[PATCH v4 00/25] linux-user: Move signal trampolines to new page

[PATCH v4 00/25] linux-user: Move signal trampolines to new page

[Richard Henderson]

Changes for v4:
  * Drop nios2 changes -- I still haven't built a full toolchain.
  * Clean up arm changes.
  * Minur i386 pointer type changes.

Changes for v3:
  * Drop vdsos, reinstate setup_sigtramp for all targets.
  * Incorporate nios2 kuser page emulation, which contains
    the sigtramp for that target.

Changes for v2:
  * Add vdsos for aarch64, arm, i386, riscv.
  * Drop setup_sigtramp for any target with a vdso.
  * Drop arm v1 signal support.
  * Simplify ppc encode_trampoline.


r~


Richard Henderson (25):
  linux-user: Add infrastructure for a signal trampoline page
  linux-user/aarch64: Implement setup_sigtramp
  linux-user/arm: Drop v1 signal frames
  linux-user/arm: Drop "_v2" from symbols in signal.c
  linux-user/arm: Implement setup_sigtramp
  linux-user/alpha: Implement setup_sigtramp
  linux-user/cris: Implement setup_sigtramp
  linux-user/hexagon: Implement setup_sigtramp
  linux-user/hppa: Document non-use of setup_sigtramp
  linux-user/i386: Implement setup_sigtramp
  linux-user/x86_64: Raise SIGSEGV if SA_RESTORER not set
  linux-user/m68k: Implement setup_sigtramp
  linux-user/microblaze: Implement setup_sigtramp
  linux-user/mips: Tidy install_sigtramp
  linux-user/mips: Implement setup_sigtramp
  linux-user/nios2: Document non-use of setup_sigtramp
  linux-user/openrisc: Implement setup_sigtramp
  linux-user/ppc: Simplify encode_trampoline
  linux-user/ppc: Implement setup_sigtramp
  linux-user/riscv: Implement setup_sigtramp
  linux-user/s390x: Implement setup_sigtramp
  linux-user/sh4: Implement setup_sigtramp
  linux-user/sparc: Implement setup_sigtramp
  linux-user/xtensa: Implement setup_sigtramp
  linux-user: Remove default for TARGET_ARCH_HAS_SIGTRAMP_PAGE

 linux-user/aarch64/target_signal.h    |   2 +
 linux-user/alpha/target_signal.h      |   1 +
 linux-user/arm/target_signal.h        |   2 +
 linux-user/cris/target_signal.h       |   2 +
 linux-user/hexagon/target_signal.h    |   2 +
 linux-user/hppa/target_signal.h       |  14 +
 linux-user/i386/target_signal.h       |   2 +
 linux-user/m68k/target_signal.h       |   2 +
 linux-user/microblaze/target_signal.h |   2 +
 linux-user/mips/target_signal.h       |   1 +
 linux-user/mips64/target_signal.h     |   2 +
 linux-user/nios2/target_signal.h      |   3 +
 linux-user/openrisc/target_signal.h   |   2 +
 linux-user/ppc/target_signal.h        |   2 +
 linux-user/riscv/target_signal.h      |   2 +
 linux-user/s390x/target_signal.h      |   2 +
 linux-user/sh4/target_signal.h        |   2 +
 linux-user/signal-common.h            |   6 +
 linux-user/sparc/target_signal.h      |   4 +
 linux-user/x86_64/target_signal.h     |   3 +
 linux-user/xtensa/target_signal.h     |   2 +
 linux-user/aarch64/signal.c           |  34 +-
 linux-user/alpha/signal.c             |  34 +-
 linux-user/arm/signal.c               | 583 +++++++++-----------------
 linux-user/cris/signal.c              |  29 +-
 linux-user/elfload.c                  |  14 +
 linux-user/hexagon/signal.c           |  19 +-
 linux-user/i386/signal.c              |  65 ++-
 linux-user/m68k/signal.c              |  47 +--
 linux-user/microblaze/signal.c        |  24 +-
 linux-user/mips/signal.c              |  39 +-
 linux-user/openrisc/signal.c          |  22 +-
 linux-user/ppc/signal.c               |  40 +-
 linux-user/riscv/signal.c             |  22 +-
 linux-user/s390x/signal.c             |  24 +-
 linux-user/sh4/signal.c               |  40 +-
 linux-user/signal.c                   |   3 +
 linux-user/sparc/signal.c             |  40 +-
 linux-user/xtensa/signal.c            |  56 ++-
 39 files changed, 603 insertions(+), 592 deletions(-)

-- 
2.25.1

[PATCH v4 01/25] linux-user: Add infrastructure for a signal trampoline page

[Richard Henderson]

Allocate a page to hold the signal trampoline(s).
Invoke a guest-specific hook to fill in the contents
of the page before marking it read-execute again.

Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/signal-common.h |  6 ++++++
 linux-user/elfload.c       | 18 ++++++++++++++++++
 linux-user/signal.c        |  3 +++
 3 files changed, 27 insertions(+)

diff --git a/linux-user/signal-common.h b/linux-user/signal-common.h
index 79511becb4..7457f8025c 100644
--- a/linux-user/signal-common.h
+++ b/linux-user/signal-common.h
@@ -20,6 +20,12 @@
 #ifndef SIGNAL_COMMON_H
 #define SIGNAL_COMMON_H
 
+/* Fallback addresses into sigtramp page. */
+extern abi_ulong default_sigreturn;
+extern abi_ulong default_rt_sigreturn;
+
+void setup_sigtramp(abi_ulong tramp_page);
+
 int on_sig_stack(unsigned long sp);
 int sas_ss_flags(unsigned long sp);
 abi_ulong target_sigsp(abi_ulong sp, struct target_sigaction *ka);
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 5f9e2141ad..459a26ef1d 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -7,6 +7,7 @@
 
 #include "qemu.h"
 #include "user-internals.h"
+#include "signal-common.h"
 #include "loader.h"
 #include "user-mmap.h"
 #include "disas/disas.h"
@@ -17,6 +18,7 @@
 #include "qemu/units.h"
 #include "qemu/selfmap.h"
 #include "qapi/error.h"
+#include "target_signal.h"
 
 #ifdef _ARCH_PPC64
 #undef ARCH_DLINFO
@@ -28,6 +30,10 @@
 #undef ELF_ARCH
 #endif
 
+#ifndef TARGET_ARCH_HAS_SIGTRAMP_PAGE
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
+#endif
+
 #define ELF_OSABI   ELFOSABI_SYSV
 
 /* from personality.h */
@@ -3249,6 +3255,18 @@ int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
 #endif
     }
 
+    /*
+     * TODO: load a vdso, which would also contain the signal trampolines.
+     * Otherwise, allocate a private page to hold them.
+     */
+    if (TARGET_ARCH_HAS_SIGTRAMP_PAGE) {
+        abi_ulong tramp_page = target_mmap(0, TARGET_PAGE_SIZE,
+                                           PROT_READ | PROT_WRITE,
+                                           MAP_PRIVATE | MAP_ANON, -1, 0);
+        setup_sigtramp(tramp_page);
+        target_mprotect(tramp_page, TARGET_PAGE_SIZE, PROT_READ | PROT_EXEC);
+    }
+
     bprm->p = create_elf_tables(bprm->p, bprm->argc, bprm->envc, &elf_ex,
                                 info, (elf_interpreter ? &interp_info : NULL));
     info->start_stack = bprm->p;
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 2038216455..14d8fdfde1 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -35,6 +35,9 @@ static struct target_sigaction sigact_table[TARGET_NSIG];
 static void host_signal_handler(int host_signum, siginfo_t *info,
                                 void *puc);
 
+/* Fallback addresses into sigtramp page. */
+abi_ulong default_sigreturn;
+abi_ulong default_rt_sigreturn;
 
 /*
  * System includes define _NSIG as SIGRTMAX + 1,
-- 
2.25.1

[PATCH v4 02/25] linux-user/aarch64: Implement setup_sigtramp

[Richard Henderson]

Create and record the rt signal trampoline.
Use it when the guest does not use SA_RESTORER.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/aarch64/target_signal.h |  2 ++
 linux-user/aarch64/signal.c        | 34 ++++++++++++++++++------------
 2 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/linux-user/aarch64/target_signal.h b/linux-user/aarch64/target_signal.h
index 18013e1b23..7580d99403 100644
--- a/linux-user/aarch64/target_signal.h
+++ b/linux-user/aarch64/target_signal.h
@@ -25,4 +25,6 @@ typedef struct target_sigaltstack {
 #define TARGET_SEGV_MTESERR  9  /* Synchronous ARM MTE exception */
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* AARCH64_TARGET_SIGNAL_H */
diff --git a/linux-user/aarch64/signal.c b/linux-user/aarch64/signal.c
index 49025648cb..29c52db3f1 100644
--- a/linux-user/aarch64/signal.c
+++ b/linux-user/aarch64/signal.c
@@ -109,7 +109,6 @@ struct target_rt_sigframe {
 struct target_rt_frame_record {
     uint64_t fp;
     uint64_t lr;
-    uint32_t tramp[2];
 };
 
 static void target_setup_general_frame(struct target_rt_sigframe *sf,
@@ -461,9 +460,9 @@ static void target_setup_frame(int usig, struct target_sigaction *ka,
     layout.total_size = MAX(layout.total_size,
                             sizeof(struct target_rt_sigframe));
 
-    /* Reserve space for the return code.  On a real system this would
-     * be within the VDSO.  So, despite the name this is not a "real"
-     * record within the frame.
+    /*
+     * Reserve space for the standard frame unwind pair: fp, lr.
+     * Despite the name this is not a "real" record within the frame.
      */
     fr_ofs = layout.total_size;
     layout.total_size += sizeof(struct target_rt_frame_record);
@@ -496,15 +495,7 @@ static void target_setup_frame(int usig, struct target_sigaction *ka,
     if (ka->sa_flags & TARGET_SA_RESTORER) {
         return_addr = ka->sa_restorer;
     } else {
-        /*
-         * mov x8,#__NR_rt_sigreturn; svc #0
-         * Since these are instructions they need to be put as little-endian
-         * regardless of target default or current CPU endianness.
-         */
-        __put_user_e(0xd2801168, &fr->tramp[0], le);
-        __put_user_e(0xd4000001, &fr->tramp[1], le);
-        return_addr = frame_addr + fr_ofs
-            + offsetof(struct target_rt_frame_record, tramp);
+        return_addr = default_rt_sigreturn;
     }
     env->xregs[0] = usig;
     env->xregs[29] = frame_addr + fr_ofs;
@@ -577,3 +568,20 @@ long do_sigreturn(CPUARMState *env)
 {
     return do_rt_sigreturn(env);
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 8, 0);
+    assert(tramp != NULL);
+
+    /*
+     * mov x8,#__NR_rt_sigreturn; svc #0
+     * Since these are instructions they need to be put as little-endian
+     * regardless of target default or current CPU endianness.
+     */
+    __put_user_e(0xd2801168, &tramp[0], le);
+    __put_user_e(0xd4000001, &tramp[1], le);
+
+    default_rt_sigreturn = sigtramp_page;
+    unlock_user(tramp, sigtramp_page, 8);
+}
-- 
2.25.1

[PATCH v4 03/25] linux-user/arm: Drop v1 signal frames

[Richard Henderson]

Version 2 signal frames are used from 2.6.12 and since cbc14e6f286,
we have set UNAME_MINIMUM_RELEASE to 2.6.32.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/arm/signal.c | 220 +---------------------------------------
 1 file changed, 4 insertions(+), 216 deletions(-)

diff --git a/linux-user/arm/signal.c b/linux-user/arm/signal.c
index ed144f9455..d0940bab47 100644
--- a/linux-user/arm/signal.c
+++ b/linux-user/arm/signal.c
@@ -46,14 +46,6 @@ struct target_sigcontext {
     abi_ulong fault_address;
 };
 
-struct target_ucontext_v1 {
-    abi_ulong tuc_flags;
-    abi_ulong tuc_link;
-    target_stack_t tuc_stack;
-    struct target_sigcontext tuc_mcontext;
-    target_sigset_t  tuc_sigmask;       /* mask last for extensibility */
-};
-
 struct target_ucontext_v2 {
     abi_ulong tuc_flags;
     abi_ulong tuc_link;
@@ -98,28 +90,12 @@ struct target_iwmmxt_sigframe {
 #define TARGET_VFP_MAGIC 0x56465001
 #define TARGET_IWMMXT_MAGIC 0x12ef842a
 
-struct sigframe_v1
-{
-    struct target_sigcontext sc;
-    abi_ulong extramask[TARGET_NSIG_WORDS-1];
-    abi_ulong retcode[4];
-};
-
 struct sigframe_v2
 {
     struct target_ucontext_v2 uc;
     abi_ulong retcode[4];
 };
 
-struct rt_sigframe_v1
-{
-    abi_ulong pinfo;
-    abi_ulong puc;
-    struct target_siginfo info;
-    struct target_ucontext_v1 uc;
-    abi_ulong retcode[4];
-};
-
 struct rt_sigframe_v2
 {
     struct target_siginfo info;
@@ -363,37 +339,6 @@ static void setup_sigframe_v2(struct target_ucontext_v2 *uc,
     }
 }
 
