mbox series

[v4,0/9] linux-user: simplify safe signal handling

Message ID 20211116110256.365484-1-richard.henderson@linaro.org
Headers show
Series linux-user: simplify safe signal handling | expand

Message

Richard Henderson Nov. 16, 2021, 11:02 a.m. UTC
Warner's v3:
https://patchew.org/QEMU/20211113045603.60391-1-imp@bsdimp.com/

Changes for v4:
  * Move errno handling into the assembly.  While returning the
    raw -errno is handy for x86 linux (and a few others), it is
    in fact more complex for other hosts that return a separate
    error indicator.  At which point we wind up jumping through
    hoops to return -errno, only to have the caller put it right
    back into +errno with -1 result, just like syscall(3).

    Pass in &errno, because the method of calculating this
    varies wildly between glibc, musl, etc.  This means that
    the assembly need only store to a provided pointer.

  * Add mips and sparc safe-syscall implementations.
    Both of which, btw, have separate error indicators.  ;-)

  * All hosts now have it, so remove HAVE_SAFE_SYSCALL.

  * Add meson.build rules for common-user/safe-syscall.S, so
    that we don't have to have weird includes from *-user.

    I'll note that this last patch will at present break bsd-user,
    because TARGET_ERESTARTSYS and the header from whence it comes
    is currently missing there.

    In addition, I think that this should be reorganized further
    so that TARGET_ERESTARTSYS is (1) renamed because in *this*
    context it is pretending to be a host errno, and (2) placed
    in a file of its own under include/user/.  At which point,
    meson.build could be simplified further so that safe-syscall.S
    is compiled once, not per target.

    Anyway, the final patch needs some bsd-user changes sorted first.


r~


Richard Henderson (4):
  common-user: Move syscall error detection into safe_syscall_base
  common-user/host/mips: Add safe-syscall.inc.S
  common-user/host/sparc64: Add safe-syscall.inc.S
  linux-user: Remove HAVE_SAFE_SYSCALL and hostdep.h

Warner Losh (5):
  linux-user: Add host_signal_set_pc to set pc in mcontext
  linux-user/signal.c: Create a common rewind_if_in_safe_syscall
  linux-user/safe-syscall.inc.S: Move to common-user
  common-user: Adjust system call return on FreeBSD
  common-user: Move safe-syscall.* from *-user

 meson.build                                   |   9 +-
 {linux-user => include/user}/safe-syscall.h   |  31 ++--
 linux-user/host/aarch64/host-signal.h         |   5 +
 linux-user/host/aarch64/hostdep.h             |  38 -----
 linux-user/host/alpha/host-signal.h           |   5 +
 linux-user/host/arm/host-signal.h             |   5 +
 linux-user/host/arm/hostdep.h                 |  38 -----
 linux-user/host/i386/host-signal.h            |   5 +
 linux-user/host/i386/hostdep.h                |  38 -----
 linux-user/host/ia64/hostdep.h                |  15 --
 linux-user/host/mips/host-signal.h            |   5 +
 linux-user/host/mips/hostdep.h                |  15 --
 linux-user/host/ppc/host-signal.h             |   5 +
 linux-user/host/ppc/hostdep.h                 |  15 --
 linux-user/host/ppc64/hostdep.h               |  38 -----
 linux-user/host/riscv/host-signal.h           |   5 +
 linux-user/host/riscv/hostdep.h               |  34 -----
 linux-user/host/s390/host-signal.h            |   5 +
 linux-user/host/s390/hostdep.h                |  15 --
 linux-user/host/s390x/hostdep.h               |  38 -----
 linux-user/host/sparc/host-signal.h           |   9 ++
 linux-user/host/sparc/hostdep.h               |  15 --
 linux-user/host/sparc64/hostdep.h             |  15 --
 linux-user/host/x32/hostdep.h                 |  15 --
 linux-user/host/x86_64/host-signal.h          |   5 +
 linux-user/host/x86_64/hostdep.h              |  38 -----
 linux-user/user-internals.h                   |   1 -
 linux-user/signal.c                           |  13 +-
 linux-user/syscall.c                          |   2 +-
 .../host/aarch64/safe-syscall.inc.S           |  65 ++++++---
 .../host/arm/safe-syscall.inc.S               |  69 ++++++---
 .../host/i386/safe-syscall.inc.S              |  61 +++++---
 common-user/host/mips/safe-syscall.inc.S      | 135 ++++++++++++++++++
 .../host/ppc64/safe-syscall.inc.S             |  63 ++++----
 .../host/riscv/safe-syscall.inc.S             |  50 ++++---
 .../host/s390x/safe-syscall.inc.S             |  50 ++++---
 common-user/host/sparc64/safe-syscall.inc.S   |  91 ++++++++++++
 .../host/x86_64/safe-syscall.inc.S            |  80 +++++++----
 common-user/meson.build                       |   2 +
 {linux-user => common-user}/safe-syscall.S    |   3 -
 linux-user/meson.build                        |   1 -
 41 files changed, 585 insertions(+), 562 deletions(-)
 rename {linux-user => include/user}/safe-syscall.h (85%)
 delete mode 100644 linux-user/host/aarch64/hostdep.h
 delete mode 100644 linux-user/host/arm/hostdep.h
 delete mode 100644 linux-user/host/i386/hostdep.h
 delete mode 100644 linux-user/host/ia64/hostdep.h
 delete mode 100644 linux-user/host/mips/hostdep.h
 delete mode 100644 linux-user/host/ppc/hostdep.h
 delete mode 100644 linux-user/host/ppc64/hostdep.h
 delete mode 100644 linux-user/host/riscv/hostdep.h
 delete mode 100644 linux-user/host/s390/hostdep.h
 delete mode 100644 linux-user/host/s390x/hostdep.h
 delete mode 100644 linux-user/host/sparc/hostdep.h
 delete mode 100644 linux-user/host/sparc64/hostdep.h
 delete mode 100644 linux-user/host/x32/hostdep.h
 delete mode 100644 linux-user/host/x86_64/hostdep.h
 rename {linux-user => common-user}/host/aarch64/safe-syscall.inc.S (64%)
 rename {linux-user => common-user}/host/arm/safe-syscall.inc.S (64%)
 rename {linux-user => common-user}/host/i386/safe-syscall.inc.S (71%)
 create mode 100644 common-user/host/mips/safe-syscall.inc.S
 rename {linux-user => common-user}/host/ppc64/safe-syscall.inc.S (68%)
 rename {linux-user => common-user}/host/riscv/safe-syscall.inc.S (77%)
 rename {linux-user => common-user}/host/s390x/safe-syscall.inc.S (71%)
 create mode 100644 common-user/host/sparc64/safe-syscall.inc.S
 rename {linux-user => common-user}/host/x86_64/safe-syscall.inc.S (64%)
 create mode 100644 common-user/meson.build
 rename {linux-user => common-user}/safe-syscall.S (94%)

