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ptrace: Report error in PT_PEEK via errno

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The syscall wrapper for ptrace needs to return the peeked value when
using  PT_PEEK.
Because of this, the user has to check errno to detect an error in
PT_PEEK.

This commit changes the actual syscall's interface (only for PT_PEEK) to
allow the syscall wrapper to detect an error and change errno.
This commit is contained in:
Itamar 2020-04-10 17:34:31 +03:00 • committed by Andreas Kling
parent aae3f7b914
commit 50fd2cabff
3 changed files with 47 additions and 3 deletions
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25
Libraries/LibC/sys/ptrace.cpp
View file

@ -24,6 +24,7 @@
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/LogStream.h>
#include <Kernel/Syscall.h>
#include <errno.h>
#include <sys/ptrace.h>
@ -32,6 +33,20 @@ extern "C" {
int ptrace(int request, pid_t pid, void* addr, int data)
{
// PT_PEEK needs special handling since the syscall wrapper
// returns the peeked value as an int, which can be negative because of the cast.
// When using PT_PEEK, the user can check if an error occured
// by looking at errno rather than the return value.
u32 out_data;
Syscall::SC_ptrace_peek_params peek_params;
if (request == PT_PEEK) {
peek_params.address = reinterpret_cast<u32*>(addr);
peek_params.out_data = &out_data;
addr = &peek_params;
}
Syscall::SC_ptrace_params params {
request,
pid,
@ -39,6 +54,16 @@ int ptrace(int request, pid_t pid, void* addr, int data)
data
};
int rc = syscall(SC_ptrace, &params);
if (request == PT_PEEK) {
if (rc < 0) {
errno = -rc;
return -1;
}
errno = 0;
return static_cast<int>(out_data);
}
__RETURN_WITH_ERRNO(rc, rc, -1);
}
}