Hi,
This is a short diff to add "machine sysregs" to ddb on amd64 (plus it
also prints out gsbase/kgsbase). This command is available on i386 but
not amd64. I swear I remember discussing this with mlarkin at some point
but I couldn't find a previous patch for it on tech@. If I missed it
somehow, I am super sorry, and please hit me with the search stick.
This command is mostly useful if you're futzing with page tables or
GDT/IDT setup etc, but it's also useful for sanity-checking state
generally sometimes, and quite useful for teaching demos showing how it
all works (which is the main reason I want it right now).
Index: sys/arch/amd64//amd64/db_interface.c
===================================================================
RCS file: /cvs/./src/sys/arch/amd64/amd64/db_interface.c,v
retrieving revision 1.35
diff -u -p -r1.35 db_interface.c
--- sys/arch/amd64//amd64/db_interface.c 6 Nov 2019 07:34:35 -0000
1.35
+++ sys/arch/amd64//amd64/db_interface.c 31 Aug 2021 08:12:06 -0000
@@ -46,6 +46,7 @@
#include <machine/cpuvar.h>
#include <machine/i82093var.h>
#include <machine/atomic.h>
+#include <machine/specialreg.h>
#include <ddb/db_sym.h>
#include <ddb/db_command.h>
@@ -160,6 +161,45 @@ db_ktrap(int type, int code, db_regs_t *
return (1);
}
+void
+db_sysregs_cmd(db_expr_t addr, int have_addr, db_expr_t count, char *modif)
+{
+ int64_t idtr, gdtr;
+ uint64_t cr;
+ uint16_t ldtr, tr;
+ uint64_t gsb;
+
+ __asm__ volatile("sidt %0" : "=m" (idtr));
+ db_printf("idtr: 0x%08llx/%04llx\n", idtr >> 16, idtr & 0xffff);
+
+ __asm__ volatile("sgdt %0" : "=m" (gdtr));
+ db_printf("gdtr: 0x%08llx/%04llx\n", gdtr >> 16, gdtr & 0xffff);
+
+ __asm__ volatile("sldt %0" : "=g" (ldtr));
+ db_printf("ldtr: 0x%04x\n", ldtr);
+
+ __asm__ volatile("str %0" : "=g" (tr));
+ db_printf("tr: 0x%04x\n", tr);
+
+ __asm__ volatile("movq %%cr0,%0" : "=r" (cr));
+ db_printf("cr0: 0x%016llx\n", cr);
+
+ __asm__ volatile("movq %%cr2,%0" : "=r" (cr));
+ db_printf("cr2: 0x%016llx\n", cr);
+
+ __asm__ volatile("movq %%cr3,%0" : "=r" (cr));
+ db_printf("cr3: 0x%016llx\n", cr);
+
+ __asm__ volatile("movq %%cr4,%0" : "=r" (cr));
+ db_printf("cr4: 0x%016llx\n", cr);
+
+ gsb = rdmsr(MSR_GSBASE);
+ db_printf("gsb: 0x%016llx\n", gsb);
+
+ gsb = rdmsr(MSR_KERNELGSBASE);
+ db_printf("kgsb: 0x%016llx\n", gsb);
+}
+
#ifdef MULTIPROCESSOR
void
@@ -368,6 +408,7 @@ struct db_command db_machine_command_tab
{ "startcpu", db_startproc_cmd, 0, 0 },
{ "stopcpu", db_stopproc_cmd, 0, 0 },
{ "ddbcpu", db_ddbproc_cmd, 0, 0 },
+ { "sysregs", db_sysregs_cmd, 0, 0 },
#endif
#if NACPI > 0
{ "acpi", NULL, 0, db_acpi_cmds },
