;
+ *off = reloc->addend;
+ return true;
+
+ default:
+ return false;
+ }
+}
+
static int get_alt_entry(struct elf *elf, struct special_entry *entry,
struct section *sec, int idx,
struct special_alt *alt)
@@ -91,15 +109,12 @@ static int get_alt_entry(struct elf *elf
WARN_FUNC("can't find orig reloc", sec, offset + entry->orig);
return -1;
}
- if (orig_reloc->sym->type != STT_SECTION) {
- WARN_FUNC("don't know how to handle non-section reloc symbol %s",
+ if (!reloc2sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off)) {
+ WARN_FUNC("don't know how to handle reloc symbol type: %s",
sec, offset + entry->orig, orig_reloc->sym->name);
return -1;
}
- alt->orig_sec = orig_reloc->sym->sec;
- alt->orig_off = orig_reloc->addend;
-
if (!entry->group || alt->new_len) {
new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new);
if (!new_reloc) {
@@ -116,8 +131,11 @@ static int get_alt_entry(struct elf *elf
if (arch_is_retpoline(new_reloc->sym))
return 1;
- alt->new_sec = new_reloc->sym->sec;
- alt->new_off = (unsigned int)new_reloc->addend;
+ if (!reloc2sec_off(new_reloc, &alt->new_sec, &alt->new_off)) {
+ WARN_FUNC("don't know how to handle reloc symbol type: %s",
+ sec, offset + entry->new, new_reloc->sym->name);
+ return -1;
+ }
/* _ASM_EXTABLE_EX hack */
if (alt->new_off >= 0x7ffffff0)
On Thu, Sep 30, 2021 at 12:43:10PM +0200, Peter Zijlstra wrote:
>
> Occasionally objtool encounters symbol (as opposed to section)
> relocations in .altinstructions. Typically they are the alternatives
> written by elf_add_alternative() as encountered on a noinstr
> validation run on vmlinux after having already ran objtool on the
> individual .o files.
>
> Basically this is the counterpart of commit 44f6a7c0755d ("objtool:
> Fix seg fault with Clang non-section symbols"), because when these new
> assemblers (binutils now also does this) strip the section symbols,
> elf_add_reloc_to_insn() is forced to emit symbol based relocations.
>
> As such, teach get_alt_entry() about different relocation types.
>
> Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls")
> Reported-by: Stephen Rothwell <[email protected]>
> Reported-by: Borislav Petkov <[email protected]>
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
This resolves the instance of the warning that I see with clang-12:
Tested-by: Nathan Chancellor <[email protected]>
> ---
> tools/objtool/special.c | 32 +++++++++++++++++++++++++-------
> 1 file changed, 25 insertions(+), 7 deletions(-)
>
> --- a/tools/objtool/special.c
> +++ b/tools/objtool/special.c
> @@ -58,6 +58,24 @@ void __weak arch_handle_alternative(unsi
> {
> }
>
> +static bool reloc2sec_off(struct reloc *reloc, struct section **sec, unsigned long *off)
> +{
> + switch (reloc->sym->type) {
> + case STT_FUNC:
> + *sec = reloc->sym->sec;
> + *off = reloc->sym->offset + reloc->addend;
> + return true;
> +
> + case STT_SECTION:
> + *sec = reloc->sym->sec;
> + *off = reloc->addend;
> + return true;
> +
> + default:
> + return false;
> + }
> +}
> +
> static int get_alt_entry(struct elf *elf, struct special_entry *entry,
> struct section *sec, int idx,
> struct special_alt *alt)
> @@ -91,15 +109,12 @@ static int get_alt_entry(struct elf *elf
> WARN_FUNC("can't find orig reloc", sec, offset + entry->orig);
> return -1;
> }
> - if (orig_reloc->sym->type != STT_SECTION) {
> - WARN_FUNC("don't know how to handle non-section reloc symbol %s",
> + if (!reloc2sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off)) {
> + WARN_FUNC("don't know how to handle reloc symbol type: %s",
> sec, offset + entry->orig, orig_reloc->sym->name);
> return -1;
> }
>
> - alt->orig_sec = orig_reloc->sym->sec;
> - alt->orig_off = orig_reloc->addend;
> -
> if (!entry->group || alt->new_len) {
> new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new);
> if (!new_reloc) {
> @@ -116,8 +131,11 @@ static int get_alt_entry(struct elf *elf
> if (arch_is_retpoline(new_reloc->sym))
> return 1;
>
> - alt->new_sec = new_reloc->sym->sec;
> - alt->new_off = (unsigned int)new_reloc->addend;
> + if (!reloc2sec_off(new_reloc, &alt->new_sec, &alt->new_off)) {
> + WARN_FUNC("don't know how to handle reloc symbol type: %s",
> + sec, offset + entry->new, new_reloc->sym->name);
> + return -1;
> + }
>
> /* _ASM_EXTABLE_EX hack */
> if (alt->new_off >= 0x7ffffff0)
>
On Thu, Sep 30, 2021 at 12:43:10PM +0200, Peter Zijlstra wrote:
>
> Occasionally objtool encounters symbol (as opposed to section)
> relocations in .altinstructions. Typically they are the alternatives
> written by elf_add_alternative() as encountered on a noinstr
> validation run on vmlinux after having already ran objtool on the
> individual .o files.
