When the user creates a LUKS-encrypted qcow2 image using the qemu-img
program, the passphrase is hashed using PBKDF2 with a dynamic
number of iterations. The number of iterations is determined by
measuring thread cpu time usage, such that it takes approximately
2 seconds to compute the hash.

Because Darwin doesn't implement getrusage(RUSAGE_THREAD), we get an
error message:
> qemu-img: test.qcow2: Unable to calculate thread CPU usage on this platform
for this command:
> qemu-img create --object secret,id=key,data=1234 -f qcow2 -o 'encrypt.format=luks,encrypt.key-secret=key' test.qcow2 100M

This patch implements qcrypto_pbkdf2_get_thread_cpu() for Darwin so that
the above command works.

Signed-off-by: Jungmin Park <pjm0616@gmail.com>
---
 crypto/pbkdf.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/crypto/pbkdf.c b/crypto/pbkdf.c
index 3775ddc6c5..8d198c152c 100644
--- a/crypto/pbkdf.c
+++ b/crypto/pbkdf.c
@@ -24,6 +24,11 @@
 #ifndef _WIN32
 #include <sys/resource.h>
 #endif
+#ifdef CONFIG_DARWIN
+#include <mach/mach_init.h>
+#include <mach/thread_act.h>
+#include <mach/mach_port.h>
+#endif
 
 
 static int qcrypto_pbkdf2_get_thread_cpu(unsigned long long *val_ms,
@@ -45,6 +50,24 @@ static int qcrypto_pbkdf2_get_thread_cpu(unsigned long long *val_ms,
     /* QuadPart is units of 100ns and we want ms as unit */
     *val_ms = thread_time.QuadPart / 10000ll;
     return 0;
+#elif defined(CONFIG_DARWIN)
+    mach_port_t thread;
+    kern_return_t kr;
+    mach_msg_type_number_t count;
+    thread_basic_info_data_t info;
+
+    thread = mach_thread_self();
+    count = THREAD_BASIC_INFO_COUNT;
+    kr = thread_info(thread, THREAD_BASIC_INFO, (thread_info_t)&info, &count);
+    mach_port_deallocate(mach_task_self(), thread);
+    if (kr != KERN_SUCCESS || (info.flags & TH_FLAGS_IDLE) != 0) {
+        error_setg_errno(errp, errno, "Unable to get thread CPU usage");
+        return -1;
+    }
+
+    *val_ms = ((info.user_time.seconds * 1000ll) +
+               (info.user_time.microseconds / 1000));
+    return 0;
 #elif defined(RUSAGE_THREAD)
     struct rusage ru;
     if (getrusage(RUSAGE_THREAD, &ru) < 0) {
-- 
2.34.1

On Wed, Aug 24, 2022 at 09:37:06PM +0900, Jungmin Park wrote:
> When the user creates a LUKS-encrypted qcow2 image using the qemu-img
> program, the passphrase is hashed using PBKDF2 with a dynamic
> number of iterations. The number of iterations is determined by
> measuring thread cpu time usage, such that it takes approximately
> 2 seconds to compute the hash.
> 
> Because Darwin doesn't implement getrusage(RUSAGE_THREAD), we get an
> error message:
> > qemu-img: test.qcow2: Unable to calculate thread CPU usage on this platform
> for this command:
> > qemu-img create --object secret,id=key,data=1234 -f qcow2 -o 'encrypt.format=luks,encrypt.key-secret=key' test.qcow2 100M
> 
> This patch implements qcrypto_pbkdf2_get_thread_cpu() for Darwin so that
> the above command works.
> 
> Signed-off-by: Jungmin Park <pjm0616@gmail.com>
> ---
>  crypto/pbkdf.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Afraid this is too late to get into 7.1 release, but I'll queue it for
the next dev cycle.


With regards,
Daniel
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