-/* compare linux/arch/arm/kernel/signal.c:setup_frame() */
-static void setup_frame_v1(int usig, struct target_sigaction *ka,
-                           target_sigset_t *set, CPUARMState *regs)
-{
-    struct sigframe_v1 *frame;
-    abi_ulong frame_addr = get_sigframe(ka, regs, sizeof(*frame));
-    int i;
-
-    trace_user_setup_frame(regs, frame_addr);
-    if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
-        goto sigsegv;
-    }
-
-    setup_sigcontext(&frame->sc, regs, set->sig[0]);
-
-    for(i = 1; i < TARGET_NSIG_WORDS; i++) {
-        __put_user(set->sig[i], &frame->extramask[i - 1]);
-    }
-
-    if (setup_return(regs, ka, frame->retcode, frame_addr, usig,
-                     frame_addr + offsetof(struct sigframe_v1, retcode))) {
-        goto sigsegv;
-    }
-
-    unlock_user_struct(frame, frame_addr, 1);
-    return;
-sigsegv:
-    unlock_user_struct(frame, frame_addr, 1);
-    force_sigsegv(usig);
-}
-
 static void setup_frame_v2(int usig, struct target_sigaction *ka,
                            target_sigset_t *set, CPUARMState *regs)
 {
@@ -422,60 +367,7 @@ sigsegv:
 void setup_frame(int usig, struct target_sigaction *ka,
                  target_sigset_t *set, CPUARMState *regs)
 {
-    if (get_osversion() >= 0x020612) {
-        setup_frame_v2(usig, ka, set, regs);
-    } else {
-        setup_frame_v1(usig, ka, set, regs);
-    }
-}
-
-/* compare linux/arch/arm/kernel/signal.c:setup_rt_frame() */
-static void setup_rt_frame_v1(int usig, struct target_sigaction *ka,
-                              target_siginfo_t *info,
-                              target_sigset_t *set, CPUARMState *env)
-{
-    struct rt_sigframe_v1 *frame;
-    abi_ulong frame_addr = get_sigframe(ka, env, sizeof(*frame));
-    struct target_sigaltstack stack;
-    int i;
-    abi_ulong info_addr, uc_addr;
-
-    trace_user_setup_rt_frame(env, frame_addr);
-    if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
-        goto sigsegv;
-    }
-
-    info_addr = frame_addr + offsetof(struct rt_sigframe_v1, info);
-    __put_user(info_addr, &frame->pinfo);
-    uc_addr = frame_addr + offsetof(struct rt_sigframe_v1, uc);
-    __put_user(uc_addr, &frame->puc);
-    tswap_siginfo(&frame->info, info);
-
-    /* Clear all the bits of the ucontext we don't use.  */
-    memset(&frame->uc, 0, offsetof(struct target_ucontext_v1, tuc_mcontext));
-
-    memset(&stack, 0, sizeof(stack));
-    target_save_altstack(&stack, env);
-    memcpy(&frame->uc.tuc_stack, &stack, sizeof(stack));
-
-    setup_sigcontext(&frame->uc.tuc_mcontext, env, set->sig[0]);
-    for(i = 0; i < TARGET_NSIG_WORDS; i++) {
-        __put_user(set->sig[i], &frame->uc.tuc_sigmask.sig[i]);
-    }
-
-    if (setup_return(env, ka, frame->retcode, frame_addr, usig,
-                     frame_addr + offsetof(struct rt_sigframe_v1, retcode))) {
-        goto sigsegv;
-    }
-
-    env->regs[1] = info_addr;
-    env->regs[2] = uc_addr;
-
-    unlock_user_struct(frame, frame_addr, 1);
-    return;
-sigsegv:
-    unlock_user_struct(frame, frame_addr, 1);
-    force_sigsegv(usig);
+    setup_frame_v2(usig, ka, set, regs);
 }
 
 static void setup_rt_frame_v2(int usig, struct target_sigaction *ka,
@@ -516,11 +408,7 @@ void setup_rt_frame(int usig, struct target_sigaction *ka,
                     target_siginfo_t *info,
                     target_sigset_t *set, CPUARMState *env)
 {
-    if (get_osversion() >= 0x020612) {
-        setup_rt_frame_v2(usig, ka, info, set, env);
-    } else {
-        setup_rt_frame_v1(usig, ka, info, set, env);
-    }
+    setup_rt_frame_v2(usig, ka, info, set, env);
 }
 
 static int
@@ -553,54 +441,6 @@ restore_sigcontext(CPUARMState *env, struct target_sigcontext *sc)
     return err;
 }
 
-static long do_sigreturn_v1(CPUARMState *env)
-{
-    abi_ulong frame_addr;
-    struct sigframe_v1 *frame = NULL;
-    target_sigset_t set;
-    sigset_t host_set;
-    int i;
-
-    /*
-     * Since we stacked the signal on a 64-bit boundary,
-     * then 'sp' should be word aligned here.  If it's
-     * not, then the user is trying to mess with us.
-     */
-    frame_addr = env->regs[13];
-    trace_user_do_sigreturn(env, frame_addr);
-    if (frame_addr & 7) {
-        goto badframe;
-    }
-
-    if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
-        goto badframe;
-    }
-
-    __get_user(set.sig[0], &frame->sc.oldmask);
-    for(i = 1; i < TARGET_NSIG_WORDS; i++) {
-        __get_user(set.sig[i], &frame->extramask[i - 1]);
-    }
-
-    target_to_host_sigset_internal(&host_set, &set);
-    set_sigmask(&host_set);
-
-    if (restore_sigcontext(env, &frame->sc)) {
-        goto badframe;
-    }
-
-#if 0
-    /* Send SIGTRAP if we're single-stepping */
-    if (ptrace_cancel_bpt(current))
-        send_sig(SIGTRAP, current, 1);
-#endif
-    unlock_user_struct(frame, frame_addr, 0);
-    return -TARGET_QEMU_ESIGRETURN;
-
-badframe:
-    force_sig(TARGET_SIGSEGV);
-    return -TARGET_QEMU_ESIGRETURN;
-}
-
 static abi_ulong *restore_sigframe_v2_vfp(CPUARMState *env, abi_ulong *regspace)
 {
     int i;
@@ -733,55 +573,7 @@ badframe:
 
 long do_sigreturn(CPUARMState *env)
 {
-    if (get_osversion() >= 0x020612) {
-        return do_sigreturn_v2(env);
-    } else {
-        return do_sigreturn_v1(env);
-    }
-}
-
-static long do_rt_sigreturn_v1(CPUARMState *env)
-{
-    abi_ulong frame_addr;
-    struct rt_sigframe_v1 *frame = NULL;
-    sigset_t host_set;
-
-    /*
-     * Since we stacked the signal on a 64-bit boundary,
-     * then 'sp' should be word aligned here.  If it's
-     * not, then the user is trying to mess with us.
-     */
-    frame_addr = env->regs[13];
-    trace_user_do_rt_sigreturn(env, frame_addr);
-    if (frame_addr & 7) {
-        goto badframe;
-    }
-
-    if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
-        goto badframe;
-    }
-
-    target_to_host_sigset(&host_set, &frame->uc.tuc_sigmask);
-    set_sigmask(&host_set);
-
-    if (restore_sigcontext(env, &frame->uc.tuc_mcontext)) {
-        goto badframe;
-    }
-
-    target_restore_altstack(&frame->uc.tuc_stack, env);
-
-#if 0
-    /* Send SIGTRAP if we're single-stepping */
-    if (ptrace_cancel_bpt(current))
-        send_sig(SIGTRAP, current, 1);
-#endif
-    unlock_user_struct(frame, frame_addr, 0);
-    return -TARGET_QEMU_ESIGRETURN;
-
-badframe:
-    unlock_user_struct(frame, frame_addr, 0);
-    force_sig(TARGET_SIGSEGV);
-    return -TARGET_QEMU_ESIGRETURN;
+    return do_sigreturn_v2(env);
 }
 
 static long do_rt_sigreturn_v2(CPUARMState *env)
@@ -822,9 +614,5 @@ badframe:
 
 long do_rt_sigreturn(CPUARMState *env)
 {
-    if (get_osversion() >= 0x020612) {
-        return do_rt_sigreturn_v2(env);
-    } else {
-        return do_rt_sigreturn_v1(env);
-    }
+    return do_rt_sigreturn_v2(env);
 }
-- 
2.25.1

[PATCH v4 04/25] linux-user/arm: Drop "_v2" from symbols in signal.c

[Richard Henderson]

Since we no longer support "v1", there's no need to distinguish "v2".

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/arm/signal.c | 155 +++++++++++++++++-----------------------
 1 file changed, 65 insertions(+), 90 deletions(-)

diff --git a/linux-user/arm/signal.c b/linux-user/arm/signal.c
index d0940bab47..ed7d1d80bb 100644
--- a/linux-user/arm/signal.c
+++ b/linux-user/arm/signal.c
@@ -46,7 +46,7 @@ struct target_sigcontext {
     abi_ulong fault_address;
 };
 
-struct target_ucontext_v2 {
+struct target_ucontext {
     abi_ulong tuc_flags;
     abi_ulong tuc_link;
     target_stack_t tuc_stack;
@@ -90,16 +90,16 @@ struct target_iwmmxt_sigframe {
 #define TARGET_VFP_MAGIC 0x56465001
 #define TARGET_IWMMXT_MAGIC 0x12ef842a
 
-struct sigframe_v2
+struct sigframe
 {
-    struct target_ucontext_v2 uc;
+    struct target_ucontext uc;
     abi_ulong retcode[4];
 };
 
-struct rt_sigframe_v2
+struct rt_sigframe
 {
     struct target_siginfo info;
-    struct target_ucontext_v2 uc;
+    struct target_ucontext uc;
     abi_ulong retcode[4];
 };
 
@@ -270,7 +270,7 @@ setup_return(CPUARMState *env, struct target_sigaction *ka,
     return 0;
 }
 
-static abi_ulong *setup_sigframe_v2_vfp(abi_ulong *regspace, CPUARMState *env)
+static abi_ulong *setup_sigframe_vfp(abi_ulong *regspace, CPUARMState *env)
 {
     int i;
     struct target_vfp_sigframe *vfpframe;
@@ -287,8 +287,7 @@ static abi_ulong *setup_sigframe_v2_vfp(abi_ulong *regspace, CPUARMState *env)
     return (abi_ulong*)(vfpframe+1);
 }
 
-static abi_ulong *setup_sigframe_v2_iwmmxt(abi_ulong *regspace,
-                                           CPUARMState *env)
+static abi_ulong *setup_sigframe_iwmmxt(abi_ulong *regspace, CPUARMState *env)
 {
     int i;
     struct target_iwmmxt_sigframe *iwmmxtframe;
@@ -307,15 +306,15 @@ static abi_ulong *setup_sigframe_v2_iwmmxt(abi_ulong *regspace,
     return (abi_ulong*)(iwmmxtframe+1);
 }
 
-static void setup_sigframe_v2(struct target_ucontext_v2 *uc,
-                              target_sigset_t *set, CPUARMState *env)
+static void setup_sigframe(struct target_ucontext *uc,
+                           target_sigset_t *set, CPUARMState *env)
 {
     struct target_sigaltstack stack;
     int i;
     abi_ulong *regspace;
 
     /* Clear all the bits of the ucontext we don't use.  */
-    memset(uc, 0, offsetof(struct target_ucontext_v2, tuc_mcontext));
+    memset(uc, 0, offsetof(struct target_ucontext, tuc_mcontext));
 
     memset(&stack, 0, sizeof(stack));
     target_save_altstack(&stack, env);
@@ -325,10 +324,10 @@ static void setup_sigframe_v2(struct target_ucontext_v2 *uc,
     /* Save coprocessor signal frame.  */
     regspace = uc->tuc_regspace;
     if (cpu_isar_feature(aa32_vfp_simd, env_archcpu(env))) {
-        regspace = setup_sigframe_v2_vfp(regspace, env);
+        regspace = setup_sigframe_vfp(regspace, env);
     }
     if (arm_feature(env, ARM_FEATURE_IWMMXT)) {
-        regspace = setup_sigframe_v2_iwmmxt(regspace, env);
+        regspace = setup_sigframe_iwmmxt(regspace, env);
     }
 
     /* Write terminating magic word */
@@ -339,10 +338,10 @@ static void setup_sigframe_v2(struct target_ucontext_v2 *uc,
     }
 }
 
-static void setup_frame_v2(int usig, struct target_sigaction *ka,
-                           target_sigset_t *set, CPUARMState *regs)
+void setup_frame(int usig, struct target_sigaction *ka,
+                 target_sigset_t *set, CPUARMState *regs)
 {
-    struct sigframe_v2 *frame;
+    struct sigframe *frame;
     abi_ulong frame_addr = get_sigframe(ka, regs, sizeof(*frame));
 
     trace_user_setup_frame(regs, frame_addr);
@@ -350,10 +349,10 @@ static void setup_frame_v2(int usig, struct target_sigaction *ka,
         goto sigsegv;
     }
 
-    setup_sigframe_v2(&frame->uc, set, regs);
+    setup_sigframe(&frame->uc, set, regs);
 
     if (setup_return(regs, ka, frame->retcode, frame_addr, usig,
-                     frame_addr + offsetof(struct sigframe_v2, retcode))) {
+                     frame_addr + offsetof(struct sigframe, retcode))) {
         goto sigsegv;
     }
 
@@ -364,51 +363,38 @@ sigsegv:
     force_sigsegv(usig);
 }
 
-void setup_frame(int usig, struct target_sigaction *ka,
-                 target_sigset_t *set, CPUARMState *regs)
-{
-    setup_frame_v2(usig, ka, set, regs);
-}
-
-static void setup_rt_frame_v2(int usig, struct target_sigaction *ka,
-                              target_siginfo_t *info,
-                              target_sigset_t *set, CPUARMState *env)
-{
-    struct rt_sigframe_v2 *frame;
-    abi_ulong frame_addr = get_sigframe(ka, env, sizeof(*frame));
-    abi_ulong info_addr, uc_addr;
-
-    trace_user_setup_rt_frame(env, frame_addr);
-    if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
-        goto sigsegv;
-    }
-
-    info_addr = frame_addr + offsetof(struct rt_sigframe_v2, info);
-    uc_addr = frame_addr + offsetof(struct rt_sigframe_v2, uc);
-    tswap_siginfo(&frame->info, info);
-
-    setup_sigframe_v2(&frame->uc, set, env);
-
-    if (setup_return(env, ka, frame->retcode, frame_addr, usig,
-                     frame_addr + offsetof(struct rt_sigframe_v2, retcode))) {
-        goto sigsegv;
-    }
-
-    env->regs[1] = info_addr;
-    env->regs[2] = uc_addr;
-
-    unlock_user_struct(frame, frame_addr, 1);
-    return;
-sigsegv:
-    unlock_user_struct(frame, frame_addr, 1);
-    force_sigsegv(usig);
-}
-
 void setup_rt_frame(int usig, struct target_sigaction *ka,
                     target_siginfo_t *info,
                     target_sigset_t *set, CPUARMState *env)
 {
-    setup_rt_frame_v2(usig, ka, info, set, env);
+    struct rt_sigframe *frame;
+    abi_ulong frame_addr = get_sigframe(ka, env, sizeof(*frame));
+    abi_ulong info_addr, uc_addr;
+
+    trace_user_setup_rt_frame(env, frame_addr);
+    if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
+        goto sigsegv;
+    }
+
+    info_addr = frame_addr + offsetof(struct rt_sigframe, info);
+    uc_addr = frame_addr + offsetof(struct rt_sigframe, uc);
+    tswap_siginfo(&frame->info, info);
+
+    setup_sigframe(&frame->uc, set, env);
+
+    if (setup_return(env, ka, frame->retcode, frame_addr, usig,
+                     frame_addr + offsetof(struct rt_sigframe, retcode))) {
+        goto sigsegv;
+    }
+
+    env->regs[1] = info_addr;
+    env->regs[2] = uc_addr;
+
+    unlock_user_struct(frame, frame_addr, 1);
+    return;
+sigsegv:
+    unlock_user_struct(frame, frame_addr, 1);
+    force_sigsegv(usig);
 }
 
 static int
@@ -441,7 +427,7 @@ restore_sigcontext(CPUARMState *env, struct target_sigcontext *sc)
     return err;
 }
 
