labath added a comment.
In D62715#1525085 <https://reviews.llvm.org/D62715#1525085>, @aadsm wrote:
> That's a good idea for the tests, will look into that.
Actually, it looks like getting `process_vm_readv` to fail is as simple as
running `mprotect(..., PROT_NONE)` on the piece of memory. Here's my test
program, in case you find it useful for anything:
#include <cassert>
#include <cerrno>
#include <cstdio>
#include <cstring>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/ptrace.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <unistd.h>
long *mem;
void child() {
assert(ptrace(PTRACE_TRACEME, 0, 0, 0) == 0);
raise(SIGSTOP);
_exit(0);
}
void parent(pid_t child) {
int status;
assert(waitpid(child, &status, __WALL) == child);
assert(WIFSTOPPED(status));
assert(WSTOPSIG(status) == SIGSTOP);
unsigned long myx;
struct iovec local;
local.iov_base = &myx;
local.iov_len = sizeof myx;
struct iovec remote;
remote.iov_base = mem;
remote.iov_len = sizeof myx;
ssize_t s = process_vm_readv(child, &local, 1, &remote, 1, 0);
fprintf(stderr, "readv: %zd (%d - %s)\n", s, errno, strerror(errno));
myx = ptrace(PTRACE_PEEKDATA, child, mem, 0);
fprintf(stderr, "peek: %lx (%d - %s)\n", myx, errno, strerror(errno));
_exit(0);
}
int main() {
mem = reinterpret_cast<long *>(mmap(nullptr, 0x1000, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, 0, 0));
assert(mem != MAP_FAILED);
*mem = 0x424344454647;
assert(mprotect(mem, 0x1000, PROT_NONE) == 0);
pid_t pid = fork();
assert(pid != -1);
if (pid)
parent(pid);
else
child();
}
$ g++ a.cc
$ ./a.out
readv: -1 (14 - Bad address)
peek: 424344454647 (0 - Success)
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D62715/new/
https://reviews.llvm.org/D62715
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