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[PATCH 4.14 34/77] ftrace/x86_64: Emulate call function while updating in breakpoint handler

by Greg Kroah-Hartman

From: Peter Zijlstra <peterz(a)infradead.org> commit 9e298e8604088a600d8100a111a532a9d342af09 upstream. Nicolai Stange discovered[1] that if live kernel patching is enabled, and the function tracer started tracing the same function that was patched, the conversion of the fentry call site during the translation of going from calling the live kernel patch trampoline to the iterator trampoline, would have as slight window where it didn't call anything. As live kernel patching depends on ftrace to always call its code (to prevent the function being traced from being called, as it will redirect it). This small window would allow the old buggy function to be called, and this can cause undesirable results. Nicolai submitted new patches[2] but these were controversial. As this is similar to the static call emulation issues that came up a while ago[3]. But after some debate[4][5] adding a gap in the stack when entering the breakpoint handler allows for pushing the return address onto the stack to easily emulate a call. [1] http://lkml.kernel.org/r/20180726104029.7736-1-nstange@suse.de [2] http://lkml.kernel.org/r/20190427100639.15074-1-nstange@suse.de [3] http://lkml.kernel.org/r/3cf04e113d71c9f8e4be95fb84a510f085aa4afa.154171145… [4] http://lkml.kernel.org/r/CAHk-=wh5OpheSU8Em_Q3Hg8qw_JtoijxOdPtHru6d+5K8TWM=… [5] http://lkml.kernel.org/r/CAHk-=wjvQxY4DvPrJ6haPgAa6b906h=MwZXO6G8OtiTGe=N7_… [ Live kernel patching is not implemented on x86_32, thus the emulate calls are only for x86_64. ] Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Nicolai Stange <nstange(a)suse.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Borislav Petkov <bp(a)alien8.de> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: the arch/x86 maintainers <x86(a)kernel.org> Cc: Josh Poimboeuf <jpoimboe(a)redhat.com> Cc: Jiri Kosina <jikos(a)kernel.org> Cc: Miroslav Benes <mbenes(a)suse.cz> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Joe Lawrence <joe.lawrence(a)redhat.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk(a)oracle.com> Cc: Tim Chen <tim.c.chen(a)linux.intel.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Mimi Zohar <zohar(a)linux.ibm.com> Cc: Juergen Gross <jgross(a)suse.com> Cc: Nick Desaulniers <ndesaulniers(a)google.com> Cc: Nayna Jain <nayna(a)linux.ibm.com> Cc: Masahiro Yamada <yamada.masahiro(a)socionext.com> Cc: Joerg Roedel <jroedel(a)suse.de> Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest(a)vger.kernel.org> Cc: stable(a)vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Masami Hiramatsu <mhiramat(a)kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> [ Changed to only implement emulated calls for x86_64 ] Signed-off-by: Steven Rostedt (VMware) <rostedt(a)goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- arch/x86/kernel/ftrace.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-) --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -30,6 +30,7 @@ #include <asm/sections.h> #include <asm/ftrace.h> #include <asm/nops.h> +#include <asm/text-patching.h> #ifdef CONFIG_DYNAMIC_FTRACE @@ -229,6 +230,7 @@ int ftrace_modify_call(struct dyn_ftrace } static unsigned long ftrace_update_func; +static unsigned long ftrace_update_func_call; static int update_ftrace_func(unsigned long ip, void *new) { @@ -257,6 +259,8 @@ int ftrace_update_ftrace_func(ftrace_fun unsigned char *new; int ret; + ftrace_update_func_call = (unsigned long)func; + new = ftrace_call_replace(ip, (unsigned long)func); ret = update_ftrace_func(ip, new); @@ -292,13 +296,28 @@ int ftrace_int3_handler(struct pt_regs * if (WARN_ON_ONCE(!regs)) return 0; - ip = regs->ip - 1; - if (!ftrace_location(ip) && !is_ftrace_caller(ip)) - return 0; + ip = regs->ip - INT3_INSN_SIZE; - regs->ip += MCOUNT_INSN_SIZE - 1; +#ifdef CONFIG_X86_64 + if (ftrace_location(ip)) { + int3_emulate_call(regs, (unsigned long)ftrace_regs_caller); + return 1; + } else if (is_ftrace_caller(ip)) { + if (!ftrace_update_func_call) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } + int3_emulate_call(regs, ftrace_update_func_call); + return 1; + } +#else + if (ftrace_location(ip) || is_ftrace_caller(ip)) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } +#endif - return 1; + return 0; } static int ftrace_write(unsigned long ip, const char *val, int size) @@ -869,6 +888,8 @@ void arch_ftrace_update_trampoline(struc func = ftrace_ops_get_func(ops); + ftrace_update_func_call = (unsigned long)func; + /* Do a safe modify in case the trampoline is executing */ new = ftrace_call_replace(ip, (unsigned long)func); ret = update_ftrace_func(ip, new); @@ -965,6 +986,7 @@ static int ftrace_mod_jmp(unsigned long { unsigned char *new; + ftrace_update_func_call = 0UL; new = ftrace_jmp_replace(ip, (unsigned long)func); return update_ftrace_func(ip, new);

