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nova: add exception handlers for all core threads
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The commit will improve diagnostics, if a core thread dies
(which should never happen) with an hardware exception beside a page fault,
e.g. general protection fault or undefined opcode.

Without the commit we may not see this circumstance easily.

Issue #5443
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@alex-ab @nfeske
alex-ab authored and nfeske committed Feb 5, 2025
1 parent 3fc1fff commit 8e35d7e
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Showing 2 changed files with 63 additions and 40 deletions.
86 changes: 52 additions & 34 deletions repos/base-nova/src/core/platform.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -109,30 +109,37 @@ enum { CORE_PAGER_UTCB_ADDR = 0xbff02000 };
/**
* IDC handler for the page-fault portal
*/
static void page_fault_handler()
__attribute__((regparm(1)))
static void exception_handler(addr_t const pt_id)
{
Utcb *utcb = (Utcb *)CORE_PAGER_UTCB_ADDR;

addr_t const pf_addr = utcb->pf_addr();
addr_t const pf_ip = utcb->ip;
addr_t const pf_sp = utcb->sp;
uint8_t const pf_type = utcb->pf_type();

error("\nPAGE-FAULT IN CORE addr=", Hex(pf_addr), " ip=", Hex(pf_ip),
" (", (pf_type & Ipc_pager::ERR_W) ? "write" : "read", ")");

log("\nstack pointer ", Hex(pf_sp), ", qualifiers ", Hex(pf_type), " ",
pf_type & Ipc_pager::ERR_I ? "I" : "i",
pf_type & Ipc_pager::ERR_R ? "R" : "r",
pf_type & Ipc_pager::ERR_U ? "U" : "u",
pf_type & Ipc_pager::ERR_W ? "W" : "w",
pf_type & Ipc_pager::ERR_P ? "P" : "p");
addr_t const ip = utcb->ip;
addr_t const sp = utcb->sp;

if (pt_id == PT_SEL_PAGE_FAULT) {
addr_t const pf_addr = utcb->pf_addr();
uint8_t const pf_type = utcb->pf_type();

error("\nPAGE-FAULT IN CORE addr=", Hex(pf_addr), " ip=", Hex(ip),
" (", (pf_type & Ipc_pager::ERR_W) ? "write" : "read", ")");

log("\nstack pointer ", Hex(sp), ", qualifiers ", Hex(pf_type), " ",
pf_type & Ipc_pager::ERR_I ? "I" : "i",
pf_type & Ipc_pager::ERR_R ? "R" : "r",
pf_type & Ipc_pager::ERR_U ? "U" : "u",
pf_type & Ipc_pager::ERR_W ? "W" : "w",
pf_type & Ipc_pager::ERR_P ? "P" : "p");
} else {
error("\nEXCEPTION IN CORE ip=", Hex(ip), " sp=", Hex(sp),
" exception=", Hex(pt_id));
}

if ((stack_area_virtual_base() <= pf_sp) &&
(pf_sp < stack_area_virtual_base() +
if ((stack_area_virtual_base() <= sp) &&
(sp < stack_area_virtual_base() +
stack_area_virtual_size()))
{
addr_t utcb_addr_f = pf_sp / stack_virtual_size();
addr_t utcb_addr_f = sp / stack_virtual_size();
utcb_addr_f *= stack_virtual_size();
utcb_addr_f += stack_virtual_size();
utcb_addr_f -= 4096;
Expand Down Expand Up @@ -184,10 +191,10 @@ static void page_fault_handler()
};

int count = 1;
log(" #", count++, " ", Hex(pf_sp, Hex::PREFIX, Hex::PAD), " ",
Hex(pf_ip, Hex::PREFIX, Hex::PAD));
log(" #", count++, " ", Hex(sp, Hex::PREFIX, Hex::PAD), " ",
Hex(ip, Hex::PREFIX, Hex::PAD));

