Some distributions (ie. Ubuntu) have their libc debug
info in separate files. This change allows the stack walking
code to read that debug info.
- add support for reading compressed ELF sections
- support reading the build-id from the elf headers in order to lookup external debug info
- support reading the .gnu_debuglink section to look up external debug info
This is consistent with what clang and gcc are doing, because
headers such as <cet.h> are specifically designed to be used
in the context of assembly code.
Fixes#16449
At the moment, the LLVM IR we generate for this fn is
define internal fastcc void @AstGen.numberLiteral ... {
Entry:
...
%16 = alloca %"fmt.parse_float.decimal.Decimal(f128)", align 8
...
That `Decimal` is huuuge! It stores
pub const max_digits = 11564;
digits: [max_digits]u8,
on the stack.
It comes from `convertSlow` function, which LLVM happily inlined,
despite it being the cold path. Forbid inlining that to not penalize
callers with excessive stack usage.
Backstory: I was looking for needles memcpys in TigerBeetle, and came up
with this copyhound.zig tool for doing just that:
ee67e2ab95/src/copyhound.zig
Got curious, run it on the Zig's own code base, and looked at some of
the worst offenders.
List of worst offenders:
warning: crypto.kyber_d00.Kyber.SecretKey.decaps: 7776 bytes memcpy
warning: crypto.ff.Modulus.powPublic: 8160 bytes memcpy
warning: AstGen.numberLiteral: 11584 bytes memcpy
warning: crypto.tls.Client.init__anon_133566: 13984 bytes memcpy
warning: http.Client.connectUnproxied: 16896 bytes memcpy
warning: crypto.tls.Client.init__anon_133566: 16904 bytes memcpy
warning: objcopy.ElfFileHelper.tryCompressSection: 32768 bytes memcpy
Note from Andrew: I removed `noinline` from this commit since it should
be enough to set it to be cold.
Instead, we now have a looser helper called `checkContains(...)`
that will match on any occurrence similarly to `std.mem.indexOf()`.
While at it, I have cleaned up other combinators to make the entire
API more consistent, and so:
* `checkStart(phrase)` is now `checkStart()` followed by
`checkExact(phrase)`
* `checkNext(phrase)` if matching exactly is now `checkExact(phrase)`
* `checkNext(phrase)` if matching loosely is now `checkContains(phrase)`
* `checkNext(phrase)` if matching exactly with var extractors is now
`checkExtract(phrase)`
Finally, `ElfDumper` is now dumping contents of `.symtab` and `.dynsym`
symbol tables. I have also removed dumping of symtabs as optional - they
are now always dumped which cleaned up the implementation even more.
It is assumed that generating a collision requires more than 2^156
ciphertext modifications. This is plenty enough for any practical
purposes, but it hasn't been proven to be >= 2^256.
Be consistent and conservative here; just claim the same security
as the other variants.
Previously, they were only created when we had any TLS segment.
This meant that while the symbol existed, the global itself wouldn't.
The result of this was a crash during symbol names writing as it
would attempt to write the symbol name of a global that didn't exist.
Now we always create them, and instead update its `init` value during
`setupMemory`.
In the future, the entire symbol (and global) will be removed by
the garbage collector.
Implements the `start` section which will execute a given function
at startup of the program. After function execution, the _start
function will be called by the runtime. In the case of shared-memory
we set this section to the function `__wasm_init_memory` which will
initialize all memory on startup.
This also fixes the above mentioned function to ensure we correctly
lower the i32 values.
Lastly, this fixes a typo where we would retrieve a global, instead
of setting its value.