5 years, 7 months

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[PATCH 4.19 053/114] ftrace/x86_64: Emulate call function while updating in breakpoint handler

by Greg Kroah-Hartman

From: Peter Zijlstra <peterz(a)infradead.org> commit 9e298e8604088a600d8100a111a532a9d342af09 upstream. Nicolai Stange discovered[1] that if live kernel patching is enabled, and the function tracer started tracing the same function that was patched, the conversion of the fentry call site during the translation of going from calling the live kernel patch trampoline to the iterator trampoline, would have as slight window where it didn't call anything. As live kernel patching depends on ftrace to always call its code (to prevent the function being traced from being called, as it will redirect it). This small window would allow the old buggy function to be called, and this can cause undesirable results. Nicolai submitted new patches[2] but these were controversial. As this is similar to the static call emulation issues that came up a while ago[3]. But after some debate[4][5] adding a gap in the stack when entering the breakpoint handler allows for pushing the return address onto the stack to easily emulate a call. [1] http://lkml.kernel.org/r/20180726104029.7736-1-nstange@suse.de [2] http://lkml.kernel.org/r/20190427100639.15074-1-nstange@suse.de [3] http://lkml.kernel.org/r/3cf04e113d71c9f8e4be95fb84a510f085aa4afa.154171145… [4] http://lkml.kernel.org/r/CAHk-=wh5OpheSU8Em_Q3Hg8qw_JtoijxOdPtHru6d+5K8TWM=… [5] http://lkml.kernel.org/r/CAHk-=wjvQxY4DvPrJ6haPgAa6b906h=MwZXO6G8OtiTGe=N7_… [ Live kernel patching is not implemented on x86_32, thus the emulate calls are only for x86_64. ] Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Nicolai Stange <nstange(a)suse.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Borislav Petkov <bp(a)alien8.de> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: the arch/x86 maintainers <x86(a)kernel.org> Cc: Josh Poimboeuf <jpoimboe(a)redhat.com> Cc: Jiri Kosina <jikos(a)kernel.org> Cc: Miroslav Benes <mbenes(a)suse.cz> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Joe Lawrence <joe.lawrence(a)redhat.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk(a)oracle.com> Cc: Tim Chen <tim.c.chen(a)linux.intel.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Mimi Zohar <zohar(a)linux.ibm.com> Cc: Juergen Gross <jgross(a)suse.com> Cc: Nick Desaulniers <ndesaulniers(a)google.com> Cc: Nayna Jain <nayna(a)linux.ibm.com> Cc: Masahiro Yamada <yamada.masahiro(a)socionext.com> Cc: Joerg Roedel <jroedel(a)suse.de> Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest(a)vger.kernel.org> Cc: stable(a)vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Masami Hiramatsu <mhiramat(a)kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> [ Changed to only implement emulated calls for x86_64 ] Signed-off-by: Steven Rostedt (VMware) <rostedt(a)goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- arch/x86/kernel/ftrace.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-) --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -29,6 +29,7 @@ #include <asm/kprobes.h> #include <asm/ftrace.h> #include <asm/nops.h> +#include <asm/text-patching.h> #ifdef CONFIG_DYNAMIC_FTRACE @@ -228,6 +229,7 @@ int ftrace_modify_call(struct dyn_ftrace } static unsigned long ftrace_update_func; +static unsigned long ftrace_update_func_call; static int update_ftrace_func(unsigned long ip, void *new) { @@ -256,6 +258,8 @@ int ftrace_update_ftrace_func(ftrace_fun unsigned char *new; int ret; + ftrace_update_func_call = (unsigned long)func; + new = ftrace_call_replace(ip, (unsigned long)func); ret = update_ftrace_func(ip, new); @@ -291,13 +295,28 @@ int ftrace_int3_handler(struct pt_regs * if (WARN_ON_ONCE(!regs)) return 0; - ip = regs->ip - 1; - if (!ftrace_location(ip) && !is_ftrace_caller(ip)) - return 0; + ip = regs->ip - INT3_INSN_SIZE; - regs->ip += MCOUNT_INSN_SIZE - 1; +#ifdef CONFIG_X86_64 + if (ftrace_location(ip)) { + int3_emulate_call(regs, (unsigned long)ftrace_regs_caller); + return 1; + } else if (is_ftrace_caller(ip)) { + if (!ftrace_update_func_call) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } + int3_emulate_call(regs, ftrace_update_func_call); + return 1; + } +#else + if (ftrace_location(ip) || is_ftrace_caller(ip)) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } +#endif - return 1; + return 0; } static int ftrace_write(unsigned long ip, const char *val, int size) @@ -868,6 +887,8 @@ void arch_ftrace_update_trampoline(struc func = ftrace_ops_get_func(ops); + ftrace_update_func_call = (unsigned long)func; + /* Do a safe modify in case the trampoline is executing */ new = ftrace_call_replace(ip, (unsigned long)func); ret = update_ftrace_func(ip, new); @@ -964,6 +985,7 @@ static int ftrace_mod_jmp(unsigned long { unsigned char *new; + ftrace_update_func_call = 0UL; new = ftrace_jmp_replace(ip, (unsigned long)func); return update_ftrace_func(ip, new);

