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8233624: Enhance JNI linkage

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Co-authored-by: David Holmes <david.holmes@oracle.com>, Alex Buckley <alex.buckley@oracle.com>, John Rose <john.r.rose@oracle.com>
Reviewed-by: abuckley, jrose, rhalade, mschoene
This commit is contained in:
David Holmes 2020-05-13 03:33:21 -04:00 committed by Henry Jen
parent 7c05f32bc9
commit 798bfb3b9c
1 changed files with 129 additions and 11 deletions

140
src/hotspot/share/prims/nativeLookup.cpp

@ -51,27 +51,114 @@
#include "jfr/jfr.hpp"
#endif
static void mangle_name_on(outputStream* st, Symbol* name, int begin, int end) {
/*
The JNI specification defines the mapping from a Java native method name to
a C native library implementation function name as follows:
The mapping produces a native method name by concatenating the following components
derived from a `native` method declaration:
1. the prefix Java_
2. given the binary name, in internal form, of the class which declares the native method:
the result of escaping the name.
3. an underscore ("_")
4. the escaped method name
5. if the native method declaration is overloaded: two underscores ("__") followed by the
escaped parameter descriptor (JVMS 4.3.3) of the method declaration.
Escaping leaves every alphanumeric ASCII character (A-Za-z0-9) unchanged, and replaces each
UTF-16 code unit n the table below with the corresponding escape sequence. If the name to be
escaped contains a surrogate pair, then the high-surrogate code unit and the low-surrogate code
unit are escaped separately. The result of escaping is a string consisting only of the ASCII
characters A-Za-z0-9 and underscore.
------------------------------ ------------------------------------
UTF-16 code unit Escape sequence
------------------------------ ------------------------------------
Forward slash (/, U+002F) _
Underscore (_, U+005F) _1
Semicolon (;, U+003B) _2
Left square bracket ([, U+005B) _3
Any UTF-16 code unit \u_WXYZ_ that does not _0wxyz where w, x, y, and z are the lower-case
represent alphanumeric ASCII (A-Za-z0-9), forms of the hexadecimal digits W, X, Y, and Z.
forward slash, underscore, semicolon, (For example, U+ABCD becomes _0abcd.)
or left square bracket
------------------------------ ------------------------------------
Note that escape sequences can safely begin _0, _1, etc, because class and method
names in Java source code never begin with a number. However, that is not the case in
class files that were not generated from Java source code.
To preserve the 1:1 mapping to a native method name, the VM checks the resulting name as
follows. If the process of escaping any precursor string from the native method declaration
(class or method name, or argument type) causes a "0", "1", "2", or "3" character
from the precursor string to appear unchanged in the result *either* immediately after an
underscore *or* at the beginning of the escaped string (where it will follow an underscore
in the fully assembled name), then the escaping process is said to have "failed".
In such cases, no native library search is performed, and the attempt to link the native
method invocation will throw UnsatisfiedLinkError.
For example:
package/my_class/method
and
package/my/1class/method
both map to
Java_package_my_1class_method
To address this potential conflict we need only check if the character after
/ is a digit 0..3, or if the first character after an injected '_' seperator
is a digit 0..3. If we encounter an invalid identifier we reset the
stringStream and return false. Otherwise the stringStream contains the mapped
name and we return true.
*/
static bool map_escaped_name_on(stringStream* st, Symbol* name, int begin, int end) {
char* bytes = (char*)name->bytes() + begin;
char* end_bytes = (char*)name->bytes() + end;
bool check_escape_char = true; // initially true as first character here follows '_'
while (bytes < end_bytes) {
jchar c;
bytes = UTF8::next(bytes, &c);
if (c <= 0x7f && isalnum(c)) {
if (check_escape_char && (c >= '0' && c <= '3')) {
// This is a non-Java identifier and we won't escape it to
