linux-kernel - [PATCH -mm] elf: init pt

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Date:   Fri, 19 Apr 2019 23:03:43 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH -mm] elf: init pt_regs pointer later

Get "current_pt_regs" pointer right before usage.

Space savings on x86_64:

	add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-180 (-180)
	Function                           old     new   delta
	load_elf_binary                   5806    5626    -180 !!!

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 fs/binfmt_elf.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -704,12 +704,12 @@ static int load_elf_binary(struct linux_binprm *bprm)
 	unsigned long start_code, end_code, start_data, end_data;
 	unsigned long reloc_func_desc __maybe_unused = 0;
 	int executable_stack = EXSTACK_DEFAULT;
-	struct pt_regs *regs = current_pt_regs();
 	struct {
 		struct elfhdr elf_ex;
 		struct elfhdr interp_elf_ex;
 	} *loc;
 	struct arch_elf_state arch_state = INIT_ARCH_ELF_STATE;
+	struct pt_regs *regs;
 
 	loc = kmalloc(sizeof(*loc), GFP_KERNEL);
 	if (!loc) {
@@ -1159,6 +1159,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 				MAP_FIXED | MAP_PRIVATE, 0);
 	}
 
+	regs = current_pt_regs();
 #ifdef ELF_PLAT_INIT
 	/*
 	 * The ABI may specify that certain registers be set up in special