[RFC v2 08/14] arch: um: add shim to trap to allow installing a fault catcher for tests

Brendan Higgins
2018-10-23T23:57:44Z

Add context to current thread that allows a test to specify that it
wants to skip the normal checks to run an installed fault catcher.

Signed-off-by: Brendan Higgins <brendanhiggins-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
---
arch/um/include/asm/processor-generic.h | 4 +++-
arch/um/kernel/trap.c | 15 +++++++++++----
2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/um/include/asm/processor-generic.h b/arch/um/include/asm/processor-generic.h
index b58b746d3f2ca..d566cd416ff02 100644
--- a/arch/um/include/asm/processor-generic.h
+++ b/arch/um/include/asm/processor-generic.h
@@ -27,6 +27,7 @@ struct thread_struct {
struct task_struct *prev_sched;
struct arch_thread arch;
jmp_buf switch_buf;
+ bool is_running_test;
struct {
int op;
union {
@@ -51,7 +52,8 @@ struct thread_struct {
.fault_addr = NULL, \
.prev_sched = NULL, \
.arch = INIT_ARCH_THREAD, \
- .request = { 0 } \
+ .request = { 0 }, \
+ .is_running_test = false, \
}

static inline void release_thread(struct task_struct *task)
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
index cced829460427..bf90e678b3d71 100644
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -201,6 +201,12 @@ void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
}

+static void segv_run_catcher(jmp_buf *catcher, void *fault_addr)
+{
+ current->thread.fault_addr = fault_addr;
+ UML_LONGJMP(catcher, 1);
+}
+
/*
* We give a *copy* of the faultinfo in the regs to segv.
* This must be done, since nesting SEGVs could overwrite
@@ -219,7 +225,10 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
if (!is_user && regs)
current->thread.segv_regs = container_of(regs, struct pt_regs, regs);

- if (!is_user && (address >= start_vm) && (address < end_vm)) {
+ catcher = current->thread.fault_catcher;
+ if (catcher && current->thread.is_running_test)
+ segv_run_catcher(catcher, (void *) address);
+ else if (!is_user && (address >= start_vm) && (address < end_vm)) {
flush_tlb_kernel_vm();
goto out;
}
@@ -246,12 +255,10 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
address = 0;
}

- catcher = current->thread.fault_catcher;
if (!err)
goto out;
else if (catcher != NULL) {
- current->thread.fault_addr = (void *) address;
- UML_LONGJMP(catcher, 1);
+ segv_run_catcher(catcher, (void *) address);
}
else if (current->thread.fault_addr != NULL)
panic("fault_addr set but no fault catcher");
--
2.19.1.568.g152ad8e336-goog