5 years, 7 months

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[PATCH 4.19 052/114] x86_64: Allow breakpoints to emulate call instructions

by Greg Kroah-Hartman

From: Peter Zijlstra <peterz(a)infradead.org> commit 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 upstream. In order to allow breakpoints to emulate call instructions, they need to push the return address onto the stack. The x86_64 int3 handler adds a small gap to allow the stack to grow some. Use this gap to add the return address to be able to emulate a call instruction at the breakpoint location. These helper functions are added: int3_emulate_jmp(): changes the location of the regs->ip to return there. (The next two are only for x86_64) int3_emulate_push(): to push the address onto the gap in the stack int3_emulate_call(): push the return address and change regs->ip Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Nicolai Stange <nstange(a)suse.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Borislav Petkov <bp(a)alien8.de> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: the arch/x86 maintainers <x86(a)kernel.org> Cc: Josh Poimboeuf <jpoimboe(a)redhat.com> Cc: Jiri Kosina <jikos(a)kernel.org> Cc: Miroslav Benes <mbenes(a)suse.cz> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Joe Lawrence <joe.lawrence(a)redhat.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk(a)oracle.com> Cc: Tim Chen <tim.c.chen(a)linux.intel.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Mimi Zohar <zohar(a)linux.ibm.com> Cc: Juergen Gross <jgross(a)suse.com> Cc: Nick Desaulniers <ndesaulniers(a)google.com> Cc: Nayna Jain <nayna(a)linux.ibm.com> Cc: Masahiro Yamada <yamada.masahiro(a)socionext.com> Cc: Joerg Roedel <jroedel(a)suse.de> Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest(a)vger.kernel.org> Cc: stable(a)vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Masami Hiramatsu <mhiramat(a)kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> [ Modified to only work for x86_64 and added comment to int3_emulate_push() ] Signed-off-by: Steven Rostedt (VMware) <rostedt(a)goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- arch/x86/include/asm/text-patching.h | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -39,4 +39,32 @@ extern int poke_int3_handler(struct pt_r extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); extern int after_bootmem; +static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip) +{ + regs->ip = ip; +} + +#define INT3_INSN_SIZE 1 +#define CALL_INSN_SIZE 5 + +#ifdef CONFIG_X86_64 +static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val) +{ + /* + * The int3 handler in entry_64.S adds a gap between the + * stack where the break point happened, and the saving of + * pt_regs. We can extend the original stack because of + * this gap. See the idtentry macro's create_gap option. + */ + regs->sp -= sizeof(unsigned long); + *(unsigned long *)regs->sp = val; +} + +static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func) +{ + int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE); + int3_emulate_jmp(regs, func); +} +#endif + #endif /* _ASM_X86_TEXT_PATCHING_H */

