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[PSEH/x64] Fix our GCC-SEH-plugin hack

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The change is needed, because the previous version emitted multiple ".seh_handlerdata" blocks and GAS isn't able to merge them into one, but will instead only include the first one. This is fixed by generating "asm defines" in the code and pass the line number to the "REACTOS seh" pragma, which is then used to create all handler data by referring to the predefined symbols, that include the line number.
Also the EstablisherFrame parameter passed to the filter/finally function is the original stack pointer, not the frame pointer! Take this into account by passing __builtin_frame_address(0) from the filter context to the global wrapper function, which includes the frame-offset, and use that to recalculate the frame-pointer from the passed in stack pointer.
This commit is contained in:
Timo Kreuzer 2024-03-15 21:17:23 +02:00
parent f4a9f9cde3
commit 67c28b723e
2 changed files with 104 additions and 50 deletions
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64
sdk/tools/gcc_plugin_seh/main.cpp
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@ -3,6 +3,7 @@
* LICENSE: BSD Zero Clause License (https://spdx.org/licenses/0BSD)
* PURPOSE: Helper pragma implementation for pseh library (amd64)
* COPYRIGHT: Copyright 2021 Jérôme Gardou
* Copyright 2024 Timo Kreuzer <timo.kreuzer@reactos.org>
*/
#include <gcc-plugin.h>
@ -16,6 +17,13 @@
#include <sstream>
#include <unordered_map>
#include <vector>
#include <cstdio>
#if 0 // To enable tracing
#define trace(...) fprintf(stderr, __VA_ARGS__)
#else
#define trace(...)
#endif
#define is_alpha(c) (((c)>64 && (c)<91) || ((c)>96 && (c)<123))
@ -31,6 +39,14 @@ int
VISIBLE
plugin_is_GPL_compatible = 1;
constexpr size_t k_header_statement_max_size = 20000;
struct seh_handler
{
bool is_except;
unsigned int line;
};
struct seh_function
{
bool unwind;
@ -38,6 +54,7 @@ struct seh_function
tree asm_header_text;
tree asm_header;
size_t count;
std::vector<seh_handler> handlers;
seh_function(struct function* fun)
: unwind(false)
@ -45,9 +62,13 @@ struct seh_function
, count(0)
{
/* Reserve space for our header statement */
char buf[256];
#if 0 // FIXME: crashes on older GCC
asm_header_text = build_string(k_header_statement_max_size, "");
#else
char buf[k_header_statement_max_size];
memset(buf, 0, sizeof(buf));
asm_header_text = build_string(sizeof(buf), buf);
#endif
asm_header = build_stmt(fun->function_start_locus, ASM_EXPR, asm_header_text, NULL_TREE, NULL_TREE, NULL_TREE, NULL_TREE);
ASM_VOLATILE_P(asm_header) = 1;
add_stmt(asm_header);
@ -74,8 +95,9 @@ static
void
handle_seh_pragma(cpp_reader* UNUSED parser)
{
tree x, arg;
tree x, arg, line;
std::stringstream label_decl;
bool is_except;
if (!cfun)
{
@ -84,21 +106,32 @@ handle_seh_pragma(cpp_reader* UNUSED parser)
}
if ((pragma_lex(&x) != CPP_OPEN_PAREN) ||
(pragma_lex(&arg) != CPP_NAME) ||
(pragma_lex(&arg) != CPP_NAME) || // except or finally
(pragma_lex(&x) != CPP_COMMA) ||
(pragma_lex(&line) != CPP_NUMBER) || // Line number
(pragma_lex(&x) != CPP_CLOSE_PAREN) ||
(pragma_lex(&x) != CPP_EOF))
(pragma_lex(&x) != CPP_EOF)
)
{
error("%<#pragma REACTOS seh%> needs one parameter%>");
error("%<#pragma REACTOS seh%> needs two parameters%>");
return;
}
trace(stderr, "Pragma: %s, %u\n", IDENTIFIER_POINTER(arg), TREE_INT_CST_LOW(line));
const char* op = IDENTIFIER_POINTER(arg);
seh_function* seh_fun = get_seh_function();
if (strcmp(op, "except") == 0)
if (strcmp(op, "__seh$$except") == 0)
{
is_except = true;
seh_fun->except = true;
else if (strcmp(op, "finally") == 0)
}
else if (strcmp(op, "__seh$$finally") == 0)
{
is_except = false;
seh_fun->unwind = true;
}
else
{
error("Wrong argument for %<#pragma REACTOS seh%>. Expected \"except\" or \"finally\"");
@ -106,6 +139,8 @@ handle_seh_pragma(cpp_reader* UNUSED parser)
}
seh_fun->count++;
seh_fun->handlers.push_back({is_except, (unsigned int)TREE_INT_CST_LOW(line)});
/* Make sure we use a frame pointer. REACTOS' PSEH depends on this */
cfun->machine->accesses_prev_frame = 1;
}
@ -142,12 +177,25 @@ finish_seh_function(void* event_data, void* UNUSED user_data)
asm_str << "\n";
asm_str << "\t.seh_handlerdata\n";
asm_str << "\t.long " << seh_fun->count << "\n";
asm_str << "\t.seh_code";
for (auto& handler : seh_fun->handlers)
{
asm_str << "\n\t.rva " << "__seh2$$begin_try__" << handler.line; /* Begin of tried code */
asm_str << "\n\t.rva " << "__seh2$$end_try__" << handler.line; /* End of tried code */
asm_str << "\n\t.rva " << "__seh2$$filter__" << handler.line; /* Filter function */
if (handler.is_except)
asm_str << "\n\t.rva " << "__seh2$$begin_except__" << handler.line; /* Called on except */
else
asm_str << "\n\t.long 0"; /* No unwind handler */
}
asm_str << "\n\t.seh_code\n";
strncpy(const_cast<char*>(TREE_STRING_POINTER(seh_fun->asm_header_text)),
asm_str.str().c_str(),
TREE_STRING_LENGTH(seh_fun->asm_header_text));
trace(stderr, "ASM: %s\n", asm_str.str().c_str());
delete seh_fun;
}