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Subject[PATCH kvm-unit-tests] x86: Test rflags.rf is set upon faults
Date
This patch tests whether rflags.rf is set upon #UD and #GP faults as it should,
according to Intel SDM 17.3.1.1. The patch saves rflags.rf in an unused bit of
the value which is saved during exception handling to save rflags.rf.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
---
lib/x86/desc.c | 16 ++++++++++++----
lib/x86/desc.h | 1 +
x86/idt_test.c | 13 +++++++++----
3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/lib/x86/desc.c b/lib/x86/desc.c
index 9a80f48..7fbe774 100644
--- a/lib/x86/desc.c
+++ b/lib/x86/desc.c
@@ -36,8 +36,8 @@ static void check_exception_table(struct ex_regs *regs)
struct ex_record *ex;
unsigned ex_val;

- ex_val = regs->vector | (regs->error_code << 16);
-
+ ex_val = regs->vector | (regs->error_code << 16) |
+ (((regs->rflags >> 16) & 1) << 8);
asm("mov %0, %%gs:4" : : "r"(ex_val));

for (ex = &exception_table_start; ex != &exception_table_end; ++ex) {
@@ -173,9 +173,9 @@ void setup_idt(void)

unsigned exception_vector(void)
{
- unsigned short vector;
+ unsigned char vector;

- asm("mov %%gs:4, %0" : "=rm"(vector));
+ asm("movb %%gs:4, %0" : "=q"(vector));
return vector;
}

@@ -187,6 +187,14 @@ unsigned exception_error_code(void)
return error_code;
}

+bool exception_rflags_rf(void)
+{
+ unsigned char rf_flag;
+
+ asm("movb %%gs:5, %b0" : "=q"(rf_flag));
+ return rf_flag & 1;
+}
+
static char intr_alt_stack[4096];

#ifndef __x86_64__
diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index 553bce9..bd4293e 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -144,6 +144,7 @@ extern tss64_t tss;

unsigned exception_vector(void);
unsigned exception_error_code(void);
+bool exception_rflags_rf(void);
void set_idt_entry(int vec, void *addr, int dpl);
void set_idt_sel(int vec, u16 sel);
void set_gdt_entry(int sel, u32 base, u32 limit, u8 access, u8 gran);
diff --git a/x86/idt_test.c b/x86/idt_test.c
index ecb76bb..349aade 100644
--- a/x86/idt_test.c
+++ b/x86/idt_test.c
@@ -1,15 +1,16 @@
#include "libcflat.h"
#include "desc.h"

-int test_ud2(void)
+int test_ud2(bool *rflags_rf)
{
asm volatile(ASM_TRY("1f")
"ud2 \n\t"
"1:" :);
+ *rflags_rf = exception_rflags_rf();
return exception_vector();
}

-int test_gp(void)
+int test_gp(bool *rflags_rf)
{
unsigned long tmp;

@@ -18,19 +19,23 @@ int test_gp(void)
"mov %0, %%cr4\n\t"
"1:"
: "=a"(tmp));
+ *rflags_rf = exception_rflags_rf();
return exception_vector();
}

int main(void)
{
int r;
+ bool rflags_rf;

printf("Starting IDT test\n");
setup_idt();
- r = test_gp();
+ r = test_gp(&rflags_rf);
report("Testing #GP", r == GP_VECTOR);
- r = test_ud2();
+ report("Testing #GP rflags.rf", rflags_rf);
+ r = test_ud2(&rflags_rf);
report("Testing #UD", r == UD_VECTOR);
+ report("Testing #UD rflags.rf", rflags_rf);

return report_summary();
}
--
1.9.1


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