mirror/zig
1
0
Fork 0
mirror of https://github.com/ziglang/zig.git synced 2026-02-13 04:48:20 +00:00
Code Issues Packages Projects Releases Wiki Activity

elf: sort PT_LOAD by address in PHDR table

Browse Source 
Turns out order matters as otherwise we face unexplainable
segfaults to do with improper page mapping in static environments
(dynamic environments seem unaffected).
This commit is contained in:
Jakub Konka 2023-10-15 23:08:41 +02:00
parent 6993b3e23e
commit b0e2c6323b
1 changed files with 16 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
src/link/Elf.zig
View File

@ -3927,20 +3927,9 @@ fn initSpecialPhdrs(self: *Elf) !void {
.@"align" = 1,
});
const has_tls = has_tls: {
if (self.base.options.link_libc and self.isStatic()) {
// Even if we don't emit any TLS data, linking against musl-libc without
// empty TLS phdr leads to a bizarre segfault in `__copy_tls` function.
// So far I haven't been able to work out why that is, but adding an empty
// TLS phdr seems to fix it, so let's go with it for now.
// TODO try to investigate more
break :has_tls true;
}
for (self.shdrs.items) |shdr| {
if (shdr.sh_flags & elf.SHF_TLS != 0) break :has_tls true;
}
break :has_tls false;
};
const has_tls = for (self.shdrs.items) |shdr| {
if (shdr.sh_flags & elf.SHF_TLS != 0) break true;
} else false;
if (has_tls) {
self.phdr_tls_index = try self.addPhdr(.{
.type = elf.PT_TLS,
@ -4076,24 +4065,16 @@ fn setHashSections(self: *Elf) !void {
}
}
fn phdrRank(self: *Elf, phndx: u16) u8 {
const phdr = self.phdrs.items[phndx];
const flags = phdr.p_flags;
fn phdrRank(phdr: elf.Elf64_Phdr) u8 {
switch (phdr.p_type) {
elf.PT_NULL => return 0,
elf.PT_PHDR => return 1,
elf.PT_INTERP => return 2,
elf.PT_LOAD => if (flags & elf.PF_X != 0) {
return 4;
} else if (flags & elf.PF_W != 0) {
return 5;
} else {
return 3;
},
elf.PT_DYNAMIC, elf.PT_TLS => return 6,
elf.PT_GNU_EH_FRAME => return 7,
elf.PT_GNU_STACK => return 8,
else => return 0xf,
elf.PT_LOAD => return 3,
elf.PT_DYNAMIC, elf.PT_TLS => return 4,
elf.PT_GNU_EH_FRAME => return 5,
elf.PT_GNU_STACK => return 6,
else => return 7,
}
}
@ -4102,7 +4083,12 @@ fn sortPhdrs(self: *Elf) error{OutOfMemory}!void {
phndx: u16,
pub fn lessThan(elf_file: *Elf, lhs: @This(), rhs: @This()) bool {
return elf_file.phdrRank(lhs.phndx) < elf_file.phdrRank(rhs.phndx);
const lhs_phdr = elf_file.phdrs.items[lhs.phndx];
const rhs_phdr = elf_file.phdrs.items[rhs.phndx];
const lhs_rank = phdrRank(lhs_phdr);
const rhs_rank = phdrRank(rhs_phdr);
if (lhs_rank == rhs_rank) return lhs_phdr.p_vaddr < rhs_phdr.p_vaddr;
return lhs_rank < rhs_rank;
}
};
@ -4674,7 +4660,7 @@ fn allocateAllocSections(self: *Elf) error{OutOfMemory}!void {
try self.phdr_to_shdr_table.putNoClobber(gpa, shndx, phndx);
}
addr += self.page_size;
addr = mem.alignForward(u64, addr, self.page_size);
}
}