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[src/trunk]: src/sys/arch/amd64/stand/prekern Clarify.
details: https://anonhg.NetBSD.org/src/rev/738e0155ebd2
branches: trunk
changeset: 932435:738e0155ebd2
user: maxv <maxv%NetBSD.org@localhost>
date: Thu May 07 17:58:26 2020 +0000
description:
Clarify.
diffstat:
sys/arch/amd64/stand/prekern/elf.c | 77 ++++++++++++++++++++++---------------
sys/arch/amd64/stand/prekern/mm.c | 39 ++++++++++--------
2 files changed, 66 insertions(+), 50 deletions(-)
diffs (209 lines):
diff -r 235ce7058ec2 -r 738e0155ebd2 sys/arch/amd64/stand/prekern/elf.c
--- a/sys/arch/amd64/stand/prekern/elf.c Thu May 07 17:10:02 2020 +0000
+++ b/sys/arch/amd64/stand/prekern/elf.c Thu May 07 17:58:26 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: elf.c,v 1.20 2020/05/07 16:49:59 maxv Exp $ */
+/* $NetBSD: elf.c,v 1.21 2020/05/07 17:58:26 maxv Exp $ */
/*
* Copyright (c) 2017-2020 The NetBSD Foundation, Inc. All rights reserved.
@@ -300,6 +300,37 @@
}
void
+elf_fixup_boot(vaddr_t bootva, paddr_t bootpa)
+{
+ const paddr_t basepa = kernpa_start;
+ const vaddr_t headva = (vaddr_t)eif.ehdr;
+ size_t i, offboot;
+
+ /*
+ * Fix up the 'sh_offset' field of the REL/RELA/SYM/STR sections, which
+ * are all in the "boot" region.
+ */
+ for (i = 0; i < eif.ehdr->e_shnum; i++) {
+ if (eif.shdr[i].sh_type != SHT_STRTAB &&
+ eif.shdr[i].sh_type != SHT_REL &&
+ eif.shdr[i].sh_type != SHT_RELA &&
+ eif.shdr[i].sh_type != SHT_SYMTAB) {
+ continue;
+ }
+ if (eif.shdr[i].sh_offset == 0) {
+ /* The bootloader dropped it. */
+ continue;
+ }
+
+ /* Offset of the section within the boot region. */
+ offboot = basepa + eif.shdr[i].sh_offset - bootpa;
+
+ /* We want (headva + sh_offset) to be the VA of the region. */
+ eif.shdr[i].sh_offset = (bootva + offboot - headva);
+ }
+}
+
+void
elf_map_sections(void)
{
const paddr_t basepa = kernpa_start;
@@ -333,45 +364,27 @@
secva = mm_map_segment(segtype, secpa, secsz, secalign);
- /* We want (headva + sh_offset) to be the VA of the section. */
+ /*
+ * Fix up the 'sh_offset' field of the NOBITS/PROGBITS sections.
+ * We want (headva + sh_offset) to be the VA of the section.
+ */
ASSERT(secva > headva);
shdr->sh_offset = secva - headva;
}
}
void
-elf_build_boot(vaddr_t bootva, paddr_t bootpa)
+elf_build_info(void)
{
- const paddr_t basepa = kernpa_start;
- const vaddr_t headva = (vaddr_t)eif.ehdr;
- size_t i, j, offboot;
-
- for (i = 0; i < eif.ehdr->e_shnum; i++) {
- if (eif.shdr[i].sh_type != SHT_STRTAB &&
- eif.shdr[i].sh_type != SHT_REL &&
- eif.shdr[i].sh_type != SHT_RELA &&
- eif.shdr[i].sh_type != SHT_SYMTAB) {
- continue;
- }
- if (eif.shdr[i].sh_offset == 0) {
- /* hasn't been loaded */
- continue;
- }
-
- /* Offset of the section within the boot region. */
- offboot = basepa + eif.shdr[i].sh_offset - bootpa;
-
- /* We want (headva + sh_offset) to be the VA of the region. */
- eif.shdr[i].sh_offset = (bootva + offboot - headva);
- }
+ size_t i, j;
/* Locate the section names */
j = eif.ehdr->e_shstrndx;
if (j == SHN_UNDEF) {
- fatal("elf_build_boot: shstrtab not found");
+ fatal("elf_build_info: shstrtab not found");
}
if (j >= eif.ehdr->e_shnum) {
- fatal("elf_build_boot: wrong shstrtab index");
+ fatal("elf_build_info: wrong shstrtab index");
}
eif.shstrtab = (char *)((uint8_t *)eif.ehdr + eif.shdr[j].sh_offset);
eif.shstrsz = eif.shdr[j].sh_size;
@@ -382,10 +395,10 @@
break;
}
if (i == eif.ehdr->e_shnum) {
- fatal("elf_build_boot: symtab not found");
+ fatal("elf_build_info: symtab not found");
}
if (eif.shdr[i].sh_offset == 0) {
- fatal("elf_build_boot: symtab not loaded");
+ fatal("elf_build_info: symtab not loaded");
}
eif.symtab = (Elf_Sym *)((uint8_t *)eif.ehdr + eif.shdr[i].sh_offset);
eif.symcnt = eif.shdr[i].sh_size / sizeof(Elf_Sym);
@@ -393,13 +406,13 @@
/* Also locate the string table */
j = eif.shdr[i].sh_link;
if (j == SHN_UNDEF || j >= eif.ehdr->e_shnum) {
- fatal("elf_build_boot: wrong strtab index");
+ fatal("elf_build_info: wrong strtab index");
}
if (eif.shdr[j].sh_type != SHT_STRTAB) {
