Date: Fri, 28 Apr 2023 00:32:12 +0800 From: Zhenlei Huang <zlei@FreeBSD.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Hans Petter Selasky <hselasky@freebsd.org>, FreeBSD CURRENT <freebsd-current@freebsd.org>, Gleb Smirnoff <glebius@freebsd.org> Subject: Re: Link modules to DYN type Message-ID: <86DC0C8E-56E8-49B9-8441-D64C690FA5F0@FreeBSD.org> In-Reply-To: <ZEkHKJ_BRhV22gf_@kib.kiev.ua> References: <97390FE1-1DF5-43A1-A3F4-2B945D681437@FreeBSD.org> <2bb66cac-c7f1-e45b-693a-8afbda05cfa6@freebsd.org> <ZEkHKJ_BRhV22gf_@kib.kiev.ua>
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--Apple-Mail=_6539C631-52D9-4A0E-99A2-AF236413CF40 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii > On Apr 26, 2023, at 7:12 PM, Konstantin Belousov <kostikbel@gmail.com> = wrote: >=20 > On Wed, Apr 26, 2023 at 12:55:02PM +0200, Hans Petter Selasky wrote: >> On 4/26/23 12:36, Zhenlei Huang wrote: >>> Hi, >>>=20 >>> I'm recently working on https://reviews.freebsd.org/D39638 = (sysctl(9): Enable vnet sysctl variables be loader tunable), >>> the changes to `sys/kern/link_elf_obj.c` are runtime tested, but not = those to `sys/kern/link_elf.c` . >>>=20 >>> After some hacking I realized that `link_elf.c` is for EXEC = (Executable file) or DYN (Shared object file), and `link_elf_obj.c` is >>> for REL (Relocatable file). >>>=20 >>> ``` >>> /* link_elf.c */ >>> static int >>> link_elf_load_file(linker_class_t cls, const char* filename, >>> linker_file_t* result) >>> { >>> ... >>> if (hdr->e_type !=3D ET_EXEC && hdr->e_type !=3D ET_DYN) { >>> error =3D ENOSYS; >>> goto out; >>> } >>> ... >>> } >>>=20 >>>=20 >>> /* link_elf_obj.c */ >>> static int >>> link_elf_load_file(linker_class_t cls, const char *filename, >>> linker_file_t *result) >>> { >>> ... >>> if (hdr->e_type !=3D ET_REL) { >>> error =3D ENOSYS; >>> goto out; >>> } >>> ... >>> } >>> ``` >>>=20 >>> Run the following snip: >>> ``` >>> # find /boot/kernel -type f -name "*.ko" -exec readelf -h {} \; | = grep Type >>> ``` >>> shows that all the kernel modules' types are `REL (Relocatable = file)`. >>>=20 >>> I guess if some module such as if_bridge is linked to DYN type, then = I can do runtime for the changes to `sys/kern/link_elf.c`. >>>=20 >>> I'm not familiar with elf and linkers, is that ( compile module and = link it to DYN type ) possible ? >=20 > Module file type (shared object vs. object file) depends on = architecture. > For amd64 modules are objects, while kernel is shared library. > For arm64 (and all other arches, I believe) modules and kernels are = shared > libraries. >=20 > I think you can link amd64 module as shared object, but this require = enough > hacking of the build infrastructure. At least I am not aware of a = simple > knob to switch the produced type. I did some hack on `sys/conf/kmod.mk` and finally produced DYN kernel = modules. The good news is I do some basic sysctl tests, but the bad news is the = module does not function correctly. For exampe the if_disc.c ``` static void vnet_disc_init(const void *unused __unused) { /* Reference V_disc_cloner will immediately trigger page fault = panic */ V_disc_cloner =3D if_clone_simple(discname, disc_clone_create, disc_clone_destroy, 0); } VNET_SYSINIT(vnet_disc_init, SI_SUB_PSEUDO, SI_ORDER_ANY, vnet_disc_init, NULL); ``` I suspect the relocation is not done correctly for DYN elf kmod on = amd64. My local patch to kmod.mk: ``` diff --git a/sys/conf/kmod.mk b/sys/conf/kmod.mk index 134b150af1d9..1fc5386204a5 100644 --- a/sys/conf/kmod.mk +++ b/sys/conf/kmod.mk @@ -84,6 +84,7 @@ __KLD_SHARED=3Dyes .else __KLD_SHARED=3Dno .endif +__KLD_SHARED=3Dyes =20 .if !empty(CFLAGS:M-O[23s]) && empty(CFLAGS:M-fno-strict-aliasing) CFLAGS+=3D -fno-strict-aliasing @@ -167,6 +168,7 @@ CFLAGS+=3D -fno-omit-frame-pointer = -mno-omit-leaf-frame-pointer ${MACHINE_CPUARCH} =3D=3D "powerpc" CFLAGS+=3D -fPIC .endif +CFLAGS+=3D -fPIC =20 # Temporary workaround for PR 196407, which contains the fascinating = details. # Don't allow clang to use fpu instructions or registers in kernel = modules. ``` As for https://reviews.freebsd.org/D39638 = <https://reviews.freebsd.org/D39638>, for other platform such as arm, I = think the `link_elf_propagate_vnets()` should work if `parse_vnet()` = works. I'll appreciate if someone can test it on platforms those have DYN type = kernel modules.