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Tue, 18 Jun 2024 04:33:29 -0700 (PDT) Message-ID: <8a22ada3-34e6-4d6d-aebe-67bc07d0f38f@linaro.org> Date: Tue, 18 Jun 2024 13:33:28 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/3] semihosting: Restrict to TCG From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= To: Paolo Bonzini Cc: qemu-devel@nongnu.org, =?UTF-8?Q?Alex_Benn=C3=A9e?= , Anton Johansson References: <20240529155548.5878-1-philmd@linaro.org> <20240529155548.5878-4-philmd@linaro.org> <7ce86375-779d-43d6-9871-7f9587c95ba6@linaro.org> <5c913504-d917-4fd1-86d5-85d3bc293623@linaro.org> Content-Language: en-US In-Reply-To: <5c913504-d917-4fd1-86d5-85d3bc293623@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::62d; envelope-from=philmd@linaro.org; helo=mail-ej1-x62d.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org ping :) On 12/6/24 15:12, Philippe Mathieu-Daudé wrote: > Hi Paolo, > > On 30/5/24 15:58, Philippe Mathieu-Daudé wrote: >> On 30/5/24 09:31, Paolo Bonzini wrote: >>> On Thu, May 30, 2024 at 9:22 AM Philippe Mathieu-Daudé >>> wrote: >>>> >>>> On 30/5/24 08:02, Paolo Bonzini wrote: >>>>> On Wed, May 29, 2024 at 5:56 PM Philippe Mathieu-Daudé >>>>> wrote: >>>>>> It is pointless to build semihosting when TCG is not available. >>>>> >>>>> Why? I would have naively assumed that a suitable semihosting API >>>>> could be implemented by KVM. The justification (and thus the commit >>>>> message) needs to be different for each architecture if it's a matter >>>>> of instruction set or insufficient KVM userspace API. >>>> >>>> I wasn't sure where semihosting could be used so asked on IRC and >>>> Alex told me TCG only. Maybe the current implementation is TCG >>>> only, and I can reword. It certainly need some refactor to work >>>> on KVM, because currently semihosting end calling the TCG probe_access >>>> API, which I'm trying to restrict to TCG in order to ease linking >>>> multiple libtcg for the single binary (see >>>> https://lore.kernel.org/qemu-devel/20240529155918.6221-1-philmd@linaro.org/). >>> >>> Ok, that goes in the commit message though. >>> >>> "Semihosting currently uses the TCG probe_access API. It is pointless >>> to have it in the binary when TCG isn't". >>> >>> and in the first two patches: >>> >>> "Semihosting currently uses the TCG probe_access API. To prepare for >>> encoding the TCG dependency in Kconfig, do not enable it unless TCG is >>> available". >>> >>> But then, "select FOO if TCG" mean that it can be compiled out; so >>> perhaps "imply SEMIHOSTING if TCG" is better? Same for RISC-V's >>> "select ARM_COMPATIBLE_SEMIHOSTING if TCG". > > Building qemu-system-mips configured with --without-default-devices: > > Undefined symbols for architecture arm64: >   "_qemu_semihosting_console_write", referenced from: >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >   "_semihost_sys_close", referenced from: >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >   "_uaccess_strlen_user", referenced from: >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >   ... > > So this one has to use "select". > > Similarly m68k: > > Undefined symbols for architecture arm64: >   "_semihost_sys_close", referenced from: >       _do_m68k_semihosting in target_m68k_m68k-semi.c.o >   ... > > I can link m68k using semihosting stubs but I'm not sure it is right: > > -- >8 -- > diff --git a/semihosting/stubs-target-all.c > b/semihosting/stubs-target-all.c > new file mode 100644 > index 0000000000..1f33173f43 > --- /dev/null > +++ b/semihosting/stubs-target-all.c > @@ -0,0 +1,97 @@ > +/* > + * Semihosting Stubs > + * > + * Copyright (c) 2024 Linaro Ltd > + * > + * Stubs for semihosting targets that don't actually do semihosting. > + * > + * SPDX-License-Identifier: GPL-2.0-or-later > + */ > + > +#include "qemu/osdep.h" > +#include "exec/exec-all.h" > +#include "semihosting/syscalls.h" > + > +void semihost_sys_open(CPUState *cs, gdb_syscall_complete_cb complete, > +                       target_ulong fname, target_ulong