A single fix for early boot crashes of kernels built with gcc10 and

stack protector enabled.
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Merge tag 'x86_urgent_for_v5.7-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fix from Borislav Petkov:
 "A single fix for early boot crashes of kernels built with gcc10 and
  stack protector enabled"

* tag 'x86_urgent_for_v5.7-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86: Fix early boot crash on gcc-10, third try
This commit is contained in:
Linus Torvalds 2020-05-17 11:08:29 -07:00
commit 43567139f5
5 changed files with 23 additions and 1 deletions

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@ -55,8 +55,13 @@
/*
* Initialize the stackprotector canary value.
*
* NOTE: this must only be called from functions that never return,
* NOTE: this must only be called from functions that never return
* and it must always be inlined.
*
* In addition, it should be called from a compilation unit for which
* stack protector is disabled. Alternatively, the caller should not end
* with a function call which gets tail-call optimized as that would
* lead to checking a modified canary value.
*/
static __always_inline void boot_init_stack_canary(void)
{

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@ -266,6 +266,14 @@ static void notrace start_secondary(void *unused)
wmb();
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
/*
* Prevent tail call to cpu_startup_entry() because the stack protector
* guard has been changed a couple of function calls up, in
* boot_init_stack_canary() and must not be checked before tail calling
* another function.
*/
prevent_tail_call_optimization();
}
/**

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@ -93,6 +93,7 @@ asmlinkage __visible void cpu_bringup_and_idle(void)
cpu_bringup();
boot_init_stack_canary();
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
prevent_tail_call_optimization();
}
void xen_smp_intr_free_pv(unsigned int cpu)

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@ -356,4 +356,10 @@ static inline void *offset_to_ptr(const int *off)
/* &a[0] degrades to a pointer: a different type from an array */
#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
/*
* This is needed in functions which generate the stack canary, see
* arch/x86/kernel/smpboot.c::start_secondary() for an example.
*/
#define prevent_tail_call_optimization() mb()
#endif /* __LINUX_COMPILER_H */

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@ -1038,6 +1038,8 @@ asmlinkage __visible void __init start_kernel(void)
/* Do the rest non-__init'ed, we're now alive */
arch_call_rest_init();
prevent_tail_call_optimization();
}
/* Call all constructor functions linked into the kernel. */