=20 >=20 >=20 >>>=20 >>=20 >> Hi, >>=20 >> I don't have an answer for you either, but I have seen in the past, = loading >> kernel modules behaves a bit like libraries, in the following regard: >>=20 >> If two kernel modules define the same global symbol, then no warning = is >> given and the first loaded symbol definition (I think) is used to = resolve >> that symbol for all kernel modules, regardless of the prototype. = Probably we >> should not allow this. That's why building LINT is a good thing, to = avoid >> this issue. > No, in-kernel linker does not behave this way. > Modules need to contain explicit reference to all modules they depend = upon, > using the MODULE_DEPEND() macro. Only symbols from the dependencies = are > resolved. >=20 > All modules get an implicit reference to kernel. >=20 >>=20 >> Even if we don't have C++ support in the FreeBSD kernel, defining = symbol >> names the way C++ does for C could be nice for the kernel too, also = with >> regards to debugging systems. >>=20 >> Many times when I don't know what is going on, I do like this: >>=20 >> #include <sys/kdb.h> >>=20 >> .... >>=20 >> if (not too fast or my sysctl debug) { >> printf("My tracer\n"); >> kdb_backtrace(); >> } >>=20 >> Dtrace can also do this, but not during boot. Just track who is = calling >> those functions, and you'll probably find the answer to your = question! >>=20 >> --HPS >>=20 >>>=20 >>> Best regards, >>> Zhenlei --Apple-Mail=_6539C631-52D9-4A0E-99A2-AF236413CF40 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii <html><head><meta http-equiv=3D"Content-Type" content=3D"text/html; = charset=3Dus-ascii"></head><body style=3D"word-wrap: break-word; = -webkit-nbsp-mode: space; line-break: after-white-space;" class=3D""><br = class=3D""><div><br class=3D""><blockquote type=3D"cite" class=3D""><div = class=3D"">On Apr 26, 2023, at 7:12 PM, Konstantin Belousov <<a = href=3D"mailto:kostikbel@gmail.com" class=3D"">kostikbel@gmail.com</a>>= wrote:</div><br class=3D"Apple-interchange-newline"><div class=3D""><meta= charset=3D"UTF-8" class=3D""><span style=3D"caret-color: rgb(0, 0, 0); = font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">On Wed, Apr 26, 2023 at 12:55:02PM +0200, Hans Petter Selasky = wrote:</span><br style=3D"caret-color: rgb(0, 0, 0); font-family: = Menlo-Regular; font-size: 13px; font-style: normal; font-variant-caps: = normal; font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none;" class=3D""><blockquote type=3D"cite" style=3D"font-family: = Menlo-Regular; font-size: 13px; font-style: normal; font-variant-caps: = normal; font-weight: 400; letter-spacing: normal; orphans: auto; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; = -webkit-text-stroke-width: 0px; text-decoration: none;" class=3D"">On = 4/26/23 12:36, Zhenlei Huang wrote:<br class=3D""><blockquote = type=3D"cite" class=3D"">Hi,<br class=3D""><br class=3D"">I'm recently = working on <a href=3D"https://reviews.freebsd.org/D39638" = class=3D"">https://reviews.freebsd.org/D39638</a>; (sysctl(9): Enable = vnet sysctl variables be loader tunable),<br class=3D"">the changes to = `sys/kern/link_elf_obj.c` are runtime tested, but not those to = `sys/kern/link_elf.c` .<br class=3D""><br class=3D"">After some hacking = I realized that `link_elf.c` is for EXEC (Executable file) or DYN = (Shared object file), and `link_elf_obj.c` is<br class=3D"">for REL = (Relocatable file).<br class=3D""><br class=3D"">```<br class=3D"">/* = link_elf.c */<br class=3D"">static int<br = class=3D"">link_elf_load_file(linker_class_t cls, const char* = filename,<br class=3D""> linker_file_t* = result)<br class=3D"">{<br class=3D"">...<br class=3D""><span = class=3D"Apple-tab-span" style=3D"white-space: pre;"> </span>if = (hdr->e_type !=3D ET_EXEC && hdr->e_type !=3D ET_DYN) {<br = class=3D""><span class=3D"Apple-tab-span" style=3D"white-space: pre;"> = </span><span class=3D"Apple-tab-span" style=3D"white-space: pre;"> = </span>error =3D ENOSYS;<br class=3D""><span class=3D"Apple-tab-span" = style=3D"white-space: pre;"> </span><span class=3D"Apple-tab-span" = style=3D"white-space: pre;"> </span>goto out;<br class=3D""><span = class=3D"Apple-tab-span" style=3D"white-space: pre;"> </span>}<br = class=3D"">...<br class=3D"">}<br class=3D""><br class=3D""><br = class=3D"">/* link_elf_obj.c */<br class=3D"">static int<br = class=3D"">link_elf_load_file(linker_class_t cls, const char = *filename,<br class=3D""> linker_file_t = *result)<br class=3D"">{<br class=3D"">...<br class=3D""><span = class=3D"Apple-tab-span" style=3D"white-space: pre;"> </span>if = (hdr->e_type !=3D ET_REL) {<br class=3D""><span = class=3D"Apple-tab-span" style=3D"white-space: pre;"> </span><span = class=3D"Apple-tab-span" style=3D"white-space: pre;"> </span>error =3D = ENOSYS;<br class=3D""><span class=3D"Apple-tab-span" style=3D"white-space:= pre;"> </span><span class=3D"Apple-tab-span" style=3D"white-space: = pre;"> </span>goto out;<br class=3D""><span class=3D"Apple-tab-span" = style=3D"white-space: pre;"> </span>}<br class=3D"">...