-static abi_ulong *restore_sigframe_v2_vfp(CPUARMState *env, abi_ulong *regspace)
+static abi_ulong *restore_sigframe_vfp(CPUARMState *env, abi_ulong *regspace)
 {
     int i;
     abi_ulong magic, sz;
@@ -471,8 +457,8 @@ static abi_ulong *restore_sigframe_v2_vfp(CPUARMState *env, abi_ulong *regspace)
     return (abi_ulong*)(vfpframe + 1);
 }
 
-static abi_ulong *restore_sigframe_v2_iwmmxt(CPUARMState *env,
-                                             abi_ulong *regspace)
+static abi_ulong *restore_sigframe_iwmmxt(CPUARMState *env,
+                                          abi_ulong *regspace)
 {
     int i;
     abi_ulong magic, sz;
@@ -496,9 +482,9 @@ static abi_ulong *restore_sigframe_v2_iwmmxt(CPUARMState *env,
     return (abi_ulong*)(iwmmxtframe + 1);
 }
 
-static int do_sigframe_return_v2(CPUARMState *env,
-                                 target_ulong context_addr,
-                                 struct target_ucontext_v2 *uc)
+static int do_sigframe_return(CPUARMState *env,
+                              target_ulong context_addr,
+                              struct target_ucontext *uc)
 {
     sigset_t host_set;
     abi_ulong *regspace;
@@ -506,19 +492,20 @@ static int do_sigframe_return_v2(CPUARMState *env,
     target_to_host_sigset(&host_set, &uc->tuc_sigmask);
     set_sigmask(&host_set);
 
-    if (restore_sigcontext(env, &uc->tuc_mcontext))
+    if (restore_sigcontext(env, &uc->tuc_mcontext)) {
         return 1;
+    }
 
     /* Restore coprocessor signal frame */
     regspace = uc->tuc_regspace;
     if (cpu_isar_feature(aa32_vfp_simd, env_archcpu(env))) {
-        regspace = restore_sigframe_v2_vfp(env, regspace);
+        regspace = restore_sigframe_vfp(env, regspace);
         if (!regspace) {
             return 1;
         }
     }
     if (arm_feature(env, ARM_FEATURE_IWMMXT)) {
-        regspace = restore_sigframe_v2_iwmmxt(env, regspace);
+        regspace = restore_sigframe_iwmmxt(env, regspace);
         if (!regspace) {
             return 1;
         }
@@ -535,10 +522,10 @@ static int do_sigframe_return_v2(CPUARMState *env,
     return 0;
 }
 
-static long do_sigreturn_v2(CPUARMState *env)
+long do_sigreturn(CPUARMState *env)
 {
     abi_ulong frame_addr;
-    struct sigframe_v2 *frame = NULL;
+    struct sigframe *frame = NULL;
 
     /*
      * Since we stacked the signal on a 64-bit boundary,
@@ -555,10 +542,9 @@ static long do_sigreturn_v2(CPUARMState *env)
         goto badframe;
     }
 
-    if (do_sigframe_return_v2(env,
-                              frame_addr
-                              + offsetof(struct sigframe_v2, uc),
-                              &frame->uc)) {
+    if (do_sigframe_return(env,
+                           frame_addr + offsetof(struct sigframe, uc),
+                           &frame->uc)) {
         goto badframe;
     }
 
@@ -571,15 +557,10 @@ badframe:
     return -TARGET_QEMU_ESIGRETURN;
 }
 
-long do_sigreturn(CPUARMState *env)
-{
-    return do_sigreturn_v2(env);
-}
-
-static long do_rt_sigreturn_v2(CPUARMState *env)
+long do_rt_sigreturn(CPUARMState *env)
 {
     abi_ulong frame_addr;
-    struct rt_sigframe_v2 *frame = NULL;
+    struct rt_sigframe *frame = NULL;
 
     /*
      * Since we stacked the signal on a 64-bit boundary,
@@ -596,10 +577,9 @@ static long do_rt_sigreturn_v2(CPUARMState *env)
         goto badframe;
     }
 
-    if (do_sigframe_return_v2(env,
-                              frame_addr
-                              + offsetof(struct rt_sigframe_v2, uc),
-                              &frame->uc)) {
+    if (do_sigframe_return(env,
+                           frame_addr + offsetof(struct rt_sigframe, uc),
+                           &frame->uc)) {
         goto badframe;
     }
 
@@ -611,8 +591,3 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return -TARGET_QEMU_ESIGRETURN;
 }
-
-long do_rt_sigreturn(CPUARMState *env)
-{
-    return do_rt_sigreturn_v2(env);
-}
-- 
2.25.1

[PATCH v4 05/25] linux-user/arm: Implement setup_sigtramp

[Richard Henderson]

Mirror what the kernel does in arch/arm/kernel/signal.h,
using the old sigframe struct in the rt sigframe struct.

Update the trampoline code to match the kernel: this uses
sp-relative accesses rather than pc-relative.

Copy the code into frame->retcode from the trampoline page.
This minimises the different cases wrt arm vs thumb vs fdpic.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/arm/target_signal.h |   2 +
 linux-user/arm/signal.c        | 184 ++++++++++++++++++++-------------
 2 files changed, 115 insertions(+), 71 deletions(-)

diff --git a/linux-user/arm/target_signal.h b/linux-user/arm/target_signal.h
index 0998dd6dfa..1e7fb0cecb 100644
--- a/linux-user/arm/target_signal.h
+++ b/linux-user/arm/target_signal.h
@@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
 #include "../generic/signal.h"
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* ARM_TARGET_SIGNAL_H */
diff --git a/linux-user/arm/signal.c b/linux-user/arm/signal.c
index ed7d1d80bb..67a3d1428b 100644
--- a/linux-user/arm/signal.c
+++ b/linux-user/arm/signal.c
@@ -99,43 +99,21 @@ struct sigframe
 struct rt_sigframe
 {
     struct target_siginfo info;
-    struct target_ucontext uc;
-    abi_ulong retcode[4];
+    struct sigframe sig;
 };
 
+static abi_ptr sigreturn_fdpic_tramp;
+
 /*
- * For ARM syscalls, we encode the syscall number into the instruction.
+ * Up to 3 words of 'retcode' in the sigframe are code,
+ * with retcode[3] being used by fdpic for the function descriptor.
+ * This code is not actually executed, but is retained for ABI compat.
+ *
+ * We will create a table of 8 retcode variants in the sigtramp page.
+ * Let each table entry use 3 words.
  */
-#define SWI_SYS_SIGRETURN       (0xef000000|(TARGET_NR_sigreturn + ARM_SYSCALL_BASE))
-#define SWI_SYS_RT_SIGRETURN    (0xef000000|(TARGET_NR_rt_sigreturn + ARM_SYSCALL_BASE))
-
-/*
- * For Thumb syscalls, we pass the syscall number via r7.  We therefore
- * need two 16-bit instructions.
- */
-#define SWI_THUMB_SIGRETURN     (0xdf00 << 16 | 0x2700 | (TARGET_NR_sigreturn))
-#define SWI_THUMB_RT_SIGRETURN  (0xdf00 << 16 | 0x2700 | (TARGET_NR_rt_sigreturn))
-
-static const abi_ulong retcodes[4] = {
-        SWI_SYS_SIGRETURN,      SWI_THUMB_SIGRETURN,
-        SWI_SYS_RT_SIGRETURN,   SWI_THUMB_RT_SIGRETURN
-};
-
-/*
- * Stub needed to make sure the FD register (r9) contains the right
- * value.
- */
-static const unsigned long sigreturn_fdpic_codes[3] = {
-    0xe59fc004, /* ldr r12, [pc, #4] to read function descriptor */
-    0xe59c9004, /* ldr r9, [r12, #4] to setup GOT */
-    0xe59cf000  /* ldr pc, [r12] to jump into restorer */
-};
-
-static const unsigned long sigreturn_fdpic_thumb_codes[3] = {
-    0xc008f8df, /* ldr r12, [pc, #8] to read function descriptor */
-    0x9004f8dc, /* ldr r9, [r12, #4] to setup GOT */
-    0xf000f8dc  /* ldr pc, [r12] to jump into restorer */
-};
+#define RETCODE_WORDS  3
+#define RETCODE_BYTES  (RETCODE_WORDS * 4)
 
 static inline int valid_user_regs(CPUARMState *regs)
 {
@@ -183,15 +161,15 @@ get_sigframe(struct target_sigaction *ka, CPUARMState *regs, int framesize)
 }
 
 static int
-setup_return(CPUARMState *env, struct target_sigaction *ka,
-             abi_ulong *rc, abi_ulong frame_addr, int usig, abi_ulong rc_addr)
+setup_return(CPUARMState *env, struct target_sigaction *ka, int usig,
+             struct sigframe *frame, abi_ulong sp_addr)
 {
     abi_ulong handler = 0;
     abi_ulong handler_fdpic_GOT = 0;
     abi_ulong retcode;
-
-    int thumb;
+    int thumb, retcode_idx;
     int is_fdpic = info_is_fdpic(((TaskState *)thread_cpu->opaque)->info);
+    bool copy_retcode;
 
     if (is_fdpic) {
         /* In FDPIC mode, ka->_sa_handler points to a function
@@ -208,6 +186,7 @@ setup_return(CPUARMState *env, struct target_sigaction *ka,
     }
 
     thumb = handler & 1;
+    retcode_idx = thumb + (ka->sa_flags & TARGET_SA_SIGINFO ? 2 : 0);
 
     uint32_t cpsr = cpsr_read(env);
 
@@ -225,44 +204,34 @@ setup_return(CPUARMState *env, struct target_sigaction *ka,
 
     if (ka->sa_flags & TARGET_SA_RESTORER) {
         if (is_fdpic) {
-            /* For FDPIC we ensure that the restorer is called with a
-             * correct r9 value.  For that we need to write code on
-             * the stack that sets r9 and jumps back to restorer
-             * value.
-             */
-            if (thumb) {
-                __put_user(sigreturn_fdpic_thumb_codes[0], rc);
-                __put_user(sigreturn_fdpic_thumb_codes[1], rc + 1);
-                __put_user(sigreturn_fdpic_thumb_codes[2], rc + 2);
-                __put_user((abi_ulong)ka->sa_restorer, rc + 3);
-            } else {
-                __put_user(sigreturn_fdpic_codes[0], rc);
-                __put_user(sigreturn_fdpic_codes[1], rc + 1);
-                __put_user(sigreturn_fdpic_codes[2], rc + 2);
-                __put_user((abi_ulong)ka->sa_restorer, rc + 3);
-            }
-
-            retcode = rc_addr + thumb;
+            __put_user((abi_ulong)ka->sa_restorer, &frame->retcode[3]);
+            retcode = (sigreturn_fdpic_tramp +
+                       retcode_idx * RETCODE_BYTES + thumb);
+            copy_retcode = true;
         } else {
             retcode = ka->sa_restorer;
+            copy_retcode = false;
         }
     } else {
-        unsigned int idx = thumb;
+        retcode = default_sigreturn + retcode_idx * RETCODE_BYTES + thumb;
+        copy_retcode = true;
+    }
 
-        if (ka->sa_flags & TARGET_SA_SIGINFO) {
-            idx += 2;
+    /* Copy the code to the stack slot for ABI compatibility. */
+    if (copy_retcode) {
+        uint32_t *host_rc = g2h_untagged(retcode);
+        int i;
+
+        for (i = 0; i < RETCODE_WORDS; ++i) {
+            __put_user(host_rc[i], &frame->retcode[i]);
         }
-
-        __put_user(retcodes[idx], rc);
-
-        retcode = rc_addr + thumb;
     }
 
     env->regs[0] = usig;
     if (is_fdpic) {
         env->regs[9] = handler_fdpic_GOT;
     }
-    env->regs[13] = frame_addr;
+    env->regs[13] = sp_addr;
     env->regs[14] = retcode;
     env->regs[15] = handler & (thumb ? ~1 : ~3);
     cpsr_write(env, cpsr, CPSR_IT | CPSR_T | CPSR_E, CPSRWriteByInstr);
@@ -351,8 +320,7 @@ void setup_frame(int usig, struct target_sigaction *ka,
 
     setup_sigframe(&frame->uc, set, regs);
 
-    if (setup_return(regs, ka, frame->retcode, frame_addr, usig,
-                     frame_addr + offsetof(struct sigframe, retcode))) {
+    if (setup_return(regs, ka, usig, frame, frame_addr)) {
         goto sigsegv;
     }
 
