Reproducing the synchronous external abort that the device memory guard prevents requires disabling the guard at runtime. Without this, there is no way to verify the guard is actually needed or to regression-test the crash path.
Add a module parameter (skip_vmio, default true) that controls whether the guard is active. Set to 0 to disable it: Boot: stacktrace.skip_vmio=0 Runtime: echo 0 > /sys/module/stacktrace/parameters/skip_vmio When disabled, perf follows frame pointers into device memory regions, triggering a synchronous external abort and kernel panic on arm64. Assisted-by: Kiro:claude-opus-4.6 [kiro-cli] Signed-off-by: Fredrik Markstrom <[email protected]> Reviewed-by: Ivar Holmqvist <[email protected]> Reviewed-by: Malin Jonsson <[email protected]> --- arch/arm64/kernel/stacktrace.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 6426a307b8f86ae756ea444247ae329591a89b4b..ebe909012e4edee7bb1ddbebac2d3c49bdb91665 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -11,6 +11,7 @@ #include <linux/filter.h> #include <linux/ftrace.h> #include <linux/kprobes.h> +#include <linux/moduleparam.h> #include <linux/pgtable.h> #include <linux/sched.h> #include <linux/sched/debug.h> @@ -112,6 +113,10 @@ static bool addr_is_device_mem(unsigned long addr) #endif } +static bool skip_vmio = true; +module_param(skip_vmio, bool, 0644); +MODULE_PARM_DESC(skip_vmio, "Skip device memory during user callchain unwinding"); + enum kunwind_source { KUNWIND_SOURCE_UNKNOWN, KUNWIND_SOURCE_FRAME, @@ -616,7 +621,7 @@ unwind_user_frame(struct frame_tail __user *tail, void *cookie, if (!access_ok(tail, sizeof(buftail))) return NULL; - if (addr_is_device_mem((unsigned long)tail)) + if (READ_ONCE(skip_vmio) && addr_is_device_mem((unsigned long)tail)) return NULL; pagefault_disable(); @@ -667,7 +672,7 @@ unwind_compat_user_frame(struct compat_frame_tail __user *tail, void *cookie, if (!access_ok(tail, sizeof(buftail))) return NULL; - if (addr_is_device_mem((unsigned long)tail)) + if (READ_ONCE(skip_vmio) && addr_is_device_mem((unsigned long)tail)) return NULL; pagefault_disable(); -- 2.51.0
