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Fix symbolic C stack backtrace in WIN64 builds.
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In a CLang-compiled debug VM we now see
Stack backtrace:
    [00007FF7B97495AC] indirect + 0x6c in VirtendConsole.exe
    [00007FF7B97494B8] crashInThisOrAnotherThread + 0x48 in VirtendConsole.exe
    [00007FF7B966E8D6] primitiveCrashVM + 0xe6 in VirtendConsole.exe
    [00007FF7B965A83F] primitiveExternalCall + 0x2bf in VirtendConsole.exe
    [00007FF7B9653B1F] interpretMethodFromMachineCode + 0x2ff in VirtendConsole.exe
    [00007FF7B96593C2] ceSendsupertonumArgs + 0xc72 in VirtendConsole.exe
    [000000000003B863] ??? + 0x0 in (null)

Alas in a Clang-compiled -O2 VM we see only
Stack backtrace:
    [00007FF7EAEF7593] indirect + 0x43 in VirtendConsole.exe
    [00007FF7F3446A58] ??? + 0x0 in (null)

So still some investigation of Clang code generation is required, but the basic
facility works if the stack can be walked.
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@eliotmiranda
eliotmiranda committed Sep 30, 2021
1 parent 6afe5d0 commit 65d9d81
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Showing 2 changed files with 210 additions and 100 deletions.
184 changes: 136 additions & 48 deletions platforms/win32/vm/sqWin32Backtrace.c
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Expand Up @@ -162,12 +162,12 @@ typedef struct _dll_exports {
HMODULE module;
char name[MAX_PATH];
MODULEINFO info;
void (*find_symbol)(struct _dll_exports *, void *, symbolic_pc *);
void (*find_symbol)(struct _dll_exports *, ulong, symbolic_pc *);
int n;
char initialized;
ulong *functions;
union { char **funcNames; ulong *funcNameOffsets; sqInt *methods; } u;
int *sorted_ordinals;
int *sorted_ordinals; // deal with unsorted files by sorting indices
} dll_exports;

static dll_exports *dll_exports_for_pc(void *retpc);
Expand All @@ -184,7 +184,7 @@ symbolic_backtrace(int n, void **retpcs, symbolic_pc *spc)
dll_exports *exports = dll_exports_for_pc(retpcs[i]);

if (exports)
exports->find_symbol(exports, retpcs[i], spc + i);
exports->find_symbol(exports, (ulong)(retpcs[i]), spc + i);
else
spc[i].fnameOrSelector = spc[i].mname = 0, spc[i].offset = 0;
}
Expand Down Expand Up @@ -248,10 +248,10 @@ static int
expcmp(const void *a, const void *b)
{ return (sqIntptr_t)((dll_exports *)a)->info.lpBaseOfDll - (sqIntptr_t)((dll_exports *)b)->info.lpBaseOfDll; }

static void find_in_dll(dll_exports *exports, void *pc, symbolic_pc *spc);
static void find_in_exe(dll_exports *exports, void *pc, symbolic_pc *spc);
static void find_in_dll(dll_exports *exports, ulong pc, symbolic_pc *spc);
static void find_in_exe(dll_exports *exports, ulong pc, symbolic_pc *spc);
#if COGVM
static void find_in_cog(dll_exports *exports, void *pc, symbolic_pc *spc);
static void find_in_cog(dll_exports *exports, ulong pc, symbolic_pc *spc);
extern sqInt nilObject(void);
extern usqInt stackLimitAddress(void);
#endif
Expand Down Expand Up @@ -346,10 +346,10 @@ dll_exports_for_pc(void *retpc)
static void compute_dll_symbols(dll_exports *exports);

static void
find_in_dll(dll_exports *exports, void *pcval, symbolic_pc *spc)
find_in_dll(dll_exports *exports, ulong pcval, symbolic_pc *spc)
{
int i;
ulong pc = (ulong)pcval - (ulong)exports->info.lpBaseOfDll;
ulong pc = pcval - (ulong)exports->info.lpBaseOfDll;