@@ -377,13 +345,12 @@ void setup_rt_frame(int usig, struct target_sigaction *ka,
     }
 
     info_addr = frame_addr + offsetof(struct rt_sigframe, info);
-    uc_addr = frame_addr + offsetof(struct rt_sigframe, uc);
+    uc_addr = frame_addr + offsetof(struct rt_sigframe, sig.uc);
     tswap_siginfo(&frame->info, info);
 
-    setup_sigframe(&frame->uc, set, env);
+    setup_sigframe(&frame->sig.uc, set, env);
 
-    if (setup_return(env, ka, frame->retcode, frame_addr, usig,
-                     frame_addr + offsetof(struct rt_sigframe, retcode))) {
+    if (setup_return(env, ka, usig, &frame->sig, frame_addr)) {
         goto sigsegv;
     }
 
@@ -578,8 +545,8 @@ long do_rt_sigreturn(CPUARMState *env)
     }
 
     if (do_sigframe_return(env,
-                           frame_addr + offsetof(struct rt_sigframe, uc),
-                           &frame->uc)) {
+                           frame_addr + offsetof(struct rt_sigframe, sig.uc),
+                           &frame->sig.uc)) {
         goto badframe;
     }
 
@@ -591,3 +558,78 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return -TARGET_QEMU_ESIGRETURN;
 }
+
+/*
+ * EABI syscalls pass the number via r7.
+ * Note that the kernel still adds the OABI syscall number to the trap,
+ * presumably for backward ABI compatibility with unwinders.
+ */
+#define ARM_MOV_R7_IMM(X)       (0xe3a07000 | (X))
+#define ARM_SWI_SYS(X)          (0xef000000 | (X) | ARM_SYSCALL_BASE)
+
+#define THUMB_MOVS_R7_IMM(X)    (0x2700 | (X))
+#define THUMB_SWI_SYS           0xdf00
+
+static void write_arm_sigreturn(uint32_t *rc, int syscall)
+{
+    __put_user(ARM_MOV_R7_IMM(syscall), rc);
+    __put_user(ARM_SWI_SYS(syscall), rc + 1);
+    /* Wrote 8 of 12 bytes */
+}
+
+static void write_thm_sigreturn(uint32_t *rc, int syscall)
+{
+    __put_user(THUMB_SWI_SYS << 16 | THUMB_MOVS_R7_IMM(syscall), rc);
+    /* Wrote 4 of 12 bytes */
+}
+
+/*
+ * Stub needed to make sure the FD register (r9) contains the right value.
+ * Use the same instruction sequence as the kernel.
+ */
+static void write_arm_fdpic_sigreturn(uint32_t *rc, int ofs)
+{
+    assert(ofs <= 0xfff);
+    __put_user(0xe59d3000 | ofs, rc + 0);   /* ldr r3, [sp, #ofs] */
+    __put_user(0xe8930908, rc + 1);         /* ldm r3, { r3, r9 } */
+    __put_user(0xe12fff13, rc + 2);         /* bx  r3 */
+    /* Wrote 12 of 12 bytes */
+}
+
+static void write_thm_fdpic_sigreturn(void *vrc, int ofs)
+{
+    uint16_t *rc = vrc;
+
+    assert((ofs & ~0x3fc) == 0);
+    __put_user(0x9b00 | (ofs >> 2), rc + 0);      /* ldr r3, [sp, #ofs] */
+    __put_user(0xcb0c, rc + 1);                   /* ldm r3, { r2, r3 } */
+    __put_user(0x4699, rc + 2);                   /* mov r9, r3 */
+    __put_user(0x4710, rc + 3);                   /* bx  r2 */
+    /* Wrote 8 of 12 bytes */
+}
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t total_size = 8 * RETCODE_BYTES;
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, total_size, 0);
+
+    assert(tramp != NULL);
+
+    default_sigreturn = sigtramp_page;
+    write_arm_sigreturn(&tramp[0 * RETCODE_WORDS], TARGET_NR_sigreturn);
+    write_thm_sigreturn(&tramp[1 * RETCODE_WORDS], TARGET_NR_sigreturn);
+    write_arm_sigreturn(&tramp[2 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
+    write_thm_sigreturn(&tramp[3 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
+
+    sigreturn_fdpic_tramp = sigtramp_page + 4 * RETCODE_BYTES;
+    write_arm_fdpic_sigreturn(tramp + 4 * RETCODE_WORDS,
+                              offsetof(struct sigframe, retcode[3]));
+    write_thm_fdpic_sigreturn(tramp + 5 * RETCODE_WORDS,
+                                offsetof(struct sigframe, retcode[3]));
+    write_arm_fdpic_sigreturn(tramp + 6 * RETCODE_WORDS,
+                              offsetof(struct rt_sigframe, sig.retcode[3]));
+    write_thm_fdpic_sigreturn(tramp + 7 * RETCODE_WORDS,
+                              offsetof(struct rt_sigframe, sig.retcode[3]));
+
+    unlock_user(tramp, sigtramp_page, total_size);
+}
-- 
2.25.1

Re: [PATCH v4 05/25] linux-user/arm: Implement setup_sigtramp

[Peter Maydell]

On Tue, 28 Sept 2021 at 03:00, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Mirror what the kernel does in arch/arm/kernel/signal.h,
> using the old sigframe struct in the rt sigframe struct.
>
> Update the trampoline code to match the kernel: this uses
> sp-relative accesses rather than pc-relative.
>
> Copy the code into frame->retcode from the trampoline page.
> This minimises the different cases wrt arm vs thumb vs fdpic.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>


> @@ -225,44 +204,34 @@ setup_return(CPUARMState *env, struct target_sigaction *ka,
>
>      if (ka->sa_flags & TARGET_SA_RESTORER) {
>          if (is_fdpic) {
> -            /* For FDPIC we ensure that the restorer is called with a
> -             * correct r9 value.  For that we need to write code on
> -             * the stack that sets r9 and jumps back to restorer
> -             * value.
> -             */
> -            if (thumb) {
> -                __put_user(sigreturn_fdpic_thumb_codes[0], rc);
> -                __put_user(sigreturn_fdpic_thumb_codes[1], rc + 1);
> -                __put_user(sigreturn_fdpic_thumb_codes[2], rc + 2);
> -                __put_user((abi_ulong)ka->sa_restorer, rc + 3);
> -            } else {
> -                __put_user(sigreturn_fdpic_codes[0], rc);
> -                __put_user(sigreturn_fdpic_codes[1], rc + 1);
> -                __put_user(sigreturn_fdpic_codes[2], rc + 2);
> -                __put_user((abi_ulong)ka->sa_restorer, rc + 3);
> -            }
> -
> -            retcode = rc_addr + thumb;
> +            __put_user((abi_ulong)ka->sa_restorer, &frame->retcode[3]);
> +            retcode = (sigreturn_fdpic_tramp +
> +                       retcode_idx * RETCODE_BYTES + thumb);

Here 'retcode' is an interworking-PC value with the LSB indicating
Thumb mode...

> +            copy_retcode = true;
>          } else {
>              retcode = ka->sa_restorer;
> +            copy_retcode = false;
>          }
>      } else {
> -        unsigned int idx = thumb;
> +        retcode = default_sigreturn + retcode_idx * RETCODE_BYTES + thumb;
> +        copy_retcode = true;
> +    }
>
> -        if (ka->sa_flags & TARGET_SA_SIGINFO) {
> -            idx += 2;
> +    /* Copy the code to the stack slot for ABI compatibility. */
> +    if (copy_retcode) {
> +        uint32_t *host_rc = g2h_untagged(retcode);

...but here we treat it as a normal guest address that we can
convert into a host address and dereference. If the signal handler
is being entered in Thumb mode this will be a misaligned pointer.

> +        int i;
> +
> +        for (i = 0; i < RETCODE_WORDS; ++i) {
> +            __put_user(host_rc[i], &frame->retcode[i]);
>          }
> -
> -        __put_user(retcodes[idx], rc);
> -
> -        retcode = rc_addr + thumb;
>      }
>
>      env->regs[0] = usig;
>      if (is_fdpic) {
>          env->regs[9] = handler_fdpic_GOT;
>      }
> -    env->regs[13] = frame_addr;
> +    env->regs[13] = sp_addr;
>      env->regs[14] = retcode;
>      env->regs[15] = handler & (thumb ? ~1 : ~3);
>      cpsr_write(env, cpsr, CPSR_IT | CPSR_T | CPSR_E, CPSRWriteByInstr);

Otherwise
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

Re: [PATCH v4 05/25] linux-user/arm: Implement setup_sigtramp

[Richard Henderson]

On 9/28/21 5:31 AM, Peter Maydell wrote:
>> +        uint32_t *host_rc = g2h_untagged(retcode);
> 
> ...but here we treat it as a normal guest address that we can
> convert into a host address and dereference. If the signal handler
> is being entered in Thumb mode this will be a misaligned pointer.

Oops, yes.

I've no idea why the kernel works so hard to match the mode of the signal handler to the 
mode of the trampoline, but I presume it's ABI at this point.


r~

[PATCH v4 06/25] linux-user/alpha: Implement setup_sigtramp

[Richard Henderson]

Create and record the two signal trampolines.
Use them when the guest does not use ka_restorer.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/alpha/target_signal.h |  1 +
 linux-user/alpha/signal.c        | 34 +++++++++++++++++++-------------
 2 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/linux-user/alpha/target_signal.h b/linux-user/alpha/target_signal.h
index 250642913e..0b6a39de65 100644
--- a/linux-user/alpha/target_signal.h
+++ b/linux-user/alpha/target_signal.h
@@ -93,6 +93,7 @@ typedef struct target_sigaltstack {
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
 #define TARGET_ARCH_HAS_KA_RESTORER
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
 
 /* bit-flags */
 #define TARGET_SS_AUTODISARM (1U << 31) /* disable sas during sighandling */
diff --git a/linux-user/alpha/signal.c b/linux-user/alpha/signal.c
index 3a820f616b..bbe3dd175a 100644
--- a/linux-user/alpha/signal.c
+++ b/linux-user/alpha/signal.c
@@ -55,13 +55,11 @@ struct target_ucontext {
 
 struct target_sigframe {
     struct target_sigcontext sc;
-    unsigned int retcode[3];
 };
 
 struct target_rt_sigframe {
     target_siginfo_t info;
     struct target_ucontext uc;
-    unsigned int retcode[3];
 };
 
 #define INSN_MOV_R30_R16        0x47fe0410
@@ -142,12 +140,7 @@ void setup_frame(int sig, struct target_sigaction *ka,
     if (ka->ka_restorer) {
         r26 = ka->ka_restorer;
     } else {
-        __put_user(INSN_MOV_R30_R16, &frame->retcode[0]);
-        __put_user(INSN_LDI_R0 + TARGET_NR_sigreturn,
-                   &frame->retcode[1]);
-        __put_user(INSN_CALLSYS, &frame->retcode[2]);
-        /* imb() */
-        r26 = frame_addr + offsetof(struct target_sigframe, retcode);
+        r26 = default_sigreturn;
     }
 
     unlock_user_struct(frame, frame_addr, 1);
@@ -196,12 +189,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     if (ka->ka_restorer) {
         r26 = ka->ka_restorer;
     } else {
-        __put_user(INSN_MOV_R30_R16, &frame->retcode[0]);
-        __put_user(INSN_LDI_R0 + TARGET_NR_rt_sigreturn,
-                   &frame->retcode[1]);
-        __put_user(INSN_CALLSYS, &frame->retcode[2]);
-        /* imb(); */
-        r26 = frame_addr + offsetof(struct target_rt_sigframe, retcode);
+        r26 = default_rt_sigreturn;
     }
 
     if (err) {
@@ -269,3 +257,21 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return -TARGET_QEMU_ESIGRETURN;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 6 * 4, 0);
+    assert(tramp != NULL);
+
+    default_sigreturn = sigtramp_page;
+    __put_user(INSN_MOV_R30_R16, &tramp[0]);
+    __put_user(INSN_LDI_R0 + TARGET_NR_sigreturn, &tramp[1]);
+    __put_user(INSN_CALLSYS, &tramp[2]);
+
+    default_rt_sigreturn = sigtramp_page + 3 * 4;
+    __put_user(INSN_MOV_R30_R16, &tramp[3]);
+    __put_user(INSN_LDI_R0 + TARGET_NR_rt_sigreturn, &tramp[4]);
+    __put_user(INSN_CALLSYS, &tramp[5]);
+
+    unlock_user(tramp, sigtramp_page, 6 * 4);
+}
-- 
2.25.1

[PATCH v4 07/25] linux-user/cris: Implement setup_sigtramp

[Richard Henderson]

Split out setup_sigreturn so that we can continue to
initialize the words on the stack, as documented.
However, use the off-stack trampoline.

