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arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0

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When exec'ing a 32-bit task on a system with mismatched support for
32-bit EL0, try to ensure that it starts life on a CPU that can actually
run it.

Similarly, when exec'ing a 64-bit task on such a system, try to restore
the old affinity mask if it was previously restricted.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Reviewed-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20210730112443.23245-12-will@kernel.org
This commit is contained in:
Will Deacon 2021-07-30 12:24:38 +01:00 committed by Peter Zijlstra
parent d82158fa6d
commit 08cd8f4112
2 changed files with 40 additions and 5 deletions
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6
arch/arm64/include/asm/elf.h
View file

@ -213,10 +213,8 @@ typedef compat_elf_greg_t compat_elf_gregset_t[COMPAT_ELF_NGREG];
/* AArch32 EABI. */
#define EF_ARM_EABI_MASK 0xff000000
#define compat_elf_check_arch(x) (system_supports_32bit_el0() && \
((x)->e_machine == EM_ARM) && \
((x)->e_flags & EF_ARM_EABI_MASK))
int compat_elf_check_arch(const struct elf32_hdr *);
#define compat_elf_check_arch compat_elf_check_arch
#define compat_start_thread compat_start_thread
/*
* Unlike the native SET_PERSONALITY macro, the compat version maintains

39
arch/arm64/kernel/process.c
View file

@ -21,6 +21,7 @@
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/nospec.h>
#include <linux/sched.h>
#include <linux/stddef.h>
#include <linux/sysctl.h>
#include <linux/unistd.h>
@ -579,6 +580,28 @@ unsigned long arch_align_stack(unsigned long sp)
return sp & ~0xf;
}
#ifdef CONFIG_COMPAT
int compat_elf_check_arch(const struct elf32_hdr *hdr)
{
if (!system_supports_32bit_el0())
return false;
if ((hdr)->e_machine != EM_ARM)
return false;
if (!((hdr)->e_flags & EF_ARM_EABI_MASK))
return false;
/*
* Prevent execve() of a 32-bit program from a deadline task
* if the restricted affinity mask would be inadmissible on an
* asymmetric system.
*/
return !static_branch_unlikely(&arm64_mismatched_32bit_el0) ||
!dl_task_check_affinity(current, system_32bit_el0_cpumask());
}
#endif
/*
* Called from setup_new_exec() after (COMPAT_)SET_PERSONALITY.
*/
@ -588,8 +611,22 @@ void arch_setup_new_exec(void)
if (is_compat_task()) {
mmflags = MMCF_AARCH32;
if (static_branch_unlikely(&arm64_mismatched_32bit_el0))
/*
* Restrict the CPU affinity mask for a 32-bit task so that
* it contains only 32-bit-capable CPUs.
*
* From the perspective of the task, this looks similar to
* what would happen if the 64-bit-only CPUs were hot-unplugged
* at the point of execve(), although we try a bit harder to
* honour the cpuset hierarchy.
*/
if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) {
force_compatible_cpus_allowed_ptr(current);
set_tsk_thread_flag(current, TIF_NOTIFY_RESUME);
}
} else if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) {
relax_compatible_cpus_allowed_ptr(current);
}
current->mm->context.flags = mmflags;