2005-12-22 05:18:34 +00:00
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#include <stddef.h>
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#include <signal.h>
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#include <sys/ucontext.h>
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--
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SIG_BLOCK
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SIG_SETMASK
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#define ucontext(member) offsetof (ucontext_t, member)
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#define mcontext(member) ucontext (uc_mcontext.member)
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#define mreg(reg) mcontext (gregs[REG_##reg])
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oLINK ucontext (uc_link)
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oSS_SP ucontext (uc_stack.ss_sp)
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oSS_SIZE ucontext (uc_stack.ss_size)
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oGS mreg (GS)
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oFS mreg (FS)
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oEDI mreg (EDI)
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oESI mreg (ESI)
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oEBP mreg (EBP)
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oESP mreg (ESP)
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oEBX mreg (EBX)
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oEIP mreg (EIP)
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i386: Enable CET support in ucontext functions
1. getcontext and swapcontext are updated to save the caller's shadow
stack pointer and return address.
2. setcontext and swapcontext are updated to restore shadow stack and
jump to new context directly.
3. makecontext is updated to allocate a new shadow stack and set the
caller's return address to the helper code, L(exitcode).
4. Since we no longer save and restore EAX, ECX and EDX in getcontext,
setcontext and swapcontext, we can use them as scratch register slots
to enable CET in ucontext functions.
Since makecontext allocates a new shadow stack when making a new
context and kernel allocates a new shadow stack for clone/fork/vfork
syscalls, we track the current shadow stack base. In setcontext and
swapcontext, if the target shadow stack base is the same as the current
shadow stack base, we unwind the shadow stack. Otherwise it is a stack
switch and we look for a restore token.
We enable shadow stack at run-time only if program and all used shared
objects, including dlopened ones, are shadow stack enabled, which means
that they must be compiled with GCC 8 or above and glibc 2.28 or above.
We need to save and restore shadow stack only if shadow stack is enabled.
When caller of getcontext, setcontext, swapcontext and makecontext is
compiled with smaller ucontext_t, shadow stack won't be enabled at
run-time. We check if shadow stack is enabled before accessing the
extended field in ucontext_t.
Tested on i386 CET/non-CET machines.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2020-02-14 22:45:34 +00:00
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oSCRATCH1 mreg (EAX)
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oSCRATCH2 mreg (ECX)
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oSCRATCH3 mreg (EDX)
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2005-12-22 05:18:34 +00:00
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oFPREGS mcontext (fpregs)
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oSIGMASK ucontext (uc_sigmask)
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oFPREGSMEM ucontext (__fpregs_mem)
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i386: Enable CET support in ucontext functions
1. getcontext and swapcontext are updated to save the caller's shadow
stack pointer and return address.
2. setcontext and swapcontext are updated to restore shadow stack and
jump to new context directly.
3. makecontext is updated to allocate a new shadow stack and set the
caller's return address to the helper code, L(exitcode).
4. Since we no longer save and restore EAX, ECX and EDX in getcontext,
setcontext and swapcontext, we can use them as scratch register slots
to enable CET in ucontext functions.
Since makecontext allocates a new shadow stack when making a new
context and kernel allocates a new shadow stack for clone/fork/vfork
syscalls, we track the current shadow stack base. In setcontext and
swapcontext, if the target shadow stack base is the same as the current
shadow stack base, we unwind the shadow stack. Otherwise it is a stack
switch and we look for a restore token.
We enable shadow stack at run-time only if program and all used shared
objects, including dlopened ones, are shadow stack enabled, which means
that they must be compiled with GCC 8 or above and glibc 2.28 or above.
We need to save and restore shadow stack only if shadow stack is enabled.
When caller of getcontext, setcontext, swapcontext and makecontext is
compiled with smaller ucontext_t, shadow stack won't be enabled at
run-time. We check if shadow stack is enabled before accessing the
extended field in ucontext_t.
Tested on i386 CET/non-CET machines.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2020-02-14 22:45:34 +00:00
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oSSP ucontext (__ssp)
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