[PATCH v3 1/1] arm64: remove unnecessary ifdefs around is_compat_task()

[PATCH v3 1/1] arm64: remove unnecessary ifdefs around is_compat_task()

[Leonardo Bras]

Currently some parts of the codebase will test for CONFIG_COMPAT before
testing is_compat_task().

is_compat_task() is a inlined function only present on CONFIG_COMPAT.
On the other hand, for !CONFIG_COMPAT, we have in linux/compat.h:

 #define is_compat_task() (0)

Since we have this define available in every usage of is_compat_task() for
!CONFIG_COMPAT, it's unnecessary to keep the ifdefs, since the compiler is
smart enough to optimize-out those snippets on CONFIG_COMPAT=n

This requires some regset code as well as a few other defines to be made
available on !CONFIG_COMPAT, so some symbols can get resolved before
getting optimized-out.

Signed-off-by: Leonardo Bras <leobras@redhat.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
---
Changes since v2:
- Added Reviewd-by from Arnd
Link: https://lore.kernel.org/all/20240108174330.472996-2-leobras@redhat.com/

Changes since v1:
- Move some regset code and other defines outside of CONFIG_COMPAT
- Closes: https://lore.kernel.org/oe-kbuild-all/202401061219.Y2LD7LTx-lkp@intel.com/
Link: https://lore.kernel.org/all/20240105041458.126602-3-leobras@redhat.com/

Changes since RFCv1:
- Removed unnecessary new inlined is_compat_task() for arm64
- Adjusted commit text and title
Link: https://lore.kernel.org/all/20240104192433.109983-2-leobras@redhat.com/

 arch/arm64/include/asm/elf.h    | 10 +++++-----
 arch/arm64/include/asm/fpsimd.h |  2 --
 arch/arm64/kernel/ptrace.c      |  8 +++-----
 arch/arm64/kernel/syscall.c     |  5 +----
 4 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 97932fbf973d1..3f93f4eef9530 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -201,16 +201,16 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm,
 #define COMPAT_ELF_PLATFORM		("v8l")
 #endif
 
-#ifdef CONFIG_COMPAT
-
-/* PIE load location for compat arm. Must match ARM ELF_ET_DYN_BASE. */
-#define COMPAT_ELF_ET_DYN_BASE		0x000400000UL
-
 /* AArch32 registers. */
 #define COMPAT_ELF_NGREG		18
 typedef unsigned int			compat_elf_greg_t;
 typedef compat_elf_greg_t		compat_elf_gregset_t[COMPAT_ELF_NGREG];
 
+#ifdef CONFIG_COMPAT
+
+/* PIE load location for compat arm. Must match ARM ELF_ET_DYN_BASE. */
+#define COMPAT_ELF_ET_DYN_BASE		0x000400000UL
+
 /* AArch32 EABI. */
 #define EF_ARM_EABI_MASK		0xff000000
 int compat_elf_check_arch(const struct elf32_hdr *);
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 50e5f25d3024c..94c7ed82fbada 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -21,7 +21,6 @@
 #include <linux/stddef.h>
 #include <linux/types.h>
 
-#ifdef CONFIG_COMPAT
 /* Masks for extracting the FPSR and FPCR from the FPSCR */
 #define VFP_FPSCR_STAT_MASK	0xf800009f
 #define VFP_FPSCR_CTRL_MASK	0x07f79f00
@@ -30,7 +29,6 @@
  * control/status register.
  */
 #define VFP_STATE_SIZE		((32 * 8) + 4)
-#endif
 
 static inline unsigned long cpacr_save_enable_kernel_sve(void)
 {
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 20d7ef82de90a..27efd66fc1e93 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -173,7 +173,6 @@ static void ptrace_hbptriggered(struct perf_event *bp,
 	struct arch_hw_breakpoint *bkpt = counter_arch_bp(bp);
 	const char *desc = "Hardware breakpoint trap (ptrace)";
 
-#ifdef CONFIG_COMPAT
 	if (is_compat_task()) {
 		int si_errno = 0;
 		int i;
@@ -195,7 +194,7 @@ static void ptrace_hbptriggered(struct perf_event *bp,
 						  desc);
 		return;
 	}
-#endif
+
 	arm64_force_sig_fault(SIGTRAP, TRAP_HWBKPT, bkpt->trigger, desc);
 }
 
@@ -1594,7 +1593,6 @@ static const struct user_regset_view user_aarch64_view = {
 	.regsets = aarch64_regsets, .n = ARRAY_SIZE(aarch64_regsets)
 };
 
-#ifdef CONFIG_COMPAT
 enum compat_regset {
 	REGSET_COMPAT_GPR,
 	REGSET_COMPAT_VFP,
@@ -1851,6 +1849,7 @@ static const struct user_regset_view user_aarch32_ptrace_view = {
 	.regsets = aarch32_ptrace_regsets, .n = ARRAY_SIZE(aarch32_ptrace_regsets)
 };
 
+#ifdef CONFIG_COMPAT
 static int compat_ptrace_read_user(struct task_struct *tsk, compat_ulong_t off,
 				   compat_ulong_t __user *ret)
 {
@@ -2112,7 +2111,6 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 
 const struct user_regset_view *task_user_regset_view(struct task_struct *task)
 {
-#ifdef CONFIG_COMPAT
 	/*
 	 * Core dumping of 32-bit tasks or compat ptrace requests must use the
 	 * user_aarch32_view compatible with arm32. Native ptrace requests on
@@ -2123,7 +2121,7 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
 		return &user_aarch32_view;
 	else if (is_compat_thread(task_thread_info(task)))
 		return &user_aarch32_ptrace_view;
-#endif
+
 	return &user_aarch64_view;
 }
 
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index 9a70d9746b661..ad198262b9817 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -20,14 +20,11 @@ long sys_ni_syscall(void);
 
 static long do_ni_syscall(struct pt_regs *regs, int scno)
 {
-#ifdef CONFIG_COMPAT
-	long ret;
 	if (is_compat_task()) {
-		ret = compat_arm_syscall(regs, scno);
+		long ret = compat_arm_syscall(regs, scno);
 		if (ret != -ENOSYS)
 			return ret;
 	}
-#endif
 
 	return sys_ni_syscall();
 }
-- 
2.43.0

Re: [PATCH v3 1/1] arm64: remove unnecessary ifdefs around is_compat_task()

[Catalin Marinas]

On Tue, 09 Jan 2024 00:46:50 -0300, Leonardo Bras wrote:
> Currently some parts of the codebase will test for CONFIG_COMPAT before
> testing is_compat_task().
> 
> is_compat_task() is a inlined function only present on CONFIG_COMPAT.
> On the other hand, for !CONFIG_COMPAT, we have in linux/compat.h:
> 
>  #define is_compat_task() (0)
> 
> [...]

Applied to arm64 (for-next/misc), thanks!

[1/1] arm64: remove unnecessary ifdefs around is_compat_task()
      https://git.kernel.org/arm64/c/1984c805461f

-- 
Catalin