From cef721e0d53d2b64f2ba177c63a0dfdd7c0daf17 Mon Sep 17 00:00:00 2001 From: Benjamin Berg Date: Mon, 24 Feb 2025 19:18:19 +0100 Subject: [PATCH] um: Store full CSGSFS and SS register from mcontext Doing this allows using registers as retrieved from an mcontext to be pushed to a process using PTRACE_SETREGS. It is not entirely clear to me why CSGSFS was masked. Doing so creates issues when using the mcontext as process state in seccomp and simply copying the register appears to work perfectly fine for ptrace. Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20250224181827.647129-2-benjamin@sipsolutions.net Signed-off-by: Johannes Berg --- arch/x86/um/os-Linux/mcontext.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/um/os-Linux/mcontext.c b/arch/x86/um/os-Linux/mcontext.c index d2f3a595b4ef..37decaa74761 100644 --- a/arch/x86/um/os-Linux/mcontext.c +++ b/arch/x86/um/os-Linux/mcontext.c @@ -28,8 +28,7 @@ void get_regs_from_mc(struct uml_pt_regs *regs, mcontext_t *mc) COPY(RIP); COPY2(EFLAGS, EFL); COPY2(CS, CSGSFS); - regs->gp[CS / sizeof(unsigned long)] &= 0xffff; - regs->gp[CS / sizeof(unsigned long)] |= 3; + regs->gp[SS / sizeof(unsigned long)] = mc->gregs[REG_CSGSFS] >> 48; #endif } -- 2.51.0