5 years, 7 months

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[PATCH 4.14 33/77] x86_64: Allow breakpoints to emulate call instructions

by Greg Kroah-Hartman

From: Peter Zijlstra <peterz(a)infradead.org> commit 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 upstream. In order to allow breakpoints to emulate call instructions, they need to push the return address onto the stack. The x86_64 int3 handler adds a small gap to allow the stack to grow some. Use this gap to add the return address to be able to emulate a call instruction at the breakpoint location. These helper functions are added: int3_emulate_jmp(): changes the location of the regs->ip to return there. (The next two are only for x86_64) int3_emulate_push(): to push the address onto the gap in the stack int3_emulate_call(): push the return address and change regs->ip Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Nicolai Stange <nstange(a)suse.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Borislav Petkov <bp(a)alien8.de> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: the arch/x86 maintainers <x86(a)kernel.org> Cc: Josh Poimboeuf <jpoimboe(a)redhat.com> Cc: Jiri Kosina <jikos(a)kernel.org> Cc: Miroslav Benes <mbenes(a)suse.cz> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Joe Lawrence <joe.lawrence(a)redhat.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk(a)oracle.com> Cc: Tim Chen <tim.c.chen(a)linux.intel.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Mimi Zohar <zohar(a)linux.ibm.com> Cc: Juergen Gross <jgross(a)suse.com> Cc: Nick Desaulniers <ndesaulniers(a)google.com> Cc: Nayna Jain <nayna(a)linux.ibm.com> Cc: Masahiro Yamada <yamada.masahiro(a)socionext.com> Cc: Joerg Roedel <jroedel(a)suse.de> Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest(a)vger.kernel.org> Cc: stable(a)vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Masami Hiramatsu <mhiramat(a)kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> [ Modified to only work for x86_64 and added comment to int3_emulate_push() ] Signed-off-by: Steven Rostedt (VMware) <rostedt(a)goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- arch/x86/include/asm/text-patching.h | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -38,4 +38,32 @@ extern void *text_poke(void *addr, const extern int poke_int3_handler(struct pt_regs *regs); extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); +static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip) +{ + regs->ip = ip; +} + +#define INT3_INSN_SIZE 1 +#define CALL_INSN_SIZE 5 + +#ifdef CONFIG_X86_64 +static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val) +{ + /* + * The int3 handler in entry_64.S adds a gap between the + * stack where the break point happened, and the saving of + * pt_regs. We can extend the original stack because of + * this gap. See the idtentry macro's create_gap option. + */ + regs->sp -= sizeof(unsigned long); + *(unsigned long *)regs->sp = val; +} + +static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func) +{ + int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE); + int3_emulate_jmp(regs, func); +} +#endif + #endif /* _ASM_X86_TEXT_PATCHING_H */

5 years, 7 months

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[PATCH bpf v1 0/3] Test the 32bit narrow reads

by Krzesimir Nowak

These patches try to test the fix made in commit e2f7fc0ac695 ("bpf: fix undefined behavior in narrow load handling"). The problem existed in the generated BPF bytecode that was doing a 32bit narrow read of a 64bit field, so to test it the code would need to be executed. Currently the only such field exists in BPF_PROG_TYPE_PERF_EVENT, which is not supported by bpf_prog_test_run(). First commit adds the test, but since I can't run it, I'm not sure if it is even valid (because endianness, for example). Second commit adds a message to test_verifier when it couldn't run the program because of lack permissions or program type being not supported. Third commit fixes a possible problem with errno. With these patches, I get the following output on my test: /kernel/tools/testing/selftests/bpf$ sudo ./test_verifier 920 920 #920/p 32bit loads of a 64bit field (both least and most significant words) Did not run the program (not supported) OK Summary: 1 PASSED, 0 SKIPPED, 0 FAILED So it looks like I need to pick a different approach. Krzesimir Nowak (3): selftests/bpf: Test correctness of narrow 32bit read on 64bit field selftests/bpf: Print a message when tester could not run a program selftests/bpf: Avoid a clobbering of errno tools/testing/selftests/bpf/test_verifier.c | 19 +++++++++++++++---- .../testing/selftests/bpf/verifier/var_off.c | 15 +++++++++++++++ 2 files changed, 30 insertions(+), 4 deletions(-) -- 2.20.1

