[Minios-devel] [UNIKRAFT PATCH 02/23] plat: Hardware context - Set exception stack when switching to a new thread

[Costin Lupu <costin.lupu@xxxxxxxxx>]

On x86, whenever an exception is generated, SS, SP, EFLAGS, CS and IP registers
are pushed on a stack that needs to be configured beforehand. We keep such an
exception stack for each thread in the system. This patch introduces the
traps_set_interrupt_stack() function used for setting the exception stack.

Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
---
 plat/common/include/x86/traps.h | 1 +
 plat/common/x86/hw_ctx.c        | 2 ++
 plat/kvm/x86/traps.c            | 4 ++++
 3 files changed, 7 insertions(+)

diff --git a/plat/common/include/x86/traps.h b/plat/common/include/x86/traps.h
index b217b34a..fcd1697e 100644
--- a/plat/common/include/x86/traps.h
+++ b/plat/common/include/x86/traps.h
@@ -109,6 +109,7 @@ void do_##name(struct __regs *regs, unsigned long 
error_code) \
 
 void traps_init(void);
 void traps_fini(void);
+void traps_set_interrupt_stack(void *stack_address);
 
 #endif
 
diff --git a/plat/common/x86/hw_ctx.c b/plat/common/x86/hw_ctx.c
index c7b8dbac..e82beb5f 100644
--- a/plat/common/x86/hw_ctx.c
+++ b/plat/common/x86/hw_ctx.c
@@ -84,6 +84,8 @@ static void hw_ctx_switch(void *prevctx, void *nextctx)
        struct hw_ctx *prev_hw_ctx = prevctx;
        struct hw_ctx *next_hw_ctx = nextctx;
 
+       traps_set_interrupt_stack(&next_hw_ctx->regs + 1);
+
        if (ukplat_irq_context()) {
                /* IRQ context */
                prev_hw_ctx->interrupted = true;
diff --git a/plat/kvm/x86/traps.c b/plat/kvm/x86/traps.c
index fe1dd5a4..a3653c8a 100644
--- a/plat/kvm/x86/traps.c
+++ b/plat/kvm/x86/traps.c
@@ -93,6 +93,10 @@ static void tss_init(void)
        );
 }
 
+void traps_set_interrupt_stack(void *stack_address)
+{
+       cpu_tss.ist[0] = (__u64) stack_address;
+}
 
 /* Declare the traps used only by this platform: */
 DECLARE_TRAP_EC(nmi,           "NMI")
-- 
2.20.1


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