Comments

Warner Losh Nov. 16, 2021, 9:10 p.m. UTC | #1
On Tue, Nov 16, 2021 at 4:02 AM Richard Henderson <
richard.henderson@linaro.org> wrote:

> Warner's v3:
> https://patchew.org/QEMU/20211113045603.60391-1-imp@bsdimp.com/
>
> Changes for v4:
>   * Move errno handling into the assembly.  While returning the
>     raw -errno is handy for x86 linux (and a few others), it is
>     in fact more complex for other hosts that return a separate
>     error indicator.  At which point we wind up jumping through
>     hoops to return -errno, only to have the caller put it right
>     back into +errno with -1 result, just like syscall(3).
>
>     Pass in &errno, because the method of calculating this
>     varies wildly between glibc, musl, etc.  This means that
>     the assembly need only store to a provided pointer.
>
>   * Add mips and sparc safe-syscall implementations.
>     Both of which, btw, have separate error indicators.  ;-)
>
>   * All hosts now have it, so remove HAVE_SAFE_SYSCALL.
>
>   * Add meson.build rules for common-user/safe-syscall.S, so
>     that we don't have to have weird includes from *-user.
>
>     I'll note that this last patch will at present break bsd-user,
>     because TARGET_ERESTARTSYS and the header from whence it comes
>     is currently missing there.
>
>     In addition, I think that this should be reorganized further
>     so that TARGET_ERESTARTSYS is (1) renamed because in *this*
>     context it is pretending to be a host errno, and (2) placed
>     in a file of its own under include/user/.  At which point,
>     meson.build could be simplified further so that safe-syscall.S
>     is compiled once, not per target.
>
>     Anyway, the final patch needs some bsd-user changes sorted first.
>

I've got bsd-user to compile with these changes by creating
bsd-user/target_errno_defs.h that was just #include "errno_defs.h", which
suggests a simple rename and #include adjustment in bsd-user/syscall_defs.h
would also work. On *BSD, the errno namespace is the same for all
architectures since they never followed the rather divergent System V ABIs
that Linux follows (or at least did for the early ports).

I've noted a couple of other tweaks I needed as well, but there seemed to
be no good place to share this.

I'd  be happy to change these vague descriptions into actual code I can
push to gitlab that you can pull into the patch series as well (or I can
send them to the list, I'm not sure about this finer point of qemu and want
to fit in).

Thanks for expanding my start at this.

