[PATCH v3 0/4] x86/boot/compressed: Enable -Wunused and remove unused variables

[PATCH v3 0/4] x86/boot/compressed: Enable -Wunused and remove unused variables

[Thorsten Blum]

This series marks potentially unused variables and functions as
__maybe_unused and removes truly unused ones. Patch 4 enables -Wunused,
matching the W=0 kernel defaults. With WERROR=y, the warnings failed as
follows:

  arch/x86/boot/compressed/acpi.c:25:1: error: '__efi_get_rsdp_addr' defined but not used
  arch/x86/boot/compressed/acpi.c:29:6: error: unused variable 'ret'
  arch/x86/boot/compressed/acpi.c:57:15: error: unused variable 'nr_tables'
  arch/x86/boot/compressed/efi.c:64:16: error: unused variable 'et'
  arch/x86/boot/compressed/efi.c:136:6: error: unused variable 'ret'
  arch/x86/boot/compressed/kaslr.c:600:13: error: unused variable 'i'

Patch 2 also drops a redundant efi_get_system_table() call and uses the
existing efi_get_conf_table() error path.

Changes in v3:
- Rebase patch 4/4
- v2: https://lore.kernel.org/r/20260624120300.590233-6-thorsten.blum@linux.dev/

Changes in v2:
- Fix a kernel test robot issue by marking __efi_get_rsdp_addr() as
  __maybe_unused: https://lore.kernel.org/r/202606240416.cXegPpiJ-lkp@intel.com/
- v1: https://lore.kernel.org/r/20260621144116.224010-6-thorsten.blum@linux.dev/

Thorsten Blum (4):
  x86/boot/compressed: Remove unused variables in EFI helpers
  x86/boot/compressed: Clean up EFI RSDP lookup in efi_get_rsdp_addr()
  x86/boot/compressed: Mark process_mem_region() index __maybe_unused
  x86/boot/compressed: Enable -Wunused

 arch/x86/boot/compressed/Makefile |  3 +++
 arch/x86/boot/compressed/acpi.c   | 18 ++++--------------
 arch/x86/boot/compressed/efi.c    | 17 +++++------------
 arch/x86/boot/compressed/kaslr.c  |  3 ++-
 4 files changed, 14 insertions(+), 27 deletions(-)

[PATCH v3 1/4] x86/boot/compressed: Remove unused variables in EFI helpers

[Thorsten Blum]

efi_get_system_table() declares an unused et variable, and
efi_get_conf_table() declares an unused ret variable - remove both.

get_kexec_setup_data() also takes an unused et argument. Drop the
argument and update the only caller in efi_get_conf_table().

Also simplify the no EFI system table case in efi_get_system_table() by
falling through to the existing return since sys_tbl_pa is already zero.

Signed-off-by: Thorsten Blum <blum@kernel.org>
---
 arch/x86/boot/compressed/efi.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
index f2e50f9758e6..e0329a03618a 100644
--- a/arch/x86/boot/compressed/efi.c
+++ b/arch/x86/boot/compressed/efi.c
@@ -61,7 +61,6 @@ unsigned long efi_get_system_table(struct boot_params *bp)
 {
 	unsigned long sys_tbl_pa;
 	struct efi_info *ei;
-	enum efi_type et;
 
 	/* Get systab from boot params. */
 	ei = &bp->efi_info;
@@ -70,10 +69,8 @@ unsigned long efi_get_system_table(struct boot_params *bp)
 #else
 	sys_tbl_pa = ei->efi_systab;
 #endif
-	if (!sys_tbl_pa) {
+	if (!sys_tbl_pa)
 		debug_putstr("EFI system table not found.");
-		return 0;
-	}
 
 	return sys_tbl_pa;
 }
@@ -84,11 +81,10 @@ unsigned long efi_get_system_table(struct boot_params *bp)
  * the initial physical address via a struct setup_data entry, which is
  * checked for here, along with some sanity checks.
  */
-static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp,
-						   enum efi_type et)
+static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp)
 {
-#ifdef CONFIG_X86_64
 	struct efi_setup_data *esd = NULL;
+#ifdef CONFIG_X86_64
 	struct setup_data *data;
 	u64 pa_data;
 
@@ -112,10 +108,8 @@ static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp,
 		debug_putstr("kexec EFI environment missing valid configuration table.\n");
 		return NULL;
 	}
-
-	return esd;
 #endif
-	return NULL;
+	return esd;
 }
 
 /**
@@ -133,7 +127,6 @@ int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa,
 {
 	unsigned long sys_tbl_pa;
 	enum efi_type et;
-	int ret;
 
 	if (!cfg_tbl_pa || !cfg_tbl_len)
 		return -EINVAL;
@@ -149,7 +142,7 @@ int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa,
 		struct efi_setup_data *esd;
 
 		/* kexec provides an alternative EFI conf table, check for it. */
-		esd = get_kexec_setup_data(bp, et);
+		esd = get_kexec_setup_data(bp);
 
 		*cfg_tbl_pa = esd ? esd->tables : stbl->tables;
 		*cfg_tbl_len = stbl->nr_tables;

[PATCH v3 2/4] x86/boot/compressed: Clean up EFI RSDP lookup in efi_get_rsdp_addr()

[Thorsten Blum]

Mark __efi_get_rsdp_addr() as __maybe_unused and remove the unused ret
variable. In efi_get_rsdp_addr(), remove the unused nr_tables variable
and use the function return values directly in the conditions.

