linux-kernel - [PATCH 07/11] kexec_file: Simplify kexec_purgatory_setup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 26 Feb 2018 16:16:16 +0100
From:   Philipp Rudo <prudo@...ux.vnet.ibm.com>
To:     kexec@...ts.infradead.org, linux-s390@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Eric Biederman <ebiederm@...ssion.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Dave Young <dyoung@...hat.com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>
Subject: [PATCH 07/11] kexec_file: Simplify kexec_purgatory_setup_sechdrs 1

To update the entry point there is an extra loop over all section headers
although this can be done in the main loop. So move it there and eliminate
the extra loop and variable to store the 'entry section index'.

Also, in the main loop, move the usual case, i.e. non-bss section, out of
the extra if-block.

Signed-off-by: Philipp Rudo <prudo@...ux.vnet.ibm.com>
Reviewed-by: Martin Schwidefsky <schwidefsky@...ibm.com>
---
 kernel/kexec_file.c | 76 +++++++++++++++++++++--------------------------------
 1 file changed, 30 insertions(+), 46 deletions(-)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index d1c3ec8dc6b1..bb31a3b627c2 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -731,7 +731,6 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
 	unsigned char *buf_addr;
 	unsigned char *src;
 	Elf_Shdr *sechdrs;
-	int entry_sidx = -1;
 	int i;
 
 	sechdrs = vzalloc(pi->ehdr->e_shnum * sizeof(Elf_Shdr));
@@ -763,32 +762,11 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
 						sechdrs[i].sh_offset;
 	}
 
-	/*
-	 * Identify entry point section and make entry relative to section
-	 * start.
-	 */
-	kbuf->image->start = pi->ehdr->e_entry;
-	for (i = 0; i < pi->ehdr->e_shnum; i++) {
-		if (!(sechdrs[i].sh_flags & SHF_ALLOC))
-			continue;
-
-		if (!(sechdrs[i].sh_flags & SHF_EXECINSTR))
-			continue;
-
-		/* Make entry section relative */
-		if (sechdrs[i].sh_addr <= pi->ehdr->e_entry &&
-		    ((sechdrs[i].sh_addr + sechdrs[i].sh_size) >
-		     pi->ehdr->e_entry)) {
-			entry_sidx = i;
-			kbuf->image->start -= sechdrs[i].sh_addr;
-			break;
-		}
-	}
-
 	/* Load SHF_ALLOC sections */
 	buf_addr = kbuf->buffer;
 	load_addr = curr_load_addr = kbuf->mem;
 	bss_addr = load_addr + kbuf->bufsz;
+	kbuf->image->start = pi->ehdr->e_entry;
 
 	for (i = 0; i < pi->ehdr->e_shnum; i++) {
 		unsigned long align;
@@ -797,34 +775,40 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
 			continue;
 
 		align = sechdrs[i].sh_addralign;
-		if (sechdrs[i].sh_type != SHT_NOBITS) {
-			curr_load_addr = ALIGN(curr_load_addr, align);
-			offset = curr_load_addr - load_addr;
-			/* We already modifed ->sh_offset to keep src addr */
-			src = (char *) sechdrs[i].sh_offset;
-			memcpy(buf_addr + offset, src, sechdrs[i].sh_size);
-
-			/* Store load address and source address of section */
-			sechdrs[i].sh_addr = curr_load_addr;
-
-			/*
-			 * This section got copied to temporary buffer. Update
-			 * ->sh_offset accordingly.
-			 */
-			sechdrs[i].sh_offset = (unsigned long)(buf_addr + offset);
-
-			/* Advance to the next address */
-			curr_load_addr += sechdrs[i].sh_size;
-		} else {
+
+		if (sechdrs[i].sh_type == SHT_NOBITS) {
 			bss_addr = ALIGN(bss_addr, align);
 			sechdrs[i].sh_addr = bss_addr;
 			bss_addr += sechdrs[i].sh_size;
+			continue;
+		}
+
+		curr_load_addr = ALIGN(curr_load_addr, align);
+		offset = curr_load_addr - load_addr;
+		/* We already modifed ->sh_offset to keep src addr */
+		src = (char *)sechdrs[i].sh_offset;
+		memcpy(buf_addr + offset, src, sechdrs[i].sh_size);
+
+		if (sechdrs[i].sh_flags & SHF_EXECINSTR &&
+		    pi->ehdr->e_entry >= sechdrs[i].sh_addr &&
+		    pi->ehdr->e_entry < (sechdrs[i].sh_addr
+					 + sechdrs[i].sh_size)) {
+			kbuf->image->start -= sechdrs[i].sh_addr;
+			kbuf->image->start += curr_load_addr
 		}
-	}
 
-	/* Update entry point based on load address of text section */
-	if (entry_sidx >= 0)
-		kbuf->image->start += sechdrs[entry_sidx].sh_addr;
+		/* Store load address and source address of section */
+		sechdrs[i].sh_addr = curr_load_addr;
+
+		/*
+		 * This section got copied to temporary buffer. Update
+		 * ->sh_offset accordingly.
+		 */
+		sechdrs[i].sh_offset = (unsigned long)(buf_addr + offset);
+
+		/* Advance to the next address */
+		curr_load_addr += sechdrs[i].sh_size;
+	}
 
 	return 0;
 }
-- 
2.13.5