6.13-stable review patch. If anyone has any objections, please let me know.
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From: Benjamin Berg benjamin.berg@intel.com
[ Upstream commit 5298b7cffa8461009a4410f4e23f1c50ade39182 ]
It was reported that qemu may not enable the XSTATE CPU extension, which is a requirement after commit 3f17fed21491 ("um: switch to regset API and depend on XSTATE"). Add a fallback to use FXSAVE (FP registers on x86_64 and XFP on i386) which is just a shorter version of the same data. The only difference is that the XSTATE magic should not be set in the signal frame.
Note that this still drops support for the older i386 FP register layout as supporting this would require more backward compatibility to build a correct signal frame.
Fixes: 3f17fed21491 ("um: switch to regset API and depend on XSTATE") Reported-by: SeongJae Park sj@kernel.org Closes: https://lore.kernel.org/r/20241203070218.240797-1-sj@kernel.org Tested-by: SeongJae Park sj@kernel.org Signed-off-by: Benjamin Berg benjamin.berg@intel.com Link: https://patch.msgid.link/20241204074827.1582917-1-benjamin@sipsolutions.net Signed-off-by: Johannes Berg johannes.berg@intel.com Signed-off-by: Richard Weinberger richard@nod.at Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/um/os-Linux/registers.c | 21 ++++++++++++++++++--- arch/x86/um/signal.c | 5 +++++ 2 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/arch/x86/um/os-Linux/registers.c b/arch/x86/um/os-Linux/registers.c index 76eaeb93928cc..eb1cdadc8a61d 100644 --- a/arch/x86/um/os-Linux/registers.c +++ b/arch/x86/um/os-Linux/registers.c @@ -18,6 +18,7 @@ #include <registers.h> #include <sys/mman.h>
+static unsigned long ptrace_regset; unsigned long host_fp_size;
int get_fp_registers(int pid, unsigned long *regs) @@ -27,7 +28,7 @@ int get_fp_registers(int pid, unsigned long *regs) .iov_len = host_fp_size, };
- if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0) + if (ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov) < 0) return -errno; return 0; } @@ -39,7 +40,7 @@ int put_fp_registers(int pid, unsigned long *regs) .iov_len = host_fp_size, };
- if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0) + if (ptrace(PTRACE_SETREGSET, pid, ptrace_regset, &iov) < 0) return -errno; return 0; } @@ -58,9 +59,23 @@ int arch_init_registers(int pid) return -ENOMEM;
/* GDB has x86_xsave_length, which uses x86_cpuid_count */ - ret = ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov); + ptrace_regset = NT_X86_XSTATE; + ret = ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov); if (ret) ret = -errno; + + if (ret == -ENODEV) { +#ifdef CONFIG_X86_32 + ptrace_regset = NT_PRXFPREG; +#else + ptrace_regset = NT_PRFPREG; +#endif + iov.iov_len = 2 * 1024 * 1024; + ret = ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov); + if (ret) + ret = -errno; + } + munmap(iov.iov_base, 2 * 1024 * 1024);
host_fp_size = iov.iov_len; diff --git a/arch/x86/um/signal.c b/arch/x86/um/signal.c index 75087e85b6fdb..ea5b3bcc42456 100644 --- a/arch/x86/um/signal.c +++ b/arch/x86/um/signal.c @@ -187,7 +187,12 @@ static int copy_sc_to_user(struct sigcontext __user *to, * Put magic/size values for userspace. We do not bother to verify them * later on, however, userspace needs them should it try to read the * XSTATE data. And ptrace does not fill in these parts. + * + * Skip this if we do not have an XSTATE frame. */ + if (host_fp_size <= sizeof(to_fp64->fpstate)) + return 0; + BUILD_BUG_ON(sizeof(int) != FP_XSTATE_MAGIC2_SIZE); #ifdef CONFIG_X86_32 __put_user(offsetof(struct _fpstate_32, _fxsr_env) +