<br = class=3D"">}<br class=3D"">```<br class=3D""><br class=3D"">Run the = following snip:<br class=3D"">```<br class=3D""># find /boot/kernel = -type f -name "*.ko" -exec readelf -h {} \; | grep Type<br = class=3D"">```<br class=3D"">shows that all the kernel modules' types = are `REL (Relocatable file)`.<br class=3D""><br class=3D"">I guess if = some module such as if_bridge is linked to DYN type, then I can do = runtime for the changes to `sys/kern/link_elf.c`.<br class=3D""><br = class=3D"">I'm not familiar with elf and linkers, is that ( compile = module and link it to DYN type ) possible ?<br = class=3D""></blockquote></blockquote><br style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><span style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">Module file type (shared object vs. object file) depends on = architecture.</span><br style=3D"caret-color: rgb(0, 0, 0); font-family: = Menlo-Regular; font-size: 13px; font-style: normal; font-variant-caps: = normal; font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none;" class=3D""><span style=3D"caret-color: rgb(0, 0, 0); font-family: = Menlo-Regular; font-size: 13px; font-style: normal; font-variant-caps: = normal; font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none; float: none; display: inline !important;" class=3D"">For amd64 = modules are objects, while kernel is shared library.</span><br = style=3D"caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; = font-size: 13px; font-style: normal; font-variant-caps: normal; = font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none;" class=3D""><span style=3D"caret-color: rgb(0, 0, 0); font-family: = Menlo-Regular; font-size: 13px; font-style: normal; font-variant-caps: = normal; font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none; float: none; display: inline !important;" class=3D"">For arm64 = (and all other arches, I believe) modules and kernels are = shared</span><br style=3D"caret-color: rgb(0, 0, 0); font-family: = Menlo-Regular; font-size: 13px; font-style: normal; font-variant-caps: = normal; font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none;" class=3D""><span style=3D"caret-color: rgb(0, 0, 0); font-family: = Menlo-Regular; font-size: 13px; font-style: normal; font-variant-caps: = normal; font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none; float: none; display: inline !important;" = class=3D"">libraries.</span></div></blockquote><blockquote type=3D"cite" = class=3D""><div class=3D""><br style=3D"caret-color: rgb(0, 0, 0); = font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><span style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">I think you can link amd64 module as shared object, but this = require enough</span><br style=3D"caret-color: rgb(0, 0, 0); = font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><span style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">hacking of the build infrastructure. At least I am not = aware of a simple</span><br style=3D"caret-color: rgb(0, 0, 0); = font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><span style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">knob to switch the produced type.</span><br = style=3D"caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; = font-size: 13px; font-style: normal; font-variant-caps: normal; = font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none;" class=3D""></div></blockquote><div><br class=3D""></div><div><div = style=3D"caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);">I did some = hack on `sys/conf/kmod.mk` and finally produced DYN kernel = modules.</div><div style=3D"caret-color: rgb(0, 0, 0); color: rgb(0, 0, = 0);">The good news is I do some basic sysctl tests, but the bad news is = the module does not function correctly.</div><div style=3D"caret-color: = rgb(0, 0, 0); color: rgb(0, 0, 0);"><br class=3D""></div><div = style=3D"caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);">For exampe the = if_disc.c</div><div style=3D"caret-color: rgb(0, 0, 0); color: rgb(0, 0, = 0);"><br class=3D""></div><div style=3D"caret-color: rgb(0, 0, 0); = color: rgb(0, 0, 0);">```</div><div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" class=3D"">static = void</span></font></div><div><font color=3D"#000000" class=3D""><span = style=3D"caret-color: rgb(0, 0, 0);" class=3D"">vnet_disc_init(const = void *unused __unused)</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D"">{</span></font></div><div><span class=3D"Apple-tab-span" = style=3D"caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); white-space: = pre;"> </span>/* Reference V_disc_cloner will immediately trigger page = fault panic */</div><div><font color=3D"#000000" class=3D""><span = style=3D"caret-color: rgb(0, 0, 0);" class=3D""><span = class=3D"Apple-tab-span" style=3D"white-space:pre"> = </span>V_disc_cloner =3D if_clone_simple(discname, = disc_clone_create,</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" class=3D""><span = class=3D"Apple-tab-span" style=3D"white-space:pre"> </span> = disc_clone_destroy, 0);</span></font></div><div><font = color=3D"#000000" class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D"">}</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D"">VNET_SYSINIT(vnet_disc_init, SI_SUB_PSEUDO, = SI_ORDER_ANY,</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" class=3D""> = vnet_disc_init, NULL);</span></font></div></div><div = style=3D"caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);">```</div><div = style=3D"caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);"><br = class=3D""></div></div><div>I suspect the relocation is not done = correctly for <span style=3D"caret-color: rgb(0, 0, 0); color: = rgb(0, 0, 0);" class=3D"">DYN elf kmod on amd64.</span></div><div><span = style=3D"caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=3D""><br = class=3D""></span></div><div><span style=3D"caret-color: rgb(0, 0, 0); = color: rgb(0, 0, 0);" class=3D"">My local patch to = kmod.mk:</span></div><div><span style=3D"caret-color: rgb(0, 0, 0); = color: rgb(0, 0, 0);" class=3D""><br class=3D""></span></div><div><span = style=3D"caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" = class=3D"">```</span></div><div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" class=3D"">diff = --git a/sys/conf/kmod.mk = b/sys/conf/kmod.mk</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" class=3D"">index = 134b150af1d9..1fc5386204a5 100644</span></font></div><div><font = color=3D"#000000" class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D"">--- a/sys/conf/kmod.mk</span></font></div><div><font = color=3D"#000000" class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D"">+++ b/sys/conf/kmod.mk</span></font></div><div><font = color=3D"#000000" class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D"">@@ -84,6 +84,7 @@ = __KLD_SHARED=3Dyes</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D""> .else</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D""> __KLD_SHARED=3Dno</span></font></div><div><font = color=3D"#000000" class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D""> .endif</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D"">+__KLD_SHARED=3Dyes</span></font></div><div><font = color=3D"#000000" class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D""> </span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" class=3D""> .if= !empty(CFLAGS:M-O[23s]) && = empty(CFLAGS:M-fno-strict-aliasing)</span></font></div><div><font = color=3D"#000000" class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D""> CFLAGS+=3D = -fno-strict-aliasing</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" class=3D"">@@ = -167,6 +168,7 @@ CFLAGS+=3D -fno-omit-frame-pointer = -mno-omit-leaf-frame-pointer</span></font></div><div><font = color=3D"#000000" class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D""> ${MACHINE_CPUARCH} =3D=3D = "powerpc"</span></font></div><div><font color=3D"#000000" class=3D""><span= style=3D"caret-color: rgb(0, 0, 0);" class=3D""> CFLAGS+=3D = -fPIC</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D""> .endif</span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" class=3D"">+CFLAGS+=3D= -fPIC</span></font></div><div><font = color=3D"#000000" class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" = class=3D""> </span></font></div><div><font color=3D"#000000" = class=3D""><span style=3D"caret-color: rgb(0, 0, 0);" class=3D""> # = Temporary workaround for PR 196407, which contains the fascinating = details.</span></font></div><div><font color=3D"#000000" class=3D""><span = style=3D"caret-color: rgb(0, 0, 0);" class=3D""> # Don't allow = clang to use fpu instructions or registers in kernel = modules.</span></font></div></div><div><span style=3D"caret-color: = rgb(0, 0, 0); color: rgb(0, 0, 0);" class=3D"">```</span></div><div><br = class=3D""></div><div><br class=3D""></div><div>As for <a = href=3D"https://reviews.freebsd.org/D39638" = class=3D"">https://reviews.freebsd.org/D39638</a>, for other platform = such as arm, I think the `link_elf_propagate_vnets()` should work if = `parse_vnet()` works.