fname_len, > +                       int gdb_flags, int mode) > +{ > +} > + > +void semihost_sys_close(CPUState *cs, gdb_syscall_complete_cb complete, > int fd) > +{ > +} > + > +void semihost_sys_read_gf(CPUState *cs, gdb_syscall_complete_cb complete, > +                          GuestFD *gf, target_ulong buf, target_ulong len) > +{ > +} > + > +void semihost_sys_read(CPUState *cs, gdb_syscall_complete_cb complete, > +                       int fd, target_ulong buf, target_ulong len) > +{ > +} > + > +void semihost_sys_write_gf(CPUState *cs, gdb_syscall_complete_cb complete, > +                           GuestFD *gf, target_ulong buf, target_ulong > len) > +{ > +} > + > +void semihost_sys_write(CPUState *cs, gdb_syscall_complete_cb complete, > +                        int fd, target_ulong buf, target_ulong len) > +{ > +} > + > +void semihost_sys_lseek(CPUState *cs, gdb_syscall_complete_cb complete, > +                        int fd, int64_t off, int gdb_whence) > +{ > +} > + > +void semihost_sys_isatty(CPUState *cs, gdb_syscall_complete_cb > complete, int fd) > +{ > +} > + > +void semihost_sys_flen(CPUState *cs, gdb_syscall_complete_cb fstat_cb, > +                       gdb_syscall_complete_cb flen_cb, int fd, > +                       target_ulong fstat_addr) > +{ > +} > + > +void semihost_sys_fstat(CPUState *cs, gdb_syscall_complete_cb complete, > +                        int fd, target_ulong addr) > +{ > +} > + > +void semihost_sys_stat(CPUState *cs, gdb_syscall_complete_cb complete, > +                       target_ulong fname, target_ulong fname_len, > +                       target_ulong addr) > +{ > +} > + > +void semihost_sys_remove(CPUState *cs, gdb_syscall_complete_cb complete, > +                         target_ulong fname, target_ulong fname_len) > +{ > +} > + > +void semihost_sys_rename(CPUState *cs, gdb_syscall_complete_cb complete, > +                         target_ulong oname, target_ulong oname_len, > +                         target_ulong nname, target_ulong nname_len) > +{ > +} > + > +void semihost_sys_system(CPUState *cs, gdb_syscall_complete_cb complete, > +                         target_ulong cmd, target_ulong cmd_len) > +{ > +} > + > +void semihost_sys_gettimeofday(CPUState *cs, gdb_syscall_complete_cb > complete, > +                               target_ulong tv_addr, target_ulong tz_addr) > +{ > +} > + > +#ifndef CONFIG_USER_ONLY > +void semihost_sys_poll_one(CPUState *cs, gdb_syscall_complete_cb complete, > +                           int fd, GIOCondition cond, int timeout) > +{ > +} > +#endif > diff --git a/semihosting/meson.build b/semihosting/meson.build > index 34933e5a19..aa8b7a9913 100644 > --- a/semihosting/meson.build > +++ b/semihosting/meson.build > @@ -7,7 +7,7 @@ specific_ss.add(when: ['CONFIG_SEMIHOSTING', > 'CONFIG_SYSTEM_ONLY'], if_true: fil >    'config.c', >    'console.c', >    'uaccess.c', > -)) > +), if_false: files('stubs-target-all.c')) > >  common_ss.add(when: ['CONFIG_SEMIHOSTING', 'CONFIG_SYSTEM_ONLY'], > if_false: files('stubs-all.c')) >  system_ss.add(when: ['CONFIG_SEMIHOSTING'], if_false: > files('stubs-system.c')) > --- > > For mips more stubs are needed: > > Undefined symbols for architecture arm64: >   "_qemu_semihosting_console_write", referenced from: >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >   "_uaccess_lock_user", referenced from: >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _uhi_fstat_cb in target_mips_tcg_sysemu_mips-semi.c.o >   "_uaccess_lock_user_string", referenced from: >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _mips_semihosting.cold.6 in target_mips_tcg_sysemu_mips-semi.c.o >       _mips_semihosting.cold.6 in target_mips_tcg_sysemu_mips-semi.c.o >   "_uaccess_strlen_user", referenced from: >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >   "_uaccess_unlock_user", referenced from: >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _mips_semihosting in target_mips_tcg_sysemu_mips-semi.c.o >       _uhi_fstat_cb in target_mips_tcg_sysemu_mips-semi.c.o >       ... >