5 years, 7 months

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[RFC PATCH 0/4] KVM selftests for s390x

by Thomas Huth

This patch series enables the KVM selftests for s390x. As a first test, the sync_regs from x86 has been adapted to s390x. Please note that the ucall() interface is not used yet - since s390x neither has PIO nor MMIO, this needs some more work first before it becomes usable (we likely should use a DIAG hypercall here, which is what the sync_reg test is currently using, too...). Thomas Huth (4): KVM: selftests: Guard struct kvm_vcpu_events with __KVM_HAVE_VCPU_EVENTS KVM: selftests: Align memory region addresses to 1M on s390x KVM: selftests: Add processor code for s390x KVM: selftests: Add the sync_regs test for s390x MAINTAINERS | 2 + tools/testing/selftests/kvm/Makefile | 3 + .../testing/selftests/kvm/include/kvm_util.h | 2 + .../selftests/kvm/include/s390x/processor.h | 22 ++ tools/testing/selftests/kvm/lib/kvm_util.c | 24 +- .../selftests/kvm/lib/s390x/processor.c | 277 ++++++++++++++++++ .../selftests/kvm/s390x/sync_regs_test.c | 151 ++++++++++ 7 files changed, 476 insertions(+), 5 deletions(-) create mode 100644 tools/testing/selftests/kvm/include/s390x/processor.h create mode 100644 tools/testing/selftests/kvm/lib/s390x/processor.c create mode 100644 tools/testing/selftests/kvm/s390x/sync_regs_test.c -- 2.21.0

5 years, 7 months

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FAILED: patch "[PATCH] ftrace/x86_64: Emulate call function while updating in" failed to apply to 4.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 9e298e8604088a600d8100a111a532a9d342af09 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra <peterz(a)infradead.org> Date: Wed, 1 May 2019 15:11:17 +0200 Subject: [PATCH] ftrace/x86_64: Emulate call function while updating in breakpoint handler Nicolai Stange discovered[1] that if live kernel patching is enabled, and the function tracer started tracing the same function that was patched, the conversion of the fentry call site during the translation of going from calling the live kernel patch trampoline to the iterator trampoline, would have as slight window where it didn't call anything. As live kernel patching depends on ftrace to always call its code (to prevent the function being traced from being called, as it will redirect it). This small window would allow the old buggy function to be called, and this can cause undesirable results. Nicolai submitted new patches[2] but these were controversial. As this is similar to the static call emulation issues that came up a while ago[3]. But after some debate[4][5] adding a gap in the stack when entering the breakpoint handler allows for pushing the return address onto the stack to easily emulate a call. [1] http://lkml.kernel.org/r/20180726104029.7736-1-nstange@suse.de [2] http://lkml.kernel.org/r/20190427100639.15074-1-nstange@suse.de [3] http://lkml.kernel.org/r/3cf04e113d71c9f8e4be95fb84a510f085aa4afa.154171145… [4] http://lkml.kernel.org/r/CAHk-=wh5OpheSU8Em_Q3Hg8qw_JtoijxOdPtHru6d+5K8TWM=… [5] http://lkml.kernel.org/r/CAHk-=wjvQxY4DvPrJ6haPgAa6b906h=MwZXO6G8OtiTGe=N7_… [ Live kernel patching is not implemented on x86_32, thus the emulate calls are only for x86_64. ] Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Nicolai Stange <nstange(a)suse.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Borislav Petkov <bp(a)alien8.de> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: the arch/x86 maintainers <x86(a)kernel.org> Cc: Josh Poimboeuf <jpoimboe(a)redhat.com> Cc: Jiri Kosina <jikos(a)kernel.org> Cc: Miroslav Benes <mbenes(a)suse.cz> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Joe Lawrence <joe.lawrence(a)redhat.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk(a)oracle.com> Cc: Tim Chen <tim.c.chen(a)linux.intel.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Mimi Zohar <zohar(a)linux.ibm.com> Cc: Juergen Gross <jgross(a)suse.com> Cc: Nick Desaulniers <ndesaulniers(a)google.com> Cc: Nayna Jain <nayna(a)linux.ibm.com> Cc: Masahiro Yamada <yamada.masahiro(a)socionext.com> Cc: Joerg Roedel <jroedel(a)suse.de> Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest(a)vger.kernel.org> Cc: stable(a)vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Masami Hiramatsu <mhiramat(a)kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> [ Changed to only implement emulated calls for x86_64 ] Signed-off-by: Steven Rostedt (VMware) <rostedt(a)goodmis.org> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index ef49517f6bb2..bd553b3af22e 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -29,6 +29,7 @@ #include <asm/kprobes.h> #include <asm/ftrace.h> #include <asm/nops.h> +#include <asm/text-patching.h> #ifdef CONFIG_DYNAMIC_FTRACE @@ -231,6 +232,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, } static unsigned long ftrace_update_func; +static unsigned long ftrace_update_func_call; static int update_ftrace_func(unsigned long ip, void *new) { @@ -259,6 +261,8 @@ int ftrace_update_ftrace_func(ftrace_func_t func) unsigned char *new; int ret; + ftrace_update_func_call = (unsigned long)func; + new = ftrace_call_replace(ip, (unsigned long)func); ret = update_ftrace_func(ip, new); @@ -294,13 +298,28 @@ int ftrace_int3_handler(struct pt_regs *regs) if (WARN_ON_ONCE(!regs)) return 0; - ip = regs->ip - 1; - if (!ftrace_location(ip) && !is_ftrace_caller(ip)) - return 0; + ip = regs->ip - INT3_INSN_SIZE; - regs->ip += MCOUNT_INSN_SIZE - 1; +#ifdef CONFIG_X86_64 + if (ftrace_location(ip)) { + int3_emulate_call(regs, (unsigned long)ftrace_regs_caller); + return 1; + } else if (is_ftrace_caller(ip)) { + if (!ftrace_update_func_call) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } + int3_emulate_call(regs, ftrace_update_func_call); + return 1; + } +#else + if (ftrace_location(ip) || is_ftrace_caller(ip)) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } +#endif - return 1; + return 0; } NOKPROBE_SYMBOL(ftrace_int3_handler); @@ -859,6 +878,8 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops) func = ftrace_ops_get_func(ops); + ftrace_update_func_call = (unsigned long)func; + /* Do a safe modify in case the trampoline is executing */ new = ftrace_call_replace(ip, (unsigned long)func); ret = update_ftrace_func(ip, new); @@ -960,6 +981,7 @@ static int ftrace_mod_jmp(unsigned long ip, void *func) { unsigned char *new; + ftrace_update_func_call = 0UL; new = ftrace_jmp_replace(ip, (unsigned long)func); return update_ftrace_func(ip, new);