spc->mname = strrchr(exports->name,'\\')
? strrchr(exports->name,'\\') + 1
Expand All @@ -359,13 +359,14 @@ find_in_dll(dll_exports *exports, void *pcval, symbolic_pc *spc)
compute_dll_symbols(exports);

for (i = 0; i < exports->n; i++) {
ulong addr = exports->functions[exports->sorted_ordinals[i]];
int ordinal = exports->sorted_ordinals[i];
ulong addr = exports->functions[ordinal];
if (pc >= addr
&& ( i + 1 >= exports->n
|| pc < exports->functions[exports->sorted_ordinals[i + 1]])) {
spc->fnameOrSelector = (char *)
(exports->u.funcNameOffsets[exports->sorted_ordinals[i]]
+ (ulong)exports->module);
(exports->u.funcNameOffsets[ordinal]
+ (ulong)exports->module);
spc->offset = pc - addr;
return;
}
Expand All @@ -377,7 +378,7 @@ find_in_dll(dll_exports *exports, void *pcval, symbolic_pc *spc)
static void compute_exe_symbols(dll_exports *exports);

static void
find_in_exe(dll_exports *exports, void *pc, symbolic_pc *spc)
find_in_exe(dll_exports *exports, ulong pc, symbolic_pc *spc)
{
int i;

Expand All @@ -388,27 +389,58 @@ find_in_exe(dll_exports *exports, void *pc, symbolic_pc *spc)
if (!exports->initialized)
compute_exe_symbols(exports);

// With MSVC/Clang the map file is unsorted, so there are sorted ordinals
// With cygwin/mingw the map file is sorted, so there are no sorted_ordinals
#if _MSC_VER
for (i = 0; i < exports->n; i++) {
int ordinal = exports->sorted_ordinals[i];
ulong addr = exports->functions[ordinal];
if (pc >= addr
&& ( ordinal + 1 >= exports->n
|| pc < exports->functions[exports->sorted_ordinals[i + 1]])) {
spc->fnameOrSelector = (char *)exports->u.funcNames[ordinal];
spc->offset = pc - addr;
return;
}
}
#else
for (i = 0; i < exports->n; i++) {
ulong addr = exports->functions[i];
if ((ulong)pc >= addr
if (pc >= addr
&& ( i + 1 >= exports->n
|| (ulong)pc < exports->functions[i + 1])) {
|| pc < exports->functions[i + 1])) {
spc->fnameOrSelector = exports->u.funcNames[i];
spc->offset = (ulong)pc - addr;
spc->offset = pc - addr;
return;
}
}
#endif
spc->fnameOrSelector = 0;
spc->offset = (ulong)pc - (ulong)exports->module;
spc->offset = pc - (ulong)exports->module;
}

// Rather than sort entries we deal with unsorted files by sorting indices into
// them.
static ulong *funcs_for_ordcmp;
static int
ordcmp(const void *a, const void *b)
{ return funcs_for_ordcmp[*(int *)a] - funcs_for_ordcmp[*(int *)b]; }

static void
compute_exe_symbols(dll_exports *exports)
{
#if defined(_MSV_VER)
# error parse of MSVC .map file as yet unimplemented
# error Let me (eliot) suggest you get the Makefile to generate a BSD-style
# error format from the MSVC /map file instead of writing the parser here.
char filename[MAX_PATH];
FILE *f;

strcpy(filename, exports->name);
strcpy(strrchr(filename,'.')+1,"map");

if (!(f = fopen(filename,"r"))) {
printLastError(TEXT("fopen"));
return;
}

#if defined(_MSC_VER)
/* Create the file using "cl .... /link /map"
* Parse it by looking for lines beginning with " 0001:" where 0001 is the
* segment number of the .text segment. Representative lines look like
Expand All @@ -421,6 +453,71 @@ compute_exe_symbols(dll_exports *exports)
* Be sure to look for global and static symbols. The character "f" tells you
* that this is a line for a function.
*/
int nsyms = 0, nchars = 0, n = 0;
ulong offset, interpretLogicalAddress = 0;
char fname[256], *symbols;