Warner


>
> r~
>
>
> Richard Henderson (4):
>   common-user: Move syscall error detection into safe_syscall_base
>   common-user/host/mips: Add safe-syscall.inc.S
>   common-user/host/sparc64: Add safe-syscall.inc.S
>   linux-user: Remove HAVE_SAFE_SYSCALL and hostdep.h
>
> Warner Losh (5):
>   linux-user: Add host_signal_set_pc to set pc in mcontext
>   linux-user/signal.c: Create a common rewind_if_in_safe_syscall
>   linux-user/safe-syscall.inc.S: Move to common-user
>   common-user: Adjust system call return on FreeBSD
>   common-user: Move safe-syscall.* from *-user
>
>  meson.build                                   |   9 +-
>  {linux-user => include/user}/safe-syscall.h   |  31 ++--
>  linux-user/host/aarch64/host-signal.h         |   5 +
>  linux-user/host/aarch64/hostdep.h             |  38 -----
>  linux-user/host/alpha/host-signal.h           |   5 +
>  linux-user/host/arm/host-signal.h             |   5 +
>  linux-user/host/arm/hostdep.h                 |  38 -----
>  linux-user/host/i386/host-signal.h            |   5 +
>  linux-user/host/i386/hostdep.h                |  38 -----
>  linux-user/host/ia64/hostdep.h                |  15 --
>  linux-user/host/mips/host-signal.h            |   5 +
>  linux-user/host/mips/hostdep.h                |  15 --
>  linux-user/host/ppc/host-signal.h             |   5 +
>  linux-user/host/ppc/hostdep.h                 |  15 --
>  linux-user/host/ppc64/hostdep.h               |  38 -----
>  linux-user/host/riscv/host-signal.h           |   5 +
>  linux-user/host/riscv/hostdep.h               |  34 -----
>  linux-user/host/s390/host-signal.h            |   5 +
>  linux-user/host/s390/hostdep.h                |  15 --
>  linux-user/host/s390x/hostdep.h               |  38 -----
>  linux-user/host/sparc/host-signal.h           |   9 ++
>  linux-user/host/sparc/hostdep.h               |  15 --
>  linux-user/host/sparc64/hostdep.h             |  15 --
>  linux-user/host/x32/hostdep.h                 |  15 --
>  linux-user/host/x86_64/host-signal.h          |   5 +
>  linux-user/host/x86_64/hostdep.h              |  38 -----
>  linux-user/user-internals.h                   |   1 -
>  linux-user/signal.c                           |  13 +-
>  linux-user/syscall.c                          |   2 +-
>  .../host/aarch64/safe-syscall.inc.S           |  65 ++++++---
>  .../host/arm/safe-syscall.inc.S               |  69 ++++++---
>  .../host/i386/safe-syscall.inc.S              |  61 +++++---
>  common-user/host/mips/safe-syscall.inc.S      | 135 ++++++++++++++++++
>  .../host/ppc64/safe-syscall.inc.S             |  63 ++++----
>  .../host/riscv/safe-syscall.inc.S             |  50 ++++---
>  .../host/s390x/safe-syscall.inc.S             |  50 ++++---
>  common-user/host/sparc64/safe-syscall.inc.S   |  91 ++++++++++++
>  .../host/x86_64/safe-syscall.inc.S            |  80 +++++++----
>  common-user/meson.build                       |   2 +
>  {linux-user => common-user}/safe-syscall.S    |   3 -
>  linux-user/meson.build                        |   1 -
>  41 files changed, 585 insertions(+), 562 deletions(-)
>  rename {linux-user => include/user}/safe-syscall.h (85%)
>  delete mode 100644 linux-user/host/aarch64/hostdep.h
>  delete mode 100644 linux-user/host/arm/hostdep.h
>  delete mode 100644 linux-user/host/i386/hostdep.h
>  delete mode 100644 linux-user/host/ia64/hostdep.h
>  delete mode 100644 linux-user/host/mips/hostdep.h
>  delete mode 100644 linux-user/host/ppc/hostdep.h
>  delete mode 100644 linux-user/host/ppc64/hostdep.h
>  delete mode 100644 linux-user/host/riscv/hostdep.h
>  delete mode 100644 linux-user/host/s390/hostdep.h
>  delete mode 100644 linux-user/host/s390x/hostdep.h
>  delete mode 100644 linux-user/host/sparc/hostdep.h
>  delete mode 100644 linux-user/host/sparc64/hostdep.h
>  delete mode 100644 linux-user/host/x32/hostdep.h
>  delete mode 100644 linux-user/host/x86_64/hostdep.h
>  rename {linux-user => common-user}/host/aarch64/safe-syscall.inc.S (64%)
>  rename {linux-user => common-user}/host/arm/safe-syscall.inc.S (64%)
>  rename {linux-user => common-user}/host/i386/safe-syscall.inc.S (71%)
>  create mode 100644 common-user/host/mips/safe-syscall.inc.S
>  rename {linux-user => common-user}/host/ppc64/safe-syscall.inc.S (68%)
>  rename {linux-user => common-user}/host/riscv/safe-syscall.inc.S (77%)
>  rename {linux-user => common-user}/host/s390x/safe-syscall.inc.S (71%)
>  create mode 100644 common-user/host/sparc64/safe-syscall.inc.S
>  rename {linux-user => common-user}/host/x86_64/safe-syscall.inc.S (64%)
>  create mode 100644 common-user/meson.build
>  rename {linux-user => common-user}/safe-syscall.S (94%)
>
> --
> 2.25.1
>
>