Since efi_get_conf_table() already calls efi_get_system_table(), drop
the redundant efi_get_system_table() call and keep a single error path.

Signed-off-by: Thorsten Blum <blum@kernel.org>
---
 arch/x86/boot/compressed/acpi.c | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index aed27604c11f..5b2064b9c199 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -21,12 +21,11 @@
  */
 struct mem_vector immovable_mem[MAX_NUMNODES*2];
 
-static acpi_physical_address
+static acpi_physical_address __maybe_unused
 __efi_get_rsdp_addr(unsigned long cfg_tbl_pa, unsigned int cfg_tbl_len)
 {
 #ifdef CONFIG_EFI
 	unsigned long rsdp_addr;
-	int ret;
 
 	/*
 	 * Search EFI system tables for RSDP. Preferred is ACPI_20_TABLE_GUID to
@@ -53,21 +52,12 @@ static acpi_physical_address efi_get_rsdp_addr(void)
 #ifdef CONFIG_EFI
 	unsigned long cfg_tbl_pa = 0;
 	unsigned int cfg_tbl_len;
-	unsigned long systab_pa;
-	unsigned int nr_tables;
-	enum efi_type et;
-	int ret;
 
-	et = efi_get_type(boot_params_ptr);
-	if (et == EFI_TYPE_NONE)
+	if (efi_get_type(boot_params_ptr) == EFI_TYPE_NONE)
 		return 0;
 
-	systab_pa = efi_get_system_table(boot_params_ptr);
-	if (!systab_pa)
-		error("EFI support advertised, but unable to locate system table.");
-
-	ret = efi_get_conf_table(boot_params_ptr, &cfg_tbl_pa, &cfg_tbl_len);
-	if (ret || !cfg_tbl_pa)
+	if (efi_get_conf_table(boot_params_ptr, &cfg_tbl_pa, &cfg_tbl_len) ||
+	    !cfg_tbl_pa)
 		error("EFI config table not found.");
 
 	return __efi_get_rsdp_addr(cfg_tbl_pa, cfg_tbl_len);

[PATCH v3 3/4] x86/boot/compressed: Mark process_mem_region() index __maybe_unused

[Thorsten Blum]

The local index variable i in process_mem_region() is unused when either
CONFIG_MEMORY_HOTREMOVE or CONFIG_ACPI is disabled.

Mark it __maybe_unused accordingly.

Signed-off-by: Thorsten Blum <blum@kernel.org>
---
 arch/x86/boot/compressed/kaslr.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 290153818d0f..6f95092fa97e 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -599,7 +599,8 @@ static bool process_mem_region(struct mem_vector *region,
 			       unsigned long minimum,
 			       unsigned long image_size)
 {
-	int i;
+	int i __maybe_unused;
+
 	/*
 	 * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
 	 * use @region directly.

[PATCH v3 4/4] x86/boot/compressed: Enable -Wunused

[Thorsten Blum]

arch/x86/boot/compressed/Makefile resets KBUILD_CFLAGS for this
directory, but does not re-enable -Wunused. Therefore, unused variables
and static functions in arch/x86/boot/compressed/ currently do not emit
warnings.

Add -Wunused to warn about these, and -Wno-unused-but-set-variable as
well as -Wno-unused-const-variable to match the W=0 kernel defaults.

Signed-off-by: Thorsten Blum <blum@kernel.org>
---
 arch/x86/boot/compressed/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 680ad803cba7..3ff75bc2239b 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -29,6 +29,9 @@ KBUILD_CFLAGS += $(CC_FLAGS_DIALECT)
 KBUILD_CFLAGS += -fno-strict-aliasing -fPIE
 KBUILD_CFLAGS += -fno-jump-tables
 KBUILD_CFLAGS += -Wundef
+KBUILD_CFLAGS += -Wunused
+KBUILD_CFLAGS += -Wno-unused-but-set-variable
+KBUILD_CFLAGS += -Wno-unused-const-variable
 KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
 cflags-$(CONFIG_X86_32) := -march=i386
 cflags-$(CONFIG_X86_64) := -mcmodel=small -mno-red-zone