Cc: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/cris/target_signal.h |  2 ++
 linux-user/cris/signal.c        | 29 +++++++++++++++++++++--------
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/linux-user/cris/target_signal.h b/linux-user/cris/target_signal.h
index 495a142896..83a5155507 100644
--- a/linux-user/cris/target_signal.h
+++ b/linux-user/cris/target_signal.h
@@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
 #include "../generic/signal.h"
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* CRIS_TARGET_SIGNAL_H */
diff --git a/linux-user/cris/signal.c b/linux-user/cris/signal.c
index 2c39bdf727..7f6aca934e 100644
--- a/linux-user/cris/signal.c
+++ b/linux-user/cris/signal.c
@@ -97,6 +97,14 @@ static abi_ulong get_sigframe(CPUCRISState *env, int framesize)
     return sp - framesize;
 }
 
+static void setup_sigreturn(uint16_t *retcode)
+{
+    /* This is movu.w __NR_sigreturn, r9; break 13; */
+    __put_user(0x9c5f, retcode + 0);
+    __put_user(TARGET_NR_sigreturn, retcode + 1);
+    __put_user(0xe93d, retcode + 2);
+}
+
 void setup_frame(int sig, struct target_sigaction *ka,
                  target_sigset_t *set, CPUCRISState *env)
 {
@@ -112,14 +120,8 @@ void setup_frame(int sig, struct target_sigaction *ka,
     /*
      * The CRIS signal return trampoline. A real linux/CRIS kernel doesn't
      * use this trampoline anymore but it sets it up for GDB.
-     * In QEMU, using the trampoline simplifies things a bit so we use it.
-     *
-     * This is movu.w __NR_sigreturn, r9; break 13;
      */
-    __put_user(0x9c5f, frame->retcode+0);
-    __put_user(TARGET_NR_sigreturn,
-               frame->retcode + 1);
-    __put_user(0xe93d, frame->retcode + 2);
+    setup_sigreturn(frame->retcode);
 
     /* Save the mask.  */
     __put_user(set->sig[0], &frame->sc.oldmask);
@@ -135,7 +137,7 @@ void setup_frame(int sig, struct target_sigaction *ka,
     env->regs[10] = sig;
     env->pc = (unsigned long) ka->_sa_handler;
     /* Link SRP so the guest returns through the trampoline.  */
-    env->pregs[PR_SRP] = frame_addr + offsetof(typeof(*frame), retcode);
+    env->pregs[PR_SRP] = default_sigreturn;
 
     unlock_user_struct(frame, frame_addr, 1);
     return;
@@ -187,3 +189,14 @@ long do_rt_sigreturn(CPUCRISState *env)
     qemu_log_mask(LOG_UNIMP, "do_rt_sigreturn: not implemented\n");
     return -TARGET_ENOSYS;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 6, 0);
+    assert(tramp != NULL);
+
+    default_sigreturn = sigtramp_page;
+    setup_sigreturn(tramp);
+
+    unlock_user(tramp, sigtramp_page, 6);
+}
-- 
2.25.1

[PATCH v4 08/25] linux-user/hexagon: Implement setup_sigtramp

[Richard Henderson]

Continue to initialize the words on the stack, as documented.
However, use the off-stack trampoline.

Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/hexagon/target_signal.h |  2 ++
 linux-user/hexagon/signal.c        | 19 +++++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/linux-user/hexagon/target_signal.h b/linux-user/hexagon/target_signal.h
index 345cf1cbb8..9e0223d322 100644
--- a/linux-user/hexagon/target_signal.h
+++ b/linux-user/hexagon/target_signal.h
@@ -31,4 +31,6 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/hexagon/signal.c b/linux-user/hexagon/signal.c
index c7f0bf6b92..74e61739a0 100644
--- a/linux-user/hexagon/signal.c
+++ b/linux-user/hexagon/signal.c
@@ -162,6 +162,11 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 
     setup_ucontext(&frame->uc, env, set);
     tswap_siginfo(&frame->info, info);
+    /*
+     * The on-stack signal trampoline is no longer executed;
+     * however, the libgcc signal frame unwinding code checks
+     * for the presence of these two numeric magic values.
+     */
     install_sigtramp(frame->tramp);
 
     env->gpr[HEX_REG_PC] = ka->_sa_handler;
@@ -171,8 +176,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         frame_addr + offsetof(struct target_rt_sigframe, info);
     env->gpr[HEX_REG_R02] =
         frame_addr + offsetof(struct target_rt_sigframe, uc);
-    env->gpr[HEX_REG_LR] =
-        frame_addr + offsetof(struct target_rt_sigframe, tramp);
+    env->gpr[HEX_REG_LR] = default_rt_sigreturn;
 
     return;
 
@@ -271,3 +275,14 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return 0;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 4 * 2, 0);
+    assert(tramp != NULL);
+
+    default_rt_sigreturn = sigtramp_page;
+    install_sigtramp(tramp);
+
+    unlock_user(tramp, sigtramp_page, 4 * 2);
+}
-- 
2.25.1

[PATCH v4 09/25] linux-user/hppa: Document non-use of setup_sigtramp

[Richard Henderson]

We cannot use a raw sigtramp page for hppa,
but must wait for full vdso support.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/hppa/target_signal.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/linux-user/hppa/target_signal.h b/linux-user/hppa/target_signal.h
index 7f525362e9..d558119ee7 100644
--- a/linux-user/hppa/target_signal.h
+++ b/linux-user/hppa/target_signal.h
@@ -71,4 +71,18 @@ typedef struct target_sigaltstack {
 /* mask for all SS_xxx flags */
 #define TARGET_SS_FLAG_BITS  TARGET_SS_AUTODISARM
 
+/*
+ * We cannot use a bare sigtramp page for hppa-linux.
+ *
+ * Unlike other guests where we use the instructions at PC to validate
+ * an offset from SP, the hppa libgcc signal frame fallback unwinding uses
+ * the PC address itself to find the frame.  This is due to the fact that
+ * the hppa grows the stack upward, and the frame is of unknown size.
+ *
+ * TODO: We should be able to use a VDSO to address this, by providing
+ * proper unwind info for the sigtramp code, at which point the fallback
+ * unwinder will not be used.
+ */
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
+
 #endif /* HPPA_TARGET_SIGNAL_H */
-- 
2.25.1

[PATCH v4 10/25] linux-user/i386: Implement setup_sigtramp

[Richard Henderson]

Create and record the two signal trampolines.
Use them when the guest does not use SA_RESTORER.
Note that x86_64 does not use this code.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/i386/target_signal.h   |  2 ++
 linux-user/x86_64/target_signal.h |  3 ++
 linux-user/i386/signal.c          | 56 +++++++++++++++++++++----------
 3 files changed, 43 insertions(+), 18 deletions(-)

diff --git a/linux-user/i386/target_signal.h b/linux-user/i386/target_signal.h
index 50361af874..64d09f2e75 100644
--- a/linux-user/i386/target_signal.h
+++ b/linux-user/i386/target_signal.h
@@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
 #include "../generic/signal.h"
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* I386_TARGET_SIGNAL_H */
diff --git a/linux-user/x86_64/target_signal.h b/linux-user/x86_64/target_signal.h
index 4ea74f20dd..4673c5a886 100644
--- a/linux-user/x86_64/target_signal.h
+++ b/linux-user/x86_64/target_signal.h
@@ -21,4 +21,7 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+/* For x86_64, use of SA_RESTORER is mandatory. */
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
+
 #endif /* X86_64_TARGET_SIGNAL_H */
diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c
index 3b4b55fc0a..b38b5f108e 100644
--- a/linux-user/i386/signal.c
+++ b/linux-user/i386/signal.c
@@ -310,6 +310,22 @@ get_sigframe(struct target_sigaction *ka, CPUX86State *env, size_t frame_size)
 }
 
 #ifndef TARGET_X86_64
+static void install_sigtramp(void *tramp)
+{
+    /* This is popl %eax ; movl $syscall,%eax ; int $0x80 */
+    __put_user(0xb858, (uint16_t *)(tramp + 0));
+    __put_user(TARGET_NR_sigreturn, (int32_t *)(tramp + 2));
+    __put_user(0x80cd, (uint16_t *)(tramp + 6));
+}
+
+static void install_rt_sigtramp(void *tramp)
+{
+    /* This is movl $syscall,%eax ; int $0x80 */
+    __put_user(0xb8, (uint8_t *)(tramp + 0));
+    __put_user(TARGET_NR_rt_sigreturn, (int32_t *)(tramp + 1));
+    __put_user(0x80cd, (uint16_t *)(tramp + 5));
+}
+
 /* compare linux/arch/i386/kernel/signal.c:setup_frame() */
 void setup_frame(int sig, struct target_sigaction *ka,
                  target_sigset_t *set, CPUX86State *env)
@@ -338,16 +354,9 @@ void setup_frame(int sig, struct target_sigaction *ka,
     if (ka->sa_flags & TARGET_SA_RESTORER) {
         __put_user(ka->sa_restorer, &frame->pretcode);
     } else {
-        uint16_t val16;
-        abi_ulong retcode_addr;
-        retcode_addr = frame_addr + offsetof(struct sigframe, retcode);
-        __put_user(retcode_addr, &frame->pretcode);
-        /* This is popl %eax ; movl $,%eax ; int $0x80 */
-        val16 = 0xb858;
-        __put_user(val16, (uint16_t *)(frame->retcode+0));
-        __put_user(TARGET_NR_sigreturn, (int *)(frame->retcode+2));
-        val16 = 0x80cd;
-        __put_user(val16, (uint16_t *)(frame->retcode+6));
+        /* This is no longer used, but is retained for ABI compatibility. */
+        install_sigtramp(frame->retcode);
+        __put_user(default_sigreturn, &frame->pretcode);
     }
 
     /* Set up registers for signal handler */
@@ -416,14 +425,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     if (ka->sa_flags & TARGET_SA_RESTORER) {
         __put_user(ka->sa_restorer, &frame->pretcode);
     } else {
-        uint16_t val16;
-        addr = frame_addr + offsetof(struct rt_sigframe, retcode);
-        __put_user(addr, &frame->pretcode);
-        /* This is movl $,%eax ; int $0x80 */
-        __put_user(0xb8, (char *)(frame->retcode+0));
-        __put_user(TARGET_NR_rt_sigreturn, (int *)(frame->retcode+1));
-        val16 = 0x80cd;
-        __put_user(val16, (uint16_t *)(frame->retcode+5));
+        /* This is no longer used, but is retained for ABI compatibility. */
+        install_rt_sigtramp(frame->retcode);
+        __put_user(default_rt_sigreturn, &frame->pretcode);
     }
 #else
     /* XXX: Would be slightly better to return -EFAULT here if test fails
@@ -592,3 +596,19 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return -TARGET_QEMU_ESIGRETURN;
 }
+
+#ifndef TARGET_X86_64
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);
+    assert(tramp != NULL);
+
+    default_sigreturn = sigtramp_page;
+    install_sigtramp(tramp);
+
+    default_rt_sigreturn = sigtramp_page + 8;
+    install_rt_sigtramp(tramp + 8);
+
+    unlock_user(tramp, sigtramp_page, 2 * 8);
+}
+#endif
-- 
2.25.1

Re: [PATCH v4 10/25] linux-user/i386: Implement setup_sigtramp

[Philippe Mathieu-Daudé]

On 9/28/21 04:00, Richard Henderson wrote:
> Create and record the two signal trampolines.
> Use them when the guest does not use SA_RESTORER.
> Note that x86_64 does not use this code.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  linux-user/i386/target_signal.h   |  2 ++
>  linux-user/x86_64/target_signal.h |  3 ++
>  linux-user/i386/signal.c          | 56 +++++++++++++++++++++----------
>  3 files changed, 43 insertions(+), 18 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

[PATCH v4 11/25] linux-user/x86_64: Raise SIGSEGV if SA_RESTORER not set

[Richard Henderson]

This has been a fixme for some time.  The effect of
returning -EFAULT from the kernel code is to raise SIGSEGV.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/i386/signal.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c
index b38b5f108e..433efa3d69 100644
--- a/linux-user/i386/signal.c
+++ b/linux-user/i386/signal.c
@@ -421,19 +421,18 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 
     /* Set up to return from userspace.  If provided, use a stub
        already in userspace.  */
-#ifndef TARGET_X86_64
     if (ka->sa_flags & TARGET_SA_RESTORER) {
         __put_user(ka->sa_restorer, &frame->pretcode);
     } else {
+#ifdef TARGET_X86_64
+        /* For x86_64, SA_RESTORER is required ABI.  */
+        goto give_sigsegv;
+#else
         /* This is no longer used, but is retained for ABI compatibility. */
         install_rt_sigtramp(frame->retcode);
         __put_user(default_rt_sigreturn, &frame->pretcode);
-    }
-#else
-    /* XXX: Would be slightly better to return -EFAULT here if test fails
-       assert(ka->sa_flags & TARGET_SA_RESTORER); */
-    __put_user(ka->sa_restorer, &frame->pretcode);
 #endif
+    }
 
     /* Set up registers for signal handler */
     env->regs[R_ESP] = frame_addr;
-- 
2.25.1

[PATCH v4 12/25] linux-user/m68k: Implement setup_sigtramp

[Richard Henderson]

Create and record the two signal trampolines.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/m68k/target_signal.h |  2 ++
 linux-user/m68k/signal.c        | 47 +++++++++++++++------------------
 2 files changed, 24 insertions(+), 25 deletions(-)

diff --git a/linux-user/m68k/target_signal.h b/linux-user/m68k/target_signal.h
index d096544ef8..94157bf1f4 100644
--- a/linux-user/m68k/target_signal.h
+++ b/linux-user/m68k/target_signal.h
@@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
 #include "../generic/signal.h"
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* M68K_TARGET_SIGNAL_H */
diff --git a/linux-user/m68k/signal.c b/linux-user/m68k/signal.c
index 4f8eb6f727..ec33482e14 100644
--- a/linux-user/m68k/signal.c
+++ b/linux-user/m68k/signal.c
@@ -39,7 +39,6 @@ struct target_sigframe
     int sig;
     int code;
     abi_ulong psc;
-    char retcode[8];
     abi_ulong extramask[TARGET_NSIG_WORDS-1];
     struct target_sigcontext sc;
 };
@@ -76,7 +75,6 @@ struct target_rt_sigframe
     int sig;
     abi_ulong pinfo;
     abi_ulong puc;
-    char retcode[8];
     struct target_siginfo info;
     struct target_ucontext uc;
 };
@@ -130,7 +128,6 @@ void setup_frame(int sig, struct target_sigaction *ka,
 {
     struct target_sigframe *frame;
     abi_ulong frame_addr;
-    abi_ulong retcode_addr;
     abi_ulong sc_addr;
     int i;
 
@@ -152,16 +149,7 @@ void setup_frame(int sig, struct target_sigaction *ka,
     }
 
     /* Set up to return from userspace.  */
-
-    retcode_addr = frame_addr + offsetof(struct target_sigframe, retcode);
-    __put_user(retcode_addr, &frame->pretcode);
-
-    /* moveq #,d0; trap #0 */
-
-    __put_user(0x70004e40 + (TARGET_NR_sigreturn << 16),
-               (uint32_t *)(frame->retcode));
-
-    /* Set up to return from userspace */
+    __put_user(default_sigreturn, &frame->pretcode);
 
     env->aregs[7] = frame_addr;
     env->pc = ka->_sa_handler;
@@ -288,7 +276,6 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 {
     struct target_rt_sigframe *frame;
     abi_ulong frame_addr;
-    abi_ulong retcode_addr;
     abi_ulong info_addr;
     abi_ulong uc_addr;
     int err = 0;
@@ -325,17 +312,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     }
 
     /* Set up to return from userspace.  */
-
-    retcode_addr = frame_addr + offsetof(struct target_sigframe, retcode);
-    __put_user(retcode_addr, &frame->pretcode);
-
-    /* moveq #,d0; notb d0; trap #0 */
-
-    __put_user(0x70004600 + ((TARGET_NR_rt_sigreturn ^ 0xff) << 16),
-               (uint32_t *)(frame->retcode + 0));
-    __put_user(0x4e40, (uint16_t *)(frame->retcode + 4));
-
-    /* Set up to return from userspace */
+    __put_user(default_rt_sigreturn, &frame->pretcode);
 
     env->aregs[7] = frame_addr;
     env->pc = ka->_sa_handler;
@@ -411,3 +388,23 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return -TARGET_QEMU_ESIGRETURN;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    void *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 4 + 6, 0);
+    assert(tramp != NULL);
+
+    default_sigreturn = sigtramp_page;
+
+    /* moveq #,d0; trap #0 */
+    __put_user(0x70004e40 + (TARGET_NR_sigreturn << 16), (uint32_t *)tramp);
+
+    default_rt_sigreturn = sigtramp_page + 4;
+
+    /* moveq #,d0; notb d0; trap #0 */
+    __put_user(0x70004600 + ((TARGET_NR_rt_sigreturn ^ 0xff) << 16),
+               (uint32_t *)(tramp + 4));
+    __put_user(0x4e40, (uint16_t *)(tramp + 8));
+
+    unlock_user(tramp, sigtramp_page, 4 + 6);
+}
-- 
2.25.1

[PATCH v4 13/25] linux-user/microblaze: Implement setup_sigtramp

[Richard Henderson]

Create and record the rt signal trampoline.