>
> Basically this is the counterpart of commit 44f6a7c0755d ("objtool:
> Fix seg fault with Clang non-section symbols"), because when these new
> assemblers (binutils now also does this) strip the section symbols,
> elf_add_reloc_to_insn() is forced to emit symbol based relocations.
>
> As such, teach get_alt_entry() about different relocation types.
>
> Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls")
> Reported-by: Stephen Rothwell <[email protected]>
> Reported-by: Borislav Petkov <[email protected]>
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
> ---
> tools/objtool/special.c | 32 +++++++++++++++++++++++++-------
> 1 file changed, 25 insertions(+), 7 deletions(-)
>
> --- a/tools/objtool/special.c
> +++ b/tools/objtool/special.c
> @@ -58,6 +58,24 @@ void __weak arch_handle_alternative(unsi
> {
> }
>
> +static bool reloc2sec_off(struct reloc *reloc, struct section **sec, unsigned long *off)
Acked-by: Josh Poimboeuf <[email protected]>
Though I'd prefer U change it 2 a function name which doesn't look like
a Prince song title.
--
Josh
The following commit has been merged into the objtool/urgent branch of tip:
Commit-ID: 24ff652573754fe4c03213ebd26b17e86842feb3
Gitweb: https://git.kernel.org/tip/24ff652573754fe4c03213ebd26b17e86842feb3
Author: Peter Zijlstra <[email protected]>
AuthorDate: Thu, 30 Sep 2021 12:43:10 +02:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Fri, 01 Oct 2021 13:57:47 +02:00
objtool: Teach get_alt_entry() about more relocation types
Occasionally objtool encounters symbol (as opposed to section)
relocations in .altinstructions. Typically they are the alternatives
written by elf_add_alternative() as encountered on a noinstr
validation run on vmlinux after having already ran objtool on the
individual .o files.
Basically this is the counterpart of commit 44f6a7c0755d ("objtool:
Fix seg fault with Clang non-section symbols"), because when these new
assemblers (binutils now also does this) strip the section symbols,
elf_add_reloc_to_insn() is forced to emit symbol based relocations.
As such, teach get_alt_entry() about different relocation types.
Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls")
Reported-by: Stephen Rothwell <[email protected]>
Reported-by: Borislav Petkov <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
tools/objtool/special.c | 32 +++++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 7 deletions(-)
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index bc925cf..f58ecc5 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -58,6 +58,24 @@ void __weak arch_handle_alternative(unsigned short feature, struct special_alt *
{
}
+static bool reloc2sec_off(struct reloc *reloc, struct section **sec, unsigned long *off)
+{
+ switch (reloc->sym->type) {
+ case STT_FUNC:
+ *sec = reloc->sym->sec;
+ *off = reloc->sym->offset + reloc->addend;
+ return true;
+
+ case STT_SECTION:
+ *sec = reloc->sym->sec;
+ *off = reloc->addend;
+ return true;
+
+ default:
+ return false;
+ }
+}
+
static int get_alt_entry(struct elf *elf, struct special_entry *entry,
struct section *sec, int idx,
struct special_alt *alt)
@@ -91,15 +109,12 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
WARN_FUNC("can't find orig reloc", sec, offset + entry->orig);
return -1;
}
- if (orig_reloc->sym->type != STT_SECTION) {
- WARN_FUNC("don't know how to handle non-section reloc symbol %s",
+ if (!reloc2sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off)) {
+ WARN_FUNC("don't know how to handle reloc symbol type: %s",
sec, offset + entry->orig, orig_reloc->sym->name);
return -1;
}
- alt->orig_sec = orig_reloc->sym->sec;
- alt->orig_off = orig_reloc->addend;
-
if (!entry->group || alt->new_len) {
new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new);
if (!new_reloc) {
@@ -116,8 +131,11 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
if (arch_is_retpoline(new_reloc->sym))
return 1;
- alt->new_sec = new_reloc->sym->sec;
- alt->new_off = (unsigned int)new_reloc->addend;
+ if (!reloc2sec_off(new_reloc, &alt->new_sec, &alt->new_off)) {
+ WARN_FUNC("don't know how to handle reloc symbol type: %s",
+ sec, offset + entry->new, new_reloc->sym->name);
+ return -1;
+ }
/* _ASM_EXTABLE_EX hack */
if (alt->new_off >= 0x7ffffff0)