while (!feof(f)) {
// First scan to find number of symbols, the total symbol string size,
// and the logical address of interpret.
if (fscanf(f,
# if _WIN64
" 0001:%llx %[^ ] %*llx f %*[^ \n]\n",
# else
" 0001:%lx %[^ ] %*lx f %*[^ \n]\n",
# endif
&offset, fname) == 2) {
nsyms += 1;
nchars += strlen(fname) + 1;
if (!interpretLogicalAddress
&& !strcmp("interpret",fname[0] == '_' ? fname + 1 : fname))
interpretLogicalAddress = offset;
}
else
fscanf(f,"%*[^\n]\n");
}
_fseeki64(f,0,SEEK_SET);
if (!(exports->functions = calloc(nsyms,sizeof(ulong)))
|| !(exports->u.funcNames = calloc(nsyms,sizeof(char *)))
|| !(exports->sorted_ordinals = calloc(nsyms,sizeof(int)))
|| !(symbols = calloc(nchars,sizeof(char)))) {
printLastError(TEXT("malloc"));
fclose(f);
return;
}
while (!feof(f)) {
if (fscanf(f,
# if _WIN64
" 0001:%llx %[^ ] %*llx f %*[^ \n]\n",
# else
" 0001:%lx %[^ ] %*lx f %*[^ \n]\n",
# endif
&offset, symbols) == 2) {
exports->functions[n] = offset + ((ulong)interpret
- interpretLogicalAddress);
exports->u.funcNames[n] = symbols;
exports->sorted_ordinals[n] = n;
++n;
symbols += strlen(symbols) + 1;
}
else
fscanf(f,"%*[^\n]\n");
}
fclose(f);
exports->n = n;
exports->initialized = 1;
funcs_for_ordcmp = exports->functions;
qsort(exports->sorted_ordinals, n, sizeof(int), ordcmp);

# if DBGPRINT // this to dump the symbols once sorted for checking
int i;
for (i = 0; i < n; i++)
printf("%3d %" PRIxSQINT " %s\n",
exports->sorted_ordinals[i],
exports->functions[exports->sorted_ordinals[i]]
+ (ulong)exports->module,
exports->u.funcNames[exports->sorted_ordinals[i]]);
# endif
#else /* assume a BSD-style nm output as in
* nm --numeric-sort --defined-only -f bsd $(VMEXE) >$(VMMAP)
* where typical lines look like
Expand All @@ -442,18 +539,9 @@ compute_exe_symbols(dll_exports *exports)
/* Read the entire file into memory. We can use the string as the string table.
* Once we've counted the lines we can parse and read the start addresses.
*/
char filename[MAX_PATH];
char *contents;
FILE *f;
int pos, len, nlines, n;

strcpy(filename, exports->name);
strcpy(strrchr(filename,'.')+1,"map");

if (!(f = fopen(filename,"r"))) {
printLastError(TEXT("fopen"));
return;
}
_fseeki64(f,0,SEEK_END);
len = _ftelli64(f);
_fseeki64(f,0,SEEK_SET);
Expand Down Expand Up @@ -489,8 +577,11 @@ compute_exe_symbols(dll_exports *exports)
ulong addr;
char type, *symname;

/* Note: Scan format should better be SCNuSQPTR according to C99, if ever different from print format - but we did not define that macro */
asserta(sscanf(contents + pos, "%" PRIxSQPTR " %c", &addr, &type) == 2);
# if _WIN64
asserta(sscanf(contents + pos, "%llx %c", &addr, &type) == 2);
# else
asserta(sscanf(contents + pos, "%lx %c", &addr, &type) == 2);
# endif
symname = strrchr(contents + pos, ' ') + 1;
if ((type == 't' || type == 'T')
&& strcmp(symname,".text")) {
Expand All @@ -501,26 +592,23 @@ compute_exe_symbols(dll_exports *exports)
pos += strlen(contents + pos) + 1;
}
exports->n = n;
#endif
#if DBGPRINT
exports->initialized = 1;
assert(exports->sorted_ordinals == 0);