Core_img dump(pf_sp);
Core_img dump(sp);
while (dump.ip_valid()) {
log(" #", count++, " ", Hex((addr_t)dump.ip(), Hex::PREFIX, Hex::PAD),
" ", Hex(*dump.ip(), Hex::PREFIX, Hex::PAD));
Expand Down Expand Up @@ -224,30 +231,41 @@ static void startup_handler()

static addr_t init_core_page_fault_handler(addr_t const core_pd_sel)
{
/* create fault handler EC for core main thread */
/* create fault handler EC used by all core threads */
enum {
GLOBAL = false,
EXC_BASE = 0
};

addr_t ec_sel = cap_map().insert(1);

uint8_t ret = create_ec(ec_sel, core_pd_sel, boot_cpu(),
CORE_PAGER_UTCB_ADDR, core_pager_stack_top(),
EXC_BASE, GLOBAL);
if (ret)
auto ret = create_ec(ec_sel, core_pd_sel, boot_cpu(),
CORE_PAGER_UTCB_ADDR, core_pager_stack_top(),
EXC_BASE, GLOBAL);
if (ret != Nova::NOVA_OK)
log(__func__, ": create_ec returned ", ret);

/* set up page-fault portal */
create_pt(PT_SEL_PAGE_FAULT, core_pd_sel, ec_sel,
Mtd(Mtd::QUAL | Mtd::ESP | Mtd::EIP),
(addr_t)page_fault_handler);
revoke(Obj_crd(PT_SEL_PAGE_FAULT, 0, Obj_crd::RIGHT_PT_CTRL));
for (unsigned i = 0; i < NUM_INITIAL_PT; i++) {
if (i == PT_SEL_PAGE_FAULT || i == PT_SEL_STARTUP || i == SM_SEL_EC)
continue;

ret = create_pt(i, core_pd_sel, ec_sel,
Mtd(Mtd::QUAL | Mtd::ESP | Mtd::EIP),
(addr_t)exception_handler);
if (ret != Nova::NOVA_OK)
warning(__func__, " exception handler ", i,
" could not be setup, error=", ret);

revoke(Obj_crd(i, 0, Obj_crd::RIGHT_PT_CTRL));
}

/* startup portal for global core threads */
create_pt(PT_SEL_STARTUP, core_pd_sel, ec_sel,
Mtd(Mtd::EIP | Mtd::ESP),
(addr_t)startup_handler);
ret = create_pt(PT_SEL_STARTUP, core_pd_sel, ec_sel,
Mtd(Mtd::EIP | Mtd::ESP),
(addr_t)startup_handler);
if (ret != Nova::NOVA_OK)
warning(__func__, " startup handler ", unsigned(PT_SEL_STARTUP),
" could not be setup, error=", ret);
revoke(Obj_crd(PT_SEL_STARTUP, 0, Obj_crd::RIGHT_PT_CTRL));

return ec_sel;
Expand Down
17 changes: 11 additions & 6 deletions repos/base-nova/src/core/thread_start.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -105,12 +105,17 @@ Thread::Start_result Thread::start()
utcb.crd_rcv = Obj_crd();
utcb.crd_xlt = Obj_crd();

if (map_local(platform_specific().core_pd_sel(),
*reinterpret_cast<Nova::Utcb *>(Thread::myself()->utcb()),
Obj_crd(PT_SEL_PAGE_FAULT, 0),
Obj_crd(native_thread().exc_pt_sel + PT_SEL_PAGE_FAULT, 0))) {
error("Thread::start: failed to create page-fault portal");
return Start_result::DENIED;
for (unsigned i = 0; i < NUM_INITIAL_PT; i++) {
if (i == SM_SEL_EC)
continue;

if (map_local(platform_specific().core_pd_sel(),
*reinterpret_cast<Nova::Utcb *>(Thread::myself()->utcb()),
Obj_crd(i, 0),
Obj_crd(native_thread().exc_pt_sel + i, 0))) {
error("Thread::start: failed to create page-fault portal");
return Start_result::DENIED;
}
}

struct Core_trace_source : public Core::Trace::Source::Info_accessor,
Expand Down

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