Cc: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/microblaze/target_signal.h |  2 ++
 linux-user/microblaze/signal.c        | 24 +++++++++++++++++-------
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/linux-user/microblaze/target_signal.h b/linux-user/microblaze/target_signal.h
index 1c326296de..e8b510f6b1 100644
--- a/linux-user/microblaze/target_signal.h
+++ b/linux-user/microblaze/target_signal.h
@@ -21,4 +21,6 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* MICROBLAZE_TARGET_SIGNAL_H */
diff --git a/linux-user/microblaze/signal.c b/linux-user/microblaze/signal.c
index b822679d18..8ebb6a1b7d 100644
--- a/linux-user/microblaze/signal.c
+++ b/linux-user/microblaze/signal.c
@@ -161,17 +161,11 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 
     /* Kernel does not use SA_RESTORER. */
 
-    /* addi r12, r0, __NR_sigreturn */
-    __put_user(0x31800000U | TARGET_NR_rt_sigreturn, frame->tramp + 0);
-    /* brki r14, 0x8 */
-    __put_user(0xb9cc0008U, frame->tramp + 1);
-
     /*
      * Return from sighandler will jump to the tramp.
      * Negative 8 offset because return is rtsd r15, 8
      */
-    env->regs[15] =
-        frame_addr + offsetof(struct target_rt_sigframe, tramp) - 8;
+    env->regs[15] = default_rt_sigreturn - 8;
 
     /* Set up registers for signal handler */
     env->regs[1] = frame_addr;
@@ -220,3 +214,19 @@ long do_rt_sigreturn(CPUMBState *env)
     force_sig(TARGET_SIGSEGV);
     return -TARGET_QEMU_ESIGRETURN;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 8, 0);
+    assert(tramp != NULL);
+
+    /*
+     * addi r12, r0, __NR_rt_sigreturn
+     * brki r14, 0x8
+     */
+    __put_user(0x31800000U | TARGET_NR_rt_sigreturn, tramp);
+    __put_user(0xb9cc0008U, tramp + 1);
+
+    default_rt_sigreturn = sigtramp_page;
+    unlock_user(tramp, sigtramp_page, 8);
+}
-- 
2.25.1

[PATCH v4 14/25] linux-user/mips: Tidy install_sigtramp

[Richard Henderson]

The return value is constant 0, and unused as well -- change to void.
Drop inline marker.  Change tramp type to uint32_t* for clarity.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/mips/signal.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/linux-user/mips/signal.c b/linux-user/mips/signal.c
index d174b3453c..64072779b9 100644
--- a/linux-user/mips/signal.c
+++ b/linux-user/mips/signal.c
@@ -87,10 +87,8 @@ struct target_rt_sigframe {
 };
 
 /* Install trampoline to jump back from signal handler */
-static inline int install_sigtramp(unsigned int *tramp,   unsigned int syscall)
+static void install_sigtramp(uint32_t *tramp, unsigned int syscall)
 {
-    int err = 0;
-
     /*
      * Set up the return code ...
      *
@@ -100,7 +98,6 @@ static inline int install_sigtramp(unsigned int *tramp,   unsigned int syscall)
 
     __put_user(0x24020000 + syscall, tramp + 0);
     __put_user(0x0000000c          , tramp + 1);
-    return err;
 }
 
 static inline void setup_sigcontext(CPUMIPSState *regs,
-- 
2.25.1

[PATCH v4 15/25] linux-user/mips: Implement setup_sigtramp

[Richard Henderson]

Create and record the two signal trampolines.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/mips/target_signal.h   |  1 +
 linux-user/mips64/target_signal.h |  2 ++
 linux-user/mips/signal.c          | 34 ++++++++++++++++++++++---------
 3 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/linux-user/mips/target_signal.h b/linux-user/mips/target_signal.h
index d521765f6b..780a4ddf29 100644
--- a/linux-user/mips/target_signal.h
+++ b/linux-user/mips/target_signal.h
@@ -73,6 +73,7 @@ typedef struct target_sigaltstack {
 /* compare linux/arch/mips/kernel/signal.c:setup_frame() */
 #define TARGET_ARCH_HAS_SETUP_FRAME
 #endif
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
 
 /* bit-flags */
 #define TARGET_SS_AUTODISARM (1U << 31) /* disable sas during sighandling */
diff --git a/linux-user/mips64/target_signal.h b/linux-user/mips64/target_signal.h
index d857c55e4c..275e9b7f9a 100644
--- a/linux-user/mips64/target_signal.h
+++ b/linux-user/mips64/target_signal.h
@@ -76,4 +76,6 @@ typedef struct target_sigaltstack {
 /* compare linux/arch/mips/kernel/signal.c:setup_frame() */
 #define TARGET_ARCH_HAS_SETUP_FRAME
 #endif
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* MIPS64_TARGET_SIGNAL_H */
diff --git a/linux-user/mips/signal.c b/linux-user/mips/signal.c
index 64072779b9..8f79e405ec 100644
--- a/linux-user/mips/signal.c
+++ b/linux-user/mips/signal.c
@@ -209,8 +209,6 @@ void setup_frame(int sig, struct target_sigaction * ka,
         goto give_sigsegv;
     }
 
-    install_sigtramp(frame->sf_code, TARGET_NR_sigreturn);
-
     setup_sigcontext(regs, &frame->sf_sc);
 
     for(i = 0; i < TARGET_NSIG_WORDS; i++) {
@@ -231,7 +229,7 @@ void setup_frame(int sig, struct target_sigaction * ka,
     regs->active_tc.gpr[ 5] = 0;
     regs->active_tc.gpr[ 6] = frame_addr + offsetof(struct sigframe, sf_sc);
     regs->active_tc.gpr[29] = frame_addr;
-    regs->active_tc.gpr[31] = frame_addr + offsetof(struct sigframe, sf_code);
+    regs->active_tc.gpr[31] = default_sigreturn;
     /* The original kernel code sets CP0_EPC to the handler
     * since it returns to userland using eret
     * we cannot do this here, and we must set PC directly */
@@ -305,8 +303,6 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         goto give_sigsegv;
     }
 
-    install_sigtramp(frame->rs_code, TARGET_NR_rt_sigreturn);
-
     tswap_siginfo(&frame->rs_info, info);
 
     __put_user(0, &frame->rs_uc.tuc_flags);
@@ -335,11 +331,13 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     env->active_tc.gpr[ 6] = frame_addr
                              + offsetof(struct target_rt_sigframe, rs_uc);
     env->active_tc.gpr[29] = frame_addr;
-    env->active_tc.gpr[31] = frame_addr
-                             + offsetof(struct target_rt_sigframe, rs_code);
-    /* The original kernel code sets CP0_EPC to the handler
-    * since it returns to userland using eret
-    * we cannot do this here, and we must set PC directly */
+    env->active_tc.gpr[31] = default_rt_sigreturn;
+
+    /*
+     * The original kernel code sets CP0_EPC to the handler
+     * since it returns to userland using eret
+     * we cannot do this here, and we must set PC directly
+     */
     env->active_tc.PC = env->active_tc.gpr[25] = ka->_sa_handler;
     mips_set_hflags_isa_mode_from_pc(env);
     unlock_user_struct(frame, frame_addr, 1);
@@ -379,3 +377,19 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return -TARGET_QEMU_ESIGRETURN;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);
+    assert(tramp != NULL);
+
+#ifdef TARGET_ARCH_HAS_SETUP_FRAME
+    default_sigreturn = sigtramp_page;
+    install_sigtramp(tramp, TARGET_NR_sigreturn);
+#endif
+
+    default_rt_sigreturn = sigtramp_page + 8;
+    install_sigtramp(tramp + 2, TARGET_NR_rt_sigreturn);
+
+    unlock_user(tramp, sigtramp_page, 2 * 8);
+}
-- 
2.25.1

[PATCH v4 16/25] linux-user/nios2: Document non-use of setup_sigtramp

[Richard Henderson]

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/nios2/target_signal.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/linux-user/nios2/target_signal.h b/linux-user/nios2/target_signal.h
index aebf749f12..fe266c4c51 100644
--- a/linux-user/nios2/target_signal.h
+++ b/linux-user/nios2/target_signal.h
@@ -19,4 +19,7 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+/* Nios2 uses a fixed address on the kuser page for sigreturn. */
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
+
 #endif /* NIOS2_TARGET_SIGNAL_H */
-- 
2.25.1

Re: [PATCH v4 16/25] linux-user/nios2: Document non-use of setup_sigtramp

[Peter Maydell]

On Tue, 28 Sept 2021 at 03:00, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  linux-user/nios2/target_signal.h | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/linux-user/nios2/target_signal.h b/linux-user/nios2/target_signal.h
> index aebf749f12..fe266c4c51 100644
> --- a/linux-user/nios2/target_signal.h
> +++ b/linux-user/nios2/target_signal.h
> @@ -19,4 +19,7 @@ typedef struct target_sigaltstack {
>
>  #include "../generic/signal.h"
>
> +/* Nios2 uses a fixed address on the kuser page for sigreturn. */
> +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
> +

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

[PATCH v4 17/25] linux-user/openrisc: Implement setup_sigtramp

[Richard Henderson]

Create and record the rt signal trampoline.

Reviewed-by: Stafford Horne <shorne@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/openrisc/target_signal.h |  2 ++
 linux-user/openrisc/signal.c        | 22 ++++++++++++++--------
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/linux-user/openrisc/target_signal.h b/linux-user/openrisc/target_signal.h
index 8283eaf544..077ec3d5e8 100644
--- a/linux-user/openrisc/target_signal.h
+++ b/linux-user/openrisc/target_signal.h
@@ -26,4 +26,6 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* OPENRISC_TARGET_SIGNAL_H */
diff --git a/linux-user/openrisc/signal.c b/linux-user/openrisc/signal.c
index ca2532bf50..be8b68784a 100644
--- a/linux-user/openrisc/signal.c
+++ b/linux-user/openrisc/signal.c
@@ -38,7 +38,6 @@ typedef struct target_ucontext {
 typedef struct target_rt_sigframe {
     struct target_siginfo info;
     target_ucontext uc;
-    uint32_t retcode[4];  /* trampoline code */
 } target_rt_sigframe;
 
 static void restore_sigcontext(CPUOpenRISCState *env, target_sigcontext *sc)
@@ -116,14 +115,8 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         __put_user(set->sig[i], &frame->uc.tuc_sigmask.sig[i]);
     }
 
-    /* This is l.ori r11,r0,__NR_sigreturn; l.sys 1; l.nop; l.nop */
-    __put_user(0xa9600000 | TARGET_NR_rt_sigreturn, frame->retcode + 0);
-    __put_user(0x20000001, frame->retcode + 1);
-    __put_user(0x15000000, frame->retcode + 2);
-    __put_user(0x15000000, frame->retcode + 3);
-
     /* Set up registers for signal handler */
-    cpu_set_gpr(env, 9, frame_addr + offsetof(target_rt_sigframe, retcode));
+    cpu_set_gpr(env, 9, default_rt_sigreturn);
     cpu_set_gpr(env, 3, sig);
     cpu_set_gpr(env, 4, frame_addr + offsetof(target_rt_sigframe, info));
     cpu_set_gpr(env, 5, frame_addr + offsetof(target_rt_sigframe, uc));
@@ -169,3 +162,16 @@ long do_rt_sigreturn(CPUOpenRISCState *env)
     force_sig(TARGET_SIGSEGV);
     return 0;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 8, 0);
+    assert(tramp != NULL);
+
+    /* This is l.ori r11,r0,__NR_sigreturn; l.sys 1 */
+    __put_user(0xa9600000 | TARGET_NR_rt_sigreturn, tramp + 0);
+    __put_user(0x20000001, tramp + 1);
+
+    default_rt_sigreturn = sigtramp_page;
+    unlock_user(tramp, sigtramp_page, 8);
+}
-- 
2.25.1

[PATCH v4 18/25] linux-user/ppc: Simplify encode_trampoline

[Richard Henderson]

The sigret parameter is never 0, and even if it was the encoding
of the LI instruction would still work.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/ppc/signal.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c
index e4d0dfa3bf..77f37b9f01 100644
--- a/linux-user/ppc/signal.c
+++ b/linux-user/ppc/signal.c
@@ -309,10 +309,8 @@ static void save_user_regs(CPUPPCState *env, struct target_mcontext *frame)
 static void encode_trampoline(int sigret, uint32_t *tramp)
 {
     /* Set up the sigreturn trampoline: li r0,sigret; sc.  */
-    if (sigret) {
-        __put_user(0x38000000 | sigret, &tramp[0]);
-        __put_user(0x44000002, &tramp[1]);
-    }
+    __put_user(0x38000000 | sigret, &tramp[0]);
+    __put_user(0x44000002, &tramp[1]);
 }
 
 static void restore_user_regs(CPUPPCState *env,
-- 
2.25.1

[PATCH v4 19/25] linux-user/ppc: Implement setup_sigtramp

[Richard Henderson]

Create and record the two signal trampolines.

