# HG changeset patch
# User Taylor R Campbell <riastradh@NetBSD.org>
# Date 1759237896 0
#      Tue Sep 30 13:11:36 2025 +0000
# Branch trunk
# Node ID e2d8f31f7802ff9eea5abe327987470c09e162c6
# Parent  84d93e4dac07509dd1eb2f240eda797025d702bb
# EXP-Topic riastradh-pr58010-crashmachcpu
WIP: crash(8): Add support for `mach cpu N' on x86.

PR bin/58010: crash(8) doesn't support `mach cpu N' to examine
registers/stack of other CPUs

diff -r 84d93e4dac07 -r e2d8f31f7802 usr.sbin/crash/Makefile
--- a/usr.sbin/crash/Makefile	Sat Sep 06 07:16:28 2025 +0000
+++ b/usr.sbin/crash/Makefile	Tue Sep 30 13:11:36 2025 +0000
@@ -51,7 +51,10 @@ S=		${.CURDIR}/../../sys
 
 CPPFLAGS+=	-I${.CURDIR} -I${.OBJDIR} -I${S} -fno-strict-aliasing
 CPPFLAGS+=	-DDDB_VERBOSE_HELP -DDB_MAX_LINE=10000000 -D_KMEMUSER
+
+.if ${MACHINE} != "amd64" && ${MACHINE} != "i386"
 CPPFLAGS+=	-UDB_MACHINE_COMMANDS
+.endif
 
 # XXX
 .if ${MACHINE} == "evbppc"
diff -r 84d93e4dac07 -r e2d8f31f7802 usr.sbin/crash/arch/x86.c
--- a/usr.sbin/crash/arch/x86.c	Sat Sep 06 07:16:28 2025 +0000
+++ b/usr.sbin/crash/arch/x86.c	Tue Sep 30 13:11:36 2025 +0000
@@ -41,6 +41,7 @@
 #include <err.h>
 #include <stdlib.h>
 
+#include <machine/cpu.h>
 #include <machine/frame.h>
 #include <machine/pcb.h>
 #include <x86/db_machdep.h>
@@ -53,6 +54,9 @@ vaddr_t vm_min_kernel_address = VM_MIN_K
 
 static struct nlist nl[] = {
 	{ .n_name = "_dumppcb" },
+	{ .n_name = "cpu_infos" },
+	{ .n_name = "cpu_info_primary" },
+	{ .n_name = "ncpu" },
 #ifdef VM_MIN_KERNEL_ADDRESS_DEFAULT
 	{ .n_name = "vm_min_kernel_address" },
 #endif
@@ -60,6 +64,9 @@ static struct nlist nl[] = {
 };
 
 struct pcb	pcb;
+struct cpu_info	**cpu_infos;
+struct cpu_info	*cpu_info_primary_p;
+int		ncpu;
 
 void
 db_mach_init(kvm_t *kd)
@@ -72,8 +79,17 @@ db_mach_init(kvm_t *kd)
 	    sizeof(pcb)) {
 		errx(EXIT_FAILURE, "cannot read dumppcb: %s", kvm_geterr(kd));
 	}
+	if ((size_t)kvm_read(kd, nl[1].n_value, &cpu_infos, sizeof(cpu_infos))
+	    != sizeof(cpu_infos)) {
+		errx(EXIT_FAILURE, "cannot read cpu_infos: %s", kvm_geterr(kd));
+	}
+	cpu_info_primary_p = (void *)(uintptr_t)nl[2].n_value;
+	if ((size_t)kvm_read(kd, nl[3].n_value, &ncpu, sizeof(ncpu)) !=
+	    sizeof(ncpu)) {
+		errx(EXIT_FAILURE, "cannot read ncpu: %s", kvm_geterr(kd));
+	}
 #ifdef VM_MIN_KERNEL_ADDRESS_DEFAULT
-	if ((size_t)kvm_read(kd, nl[1].n_value, &vm_min_kernel_address,
+	if ((size_t)kvm_read(kd, nl[4].n_value, &vm_min_kernel_address,
 	    sizeof(vm_min_kernel_address)) != sizeof(vm_min_kernel_address)) {
 		errx(EXIT_FAILURE, "cannot read vm_min_kernel_address: %s",
 		    kvm_geterr(kd));
@@ -85,3 +101,71 @@ db_mach_init(kvm_t *kd)
         	printf("Backtrace from time of crash is available.\n");
 	}
 }
+
+void db_mach_cpu(db_expr_t, bool, db_expr_t, const char *);
+
+const struct db_command db_machine_command_table[] = {
+	{ DDB_ADD_CMD("cpu",	db_mach_cpu,	0,
+	  "switch to another cpu", "cpu-no", NULL) },
+	{ DDB_END_CMD },
+};
+
+static struct cpu_info *
+cpu_lookup(unsigned i)
+{
+	struct cpu_info *ci;
+
+	if (cpu_infos == NULL) {
+		if (i != 0)
+			return NULL;
+		return cpu_info_primary_p;
+	}
+	if (ncpu < 0 || i >= (unsigned)ncpu)
+		return NULL;
+	db_read_bytes((db_addr_t)(uintptr_t)&cpu_infos[i],
+	    sizeof(ci), (char *)&ci);
+	return ci;
+}
+
+void
+db_mach_cpu(db_expr_t addr, bool have_addr, db_expr_t count, const char *modif)
+{
+	struct cpu_info *ci;
+	db_regs_t *regs;
+
+#if 0
+	if (!have_addr) {
+		cpu_debug_dump();
+		return;
+	}
+#endif
+
+	if (addr < 0) {
+		db_printf("%ld: CPU out of range\n", addr);
+		return;
+	}
+	ci = cpu_lookup(addr);
+	if (ci == NULL) {
+		db_printf("CPU %ld not configured\n", addr);
+		return;
+	}
+#if 0
+	if (ci != curcpu()) {
+		if (!(ci->ci_flags & CPUF_PAUSE)) {
+			db_printf("CPU %ld not paused\n", addr);
+			return;
+		}
+	}
+#endif
+	db_read_bytes((db_addr_t)(uintptr_t)&ci->ci_ddb_regs,
+	    sizeof(regs), (char *)&regs);
+	if (regs == NULL) {
+		db_printf("CPU %ld has no saved regs\n", addr);
+		return;
+	}
+	db_printf("using CPU %ld", addr);
+	db_read_bytes((db_addr_t)(uintptr_t)&regs->tf_sp,
+	    sizeof(ddb_regs.tf_sp), (char *)&ddb_regs.tf_sp);
+	db_read_bytes((db_addr_t)(uintptr_t)&regs->tf_bp,
+	    sizeof(ddb_regs.tf_bp), (char *)&ddb_regs.tf_bp);
+}