5 years, 7 months

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FAILED: patch "[PATCH] ftrace/x86_64: Emulate call function while updating in" failed to apply to 4.9-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 9e298e8604088a600d8100a111a532a9d342af09 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra <peterz(a)infradead.org> Date: Wed, 1 May 2019 15:11:17 +0200 Subject: [PATCH] ftrace/x86_64: Emulate call function while updating in breakpoint handler Nicolai Stange discovered[1] that if live kernel patching is enabled, and the function tracer started tracing the same function that was patched, the conversion of the fentry call site during the translation of going from calling the live kernel patch trampoline to the iterator trampoline, would have as slight window where it didn't call anything. As live kernel patching depends on ftrace to always call its code (to prevent the function being traced from being called, as it will redirect it). This small window would allow the old buggy function to be called, and this can cause undesirable results. Nicolai submitted new patches[2] but these were controversial. As this is similar to the static call emulation issues that came up a while ago[3]. But after some debate[4][5] adding a gap in the stack when entering the breakpoint handler allows for pushing the return address onto the stack to easily emulate a call. [1] http://lkml.kernel.org/r/20180726104029.7736-1-nstange@suse.de [2] http://lkml.kernel.org/r/20190427100639.15074-1-nstange@suse.de [3] http://lkml.kernel.org/r/3cf04e113d71c9f8e4be95fb84a510f085aa4afa.154171145… [4] http://lkml.kernel.org/r/CAHk-=wh5OpheSU8Em_Q3Hg8qw_JtoijxOdPtHru6d+5K8TWM=… [5] http://lkml.kernel.org/r/CAHk-=wjvQxY4DvPrJ6haPgAa6b906h=MwZXO6G8OtiTGe=N7_… [ Live kernel patching is not implemented on x86_32, thus the emulate calls are only for x86_64. ] Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Nicolai Stange <nstange(a)suse.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Borislav Petkov <bp(a)alien8.de> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: the arch/x86 maintainers <x86(a)kernel.org> Cc: Josh Poimboeuf <jpoimboe(a)redhat.com> Cc: Jiri Kosina <jikos(a)kernel.org> Cc: Miroslav Benes <mbenes(a)suse.cz> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Joe Lawrence <joe.lawrence(a)redhat.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk(a)oracle.com> Cc: Tim Chen <tim.c.chen(a)linux.intel.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Mimi Zohar <zohar(a)linux.ibm.com> Cc: Juergen Gross <jgross(a)suse.com> Cc: Nick Desaulniers <ndesaulniers(a)google.com> Cc: Nayna Jain <nayna(a)linux.ibm.com> Cc: Masahiro Yamada <yamada.masahiro(a)socionext.com> Cc: Joerg Roedel <jroedel(a)suse.de> Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest(a)vger.kernel.org> Cc: stable(a)vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Masami Hiramatsu <mhiramat(a)kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> [ Changed to only implement emulated calls for x86_64 ] Signed-off-by: Steven Rostedt (VMware) <rostedt(a)goodmis.org> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index ef49517f6bb2..bd553b3af22e 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -29,6 +29,7 @@ #include <asm/kprobes.h> #include <asm/ftrace.h> #include <asm/nops.h> +#include <asm/text-patching.h> #ifdef CONFIG_DYNAMIC_FTRACE @@ -231,6 +232,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, } static unsigned long ftrace_update_func; +static unsigned long ftrace_update_func_call; static int update_ftrace_func(unsigned long ip, void *new) { @@ -259,6 +261,8 @@ int ftrace_update_ftrace_func(ftrace_func_t func) unsigned char *new; int ret; + ftrace_update_func_call = (unsigned long)func; + new = ftrace_call_replace(ip, (unsigned long)func); ret = update_ftrace_func(ip, new); @@ -294,13 +298,28 @@ int ftrace_int3_handler(struct pt_regs *regs) if (WARN_ON_ONCE(!regs)) return 0; - ip = regs->ip - 1; - if (!ftrace_location(ip) && !is_ftrace_caller(ip)) - return 0; + ip = regs->ip - INT3_INSN_SIZE; - regs->ip += MCOUNT_INSN_SIZE - 1; +#ifdef CONFIG_X86_64 + if (ftrace_location(ip)) { + int3_emulate_call(regs, (unsigned