Cc: qemu-ppc@nongnu.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/ppc/target_signal.h |  2 ++
 linux-user/ppc/signal.c        | 34 ++++++++++++++++++----------------
 2 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/linux-user/ppc/target_signal.h b/linux-user/ppc/target_signal.h
index 72fcdd9bfa..82184ab8f2 100644
--- a/linux-user/ppc/target_signal.h
+++ b/linux-user/ppc/target_signal.h
@@ -24,4 +24,6 @@ typedef struct target_sigaltstack {
 #if !defined(TARGET_PPC64)
 #define TARGET_ARCH_HAS_SETUP_FRAME
 #endif
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* PPC_TARGET_SIGNAL_H */
diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c
index 77f37b9f01..c37744c8fc 100644
--- a/linux-user/ppc/signal.c
+++ b/linux-user/ppc/signal.c
@@ -203,9 +203,6 @@ struct target_func_ptr {
 
 #endif
 
-/* We use the mc_pad field for the signal return trampoline.  */
-#define tramp mc_pad
-
 /* See arch/powerpc/kernel/signal.c.  */
 static target_ulong get_sigframe(struct target_sigaction *ka,
                                  CPUPPCState *env,
@@ -436,12 +433,7 @@ void setup_frame(int sig, struct target_sigaction *ka,
     /* Save user regs.  */
     save_user_regs(env, &frame->mctx);
 
-    /* Construct the trampoline code on the stack. */
-    encode_trampoline(TARGET_NR_sigreturn, (uint32_t *)&frame->mctx.tramp);
-
-    /* The kernel checks for the presence of a VDSO here.  We don't
-       emulate a vdso, so use a sigreturn system call.  */
-    env->lr = (target_ulong) h2g(frame->mctx.tramp);
+    env->lr = default_sigreturn;
 
     /* Turn off all fp exceptions.  */
     env->fpscr = 0;
@@ -477,7 +469,6 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
                     target_sigset_t *set, CPUPPCState *env)
 {
     struct target_rt_sigframe *rt_sf;
-    uint32_t *trampptr = 0;
     struct target_mcontext *mctx = 0;
     target_ulong rt_sf_addr, newsp = 0;
     int i, err = 0;
@@ -507,22 +498,17 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 
 #if defined(TARGET_PPC64)
     mctx = &rt_sf->uc.tuc_sigcontext.mcontext;
-    trampptr = &rt_sf->trampoline[0];
 
     sc = &rt_sf->uc.tuc_sigcontext;
     __put_user(h2g(mctx), &sc->regs);
     __put_user(sig, &sc->signal);
 #else
     mctx = &rt_sf->uc.tuc_mcontext;
-    trampptr = (uint32_t *)&rt_sf->uc.tuc_mcontext.tramp;
 #endif
 
     save_user_regs(env, mctx);
-    encode_trampoline(TARGET_NR_rt_sigreturn, trampptr);
 
-    /* The kernel checks for the presence of a VDSO here.  We don't
-       emulate a vdso, so use a sigreturn system call.  */
-    env->lr = (target_ulong) h2g(trampptr);
+    env->lr = default_rt_sigreturn;
 
     /* Turn off all fp exceptions.  */
     env->fpscr = 0;
@@ -720,3 +706,19 @@ abi_long do_swapcontext(CPUArchState *env, abi_ulong uold_ctx,
 
     return 0;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);
+    assert(tramp != NULL);
+
+#ifdef TARGET_ARCH_HAS_SETUP_FRAME
+    default_sigreturn = sigtramp_page;
+    encode_trampoline(TARGET_NR_sigreturn, tramp + 0);
+#endif
+
+    default_rt_sigreturn = sigtramp_page + 8;
+    encode_trampoline(TARGET_NR_rt_sigreturn, tramp + 2);
+
+    unlock_user(tramp, sigtramp_page, 2 * 8);
+}
-- 
2.25.1

[PATCH v4 20/25] linux-user/riscv: Implement setup_sigtramp

[Richard Henderson]

Create and record the rt signal trampoline.

This fixes a bug wrt libgcc fallback unwinding.  It expects
the stack pointer to point to the siginfo_t, whereas we had
inexplicably placed our private signal trampoline at the start
of the signal frame instead of the end.  Now moot because we
have removed it from the stack frame entirely.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/riscv/target_signal.h |  2 ++
 linux-user/riscv/signal.c        | 22 +++++++++++++---------
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/linux-user/riscv/target_signal.h b/linux-user/riscv/target_signal.h
index f113ba9a55..3e36fddc9d 100644
--- a/linux-user/riscv/target_signal.h
+++ b/linux-user/riscv/target_signal.h
@@ -15,4 +15,6 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* RISCV_TARGET_SIGNAL_H */
diff --git a/linux-user/riscv/signal.c b/linux-user/riscv/signal.c
index f7f33bc90a..a0f9542ce3 100644
--- a/linux-user/riscv/signal.c
+++ b/linux-user/riscv/signal.c
@@ -47,7 +47,6 @@ struct target_ucontext {
 };
 
 struct target_rt_sigframe {
-    uint32_t tramp[2]; /* not in kernel, which uses VDSO instead */
     struct target_siginfo info;
     struct target_ucontext uc;
 };
@@ -105,12 +104,6 @@ static void setup_ucontext(struct target_ucontext *uc,
     setup_sigcontext(&uc->uc_mcontext, env);
 }
 
-static inline void install_sigtramp(uint32_t *tramp)
-{
-    __put_user(0x08b00893, tramp + 0);  /* li a7, 139 = __NR_rt_sigreturn */
-    __put_user(0x00000073, tramp + 1);  /* ecall */
-}
-
 void setup_rt_frame(int sig, struct target_sigaction *ka,
                     target_siginfo_t *info,
                     target_sigset_t *set, CPURISCVState *env)
@@ -127,14 +120,13 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 
     setup_ucontext(&frame->uc, env, set);
     tswap_siginfo(&frame->info, info);
-    install_sigtramp(frame->tramp);
 
     env->pc = ka->_sa_handler;
     env->gpr[xSP] = frame_addr;
     env->gpr[xA0] = sig;
     env->gpr[xA1] = frame_addr + offsetof(struct target_rt_sigframe, info);
     env->gpr[xA2] = frame_addr + offsetof(struct target_rt_sigframe, uc);
-    env->gpr[xRA] = frame_addr + offsetof(struct target_rt_sigframe, tramp);
+    env->gpr[xRA] = default_rt_sigreturn;
 
     return;
 
@@ -203,3 +195,15 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return 0;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 8, 0);
+    assert(tramp != NULL);
+
+    __put_user(0x08b00893, tramp + 0);  /* li a7, 139 = __NR_rt_sigreturn */
+    __put_user(0x00000073, tramp + 1);  /* ecall */
+
+    default_rt_sigreturn = sigtramp_page;
+    unlock_user(tramp, sigtramp_page, 8);
+}
-- 
2.25.1

[PATCH v4 21/25] linux-user/s390x: Implement setup_sigtramp

[Richard Henderson]

Create and record the two signal trampolines.
Use them when the guest does not use SA_RESTORER.

Cc: qemu-s390x@nongnu.org
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/s390x/target_signal.h |  2 ++
 linux-user/s390x/signal.c        | 24 ++++++++++++++++--------
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/linux-user/s390x/target_signal.h b/linux-user/s390x/target_signal.h
index bbfc464d44..64f5f42201 100644
--- a/linux-user/s390x/target_signal.h
+++ b/linux-user/s390x/target_signal.h
@@ -19,4 +19,6 @@ typedef struct target_sigaltstack {
 #include "../generic/signal.h"
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* S390X_TARGET_SIGNAL_H */
diff --git a/linux-user/s390x/signal.c b/linux-user/s390x/signal.c
index 80f34086d7..676b948147 100644
--- a/linux-user/s390x/signal.c
+++ b/linux-user/s390x/signal.c
@@ -68,7 +68,6 @@ typedef struct {
     target_sigregs sregs;
     int signo;
     target_sigregs_ext sregs_ext;
-    uint16_t retcode;
 } sigframe;
 
 #define TARGET_UC_VXRS 2
@@ -85,7 +84,6 @@ struct target_ucontext {
 
 typedef struct {
     uint8_t callee_used_stack[__SIGNAL_FRAMESIZE];
-    uint16_t retcode;
     struct target_siginfo info;
     struct target_ucontext uc;
 } rt_sigframe;
@@ -209,9 +207,7 @@ void setup_frame(int sig, struct target_sigaction *ka,
     if (ka->sa_flags & TARGET_SA_RESTORER) {
         restorer = ka->sa_restorer;
     } else {
-        restorer = frame_addr + offsetof(sigframe, retcode);
-        __put_user(S390_SYSCALL_OPCODE | TARGET_NR_sigreturn,
-                   &frame->retcode);
+        restorer = default_sigreturn;
     }
 
     /* Set up registers for signal handler */
@@ -262,9 +258,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     if (ka->sa_flags & TARGET_SA_RESTORER) {
         restorer = ka->sa_restorer;
     } else {
-        restorer = frame_addr + offsetof(typeof(*frame), retcode);
-        __put_user(S390_SYSCALL_OPCODE | TARGET_NR_rt_sigreturn,
-                   &frame->retcode);
+        restorer = default_rt_sigreturn;
     }
 
     /* Create siginfo on the signal stack. */
@@ -405,3 +399,17 @@ long do_rt_sigreturn(CPUS390XState *env)
     unlock_user_struct(frame, frame_addr, 0);
     return -TARGET_QEMU_ESIGRETURN;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 + 2, 0);
+    assert(tramp != NULL);
+
+    default_sigreturn = sigtramp_page;
+    __put_user(S390_SYSCALL_OPCODE | TARGET_NR_sigreturn, &tramp[0]);
+
+    default_rt_sigreturn = sigtramp_page + 2;
+    __put_user(S390_SYSCALL_OPCODE | TARGET_NR_rt_sigreturn, &tramp[1]);
+
+    unlock_user(tramp, sigtramp_page, 2 + 2);
+}
-- 
2.25.1

[PATCH v4 22/25] linux-user/sh4: Implement setup_sigtramp

[Richard Henderson]

Create and record the two signal trampolines.
Use them when the guest does not use SA_RESTORER.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/sh4/target_signal.h |  2 ++
 linux-user/sh4/signal.c        | 40 +++++++++++++++++++---------------
 2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/linux-user/sh4/target_signal.h b/linux-user/sh4/target_signal.h
index d7309b7136..04069cba66 100644
--- a/linux-user/sh4/target_signal.h
+++ b/linux-user/sh4/target_signal.h
@@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
 #include "../generic/signal.h"
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* SH4_TARGET_SIGNAL_H */
diff --git a/linux-user/sh4/signal.c b/linux-user/sh4/signal.c
index d70d744bef..faa869fb19 100644
--- a/linux-user/sh4/signal.c
+++ b/linux-user/sh4/signal.c
@@ -52,7 +52,6 @@ struct target_sigframe
 {
     struct target_sigcontext sc;
     target_ulong extramask[TARGET_NSIG_WORDS-1];
-    uint16_t retcode[3];
 };
 
 
@@ -68,7 +67,6 @@ struct target_rt_sigframe
 {
     struct target_siginfo info;
     struct target_ucontext uc;
-    uint16_t retcode[3];
 };
 
 
@@ -190,15 +188,9 @@ void setup_frame(int sig, struct target_sigaction *ka,
     /* Set up to return from userspace.  If provided, use a stub
        already in userspace.  */
     if (ka->sa_flags & TARGET_SA_RESTORER) {
-        regs->pr = (unsigned long) ka->sa_restorer;
+        regs->pr = ka->sa_restorer;
     } else {
-        /* Generate return code (system call to sigreturn) */
-        abi_ulong retcode_addr = frame_addr +
-                                 offsetof(struct target_sigframe, retcode);
-        __put_user(MOVW(2), &frame->retcode[0]);
-        __put_user(TRAP_NOARG, &frame->retcode[1]);
-        __put_user((TARGET_NR_sigreturn), &frame->retcode[2]);
-        regs->pr = (unsigned long) retcode_addr;
+        regs->pr = default_sigreturn;
     }
 
     /* Set up registers for signal handler */
@@ -248,15 +240,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     /* Set up to return from userspace.  If provided, use a stub
        already in userspace.  */
     if (ka->sa_flags & TARGET_SA_RESTORER) {
-        regs->pr = (unsigned long) ka->sa_restorer;
+        regs->pr = ka->sa_restorer;
     } else {
-        /* Generate return code (system call to sigreturn) */
-        abi_ulong retcode_addr = frame_addr +
-                                 offsetof(struct target_rt_sigframe, retcode);
-        __put_user(MOVW(2), &frame->retcode[0]);
-        __put_user(TRAP_NOARG, &frame->retcode[1]);
-        __put_user((TARGET_NR_rt_sigreturn), &frame->retcode[2]);
-        regs->pr = (unsigned long) retcode_addr;
+        regs->pr = default_rt_sigreturn;
     }
 
     /* Set up registers for signal handler */
@@ -334,3 +320,21 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return -TARGET_QEMU_ESIGRETURN;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint16_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 6, 0);
+    assert(tramp != NULL);
+
+    default_sigreturn = sigtramp_page;
+    __put_user(MOVW(2), &tramp[0]);
+    __put_user(TRAP_NOARG, &tramp[1]);
+    __put_user(TARGET_NR_sigreturn, &tramp[2]);
+
+    default_rt_sigreturn = sigtramp_page + 6;
+    __put_user(MOVW(2), &tramp[3]);
+    __put_user(TRAP_NOARG, &tramp[4]);
+    __put_user(TARGET_NR_rt_sigreturn, &tramp[5]);
+
+    unlock_user(tramp, sigtramp_page, 2 * 6);
+}
-- 
2.25.1

[PATCH v4 23/25] linux-user/sparc: Implement setup_sigtramp

[Richard Henderson]

Create and record the two signal trampolines.
Use them when the guest does not use SA_RESTORER.

Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/sparc/target_signal.h |  4 ++++
 linux-user/sparc/signal.c        | 40 +++++++++++++++++++++-----------
 2 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/linux-user/sparc/target_signal.h b/linux-user/sparc/target_signal.h
index 34f9a12519..e661ddd6ab 100644
--- a/linux-user/sparc/target_signal.h
+++ b/linux-user/sparc/target_signal.h
@@ -69,6 +69,10 @@ typedef struct target_sigaltstack {
 
 #ifdef TARGET_ABI32
 #define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+#else
+/* For sparc64, use of KA_RESTORER is mandatory. */
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
 #endif
 
 /* bit-flags */
diff --git a/linux-user/sparc/signal.c b/linux-user/sparc/signal.c
index 3bc023d281..23e1e761de 100644
--- a/linux-user/sparc/signal.c
+++ b/linux-user/sparc/signal.c
@@ -242,6 +242,12 @@ static void restore_fpu(struct target_siginfo_fpu *fpu, CPUSPARCState *env)
 }
 
 #ifdef TARGET_ARCH_HAS_SETUP_FRAME
+static void install_sigtramp(uint32_t *tramp, int syscall)
+{
+    __put_user(0x82102000u + syscall, &tramp[0]); /* mov syscall, %g1 */
+    __put_user(0x91d02010u, &tramp[1]);           /* t 0x10 */
+}
+
 void setup_frame(int sig, struct target_sigaction *ka,
                  target_sigset_t *set, CPUSPARCState *env)
 {
@@ -291,13 +297,9 @@ void setup_frame(int sig, struct target_sigaction *ka,
     if (ka->ka_restorer) {
         env->regwptr[WREG_O7] = ka->ka_restorer;
     } else {
-        env->regwptr[WREG_O7] = sf_addr +
-                offsetof(struct target_signal_frame, insns) - 2 * 4;
-
-        /* mov __NR_sigreturn, %g1 */
-        __put_user(0x821020d8u, &sf->insns[0]);
-        /* t 0x10 */
-        __put_user(0x91d02010u, &sf->insns[1]);
+        /* Not used, but retain for ABI compatibility. */
+        install_sigtramp(sf->insns, TARGET_NR_sigreturn);
+        env->regwptr[WREG_O7] = default_sigreturn;
     }
     unlock_user(sf, sf_addr, sf_size);
 }
@@ -358,13 +360,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     if (ka->ka_restorer) {
         env->regwptr[WREG_O7] = ka->ka_restorer;
     } else {
-        env->regwptr[WREG_O7] =
-            sf_addr + offsetof(struct target_rt_signal_frame, insns) - 2 * 4;
-
-        /* mov __NR_rt_sigreturn, %g1 */
-        __put_user(0x82102065u, &sf->insns[0]);
-        /* t 0x10 */
-        __put_user(0x91d02010u, &sf->insns[1]);
+        /* Not used, but retain for ABI compatibility. */
+        install_sigtramp(sf->insns, TARGET_NR_rt_sigreturn);
+        env->regwptr[WREG_O7] = default_rt_sigreturn;
     }
 #else
     env->regwptr[WREG_O7] = ka->ka_restorer;
@@ -775,4 +773,18 @@ do_sigsegv:
     unlock_user_struct(ucp, ucp_addr, 1);
     force_sig(TARGET_SIGSEGV);
 }
+#else
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);
+    assert(tramp != NULL);
+
+    default_sigreturn = sigtramp_page;
+    install_sigtramp(tramp, TARGET_NR_sigreturn);
+
+    default_rt_sigreturn = sigtramp_page + 8;
+    install_sigtramp(tramp + 2, TARGET_NR_rt_sigreturn);
+
+    unlock_user(tramp, sigtramp_page, 2 * 8);
+}
 #endif
-- 
2.25.1

Re: [PATCH v4 23/25] linux-user/sparc: Implement setup_sigtramp

[Philippe Mathieu-Daudé]

On 9/28/21 04:00, Richard Henderson wrote:
> Create and record the two signal trampolines.
> Use them when the guest does not use SA_RESTORER.
> 
> Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  linux-user/sparc/target_signal.h |  4 ++++
>  linux-user/sparc/signal.c        | 40 +++++++++++++++++++++-----------
>  2 files changed, 30 insertions(+), 14 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Re: [PATCH v4 23/25] linux-user/sparc: Implement setup_sigtramp

[Mark Cave-Ayland]

On 28/09/2021 03:00, Richard Henderson wrote:

> Create and record the two signal trampolines.
> Use them when the guest does not use SA_RESTORER.
> 
> Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   linux-user/sparc/target_signal.h |  4 ++++
>   linux-user/sparc/signal.c        | 40 +++++++++++++++++++++-----------
>   2 files changed, 30 insertions(+), 14 deletions(-)
> 
> diff --git a/linux-user/sparc/target_signal.h b/linux-user/sparc/target_signal.h
> index 34f9a12519..e661ddd6ab 100644
> --- a/linux-user/sparc/target_signal.h
> +++ b/linux-user/sparc/target_signal.h
> @@ -69,6 +69,10 @@ typedef struct target_sigaltstack {
>   
>   #ifdef TARGET_ABI32
>   #define TARGET_ARCH_HAS_SETUP_FRAME
> +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
> +#else
> +/* For sparc64, use of KA_RESTORER is mandatory. */
> +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
>   #endif
>   
>   /* bit-flags */
> diff --git a/linux-user/sparc/signal.c b/linux-user/sparc/signal.c
> index 3bc023d281..23e1e761de 100644
> --- a/linux-user/sparc/signal.c
> +++ b/linux-user/sparc/signal.c
> @@ -242,6 +242,12 @@ static void restore_fpu(struct target_siginfo_fpu *fpu, CPUSPARCState *env)
>   }
>   
>   #ifdef TARGET_ARCH_HAS_SETUP_FRAME
> +static void install_sigtramp(uint32_t *tramp, int syscall)
> +{
> +    __put_user(0x82102000u + syscall, &tramp[0]); /* mov syscall, %g1 */
> +    __put_user(0x91d02010u, &tramp[1]);           /* t 0x10 */
> +}
> +
>   void setup_frame(int sig, struct target_sigaction *ka,
>                    target_sigset_t *set, CPUSPARCState *env)
>   {
> @@ -291,13 +297,9 @@ void setup_frame(int sig, struct target_sigaction *ka,
>       if (ka->ka_restorer) {
>           env->regwptr[WREG_O7] = ka->ka_restorer;
>       } else {
> -        env->regwptr[WREG_O7] = sf_addr +
> -                offsetof(struct target_signal_frame, insns) - 2 * 4;
> -
> -        /* mov __NR_sigreturn, %g1 */
> -        __put_user(0x821020d8u, &sf->insns[0]);
> -        /* t 0x10 */
> -        __put_user(0x91d02010u, &sf->insns[1]);
> +        /* Not used, but retain for ABI compatibility. */
> +        install_sigtramp(sf->insns, TARGET_NR_sigreturn);
> +        env->regwptr[WREG_O7] = default_sigreturn;
>       }
>       unlock_user(sf, sf_addr, sf_size);
>   }
> @@ -358,13 +360,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
>       if (ka->ka_restorer) {
>           env->regwptr[WREG_O7] = ka->ka_restorer;
>       } else {
> -        env->regwptr[WREG_O7] =
> -            sf_addr + offsetof(struct target_rt_signal_frame, insns) - 2 * 4;
> -
> -        /* mov __NR_rt_sigreturn, %g1 */
> -        __put_user(0x82102065u, &sf->insns[0]);
> -        /* t 0x10 */
> -        __put_user(0x91d02010u, &sf->insns[1]);
> +        /* Not used, but retain for ABI compatibility. */
> +        install_sigtramp(sf->insns, TARGET_NR_rt_sigreturn);
> +        env->regwptr[WREG_O7] = default_rt_sigreturn;
>       }
>   #else
>       env->regwptr[WREG_O7] = ka->ka_restorer;
> @@ -775,4 +773,18 @@ do_sigsegv:
>       unlock_user_struct(ucp, ucp_addr, 1);
>       force_sig(TARGET_SIGSEGV);
>   }
> +#else
> +void setup_sigtramp(abi_ulong sigtramp_page)
> +{
> +    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 2 * 8, 0);
> +    assert(tramp != NULL);
> +
> +    default_sigreturn = sigtramp_page;
> +    install_sigtramp(tramp, TARGET_NR_sigreturn);
> +
> +    default_rt_sigreturn = sigtramp_page + 8;
> +    install_sigtramp(tramp + 2, TARGET_NR_rt_sigreturn);
> +
> +    unlock_user(tramp, sigtramp_page, 2 * 8);
> +}
>   #endif

This is certainly outside of my knowledge domain, however if it works in your tests 
then happy to give:

Acked-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>


ATB,

Mark.

[PATCH v4 24/25] linux-user/xtensa: Implement setup_sigtramp

[Richard Henderson]

Create and record the rt signal trampoline.
Use it when the guest does not use SA_RESTORER.

Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/xtensa/target_signal.h |  2 ++
 linux-user/xtensa/signal.c        | 56 ++++++++++++++++++++-----------
 2 files changed, 38 insertions(+), 20 deletions(-)

diff --git a/linux-user/xtensa/target_signal.h b/linux-user/xtensa/target_signal.h
index c60bf656f6..1c7ee73154 100644
--- a/linux-user/xtensa/target_signal.h
+++ b/linux-user/xtensa/target_signal.h
@@ -20,4 +20,6 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif
diff --git a/linux-user/xtensa/signal.c b/linux-user/xtensa/signal.c
index 7a3bfb92ca..81572a5fc7 100644
--- a/linux-user/xtensa/signal.c
+++ b/linux-user/xtensa/signal.c
@@ -128,6 +128,29 @@ static int setup_sigcontext(struct target_rt_sigframe *frame,
     return 1;
 }
 
+static void install_sigtramp(uint8_t *tramp)
+{
+#ifdef TARGET_WORDS_BIGENDIAN
+    /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
+    __put_user(0x22, &tramp[0]);
+    __put_user(0x0a, &tramp[1]);
+    __put_user(TARGET_NR_rt_sigreturn, &tramp[2]);
+    /* Generate instruction:  SYSCALL */
+    __put_user(0x00, &tramp[3]);
+    __put_user(0x05, &tramp[4]);
+    __put_user(0x00, &tramp[5]);
+#else
+    /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
+    __put_user(0x22, &tramp[0]);
+    __put_user(0xa0, &tramp[1]);
+    __put_user(TARGET_NR_rt_sigreturn, &tramp[2]);
+    /* Generate instruction:  SYSCALL */
+    __put_user(0x00, &tramp[3]);
+    __put_user(0x50, &tramp[4]);
+    __put_user(0x00, &tramp[5]);
+#endif
+}
+
 void setup_rt_frame(int sig, struct target_sigaction *ka,
                     target_siginfo_t *info,
                     target_sigset_t *set, CPUXtensaState *env)
@@ -164,26 +187,9 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     if (ka->sa_flags & TARGET_SA_RESTORER) {
         ra = ka->sa_restorer;
     } else {
-        ra = frame_addr + offsetof(struct target_rt_sigframe, retcode);
-#ifdef TARGET_WORDS_BIGENDIAN
-        /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
-        __put_user(0x22, &frame->retcode[0]);
-        __put_user(0x0a, &frame->retcode[1]);
-        __put_user(TARGET_NR_rt_sigreturn, &frame->retcode[2]);
-        /* Generate instruction:  SYSCALL */
-        __put_user(0x00, &frame->retcode[3]);
-        __put_user(0x05, &frame->retcode[4]);
-        __put_user(0x00, &frame->retcode[5]);
-#else
-        /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
-        __put_user(0x22, &frame->retcode[0]);
-        __put_user(0xa0, &frame->retcode[1]);
-        __put_user(TARGET_NR_rt_sigreturn, &frame->retcode[2]);
-        /* Generate instruction:  SYSCALL */
-        __put_user(0x00, &frame->retcode[3]);
-        __put_user(0x50, &frame->retcode[4]);
-        __put_user(0x00, &frame->retcode[5]);
-#endif
+        /* Not used, but retain for ABI compatibility. */
+        install_sigtramp(frame->retcode);
+        ra = default_rt_sigreturn;
     }
     memset(env->regs, 0, sizeof(env->regs));
     env->pc = ka->_sa_handler;
@@ -264,3 +270,13 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return -TARGET_QEMU_ESIGRETURN;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint8_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 6, 0);
+    assert(tramp != NULL);
+
+    default_rt_sigreturn = sigtramp_page;
+    install_sigtramp(tramp);
+    unlock_user(tramp, sigtramp_page, 6);
+}
-- 
2.25.1

[PATCH v4 25/25] linux-user: Remove default for TARGET_ARCH_HAS_SIGTRAMP_PAGE

[Richard Henderson]

All targets now define TARGET_ARCH_HAS_SIGTRAMP_PAGE.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/elfload.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 459a26ef1d..2404d482ba 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -30,10 +30,6 @@
 #undef ELF_ARCH
 #endif
 
-#ifndef TARGET_ARCH_HAS_SIGTRAMP_PAGE
-#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
-#endif
-
 #define ELF_OSABI   ELFOSABI_SYSV
 
 /* from personality.h */
-- 
2.25.1