From 13e3e9fd0231fda3d7f7dec351a439b26fe94d34 Mon Sep 17 00:00:00 2001 From: kan Date: Sun, 19 Jun 2011 13:35:41 +0000 Subject: Minimize backward seeks when trying to load ELF relocatable modules. Some of loader filesystems are very ill equipped to handle seeking backwards within the file. Namely, tftp requires trasfer to be restarted from the start of the file every time we go backwards. --- sys/boot/common/load_elf_obj.c | 37 ++++++++++++++++++++++++++++++------- 1 file changed, 30 insertions(+), 7 deletions(-) (limited to 'sys/boot/common/load_elf_obj.c') diff --git a/sys/boot/common/load_elf_obj.c b/sys/boot/common/load_elf_obj.c index dcd71ef..54d9b10 100644 --- a/sys/boot/common/load_elf_obj.c +++ b/sys/boot/common/load_elf_obj.c @@ -196,7 +196,7 @@ static int __elfN(obj_loadimage)(struct preloaded_file *fp, elf_file_t ef, u_int64_t off) { Elf_Ehdr *hdr; - Elf_Shdr *shdr; + Elf_Shdr *shdr, *cshdr, *lshdr; vm_offset_t firstaddr, lastaddr; int i, nsym, res, ret, shdrbytes, symstrindex; @@ -294,12 +294,35 @@ __elfN(obj_loadimage)(struct preloaded_file *fp, elf_file_t ef, u_int64_t off) /* Clear the whole area, including bss regions. */ kern_bzero(firstaddr, lastaddr - firstaddr); - /* Now read it all in. */ - for (i = 0; i < hdr->e_shnum; i++) { - if (shdr[i].sh_addr == 0 || shdr[i].sh_type == SHT_NOBITS) - continue; - if (kern_pread(ef->fd, (vm_offset_t)shdr[i].sh_addr, - shdr[i].sh_size, (off_t)shdr[i].sh_offset) != 0) { + /* Figure section with the lowest file offset we haven't loaded yet. */ + for (cshdr = NULL; /* none */; /* none */) + { + /* + * Find next section to load. The complexity of this loop is + * O(n^2), but with the number of sections being typically + * small, we do not care. + */ + lshdr = cshdr; + + for (i = 0; i < hdr->e_shnum; i++) { + if (shdr[i].sh_addr == 0 || + shdr[i].sh_type == SHT_NOBITS) + continue; + /* Skip sections that were loaded already. */ + if (lshdr != NULL && + lshdr->sh_offset >= shdr[i].sh_offset) + continue; + /* Find section with smallest offset. */ + if (cshdr == lshdr || + cshdr->sh_offset > shdr[i].sh_offset) + cshdr = &shdr[i]; + } + + if (cshdr == lshdr) + break; + + if (kern_pread(ef->fd, (vm_offset_t)cshdr->sh_addr, + cshdr->sh_size, (off_t)cshdr->sh_offset) != 0) { printf("\nelf" __XSTRING(__ELF_WORD_SIZE) "_obj_loadimage: read failed\n"); goto out; -- cgit v1.1