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Linux 6.13 (662df3e5c3766) added a lightweight way to define guard areas through madvise syscall. Instead of PROT_NONE the guard region through mprotect, userland can madvise the same area with a special flag, and the kernel ensures that accessing the area will trigger a SIGSEGV (as for PROT_NONE mapping). The madvise way has the advantage of less kernel memory consumption for the process page-table (one less VMA per guard area), and slightly less contention on kernel (also due to the fewer VMA areas being tracked). The pthread_create allocates a new thread stack in two ways: if a guard area is set (the default) it allocates the memory range required using PROT_NONE and then mprotect the usable stack area. Otherwise, if a guard page is not set it allocates the region with the required flags. For the MADV_GUARD_INSTALL support, the stack area region is allocated with required flags and then the guard region is installed. If the kernel does not support it, the usual way is used instead (and MADV_GUARD_INSTALL is disabled for future stack creations). The stack allocation strategy is recorded on the pthread struct, and it is used in case the guard region needs to be resized. To avoid needing an extra field, the 'user_stack' is repurposed and renamed to 'stack_mode'. This patch also adds a proper test for the pthread guard. I checked on x86_64, aarch64, powerpc64le, and hppa with kernel 6.13.0-rc7. Reviewed-by: DJ Delorie <dj@redhat.com>
12 lines
161 B
Text
12 lines
161 B
Text
pthread_attr_[sg]etschedparam
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what to test?
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pthread_attr_[sg]etstack
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some more tests needed
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pthread_getschedparam
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pthread_setschedparam
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what to test?
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