From: Shivang Upadhyay <shivangu@linux.ibm.com>
To: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org
Cc: sv@linux.ibm.com, alexandre.chartre@oracle.com,
alexghiti@rivosinc.com, aliceryhl@google.com, ardb@kernel.org,
bp@alien8.de, chleroy@kernel.org, elver@google.com,
ihor.solodrai@linux.dev, jpoimboe@kernel.org, kees@kernel.org,
legion@kernel.org, lossin@kernel.org, maddy@linux.ibm.com,
masahiroy@kernel.org, mpe@ellerman.id.au, nathan@kernel.org,
npiggin@gmail.com, nsc@kernel.org, ojeda@kernel.org,
peterz@infradead.org, pmladek@suse.com, rostedt@goodmis.org,
tamird@kernel.org, thomas.weissschuh@linutronix.de,
thuth@redhat.com, yuxuan.zuo@outlook.com,
sourabhjain@linux.ibm.com,
Shivang Upadhyay <shivangu@linux.ibm.com>
Subject: [PATCH v2 6/6] powerpc: Enable build-time feature fixup processing by default
Date: Tue, 29 Sep 2026 11:21:37 +0530 [thread overview]
Message-ID: <20260929055138.43489-7-shivangu@linux.ibm.com> (raw)
In-Reply-To: <20260929055138.43489-1-shivangu@linux.ibm.com>
From: Sathvika Vasireddy <sv@linux.ibm.com>
Enable HAVE_OBJTOOL_FTR_FIXUP by default on PowerPC architecture.
- Remove runtime branch translation logic from patch_alt_instruction()
- Add --emit-relocs linker flags for post-link fixup processing
- Update ftr_alt section attributes to include executable flag
- Strip the --emit-relocs relocation sections (.rel*) from the final
vmlinux after processing
Co-developed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: Shivang Upadhyay <shivangu@linux.ibm.com>
---
arch/powerpc/Kconfig | 3 +++
arch/powerpc/Makefile | 5 +++++
arch/powerpc/include/asm/feature-fixups.h | 2 +-
arch/powerpc/kernel/vmlinux.lds.S | 8 ++++++--
arch/powerpc/lib/feature-fixups.c | 12 ------------
scripts/Makefile.vmlinux | 8 ++++++--
6 files changed, 21 insertions(+), 17 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2580e27e4328..d9056f35da9f 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -23,6 +23,9 @@ config 64BIT
bool
default y if PPC64
+config HAVE_OBJTOOL_FTR_FIXUP
+ def_bool y
+
config LIVEPATCH_64
def_bool PPC64
depends on LIVEPATCH
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 9385db478c59..269ed76a40c6 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -112,6 +112,11 @@ LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie --no-dynamic-linker
LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) += -z notext
LDFLAGS_vmlinux := $(LDFLAGS_vmlinux-y)
+# --emit-relocs required for post-link fixup of alternate feature
+# text section relocations.
+LDFLAGS_vmlinux += --emit-relocs
+KBUILD_LDFLAGS_MODULE += --emit-relocs
+
ifdef CONFIG_PPC64
ifndef CONFIG_PPC_KERNEL_PCREL
# -mcmodel=medium breaks modules because it uses 32bit offsets from
diff --git a/arch/powerpc/include/asm/feature-fixups.h b/arch/powerpc/include/asm/feature-fixups.h
index 756a6c694018..d6ae92a292ec 100644
--- a/arch/powerpc/include/asm/feature-fixups.h
+++ b/arch/powerpc/include/asm/feature-fixups.h
@@ -32,7 +32,7 @@
#define FTR_SECTION_ELSE_NESTED(label) \
label##2: \
- .pushsection __ftr_alt_##label,"a"; \
+ .pushsection __ftr_alt_##label, "ax"; \
.align 2; \
label##3:
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 8fc11d6565bf..1a2d7c2d32f1 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -99,8 +99,8 @@ SECTIONS
.text : AT(ADDR(.text) - LOAD_OFFSET) {
ALIGN_FUNCTION();
#endif
- /* careful! __ftr_alt_* sections need to be close to .text */
- *(.text.hot .text.hot.* TEXT_MAIN .text.fixup .text.unlikely .text.unlikely.* .fixup __ftr_alt_* .ref.text);
+ *(.text.hot .text.hot.* TEXT_MAIN .text.fixup .text.unlikely
+ .text.unlikely.* .fixup .ref.text);
*(.tramp.ftrace.text);
NOINSTR_TEXT
SCHED_TEXT
@@ -267,6 +267,10 @@ SECTIONS
_einittext = .;
} :text
+ .__ftr_alternates.text : AT(ADDR(.__ftr_alternates.text) - LOAD_OFFSET) {
