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Merged
fincs merged 2 commits into from
Sep 14, 2022
+34 −20
Merged

Use __tdata_align to align thread local storage #504

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6b2d2fb
Use __tdata_align to align thread local storage
ian-h-chamberlain Aug 18, 2022
cafdcd3
Don't allocate for 8-byte header, just fake it
ian-h-chamberlain Aug 20, 2022
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10 changes: 10 additions & 0 deletions libctru/source/internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,12 @@
#define THREADVARS_MAGIC 0x21545624 // !TV$
#define FS_OVERRIDE_MAGIC 0x21465324 // !FS$

extern const size_t __tdata_align;
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ian-h-chamberlain marked this conversation as resolved.
extern const u8 __tdata_lma[];
extern const u8 __tdata_lma_end[];
extern u8 __tls_start[];
extern u8 __tls_end[];

// Keep this structure under 0x80 bytes
typedef struct
{
Expand Down Expand Up @@ -48,3 +54,7 @@ static inline ThreadVars* getThreadVars(void)
}

void initThreadVars(struct Thread_tag *thread);

static inline size_t alignTo(const size_t base, const size_t align) {
return (base + (align - 1)) & ~(align - 1);
}
11 changes: 4 additions & 7 deletions libctru/source/system/syscalls.c
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Expand Up @@ -16,10 +16,6 @@

void __ctru_exit(int rc);

extern const u8 __tdata_lma[];
extern const u8 __tdata_lma_end[];
extern u8 __tls_start[];

struct _reent* __SYSCALL(getreent)()
{
ThreadVars* tv = getThreadVars();
Expand All @@ -43,7 +39,7 @@ int __SYSCALL(clock_gettime)(clockid_t clock_id, struct timespec *tp) {
tp->tv_nsec = (ms_since_epoch % 1000) * 1000000;
}
}
else if (clock_id == CLOCK_MONOTONIC)
else if (clock_id == CLOCK_MONOTONIC)
{
if (tp != NULL)
{
Expand All @@ -66,7 +62,7 @@ int __SYSCALL(clock_gettime)(clockid_t clock_id, struct timespec *tp) {
int __SYSCALL(clock_getres)(clockid_t clock_id, struct timespec *res) {
if (clock_id == CLOCK_REALTIME)
{
if (res != NULL)
if (res != NULL)
{
res->tv_sec = 0;
res->tv_nsec = 1000000;
Expand Down Expand Up @@ -185,6 +181,7 @@ void __system_initSyscalls(void)
// Initialize thread vars for the main thread
initThreadVars(NULL);
u32 tls_size = __tdata_lma_end - __tdata_lma;
size_t tdata_start = alignTo((size_t)__tls_start, __tdata_align);
if (tls_size)
memcpy(__tls_start, __tdata_lma, tls_size);
memcpy((void*)tdata_start, __tdata_lma, tls_size);
}
33 changes: 20 additions & 13 deletions libctru/source/thread.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3,11 +3,6 @@
#include <malloc.h>
#include <string.h>

extern const u8 __tdata_lma[];
extern const u8 __tdata_lma_end[];
extern u8 __tls_start[];
extern u8 __tls_end[];

static void __panic(void)
{
svcBreak(USERBREAK_PANIC);
Expand All @@ -24,18 +19,26 @@ static void _thread_begin(void* arg)

Thread threadCreate(ThreadFunc entrypoint, void* arg, size_t stack_size, int prio, int core_id, bool detached)
{
size_t stackoffset = (sizeof(struct Thread_tag)+7)&~7;
size_t allocsize = stackoffset + ((stack_size+7)&~7);
// The stack must be 8-aligned at minimum.
size_t align = __tdata_align > 8 ? __tdata_align : 8;

size_t stackoffset = alignTo(sizeof(struct Thread_tag), align);
size_t allocsize = alignTo(stackoffset + stack_size, align);

size_t tlssize = __tls_end-__tls_start;
size_t tlsloadsize = __tdata_lma_end-__tdata_lma;
size_t tbsssize = tlssize-tlsloadsize;
size_t tbsssize = tlssize - tlsloadsize;

// memalign seems to have an implicit requirement that (size % align) == 0.
// Without this, it seems to return NULL whenever (align > 8).
size_t size = alignTo(allocsize + tlssize, align);

// Guard against overflow
if (allocsize < stackoffset) return NULL;
if ((allocsize-stackoffset) < stack_size) return NULL;
if ((allocsize+tlssize) < allocsize) return NULL;
if ((allocsize - stackoffset) < stack_size) return NULL;
if (size < allocsize) return NULL;

Thread t = (Thread)memalign(8,allocsize+tlssize);
Thread t = (Thread)memalign(align, size);
if (!t) return NULL;

t->ep = entrypoint;
Expand All @@ -44,10 +47,14 @@ Thread threadCreate(ThreadFunc entrypoint, void* arg, size_t stack_size, int pri
t->finished = false;
t->stacktop = (u8*)t + allocsize;

// ThreadVars.tls_tp must be aligned correctly, so we bump tdata_start to
// ensure that after subtracting 8 bytes for the TLS header, it will be aligned.
size_t tdata_start = 8 + alignTo((size_t)t->stacktop - 8, align);

if (tlsloadsize)
memcpy(t->stacktop, __tdata_lma, tlsloadsize);
memcpy((void*)tdata_start, __tdata_lma, tlsloadsize);
if (tbsssize)
memset((u8*)t->stacktop+tlsloadsize, 0, tbsssize);
memset((void*)tdata_start + tlsloadsize, 0, tbsssize);

// Set up child thread's reent struct, inheriting standard file handles
_REENT_INIT_PTR(&t->reent);
Expand Down