long)ftrace_regs_caller); + return 1; + } else if (is_ftrace_caller(ip)) { + if (!ftrace_update_func_call) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } + int3_emulate_call(regs, ftrace_update_func_call); + return 1; + } +#else + if (ftrace_location(ip) || is_ftrace_caller(ip)) { + int3_emulate_jmp(regs, ip + CALL_INSN_SIZE); + return 1; + } +#endif - return 1; + return 0; } NOKPROBE_SYMBOL(ftrace_int3_handler); @@ -859,6 +878,8 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops) func = ftrace_ops_get_func(ops); + ftrace_update_func_call = (unsigned long)func; + /* Do a safe modify in case the trampoline is executing */ new = ftrace_call_replace(ip, (unsigned long)func); ret = update_ftrace_func(ip, new); @@ -960,6 +981,7 @@ static int ftrace_mod_jmp(unsigned long ip, void *func) { unsigned char *new; + ftrace_update_func_call = 0UL; new = ftrace_jmp_replace(ip, (unsigned long)func); return update_ftrace_func(ip, new);

5 years, 7 months

1
0
0 0

FAILED: patch "[PATCH] x86_64: Allow breakpoints to emulate call instructions" failed to apply to 4.4-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra <peterz(a)infradead.org> Date: Wed, 1 May 2019 15:11:17 +0200 Subject: [PATCH] x86_64: Allow breakpoints to emulate call instructions In order to allow breakpoints to emulate call instructions, they need to push the return address onto the stack. The x86_64 int3 handler adds a small gap to allow the stack to grow some. Use this gap to add the return address to be able to emulate a call instruction at the breakpoint location. These helper functions are added: int3_emulate_jmp(): changes the location of the regs->ip to return there. (The next two are only for x86_64) int3_emulate_push(): to push the address onto the gap in the stack int3_emulate_call(): push the return address and change regs->ip Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Nicolai Stange <nstange(a)suse.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Borislav Petkov <bp(a)alien8.de> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: the arch/x86 maintainers <x86(a)kernel.org> Cc: Josh Poimboeuf <jpoimboe(a)redhat.com> Cc: Jiri Kosina <jikos(a)kernel.org> Cc: Miroslav Benes <mbenes(a)suse.cz> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Joe Lawrence <joe.lawrence(a)redhat.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk(a)oracle.com> Cc: Tim Chen <tim.c.chen(a)linux.intel.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Mimi Zohar <zohar(a)linux.ibm.com> Cc: Juergen Gross <jgross(a)suse.com> Cc: Nick Desaulniers <ndesaulniers(a)google.com> Cc: Nayna Jain <nayna(a)linux.ibm.com> Cc: Masahiro Yamada <yamada.masahiro(a)socionext.com> Cc: Joerg Roedel <jroedel(a)suse.de> Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest(a)vger.kernel.org> Cc: stable(a)vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Masami Hiramatsu <mhiramat(a)kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> [ Modified to only work for x86_64 and added comment to int3_emulate_push() ] Signed-off-by: Steven Rostedt (VMware) <rostedt(a)goodmis.org> diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h index e85ff65c43c3..05861cc08787 100644 --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -39,4 +39,32 @@ extern int poke_int3_handler(struct pt_regs *regs); extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); extern int after_bootmem; +static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip) +{ + regs->ip = ip; +} + +#define INT3_INSN_SIZE 1 +#define CALL_INSN_SIZE 5 + +#ifdef CONFIG_X86_64 +static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val) +{ + /* + * The int3 handler in entry_64.S adds a gap between the + * stack where the break point happened, and the saving of + * pt_regs. We can extend the original stack because of + * this gap. See the idtentry macro's create_gap option. + */ + regs->sp -= sizeof(unsigned long); + *(unsigned long *)regs->sp = val; +} + +static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func) +{ + int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE); + int3_emulate_jmp(regs, func); +} +#endif + #endif /* _ASM_X86_TEXT_PATCHING_H */