+ *(__ftr_alt*);
+ }
+
/* .exit.text is discarded at runtime, not link time,
* to deal with references from __bug_table
*/
diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c
index 587c8cf1230f..269e992b1631 100644
--- a/arch/powerpc/lib/feature-fixups.c
+++ b/arch/powerpc/lib/feature-fixups.c
@@ -53,22 +53,10 @@ static u32 *calc_addr(struct fixup_entry *fcur, long offset)
static int patch_alt_instruction(u32 *src, u32 *dest, u32 *alt_start, u32 *alt_end)
{
- int err;
ppc_inst_t instr;
instr = ppc_inst_read(src);
- if (instr_is_relative_branch(ppc_inst_read(src))) {
- u32 *target = (u32 *)branch_target(src);
-
- /* Branch within the section doesn't need translating */
- if (target < alt_start || target > alt_end) {
- err = translate_branch(&instr, dest, src);
- if (err)
- return 1;
- }
- }
-
raw_patch_instruction(dest, instr);
return 0;
diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
index a1bef0638ecb..66e5d58a6ce8 100644
--- a/scripts/Makefile.vmlinux
+++ b/scripts/Makefile.vmlinux
@@ -82,11 +82,15 @@ endif
# vmlinux
# ---------------------------------------------------------------------------
+# These configurations require vmlinux.unstripped to be linked with
+# '--emit-relocs', which need to be stripped from the final vmlinux.
+uses-emit-relocs := $(or $(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS),$(CONFIG_HAVE_OBJTOOL_FTR_FIXUP))
+
remove-section-y := .modinfo
-remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel*' '!.rel*.dyn'
+remove-section-$(uses-emit-relocs) += '.rel*' '!.rel*.dyn'
# for compatibility with binutils < 2.32
# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=c12d9fa2afe7abcbe407a00e15719e1a1350c2a7
-remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel.*'
+remove-section-$(uses-emit-relocs) += '.rel.*'
remove-symbols := -w --strip-unneeded-symbol='__mod_device_table__*'
--
2.54.0
prev parent reply other threads:[~2026-09-29 5:53 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-29 5:51 [PATCH v2 0/6] objtool: Fixup alternate feature relative addresses Shivang Upadhyay
2026-09-29 5:51 ` [PATCH v2 1/6] objtool/powerpc: Add build-time fixup of alternate feature branch targets Shivang Upadhyay
2026-09-29 5:51 ` [PATCH v2 2/6] objtool: Set ELF_F_LAYOUT flag to preserve vmlinux segment layout Shivang Upadhyay
2026-09-29 5:51 ` [PATCH v2 3/6] objtool: Fix "can't find starting instruction" warnings on vmlinux Shivang Upadhyay
2026-09-29 14:12 ` Peter Zijlstra
2026-09-29 14:24 ` Peter Zijlstra
2026-09-29 5:51 ` [PATCH v2 4/6] objtool/powerpc: Skip jump destination analysis and unnanotated intra-function call warnings for --ftr-fixup Shivang Upadhyay
2026-09-29 14:25 ` Peter Zijlstra
2026-09-29 5:51 ` [PATCH v2 5/6] kbuild: Add objtool integration for PowerPC feature fixups Shivang Upadhyay
2026-09-29 5:51 ` Shivang Upadhyay [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260929055138.43489-7-shivangu@linux.ibm.com \
--to=shivangu@linux.ibm.com \
--cc=alexandre.chartre@oracle.com \
--cc=alexghiti@rivosinc.com \
--cc=aliceryhl@google.com \
--cc=ardb@kernel.org \
--cc=bp@alien8.de \
--cc=chleroy@kernel.org \
--cc=elver@google.com \
--cc=ihor.solodrai@linux.dev \
--cc=jpoimboe@kernel.org \
--cc=kees@kernel.org \
--cc=legion@kernel.org \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=lossin@kernel.org \
--cc=maddy@linux.ibm.com \
--cc=masahiroy@kernel.org \
--cc=mpe@ellerman.id.au \
--cc=nathan@kernel.org \
--cc=npiggin@gmail.com \
--cc=nsc@kernel.org \
--cc=ojeda@kernel.org \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=sourabhjain@linux.ibm.com \
--cc=sv@linux.ibm.com \
--cc=tamird@kernel.org \
--cc=thomas.weissschuh@linutronix.de \
--cc=thuth@redhat.com \
--cc=yuxuan.zuo@outlook.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®