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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2017-07-22 18:45:33 +0100
committerMark Rutland <mark.rutland@arm.com>2017-08-09 14:07:13 +0100
commit7326749801396105aef0ed9229df746ac9e24300 (patch)
tree24d3e08bd2e124812560a0c5c12dece03c48ff78 /arch/arm64/include/asm
parentarm64: unwind: disregard frame.sp when validating frame pointer (diff)
downloadlinux-dev-7326749801396105aef0ed9229df746ac9e24300.tar.xz
linux-dev-7326749801396105aef0ed9229df746ac9e24300.zip
arm64: unwind: reference pt_regs via embedded stack frame
As it turns out, the unwind code is slightly broken, and probably has been for a while. The problem is in the dumping of the exception stack, which is intended to dump the contents of the pt_regs struct at each level in the call stack where an exception was taken and routed to a routine marked as __exception (which means its stack frame is right below the pt_regs struct on the stack). 'Right below the pt_regs struct' is ill defined, though: the unwind code assigns 'frame pointer + 0x10' to the .sp member of the stackframe struct at each level, and dump_backtrace() happily dereferences that as the pt_regs pointer when encountering an __exception routine. However, the actual size of the stack frame created by this routine (which could be one of many __exception routines we have in the kernel) is not known, and so frame.sp is pretty useless to figure out where struct pt_regs really is. So it seems the only way to ensure that we can find our struct pt_regs when walking the stack frames is to put it at a known fixed offset of the stack frame pointer that is passed to such __exception routines. The simplest way to do that is to put it inside pt_regs itself, which is the main change implemented by this patch. As a bonus, doing this allows us to get rid of a fair amount of cruft related to walking from one stack to the other, which is especially nice since we intend to introduce yet another stack for overflow handling once we add support for vmapped stacks. It also fixes an inconsistency where we only add a stack frame pointing to ELR_EL1 if we are executing from the IRQ stack but not when we are executing from the task stack. To consistly identify exceptions regs even in the presence of exceptions taken from entry code, we must check whether the next frame was created by entry text, rather than whether the current frame was crated by exception text. To avoid backtracing using PCs that fall in the idmap, or are controlled by userspace, we must explcitly zero the FP and LR in startup paths, and must ensure that the frame embedded in pt_regs is zeroed upon entry from EL0. To avoid these NULL entries showin in the backtrace, unwind_frame() is updated to avoid them. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> [Mark: compare current frame against .entry.text, avoid bogus PCs] Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: James Morse <james.morse@arm.com> Cc: Will Deacon <will.deacon@arm.com>
Diffstat (limited to '')
-rw-r--r--arch/arm64/include/asm/irq.h25
-rw-r--r--arch/arm64/include/asm/ptrace.h1
-rw-r--r--arch/arm64/include/asm/traps.h5
3 files changed, 6 insertions, 25 deletions
diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index 8155e486ce48..8ba89c4ca183 100644
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -16,31 +16,6 @@ struct pt_regs;
DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
-/*
- * The highest address on the stack, and the first to be used. Used to
- * find the dummy-stack frame put down by el?_irq() in entry.S, which
- * is structured as follows:
- *
- * ------------
- * | | <- irq_stack_ptr
- * top ------------
- * | x19 | <- irq_stack_ptr - 0x08
- * ------------
- * | x29 | <- irq_stack_ptr - 0x10
- * ------------
- *
- * where x19 holds a copy of the task stack pointer where the struct pt_regs
- * from kernel_entry can be found.
- *
- */
-#define IRQ_STACK_PTR() ((unsigned long)raw_cpu_ptr(irq_stack) + IRQ_STACK_START_SP)
-
-/*
- * The offset from irq_stack_ptr where entry.S will store the original
- * stack pointer. Used by unwind_frame() and dump_backtrace().
- */
-#define IRQ_STACK_TO_TASK_STACK(ptr) (*((unsigned long *)((ptr) - 0x08)))
-
extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
static inline int nr_legacy_irqs(void)
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
index 11403fdd0a50..ee72aa979078 100644
--- a/arch/arm64/include/asm/ptrace.h
+++ b/arch/arm64/include/asm/ptrace.h
@@ -119,6 +119,7 @@ struct pt_regs {
u64 syscallno;
u64 orig_addr_limit;
u64 unused; // maintain 16 byte alignment
+ u64 stackframe[2];
};
#define MAX_REG_OFFSET offsetof(struct pt_regs, pstate)
diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h
index 02e9035b0685..41361684580d 100644
--- a/arch/arm64/include/asm/traps.h
+++ b/arch/arm64/include/asm/traps.h
@@ -60,4 +60,9 @@ static inline int in_exception_text(unsigned long ptr)
return in ? : __in_irqentry_text(ptr);
}
+static inline int in_entry_text(unsigned long ptr)
+{
+ return ptr >= (unsigned long)&__entry_text_start &&
+ ptr < (unsigned long)&__entry_text_end;
+}
#endif