5 years, 7 months

1
0
0 0

FAILED: patch "[PATCH] x86_64: Allow breakpoints to emulate call instructions" failed to apply to 4.9-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra <peterz(a)infradead.org> Date: Wed, 1 May 2019 15:11:17 +0200 Subject: [PATCH] x86_64: Allow breakpoints to emulate call instructions In order to allow breakpoints to emulate call instructions, they need to push the return address onto the stack. The x86_64 int3 handler adds a small gap to allow the stack to grow some. Use this gap to add the return address to be able to emulate a call instruction at the breakpoint location. These helper functions are added: int3_emulate_jmp(): changes the location of the regs->ip to return there. (The next two are only for x86_64) int3_emulate_push(): to push the address onto the gap in the stack int3_emulate_call(): push the return address and change regs->ip Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Nicolai Stange <nstange(a)suse.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Borislav Petkov <bp(a)alien8.de> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: the arch/x86 maintainers <x86(a)kernel.org> Cc: Josh Poimboeuf <jpoimboe(a)redhat.com> Cc: Jiri Kosina <jikos(a)kernel.org> Cc: Miroslav Benes <mbenes(a)suse.cz> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Joe Lawrence <joe.lawrence(a)redhat.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Konrad Rzeszutek Wilk <konrad.wilk(a)oracle.com> Cc: Tim Chen <tim.c.chen(a)linux.intel.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Mimi Zohar <zohar(a)linux.ibm.com> Cc: Juergen Gross <jgross(a)suse.com> Cc: Nick Desaulniers <ndesaulniers(a)google.com> Cc: Nayna Jain <nayna(a)linux.ibm.com> Cc: Masahiro Yamada <yamada.masahiro(a)socionext.com> Cc: Joerg Roedel <jroedel(a)suse.de> Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest(a)vger.kernel.org> Cc: stable(a)vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Nicolai Stange <nstange(a)suse.de> Reviewed-by: Masami Hiramatsu <mhiramat(a)kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> [ Modified to only work for x86_64 and added comment to int3_emulate_push() ] Signed-off-by: Steven Rostedt (VMware) <rostedt(a)goodmis.org> diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h index e85ff65c43c3..05861cc08787 100644 --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -39,4 +39,32 @@ extern int poke_int3_handler(struct pt_regs *regs); extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); extern int after_bootmem; +static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip) +{ + regs->ip = ip; +} + +#define INT3_INSN_SIZE 1 +#define CALL_INSN_SIZE 5 + +#ifdef CONFIG_X86_64 +static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val) +{ + /* + * The int3 handler in entry_64.S adds a gap between the + * stack where the break point happened, and the saving of + * pt_regs. We can extend the original stack because of + * this gap. See the idtentry macro's create_gap option. + */ + regs->sp -= sizeof(unsigned long); + *(unsigned long *)regs->sp = val; +} + +static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func) +{ + int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE); + int3_emulate_jmp(regs, func); +} +#endif + #endif /* _ASM_X86_TEXT_PATCHING_H */

5 years, 7 months

1
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