Messages in this thread | | | Date | Wed, 25 Jan 2023 16:57:15 +0700 | From | Ammar Faizi <> | Subject | Re: [RFC PATCH v5 1/2] selftests/x86: sysret_rip: Handle syscall in a FRED system |
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On Wed, Jan 25, 2023 at 12:39:26AM -0800, H. Peter Anvin wrote: > > /* Set IP and CX to match so that SYSRET can happen. */ > > ctx->uc_mcontext.gregs[REG_RIP] = rip; > > ctx->uc_mcontext.gregs[REG_RCX] = rip; > > It would be interesting to have the syscall handler try both with and > without this (so it would end up doing both IRET and SYSCALL on legacy.) > Perhaps SIGUSR1 versus SIGUSR2...
Just to clarify this more so I am sure I understand it correctly.
Did you mean to have the same signal handler without modifiying 'REG_RCX' but still change 'REG_RIP'?
IOW, we want to only *remove*:
ctx->uc_mcontext.gregs[REG_RCX] = rip;
and *keep*:
ctx->uc_mcontext.gregs[REG_RIP] = rip;
for the SIGUSR2 handler. Thus, inside the entry64 we will jump to the iret path because %rcx != %r11 upon rt_sigreturn()?
-- Ammar Faizi
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