Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 220 insertions, 0 deletions

diff --git a/third_party/rust/goblin/src/elf/gnu_hash.rs b/third_party/rust/goblin/src/elf/gnu_hash.rs
new file mode 100644
index 0000000000..d785382c26
--- /dev/null
+++ b/third_party/rust/goblin/src/elf/gnu_hash.rs
@@ -0,0 +1,220 @@
+//! A Gnu Hash table as 4 sections:
+//!
+//!  1. Header
+//!  2. Bloom Filter
+//!  3. Hash Buckets
+//!  4. Chains
+//!
+//! The header has is an array of four `u32`s:
+//!
+//!  1. nbuckets
+//!  2. symndx
+//!  3. maskwords
+//!  4. shift2
+//!
+//! See more:
+//!  * http://www.linker-aliens.org/blogs/ali/entry/gnu_hash_elf_sections
+//!    or https://blogs.oracle.com/solaris/gnu-hash-elf-sections-v2
+//!  * https://flapenguin.me/2017/05/10/elf-lookup-dt-gnu-hash/
+
+/// GNU hash function: accepts a symbol name and returns a value that may be
+/// used to compute a bucket index.
+///
+/// Consequently, if the hashing function returns the value `x` for some name,
+/// `buckets[x % nbuckets]` gives an index, `y`, into both the symbol table
+/// and the chain table.
+pub fn hash(symbol: &str) -> u32 {
+    const HASH_SEED: u32 = 5381;
+    symbol.bytes().fold(HASH_SEED, |hash, b| {
+        hash.wrapping_mul(33).wrapping_add(u32::from(b))
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::hash;
+    #[test]
+    fn test_hash() {
+        assert_eq!(hash(""), 0x0000_1505);
+        assert_eq!(hash("printf"), 0x156b_2bb8);
+        assert_eq!(hash("exit"), 0x7c96_7e3f);
+        assert_eq!(hash("syscall"), 0xbac2_12a0);
+        assert_eq!(hash("flapenguin.me"), 0x8ae9_f18e);
+    }
+}
+
+macro_rules! elf_gnu_hash_impl {
+    ($IntTy:ty) => {
+        use crate::elf::sym::Sym;
+        use crate::strtab::Strtab;
+        use core::fmt;
+        use core::mem;
+        use core::slice;
+
+        const INT_SIZE: usize = mem::size_of::<$IntTy>();
+        const U32_SIZE: usize = mem::size_of::<u32>();
+        /// Size of a bits mask in bloom filter
+        const ELFCLASS_BITS: u32 = INT_SIZE as u32 * 8;
+
+        /// A better hash table for the ELF used by GNU systems in GNU-compatible software.
+        pub struct GnuHash<'a> {
+            /// Index of the first symbol in the `.dynsym` table which is accessible with
+            /// the hash table
+            symindex: u32,
+            /// Shift count used in the bloom filter
+            shift2: u32,
+            /// 2 bit bloom filter on `chains`
+            // Either 32 or 64-bit depending on the class of object
+            bloom_filter: &'a [$IntTy],
+            /// GNU hash table bucket array; indexes start at 0. This array holds symbol
+            /// table indexes and contains the index of hashes in `chains`
+            buckets: &'a [u32],
+            /// Hash values; indexes start at 0. This array holds symbol table indexes.
+            chains: &'a [u32], // => chains[dynsyms.len() - symindex]
+            dynsyms: &'a [Sym],
+        }
+
+        impl fmt::Debug for GnuHash<'_> {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                f.debug_struct("GnuHash")
+                    .field("nbuckets", &self.buckets.len())
+                    .field("symindex", &self.symindex)
+                    .field("maskwords", &(self.bloom_filter.len() - 1))
+                    .field("shift2", &self.shift2)
+                    .field("bloom_filter", &self.bloom_filter.as_ptr())
+                    .field("bucket", &self.buckets.as_ptr())
+                    .field("chains", &self.chains.as_ptr())
+                    .finish()
+            }
+        }
+
+        impl<'a> GnuHash<'a> {
+            /// Initialize a GnuHash from a pointer to `.hash` (or `.gnu.hash`) section
+            /// and total number of dynamic symbols.
