Auto merge of #2144 - kjvalencik:master, r=JohnTitor

Add dl_iterate_phdr to Android

Adds the `dl_iterate_phdr` function for Android targets. This is required for Android support in `gimli` and by proxy, `backtrace`.

I tested this in [`backtrace`](https://github.com/rust-lang/backtrace-rs/pull/415) both in an i686 emulator and a physical arm64 device.

This API is only available on Version 21+. I'm not sure how that's typically handled in `libc`, so I added a doc comment.

Let me know what else is needed!

libc-test/build.rs

@@ -1384,11 +1384,13 @@ fn test_android(target: &str) {
                "ctype.h",
                "dirent.h",
                "dlfcn.h",
+               "elf.h",
                "errno.h",
                "fcntl.h",
                "grp.h",
                "ifaddrs.h",
                "limits.h",
+               "link.h",
                "locale.h",
                "malloc.h",
                "net/ethernet.h",
@@ -1469,6 +1471,7 @@ fn test_android(target: &str) {
                 "asm/mman.h",
                 "linux/auxvec.h",
                 "linux/dccp.h",
+                "linux/elf.h",
                 "linux/errqueue.h",
                 "linux/falloc.h",
                 "linux/futex.h",
@@ -1507,7 +1510,7 @@ fn test_android(target: &str) {
     cfg.type_name(move |ty, is_struct, is_union| {
         match ty {
             // Just pass all these through, no need for a "struct" prefix
-            "FILE" | "fd_set" | "Dl_info" => ty.to_string(),
+            "FILE" | "fd_set" | "Dl_info" | "Elf32_Phdr" | "Elf64_Phdr" => ty.to_string(),
 
             t if is_union => format!("union {}", t),
 
@@ -1610,7 +1613,12 @@ fn test_android(target: &str) {
         // This is a weird union, don't check the type.
         (struct_ == "ifaddrs" && field == "ifa_ifu") ||
         // sigval is actually a union, but we pretend it's a struct
-        (struct_ == "sigevent" && field == "sigev_value")
+        (struct_ == "sigevent" && field == "sigev_value") ||
+        // FIXME: `sa_sigaction` has type `sighandler_t` but that type is
+        // incorrect, see: https://github.com/rust-lang/libc/issues/1359
+        (struct_ == "sigaction" && field == "sa_sigaction") ||
+        // signalfd had SIGSYS fields added in Android 4.19, but CI does not have that version yet.
+        (struct_ == "signalfd_siginfo" && field == "ssi_call_addr")
     });
 
     cfg.skip_field(move |struct_, field| {
@@ -1628,6 +1636,20 @@ fn test_android(target: &str) {
                                            field == "ssi_arch"))
     });
 
+    cfg.skip_field(|struct_, field| {
+        match (struct_, field) {
+            // conflicting with `p_type` macro from <resolve.h>.
+            ("Elf32_Phdr", "p_type") => true,
+            ("Elf64_Phdr", "p_type") => true,
+
+            // this is actually a union on linux, so we can't represent it well and
+            // just insert some padding.
+            ("siginfo_t", "_pad") => true,
+
+            _ => false,
+        }
+    });
+
     cfg.generate("../src/lib.rs", "main.rs");
 
     test_linux_like_apis(target);

src/unix/linux_like/android/mod.rs

@@ -26,6 +26,19 @@ pub type loff_t = ::c_longlong;
 pub type __kernel_loff_t = ::c_longlong;
 pub type __kernel_pid_t = ::c_int;
 
+// linux/elf.h
+
+pub type Elf32_Addr = u32;
+pub type Elf32_Half = u16;
+pub type Elf32_Off = u32;
+pub type Elf32_Word = u32;
+
+pub type Elf64_Addr = u64;
+pub type Elf64_Half = u16;
+pub type Elf64_Off = u64;
+pub type Elf64_Word = u32;
+pub type Elf64_Xword = u64;
+
 s! {
     pub struct stack_t {
         pub ss_sp: *mut ::c_void,
@@ -244,6 +257,57 @@ s! {
         pub svm_cid: ::c_uint,
         pub svm_zero: [u8; 4]
     }
+
+    // linux/elf.h
+
+    pub struct Elf32_Phdr {
+        pub p_type: Elf32_Word,
+        pub p_offset: Elf32_Off,
+        pub p_vaddr: Elf32_Addr,
+        pub p_paddr: Elf32_Addr,
+        pub p_filesz: Elf32_Word,
+        pub p_memsz: Elf32_Word,
+        pub p_flags: Elf32_Word,
+        pub p_align: Elf32_Word,
+    }
+
+    pub struct Elf64_Phdr {
+        pub p_type: Elf64_Word,
+        pub p_flags: Elf64_Word,
+        pub p_offset: Elf64_Off,
+        pub p_vaddr: Elf64_Addr,
+        pub p_paddr: Elf64_Addr,
+        pub p_filesz: Elf64_Xword,
+        pub p_memsz: Elf64_Xword,
+        pub p_align: Elf64_Xword,
+    }
+
+    // link.h
+
+    pub struct dl_phdr_info {
+        #[cfg(target_pointer_width = "64")]
+        pub dlpi_addr: Elf64_Addr,
+        #[cfg(target_pointer_width = "32")]
+        pub dlpi_addr: Elf32_Addr,
+
+        pub dlpi_name: *const ::c_char,
+
+        #[cfg(target_pointer_width = "64")]
+        pub dlpi_phdr: *const Elf64_Phdr,
+        #[cfg(target_pointer_width = "32")]
+        pub dlpi_phdr: *const Elf32_Phdr,
+
+        #[cfg(target_pointer_width = "64")]
+        pub dlpi_phnum: Elf64_Half,
+        #[cfg(target_pointer_width = "32")]
+        pub dlpi_phnum: Elf32_Half,
+
+        // These fields were added in Android R
+        pub dlpi_adds: ::c_ulonglong,
+        pub dlpi_subs: ::c_ulonglong,
+        pub dlpi_tls_modid: ::size_t,
+        pub dlpi_tls_data: *mut ::c_void,
+    }
 }
 
 s_no_extra_traits! {
@@ -2715,6 +2779,19 @@ extern "C" {
 
     pub fn __system_property_set(__name: *const ::c_char, __value: *const ::c_char) -> ::c_int;
     pub fn __system_property_get(__name: *const ::c_char, __value: *mut ::c_char) -> ::c_int;
+
+    // #include <link.h>
+    /// Only available in API Version 21+
+    pub fn dl_iterate_phdr(
+        callback: ::Option<
+            unsafe extern "C" fn(
+                info: *mut dl_phdr_info,
+                size: usize,
+                data: *mut ::c_void,
+            ) -> ::c_int,
+        >,
+        data: *mut ::c_void,
+    ) -> ::c_int;
 }
 
 cfg_if! {