# if DBGPRINT
for (n = 0; n < exports->n; n++)
printf("exe [%p] %s\n",
exports->functions[exports->sorted_ordinals[n]],
exports->u.funcNames[exports->sorted_ordinals[n]]);
# endif
#endif
exports->initialized = 1;
}

/* See e.g. PEDump
http://msdn.microsoft.com/en-us/library/ms809762.aspx
http://msdn.microsoft.com/en-us/library/bb985994.aspx
*/

static ulong *funcs_for_ordcmp;
static int
ordcmp(const void *a, const void *b)
{ return funcs_for_ordcmp[*(int *)a] - funcs_for_ordcmp[*(int *)b]; }

static void
compute_dll_symbols(dll_exports *exports)
{
Expand Down Expand Up @@ -585,33 +673,33 @@ compute_dll_symbols(dll_exports *exports)

#if DBGPRINT // this to dump the symbols once sorted for checking
for (i = 0; i < n; i++)
printf("%3d %lx %s\n",
printf("%3d %" PRIxSQPTR " %s\n",
exports->sorted_ordinals[i],
exports->functions[exports->sorted_ordinals[i]]
+ (ulong)exports->module,
exports->u.funcNameOffsets[exports->sorted_ordinals[i]]
+ (ulong)exports->module);
(char *)(exports->u.funcNameOffsets[exports->sorted_ordinals[i]]
+ (ulong)exports->module));
#endif
}

#if COGVM
static void
find_in_cog(dll_exports *exports, void *pc, symbolic_pc *spc)
find_in_cog(dll_exports *exports, ulong pc, symbolic_pc *spc)
{
CogMethod *cogMethod;

spc->mname = (char *)&exports->name;

if ((spc->fnameOrSelector = codeEntryNameFor(pc)))
spc->offset = (ulong)pc - (ulong)codeEntryFor(pc);
else if ((cogMethod = methodFor(pc))) {
if ((spc->fnameOrSelector = codeEntryNameFor((char *)pc)))
spc->offset = pc - (ulong)codeEntryFor((char *)pc);
else if ((cogMethod = methodFor((char *)pc))) {
spc->fnameOrSelector = cogMethod->selector == nilObject()
? "Cog method with nil selector"
: (char *)(cogMethod->selector);
spc->offset = (ulong)pc - (ulong)cogMethod;
spc->offset = pc - (ulong)cogMethod;
}
else
spc->offset = (ulong)pc - (ulong)exports->info.lpBaseOfDll;
spc->offset = pc - (ulong)exports->info.lpBaseOfDll;
}
#endif

Expand Down

2 comments on commit 65d9d81

@marceltaeumel
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N.B. As of cygwin 1.5.25 fopen("crash.dmp","a") DOES NOT WORK! crash.dmp
contains garbled output as if the file pointer gets set to the start of the
file, not the end. So we synthesize our own append mode.

Hi Eliot. Please update your Cygwin ASAP! It's hardly believeable that the append-mode in fopen is broken in a fairly recent Cygwin installation.

$ cygcheck -c cygwin
Cygwin Package Information
Package              Version        Status
cygwin               3.2.0-1        OK

$ cygcheck -f /usr/include/stdio.h
cygwin-devel-3.2.0-1

This works like a charm and as expected:

/* File name is hello_world.c */
#include <stdio.h>

int main(void)
{
	FILE *pFile;
	pFile = fopen("crash.dmp","a+t");
	fprintf(pFile, "%s", "Hello!");
	fclose(pFile);
}

PLEASE! Update your Cygwin installation. :-)

@eliotmiranda
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@eliotmiranda eliotmiranda commented on 65d9d81 Oct 2, 2021 via email

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