Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 25 Jan 2023 17:01:27 +0700 | Subject | Re: [RFC PATCH v5 1/2] selftests/x86: sysret_rip: Handle syscall in a FRED system | From | Ammar Faizi <> |
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On 1/25/23 4:57 PM, Ammar Faizi wrote: > 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()?
s/%rcx != %r11/%rcx != %rip/
-- Ammar Faizi
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