- fatal("elf_build_boot: wrong strtab type");
+ fatal("elf_build_info: wrong strtab type");
}
if (eif.shdr[j].sh_offset == 0) {
- fatal("elf_build_boot: strtab not loaded");
+ fatal("elf_build_info: strtab not loaded");
}
eif.strtab = (char *)((uint8_t *)eif.ehdr + eif.shdr[j].sh_offset);
eif.strsz = eif.shdr[j].sh_size;
diff -r 235ce7058ec2 -r 738e0155ebd2 sys/arch/amd64/stand/prekern/mm.c
--- a/sys/arch/amd64/stand/prekern/mm.c Thu May 07 17:10:02 2020 +0000
+++ b/sys/arch/amd64/stand/prekern/mm.c Thu May 07 17:58:26 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: mm.c,v 1.26 2020/05/07 17:10:02 maxv Exp $ */
+/* $NetBSD: mm.c,v 1.27 2020/05/07 17:58:26 maxv Exp $ */
/*
* Copyright (c) 2017-2020 The NetBSD Foundation, Inc. All rights reserved.
@@ -417,8 +417,8 @@
/* The "boot" region begins right after the kernel segments */
bootpa = bootspace_get_kern_segs_end_pa();
- /* The prekern consumed some memory up until pa_avail, this covers
- * SYM+REL and EXTRA */
+ /* The prekern consumed some EXTRA memory up until pa_avail, this
+ * covers REL/RELA/SYM/STR and EXTRA */
size = (pa_avail - bootpa);
npages = size / PAGE_SIZE;
@@ -428,11 +428,10 @@
randva + i * PAGE_SIZE, MM_PROT_READ|MM_PROT_WRITE);
}
- /* At this point both "head" and "boot" are mapped, so we can build
- * the ELF info */
- elf_build_boot(randva, bootpa);
+ /* Fix up the ELF sections located in the "boot" region */
+ elf_fixup_boot(randva, bootpa);
- /* Map the ISA I/O MEM right after EXTRA */
+ /* Map the ISA I/O MEM right after EXTRA, in pure VA */
iom_base = randva + npages * PAGE_SIZE;
npages = IOM_SIZE / PAGE_SIZE;
for (i = 0; i < npages; i++) {
@@ -456,15 +455,15 @@
/*
* The bootloader has set up the following layout of physical memory:
- * +------------+-----------------+---------------+------------------+-------+
- * | ELF HEADER | SECTION HEADERS | KERN SECTIONS | SYM+REL SECTIONS | EXTRA |
- * +------------+-----------------+---------------+------------------+-------+
+ * +------------+--------------+------------+------------------------+-------+
+ * | ELF HEADER | SECT HEADERS | KERN SECTS | REL/RELA/SYM/STR SECTS | EXTRA |
+ * +------------+--------------+------------+------------------------+-------+
* This was done in the loadfile_elf32.c:loadfile_dynamic() function.
*
* We abstract this layout into several "regions":
- * +------------------------------+---------------+--------------------------+
- * | Head region | Kernel segs | Boot region |
- * +------------------------------+---------------+--------------------------+
+ * +---------------------------+------------+--------------------------------+
+ * | Head region | Kern segs | Boot region |
+ * +---------------------------+------------+--------------------------------+
*
* There is a variable number of independent regions we create: one head,
* several kernel segments, one boot. They are all mapped at random VAs.
@@ -477,11 +476,15 @@
* sections, in a 1:1 manner (one segment is associated with one section).
* The segments are mapped at random VAs and referenced in bootspace.segs[].
*
- * "Boot" contains various information, including the ELF Sym+Rel sections,
- * plus extra memory the prekern has used so far; it is a region that the
- * kernel will eventually use for module_map. Boot is placed *after* the
- * other regions in physical memory. In virtual memory however there is no
- * constraint, so its VA is randomly selected in the main KASLR window.
+ * "Boot" contains miscellaneous information:
+ * - The ELF Rel/Rela/Sym/Str sections of the kernel
+ * - Some extra memory the prekern has consumed so far
+ * - The ISA I/O MEM, in pure VA
+ * - Eventually the module_map, in pure VA (the kernel uses the available VA
+ * at the end of "boot")
+ * Boot is placed *after* the other regions in physical memory. In virtual
+ * memory however there is no constraint, so its VA is randomly selected in
+ * the main KASLR window.
*
* At the end of this function, the bootspace structure is fully constructed.
*/
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