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Peter Anvin" Subject: [PATCH -tip v2 3/3] x86/kexec: Use savesegment_mem16() for segment register save in crash_setup_regs() Date: Wed, 1 Apr 2026 10:58:12 +0200 Message-ID: <20260401085832.285121-3-ubizjak@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260401085832.285121-1-ubizjak@gmail.com> References: <20260401085832.285121-1-ubizjak@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Replace open-coded inline assembly used to read segment registers (ss, cs, and on 32-bit ds/es) in crash_setup_regs() with savesegment_mem16() helper. This function only stores the segment selector into a u16 field and does not require the value in a general-purpose register. Using savesegment_mem16() avoids the unnecessary register intermediate and better matches the intended use. The generated code is improved from, e.g.: 131: 8c d0 mov %ss,%eax 133: 66 89 84 24 a0 00 00 mov %ax,0xa0(%rsp) 13a: 00 to a single direct store: 131: 8c 94 24 a0 00 00 00 mov %ss,0xa0(%rsp) This is a mechanical follow-up to the introduction of savesegment_mem16(), with no functional change. Signed-off-by: Uros Bizjak Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" --- v2: New patch. --- arch/x86/include/asm/kexec.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h index 5cfb27f26583..90a8d7ca7cf8 100644 --- a/arch/x86/include/asm/kexec.h +++ b/arch/x86/include/asm/kexec.h @@ -106,11 +106,11 @@ static inline void crash_setup_regs(struct pt_regs *newregs, asm volatile("mov %%r14,%0" : "=m"(newregs->r14)); asm volatile("mov %%r15,%0" : "=m"(newregs->r15)); #endif - asm volatile("mov %%ss,%k0" : "=a"(newregs->ss)); - asm volatile("mov %%cs,%k0" : "=a"(newregs->cs)); + savesegment_mem16(ss, newregs->ss); + savesegment_mem16(cs, newregs->cs); #ifdef CONFIG_X86_32 - asm volatile("mov %%ds,%k0" : "=a"(newregs->ds)); - asm volatile("mov %%es,%k0" : "=a"(newregs->es)); + savesegment_mem16(ds, newregs->ds); + savesegment_mem16(es, newregs->es); #endif asm volatile("pushf\n\t" "pop %0" : "=m"(newregs->flags)); -- 2.53.0