+            /// # Safety
+            ///
+            /// This function creates a `GnuHash` directly from a raw pointer
+            pub unsafe fn from_raw_table(
+                hashtab: &'a [u8],
+                dynsyms: &'a [Sym],
+            ) -> Result<Self, &'static str> {
+                if hashtab.as_ptr() as usize % INT_SIZE != 0 {
+                    return Err("hashtab is not aligned with 64-bit");
+                }
+
+                if hashtab.len() <= 16 {
+                    return Err("failed to read in number of buckets");
+                }
+
+                let [nbuckets, symindex, maskwords, shift2] =
+                    (hashtab.as_ptr() as *const u32 as *const [u32; 4]).read();
+
+                if !maskwords.is_power_of_two() {
+                    return Err("maskwords must be a power of two");
+                }
+
+                let hashtab = &hashtab[16..];
+                {
+                    // SAFETY: Condition to check for an overflow
+                    //   size_of(chains) + size_of(buckets) + size_of(bloom_filter) == size_of(hashtab)
+
+                    if dynsyms.len() <= symindex as usize {
+                        return Err("symindex must be smaller than dynsyms.len()");
+                    }
+                    let chains_size = (dynsyms.len() - symindex as usize).checked_mul(U32_SIZE);
+                    let buckets_size = (nbuckets as usize).checked_mul(U32_SIZE);
+                    let bloom_size = (maskwords as usize).checked_mul(INT_SIZE);
+
+                    let total_size = match (chains_size, buckets_size, bloom_size) {
+                        (Some(a), Some(b), Some(c)) => {
+                            a.checked_add(b).and_then(|t| t.checked_add(c))
+                        }
+                        _ => None,
+                    };
+                    match total_size {
+                        Some(size) if size == hashtab.len() => {}
+                        _ => return Err("index out of bound or non-complete hash section"),
+                    }
+                }
+
+                let bloom_filter_ptr = hashtab.as_ptr() as *const $IntTy;
+                let buckets_ptr = bloom_filter_ptr.add(maskwords as usize) as *const u32;
+                let chains_ptr = buckets_ptr.add(nbuckets as usize);
+                let bloom_filter = slice::from_raw_parts(bloom_filter_ptr, maskwords as usize);
+                let buckets = slice::from_raw_parts(buckets_ptr, nbuckets as usize);
+                let chains = slice::from_raw_parts(chains_ptr, dynsyms.len() - symindex as usize);
+                Ok(Self {
+                    symindex,
+                    shift2,
+                    bloom_filter,
+                    buckets,
+                    chains,
+                    dynsyms,
+                })
+            }
+
+            /// Locate the hash chain, and corresponding hash value element.
+            #[cold]
+            fn lookup(&self, symbol: &str, hash: u32, dynstrtab: &Strtab) -> Option<&'a Sym> {
+                const MASK_LOWEST_BIT: u32 = 0xffff_fffe;
+                let bucket = self.buckets[hash as usize % self.buckets.len()];
+
+                // Empty hash chain, symbol not present
+                if bucket < self.symindex {
+                    return None;
+                }
+                // Walk the chain until the symbol is found or the chain is exhausted.
+                let chain_idx = bucket - self.symindex;
+                let hash = hash & MASK_LOWEST_BIT;
+                let chains = &self.chains.get((chain_idx as usize)..)?;
+                let dynsyms = &self.dynsyms.get((bucket as usize)..)?;
+                for (hash2, symb) in chains.iter().zip(dynsyms.iter()) {
+                    if (hash == (hash2 & MASK_LOWEST_BIT))
+                        && (symbol == &dynstrtab[symb.st_name as usize])
+                    {
+                        return Some(symb);
+                    }
+                    // Chain ends with an element with the lowest bit set to 1.
+                    if hash2 & 1 == 1 {
+                        break;
+                    }
+                }
+                None
+            }
+
+            /// Check if symbol maybe is in the hash table, or definitely not in it.
+            #[inline]
+            fn check_maybe_match(&self, hash: u32) -> bool {
+                const MASK: u32 = ELFCLASS_BITS - 1;
+                let hash2 = hash >> self.shift2;
+                // `x & (N - 1)` is equivalent to `x % N` iff `N = 2^y`.
+                let bitmask: $IntTy = 1 << (hash & (MASK)) | 1 << (hash2 & MASK);
+                let bloom_idx = (hash / ELFCLASS_BITS) & (self.bloom_filter.len() as u32 - 1);
+                let bitmask_word = self.bloom_filter[bloom_idx as usize];
+                (bitmask_word & bitmask) == bitmask
+            }
+
+            /// Given a symbol, a hash of that symbol, a dynamic string table and
+            /// a `dynstrtab` to cross-reference names, maybe returns a Sym.
+            pub fn find(&self, symbol: &str, dynstrtab: &Strtab) -> Option<&'a Sym> {
+                let hash = self::hash(symbol);
+                self.find_with_hash(symbol, hash, dynstrtab)
+            }
+
+            /// This function will not check if the passed `hash` is really
+            /// the hash of `symbol`
+            pub fn find_with_hash(
+                &self,
+                symbol: &str,
+                hash: u32,
+                dynstrtab: &Strtab,
+            ) -> Option<&'a Sym> {
+                if self.check_maybe_match(hash) {
+                    self.lookup(symbol, hash, dynstrtab)
+                } else {
+                    None
+                }
+            }
+        }
+    };
+}