mirror of
https://github.com/bminor/binutils-gdb.git
synced 2025-12-26 01:07:52 +00:00
3cad19db4e
A delay-import symbol (of a function) is resolved when a call to it is made.
The delay loader may overwrite the `__imp_` pointer to the actual function
after it has been resolved, which requires the pointer itself be in a
writeable section.
Previously it was placed in the ordinary Import Address Table (IAT), which
is emitted into the `.idata` section, which had been changed to read-only
in db00f6c3ac, which caused segmentation
faults when functions from delay-import library were called. This is
PR 32675.
This commit makes DLLTOOL emit delay-import IAT into `.didat`, as specified
by Microsoft. Most of the code is copied from `.idata`, except that this
section is writeable. As a side-effect of this, PR 14339 is also fixed.
Using this DEF:
```
; ws2_32.def
LIBRARY "WS2_32.DLL"
EXPORTS
WSAGetLastError
```
and this C program:
```
// delay.c
#define WIN32_LEAN_AND_MEAN 1
#include <windows.h>
#include <stdio.h>
/////////////////////////////////////////////////////////
// User code
/////////////////////////////////////////////////////////
DWORD WINAPI WSAGetLastError(void);
extern PVOID __imp_WSAGetLastError;
int
main(void)
{
fprintf(stderr, "before delay load, __imp_WSAGetLastError = %p\n", __imp_WSAGetLastError);
SetLastError(123);
fprintf(stderr, "WSAGetLastError() = %d\n", WSAGetLastError());
fprintf(stderr, "after delay load, __imp_WSAGetLastError = %p\n", __imp_WSAGetLastError);
__imp_WSAGetLastError = (PVOID) 1234567;
fprintf(stderr, "after plain write, __imp_WSAGetLastError = %p\n", __imp_WSAGetLastError);
}
/////////////////////////////////////////////////////////
// Overridden `__delayLoadHelper2` facility
/////////////////////////////////////////////////////////
extern char __ImageBase[];
PVOID WINAPI ResolveDelayLoadedAPI(PVOID ParentModuleBase, LPCVOID DelayloadDescriptor,
PVOID FailureDllHook, PVOID FailureSystemHook,
FARPROC* ThunkAddress, ULONG Flags);
FARPROC WINAPI DelayLoadFailureHook(LPCSTR name, LPCSTR function);
FARPROC WINAPI __delayLoadHelper2(LPCVOID pidd, FARPROC* ppfnIATEntry)
{
return ResolveDelayLoadedAPI(&__ImageBase, pidd, NULL, (PVOID) DelayLoadFailureHook,
ppfnIATEntry, 0);
}
```
This program used to crash:
```
$ dlltool -nn -d ws2_32.def -y delay_ws2_32.a
$ gcc -g delay.c delay_ws2_32.a -o delay.exe
$ ./delay.exe
before delay load, __imp_WSAGetLastError = 00007FF6937215C6
Segmentation fault
```
After this commit, it loads and calls `WSAGetLastError()` properly, and
`__imp_WSAGetLastError` is writeable:
```
$ dlltool -nn -d ws2_32.def -y delay_ws2_32.a
$ gcc -g delay.c delay_ws2_32.a -o delay.exe
$ ./delay.exe
before delay load, __imp_WSAGetLastError = 00007FF76E2215C6
WSAGetLastError() = 123
after delay load, __imp_WSAGetLastError = 00007FFF191FA720
after plain write, __imp_WSAGetLastError = 000000000012D687
```
Reference: https://learn.microsoft.com/en-us/windows/win32/secbp/pe-metadata#import-handling
Co-authored-by: Jeremy Drake <sourceware-bugzilla@jdrake.com>
Signed-off-by: LIU Hao <lh_mouse@126.com>
Signed-off-by: Jeremy Drake <sourceware-bugzilla@jdrake.com>
The files in this directory are linker script templates.
genscripts.sh sets some shell variables, then sources
EMULATION.sc, to generate EMULATION.{x,xr,xu,xn,xbn} -- the script
files for default, -r, -Ur, -n, -N.
Copyright (C) 2012-2025 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.