</div><div><br class=3D""></div><div>I'll = appreciate if someone can test it on platforms those have DYN type = kernel modules. </div><br class=3D""><blockquote type=3D"cite" = class=3D""><div class=3D""><br style=3D"caret-color: rgb(0, 0, 0); = font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><br style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><blockquote type=3D"cite" = style=3D"font-family: Menlo-Regular; font-size: 13px; font-style: = normal; font-variant-caps: normal; font-weight: 400; letter-spacing: = normal; orphans: auto; text-align: start; text-indent: 0px; = text-transform: none; white-space: normal; widows: auto; word-spacing: = 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><blockquote type=3D"cite" = class=3D""><br class=3D""></blockquote><br class=3D"">Hi,<br = class=3D""><br class=3D"">I don't have an answer for you either, but I = have seen in the past, loading<br class=3D"">kernel modules behaves a = bit like libraries, in the following regard:<br class=3D""><br = class=3D"">If two kernel modules define the same global symbol, then no = warning is<br class=3D"">given and the first loaded symbol definition (I = think) is used to resolve<br class=3D"">that symbol for all kernel = modules, regardless of the prototype. Probably we<br class=3D"">should = not allow this. That's why building LINT is a good thing, to avoid<br = class=3D"">this issue.<br class=3D""></blockquote><span = style=3D"caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; = font-size: 13px; font-style: normal; font-variant-caps: normal; = font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none; float: none; display: inline !important;" class=3D"">No, in-kernel = linker does not behave this way.</span><br style=3D"caret-color: rgb(0, = 0, 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><span style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">Modules need to contain explicit reference to all modules = they depend upon,</span><br style=3D"caret-color: rgb(0, 0, 0); = font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><span style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">using the MODULE_DEPEND() macro. Only symbols from the = dependencies are</span><br style=3D"caret-color: rgb(0, 0, 0); = font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><span style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">resolved.</span><br style=3D"caret-color: rgb(0, 0, 0); = font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><br style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><span style=3D"caret-color: rgb(0, 0, = 0); font-family: Menlo-Regular; font-size: 13px; font-style: normal; = font-variant-caps: normal; font-weight: 400; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">All modules get an implicit reference to kernel.</span><br = style=3D"caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; = font-size: 13px; font-style: normal; font-variant-caps: normal; = font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none;" class=3D""><br style=3D"caret-color: rgb(0, 0, 0); font-family: = Menlo-Regular; font-size: 13px; font-style: normal; font-variant-caps: = normal; font-weight: 400; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none;" class=3D""><blockquote type=3D"cite" style=3D"font-family: = Menlo-Regular; font-size: 13px; font-style: normal; font-variant-caps: = normal; font-weight: 400; letter-spacing: normal; orphans: auto; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; = -webkit-text-stroke-width: 0px; text-decoration: none;" class=3D""><br = class=3D"">Even if we don't have C++ support in the FreeBSD kernel, = defining symbol<br class=3D"">names the way C++ does for C could be nice = for the kernel too, also with<br class=3D"">regards to debugging = systems.<br class=3D""><br class=3D"">Many times when I don't know what = is going on, I do like this:<br class=3D""><br class=3D"">#include = <sys/kdb.h><br class=3D""><br class=3D"">....<br class=3D""><br = class=3D"">if (not too fast or my sysctl debug) {<br = class=3D""> printf("My tracer\n");<br = class=3D""> kdb_backtrace();<br class=3D"">}<br class=3D""><br = class=3D"">Dtrace can also do this, but not during boot. Just track who = is calling<br class=3D"">those functions, and you'll probably find the = answer to your question!<br class=3D""><br class=3D"">--HPS<br = class=3D""><br class=3D""><blockquote type=3D"cite" class=3D""><br = class=3D"">Best regards,<br = class=3D"">Zhenlei</blockquote></blockquote></div></blockquote></div><br = class=3D""><div class=3D""> <div><br class=3D""></div> </div> <br class=3D""></body></html>= --Apple-Mail=_6539C631-52D9-4A0E-99A2-AF236413CF40--
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