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elf: change how we create new program headers

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We do not want to create additional ones per update that are duplicates
of existing ones.
This commit is contained in:
Jakub Konka 2024-09-24 13:07:58 +02:00
parent 992c6c3f68
commit 10c68d05db
1 changed files with 28 additions and 23 deletions
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51
src/link/Elf.zig
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@ -1048,6 +1048,7 @@ pub fn flushModule(self: *Elf, arena: Allocator, tid: Zcu.PerThread.Id, prog_nod
try self.updateMergeSectionSizes();
try self.updateSectionSizes();
try self.addLoadPhdrs();
try self.allocatePhdrTable();
try self.allocateAllocSections();
try self.sortPhdrs();
@ -3729,27 +3730,19 @@ fn getMaxNumberOfPhdrs() u64 {
return num;
}
/// Calculates how many segments (PT_LOAD progam headers) are required
/// to cover the set of sections.
/// We permit a maximum of 3**2 number of segments.
fn calcNumberOfSegments(self: *Elf) usize {
var covers: [9]bool = [_]bool{false} ** 9;
fn addLoadPhdrs(self: *Elf) error{OutOfMemory}!void {
for (self.sections.items(.shdr)) |shdr| {
if (shdr.sh_type == elf.SHT_NULL) continue;
if (shdr.sh_flags & elf.SHF_ALLOC == 0) continue;
const flags = shdrToPhdrFlags(shdr.sh_flags);
covers[flags - 1] = true;
if (self.getPhdr(.{ .flags = flags, .type = elf.PT_LOAD }) == null) {
_ = try self.addPhdr(.{ .flags = flags, .type = elf.PT_LOAD });
}
}
var count: usize = 0;
for (covers) |cover| {
if (cover) count += 1;
}
return count;
}
/// Allocates PHDR table in virtual memory and in file.
fn allocatePhdrTable(self: *Elf) error{OutOfMemory}!void {
const new_load_segments = self.calcNumberOfSegments();
const phdr_table = &self.phdrs.items[self.phdr_table_index.?];
const phdr_table_load = &self.phdrs.items[self.phdr_table_load_index.?];
@ -3761,7 +3754,7 @@ fn allocatePhdrTable(self: *Elf) error{OutOfMemory}!void {
.p32 => @sizeOf(elf.Elf32_Phdr),
.p64 => @sizeOf(elf.Elf64_Phdr),
};
const needed_size = (self.phdrs.items.len + new_load_segments) * phsize;
const needed_size = self.phdrs.items.len * phsize;
const available_space = self.allocatedSize(phdr_table.p_offset);
if (needed_size > available_space) {
@ -3904,15 +3897,14 @@ pub fn allocateAllocSections(self: *Elf) !void {
const first = slice.items(.shdr)[cover.items[0]];
var new_offset = try self.findFreeSpace(filesz, @"align");
const phndx = try self.addPhdr(.{
.type = elf.PT_LOAD,
.offset = new_offset,
.addr = first.sh_addr,
.memsz = memsz,
.filesz = filesz,
.@"align" = @"align",
.flags = shdrToPhdrFlags(first.sh_flags),
});
const phndx = self.getPhdr(.{ .type = elf.PT_LOAD, .flags = shdrToPhdrFlags(first.sh_flags) }).?;
const phdr = &self.phdrs.items[phndx];
phdr.p_offset = new_offset;
phdr.p_vaddr = first.sh_addr;
phdr.p_paddr = first.sh_addr;
phdr.p_memsz = memsz;
phdr.p_filesz = filesz;
phdr.p_align = @"align";
for (cover.items) |shndx| {
const shdr = &slice.items(.shdr)[shndx];
@ -4747,7 +4739,20 @@ pub fn isEffectivelyDynLib(self: Elf) bool {
};
}
pub fn addPhdr(self: *Elf, opts: struct {
fn getPhdr(self: *Elf, opts: struct {
type: u32 = 0,
flags: u32 = 0,
}) ?u16 {
for (self.phdrs.items, 0..) |phdr, phndx| {
if (self.phdr_table_load_index) |index| {
if (phndx == index) continue;
}
if (phdr.p_type == opts.type and phdr.p_flags == opts.flags) return @intCast(phndx);
}
return null;
}
fn addPhdr(self: *Elf, opts: struct {
type: u32 = 0,
flags: u32 = 0,
@"align": u64 = 0,