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[Sanitizer][RISCV] Fix internal_clone

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A RISC-V implementation of `internal_clone` was introduced in D87573, as
part of the RISC-V ASan patch set by @EccoTheDolphin. That function was
never used/tested until I ported LSan for RISC-V, as part of D92403. That
port revealed problems in the original implementation, so I provided a fix
in D92403. Unfortunately, my choice of replacing the assembly with regular
C++ code wasn't correct. The clone syscall arguments specify a separate
stack, so non-inlined calls, spills, etc. aren't going to work. This wasn't
a problem in practice for optimized builds of Compiler-RT, but it breaks
for debug builds. This patch fixes the original problem while keeping the
assembly.

Differential Revision: https://reviews.llvm.org/D96954
This commit is contained in:
Luís Marques 2021-03-08 22:28:19 +00:00
parent 8d79b05367
commit c5a6ad86b0
1 changed files with 34 additions and 10 deletions
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44
compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
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@ -1338,17 +1338,41 @@ uptr internal_clone(int (*fn)(void *), void *child_stack, int flags, void *arg,
int *parent_tidptr, void *newtls, int *child_tidptr) {
if (!fn || !child_stack)
return -EINVAL;
CHECK_EQ(0, (uptr)child_stack % 16);
child_stack = (char *)child_stack - 2 * sizeof(unsigned long long);
((unsigned long long *)child_stack)[0] = (uptr)fn;
((unsigned long long *)child_stack)[1] = (uptr)arg;
int tid = internal_syscall(SYSCALL(clone), (unsigned long)flags, child_stack,
parent_tidptr, newtls, child_tidptr);
if (tid != 0)
return tid;
fn(arg);
internal_syscall(SYSCALL(exit), 0);
CHECK_EQ(0, (uptr)child_stack % 16);
register int res __asm__("a0");
register int __flags __asm__("a0") = flags;
register void *__stack __asm__("a1") = child_stack;
register int *__ptid __asm__("a2") = parent_tidptr;
register void *__tls __asm__("a3") = newtls;
register int *__ctid __asm__("a4") = child_tidptr;
register int (*__fn)(void *) __asm__("a5") = fn;
register void *__arg __asm__("a6") = arg;
register int nr_clone __asm__("a7") = __NR_clone;
__asm__ __volatile__(
"ecall\n"
/* if (a0 != 0)
* return a0;
*/
"bnez a0, 1f\n"
// In the child, now. Call "fn(arg)".
"mv a0, a6\n"
"jalr a5\n"
// Call _exit(a0).
"addi a7, zero, %9\n"
"ecall\n"
"1:\n"
: "=r"(res)
: "0"(__flags), "r"(__stack), "r"(__ptid), "r"(__tls), "r"(__ctid),
"r"(__fn), "r"(__arg), "r"(nr_clone), "i"(__NR_exit)
: "memory");
return res;
}
#elif defined(__aarch64__)
uptr internal_clone(int (*fn)(void *), void *child_stack, int flags, void *arg,