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elf: hint allocateSegment where to put the segment at

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This commit is contained in:
Jakub Konka 2023-09-27 19:41:59 +02:00
parent 111349f83c
commit 8b7255c22a
1 changed files with 25 additions and 8 deletions
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33
src/link/Elf.zig
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@ -413,6 +413,7 @@ fn findFreeSpace(self: *Elf, object_size: u64, min_alignment: u64) u64 {
const AllocateSegmentOpts = struct {
size: u64,
alignment: u64,
addr: ?u64 = null,
flags: u32 = elf.PF_R,
};
@ -423,8 +424,8 @@ pub fn allocateSegment(self: *Elf, opts: AllocateSegmentOpts) error{OutOfMemory}
// Memory is always allocated in sequence.
// TODO is this correct? Or should we implement something similar to `findFreeSpace`?
// How would that impact HCS?
const addr = blk: {
assert(self.phdr_table_load_index != null);
const addr = opts.addr orelse blk: {
assert(index >= 1);
const phdr = &self.phdrs.items[index - 1];
const increased_size = padToIdeal(phdr.p_vaddr + phdr.p_memsz);
break :blk mem.alignForward(u64, increased_size, opts.alignment);
@ -532,6 +533,7 @@ pub fn populateMissingMetadata(self: *Elf) !void {
.p64 => false,
};
const ptr_size: u8 = self.ptrWidthBytes();
const is_linux = self.base.options.target.os.tag == .linux;
const image_base = self.calcImageBase();
if (self.phdr_table_index == null) {
@ -570,6 +572,7 @@ pub fn populateMissingMetadata(self: *Elf) !void {
if (self.phdr_load_re_index == null) {
self.phdr_load_re_index = try self.allocateSegment(.{
.addr = self.defaultEntryAddress(),
.size = self.base.options.program_code_size_hint,
.alignment = self.page_size,
.flags = elf.PF_X | elf.PF_R | elf.PF_W,
@ -578,10 +581,12 @@ pub fn populateMissingMetadata(self: *Elf) !void {
}
if (self.phdr_got_index == null) {
const addr: u64 = if (ptr_size >= 4) 0x4000000 else 0x8000;
// We really only need ptr alignment but since we are using PROGBITS, linux requires
// page align.
const alignment = if (self.base.options.target.os.tag == .linux) self.page_size else @as(u16, ptr_size);
const alignment = if (is_linux) self.page_size else @as(u16, ptr_size);
self.phdr_got_index = try self.allocateSegment(.{
.addr = addr,
.size = @as(u64, ptr_size) * self.base.options.symbol_count_hint,
.alignment = alignment,
.flags = elf.PF_R | elf.PF_W,
@ -589,9 +594,10 @@ pub fn populateMissingMetadata(self: *Elf) !void {
}
if (self.phdr_load_ro_index == null) {
// Same reason as for GOT
const alignment = if (self.base.options.target.os.tag == .linux) self.page_size else @as(u16, ptr_size);
const addr: u64 = if (ptr_size >= 4) 0xc000000 else 0xa000;
const alignment = if (is_linux) self.page_size else @as(u16, ptr_size);
self.phdr_load_ro_index = try self.allocateSegment(.{
.addr = addr,
.size = 1024,
.alignment = alignment,
.flags = elf.PF_R | elf.PF_W,
@ -599,9 +605,10 @@ pub fn populateMissingMetadata(self: *Elf) !void {
}
if (self.phdr_load_rw_index == null) {
// Same reason as for GOT
const alignment = if (self.base.options.target.os.tag == .linux) self.page_size else @as(u16, ptr_size);
const addr: u64 = if (ptr_size >= 4) 0x10000000 else 0xc000;
const alignment = if (is_linux) self.page_size else @as(u16, ptr_size);
self.phdr_load_rw_index = try self.allocateSegment(.{
.addr = addr,
.size = 1024,
.alignment = alignment,
.flags = elf.PF_R | elf.PF_W,
@ -609,8 +616,10 @@ pub fn populateMissingMetadata(self: *Elf) !void {
}
if (self.phdr_load_zerofill_index == null) {
const alignment = if (self.base.options.target.os.tag == .linux) self.page_size else @as(u16, ptr_size);
const addr: u64 = if (ptr_size >= 4) 0x14000000 else 0xf000;
const alignment = if (is_linux) self.page_size else @as(u16, ptr_size);
self.phdr_load_zerofill_index = try self.allocateSegment(.{
.addr = addr,
.size = 0,
.alignment = alignment,
.flags = elf.PF_R | elf.PF_W,
@ -3801,6 +3810,14 @@ pub fn calcImageBase(self: Elf) u64 {
};
}
pub fn defaultEntryAddress(self: Elf) u64 {
if (self.entry_addr) |addr| return addr;
return switch (self.base.options.target.cpu.arch) {
.spu_2 => 0,
else => default_entry_addr,
};
}
pub fn isDynLib(self: Elf) bool {
return self.base.options.output_mode == .Lib and self.base.options.link_mode == .Dynamic;
}