// ensure no name collisions with a Java identifier.
if (log_is_enabled(Debug, jni, resolve)) {
ResourceMark rm;
log_debug(jni, resolve)("[Lookup of native method with non-Java identifier rejected: %s]",
name->as_C_string());
}
st->reset(); // restore to "" on error
return false;
}
st->put((char) c);
check_escape_char = false;
} else {
if (c == '_') st->print("_1");
else if (c == '/') st->print("_");
check_escape_char = false;
if (c == '_') st->print("_1");
else if (c == '/') {
st->print("_");
// Following a / we must have non-escape character
check_escape_char = true;
}
else if (c == ';') st->print("_2");
else if (c == '[') st->print("_3");
else st->print("_%.5x", c);
}
}
return true;
}
static void mangle_name_on(outputStream* st, Symbol* name) {
mangle_name_on(st, name, 0, name->utf8_length());
static bool map_escaped_name_on(stringStream* st, Symbol* name) {
return map_escaped_name_on(st, name, 0, name->utf8_length());
}
@ -80,10 +167,14 @@ char* NativeLookup::pure_jni_name(const methodHandle& method) {
// Prefix
st.print("Java_");
// Klass name
mangle_name_on(&st, method->klass_name());
if (!map_escaped_name_on(&st, method->klass_name())) {
return NULL;
}
st.print("_");
// Method name
mangle_name_on(&st, method->name());
if (!map_escaped_name_on(&st, method->name())) {
return NULL;
}
return st.as_string();
}
@ -93,16 +184,20 @@ char* NativeLookup::critical_jni_name(const methodHandle& method) {
// Prefix
st.print("JavaCritical_");
// Klass name
mangle_name_on(&st, method->klass_name());
if (!map_escaped_name_on(&st, method->klass_name())) {
return NULL;
}
st.print("_");
// Method name
mangle_name_on(&st, method->name());
if (!map_escaped_name_on(&st, method->name())) {
return NULL;
}
return st.as_string();
}
char* NativeLookup::long_jni_name(const methodHandle& method) {
// Signature ignore the wrapping parenteses and the trailing return type
// Signatures ignore the wrapping parentheses and the trailing return type
stringStream st;
Symbol* signature = method->signature();
st.print("__");
@ -110,7 +205,10 @@ char* NativeLookup::long_jni_name(const methodHandle& method) {
int end;
for (end = 0; end < signature->utf8_length() && signature->char_at(end) != JVM_SIGNATURE_ENDFUNC; end++);
// skip first '('
mangle_name_on(&st, signature, 1, end);
if (!map_escaped_name_on(&st, signature, 1, end)) {
return NULL;
}
return st.as_string();
}
@ -233,6 +331,11 @@ address NativeLookup::lookup_entry(const methodHandle& method, bool& in_base_lib
in_base_library = false;
// Compute pure name
char* pure_name = pure_jni_name(method);
if (pure_name == NULL) {
// JNI name mapping rejected this method so return
// NULL to indicate UnsatisfiedLinkError should be thrown.
return NULL;
}
// Compute argument size
int args_size = 1 // JNIEnv
@ -245,6 +348,11 @@ address NativeLookup::lookup_entry(const methodHandle& method, bool& in_base_lib
// Compute long name
char* long_name = long_jni_name(method);
if (long_name == NULL) {
// JNI name mapping rejected this method so return
// NULL to indicate UnsatisfiedLinkError should be thrown.
return NULL;
}
// 2) Try JNI long style
entry = lookup_style(method, pure_name, long_name, args_size, true, in_base_library, CHECK_NULL);
@ -326,6 +434,11 @@ void* NativeLookup::dll_load(const methodHandle& method) {
address NativeLookup::lookup_critical_style(void* dll, const methodHandle& method, int args_size) {
address entry = NULL;
const char* critical_name = critical_jni_name(method);
if (critical_name == NULL) {
// JNI name mapping rejected this method so return
// NULL to indicate UnsatisfiedLinkError should be thrown.
return NULL;
}
// 1) Try JNI short style
entry = lookup_critical_style(dll, critical_name, "", args_size, true);
@ -334,6 +447,11 @@ address NativeLookup::lookup_critical_style(void* dll, const methodHandle& metho
}
const char* long_name = long_jni_name(method);
if (long_name == NULL) {
// JNI name mapping rejected this method so return
// NULL to indicate UnsatisfiedLinkError should be thrown.
return NULL;
}
// 2) Try JNI long style
entry = lookup_critical_style(dll, critical_name, long_name, args_size, true);