Re: Set PSTATE.PRIV for user process

[Palle Lyckegaard <palle%netbsd.org@localhost>]

On Thu, 22 Oct 2026, Sad Clouds wrote:

> I need to look at the privileged window state registers from a user
> process. Does anyone know a trick to make user process run in
> privileged mode? I tried adding this to setregs() but the kernel panics
> on boot.

Recently I committed some debug code, the SAVE_WINREGS macro in locore.s

The macro snapshots the complete register window and other relevant window 
register control registers to a per-cpu (cpuinfo) structure.

This is from privileged mode.

I have used the macro to snapshot the register windows trying to trackdown
issues with garbage in registers after a process context is restored.

This way I have traced registers at different places in the code path from 
the rft_user label in locore.s

The macro is called with two scratch registers.

Example from the last lines of rft_user:

...
 #ifdef NOTDEF_DEBUG
 	ldx	[%g6 + CC64FSZ + STKB + TF_L + (0*8)], %g5! DEBUG -- get 
proper value for %l0
@@ -5547,6 +5630,10 @@
 	tst	%g5
 	tnz	%icc, 1; nop			! Debugger if we still 
have saved windows!
 #endif

	SAVE_WINREGS	%g1, %g2

 	wrpr	%g0, 0, %pil			! Enable all interrupts
 	retry



Then I have a couple of functions that work on the snapshots. These are 
called from relevant places in trap.c.

(please ignore the '+' in the first column of each line...

...
+void clear_winregs(void)
+{
+	curcpu()->ci_winregs = 0;
+	memset(&(curcpu()->ci_rw0_local[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw0_in[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw1_local[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw1_in[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw2_local[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw2_in[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw3_local[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw3_in[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw4_local[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw4_in[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw5_local[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw5_in[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw6_local[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw6_in[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw7_local[0]), 0, 8*sizeof(int64_t));
+	memset(&(curcpu()->ci_rw7_in[0]), 0, 8*sizeof(int64_t));
+}
+
+void print_winregs(void)
+{
+#if 1
+	printf("Register window registers (WINREGS 
cansave/canrestore/otherwin/cleanwin/cwp/wstate): %016lx\n", 
curcpu()->ci_winregs);
+#endif
+
+#if 1
+	/* COMPRESSED	*/
+	/* RW 0 */
+	printf("RW 0 %%i0-%%i7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw0_in[i]);
+	}
+	printf("\n");
+	printf("RW 0 %%l0-%%l7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw0_local[i]);
+	}
+	printf("\n");
+	/* RW 1 */
+	printf("RW 1 %%i0-%%i7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw1_in[i]);
+	}
+	printf("\n");
+	printf("RW 1 %%l0-%%l7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw1_local[i]);
+	}
+	printf("\n");
+	/* RW 2 */
+	printf("RW 2 %%i0-%%i7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw2_in[i]);
+	}
+	printf("\n");
+	printf("RW 2 %%l0-%%l7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw2_local[i]);
+	}
+	printf("\n");
+	/* RW 3 */
+	printf("RW 3 %%i0-%%i7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw3_in[i]);
+	}
+	printf("\n");
+	printf("RW 3 %%l0-%%l7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw3_local[i]);
+	}
+	printf("\n");
+	/* RW 4 */
+	printf("RW 4 %%i0-%%i7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw4_in[i]);
+	}
+	printf("\n");
+	printf("RW 4 %%l0-%%l7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw4_local[i]);
+	}
+	printf("\n");
+	/* RW 5 */
+	printf("RW 5 %%i0-%%i7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw5_in[i]);
+	}
+	printf("\n");
+	printf("RW 5 %%l0-%%l7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw5_local[i]);
+	}
+	printf("\n");
+	/* RW 6 */
+	printf("RW 6 %%i0-%%i7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw6_in[i]);
+	}
+	printf("\n");
+	printf("RW 6 %%l0-%%l7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw6_local[i]);
+	}
+	printf("\n");
+	/* RW 7 */
+	printf("RW 7 %%i0-%%i7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw7_in[i]);
+	}
+	printf("\n");
+	printf("RW 7 %%l0-%%l7 ");
+	for (int i = 0; i < 8; i++) {
+	  printf("%016lx ", curcpu()->ci_rw7_local[i]);
+	}
+	printf("\n");
+
+#endif
+}
+

I hope that this can be on any use to you - please feel free to use it or 
adapt it to your needs.