From: Oleksii <oleksii.kurochko@gmail.com>
To: Julien Grall <julien@xen.org>, xen-devel@lists.xenproject.org
Cc: Jan Beulich <jbeulich@suse.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Gianluca Guida <gianluca@rivosinc.com>,
George Dunlap <george.dunlap@citrix.com>, Wei Liu <wl@xen.org>
Subject: Re: [PATCH v3 1/4] xen: introduce CONFIG_GENERIC_BUG_FRAME
Date: Tue, 28 Feb 2023 19:21:40 +0200 [thread overview]
Message-ID: <bf97a55d3e6635666090d06e3affa38c7c45b6d6.camel@gmail.com> (raw)
In-Reply-To: <8734edd9-70eb-b2bd-8763-b7468d7caba3@xen.org>
Hi Julien,
On Sat, 2023-02-25 at 16:42 +0000, Julien Grall wrote:
> Hi Oleksii,
>
> On 24/02/2023 11:31, Oleksii Kurochko wrote:
> > A large part of the content of the bug.h is repeated among all
> > architectures, so it was decided to create a new config
> > CONFIG_GENERIC_BUG_FRAME.
> >
> > The version of <bug.h> from x86 was taken as the base version.
> >
> > The patch introduces the following stuff:
> > * common bug.h header
> > * generic implementation of do_bug_frame
> > * new config CONFIG_GENERIC_BUG_FRAME
> >
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
> > ---
> > Changes in V3:
> > * Add debugger_trap_fatal() to do_bug_frame(). It simplifies
> > usage of
> > do_bug_frame() for x86 so making handle_bug_frame() and
> > find_bug_frame()
> > not needed anymore.
> > * Update do_bug_frame() to return -EINVAL if something goes
> > wrong; otherwise
> > id of bug_frame
> > * Update _ASM_BUGFRAME_TEXT to make it more portable.
> > * Drop unnecessary comments.
> > * define stub value for TRAP_invalid_op in case if wasn't defined
> > in
> > arch-specific folders.
> > ---
> > Changes in V2:
> > - Switch to x86 implementation as generic as it is more compact
> > ( at least from the point of view of bug frame structure ).
> > - Rename CONFIG_GENERIC_DO_BUG_FRAME to
> > CONFIG_GENERIC_BUG_FRAME.
> > - Change the macro bug_loc(b) to avoid the need for a cast:
> > #define bug_loc(b) ((unsigned long)(b) + (b)->loc_disp)
> > - Rename BUG_FRAME_STUFF to BUG_FRAME_STRUCT
> > - Make macros related to bug frame structure more generic.
> > - Introduce BUG_INSTR and MODIFIER to make _ASM_BUGFRAME_TEXT
> > reusable
> > between x86 and RISC-V.
> > - Rework do_bug_frame() and introduce find_bug_frame() and
> > handle_bug_frame()
> > functions to make it reusable by x86.
> > - code style fixes
> > ---
> > xen/common/Kconfig | 3 +
> > xen/common/Makefile | 1 +
> > xen/common/bug.c | 109 ++++++++++++++++++++++++++++++
> > xen/include/xen/bug.h | 150
> > ++++++++++++++++++++++++++++++++++++++++++
> > 4 files changed, 263 insertions(+)
> > create mode 100644 xen/common/bug.c
> > create mode 100644 xen/include/xen/bug.h
> >
> > diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> > index f1ea3199c8..b226323537 100644
> > --- a/xen/common/Kconfig
> > +++ b/xen/common/Kconfig
> > @@ -28,6 +28,9 @@ config ALTERNATIVE_CALL
> > config ARCH_MAP_DOMAIN_PAGE
> > bool
> >
> > +config GENERIC_BUG_FRAME
> > + bool
> > +
> > config HAS_ALTERNATIVE
> > bool
> >
> > diff --git a/xen/common/Makefile b/xen/common/Makefile
> > index bbd75b4be6..46049eac35 100644
> > --- a/xen/common/Makefile
> > +++ b/xen/common/Makefile
> > @@ -1,5 +1,6 @@
> > obj-$(CONFIG_ARGO) += argo.o
> > obj-y += bitmap.o
> > +obj-$(CONFIG_GENERIC_BUG_FRAME) += bug.o
> > obj-$(CONFIG_HYPFS_CONFIG) += config_data.o
> > obj-$(CONFIG_CORE_PARKING) += core_parking.o
> > obj-y += cpu.o
> > diff --git a/xen/common/bug.c b/xen/common/bug.c
> > new file mode 100644
> > index 0000000000..f81724fc9b
> > --- /dev/null
> > +++ b/xen/common/bug.c
> > @@ -0,0 +1,109 @@
> > +#include <xen/bug.h>
> > +#include <xen/debugger.h>
> > +#include <xen/errno.h>
> > +#include <xen/kernel.h>
> > +#include <xen/livepatch.h> > +#include <xen/string.h>
> > +#include <xen/types.h>
> > +#include <xen/virtual_region.h>
> > +
> > +#include <asm/processor.h>
> > +
> > +/* Set default value for TRAP_invalid_op as it is defined only for
> > X86 now */
> > +#ifndef TRAP_invalid_op
> > +#define TRAP_invalid_op 0
> > +#endif
>
> It feels to me that this value should be defined in the else part in
> xen/debugger.h.
As it was disscussed in the other e-mail [1] the following will be
introduced in <xen/bug.h>
#ifndef BUG_DEBUGGER_TRAP_FATAL
#define BUG_DEBUGGER_TRAP_FATAL(regs) 0
#endif
and re-defined in <asm/bug.h>.
Of course, do_bug_frame() will be updated correspondingly to use
BUG_DEBUGGER_TRAP_FATAL.
[1]
https://lore.kernel.org/xen-devel/9b66ee51-17c3-0f8e-0fc2-4ff083952e9d@suse.com/
>
> > +
> > +int do_bug_frame(const struct cpu_user_regs *regs, unsigned long
> > pc)
>
> I would suggest to document what this function is meant to return.
> AFAUI, it would return a negative value in case of an error otherwise
> the bug type.
sure. i'll added in the next patch version.
>
> > +{
> > + const struct bug_frame *bug = NULL;
> > + const struct virtual_region *region;
> > + const char *prefix = "", *filename, *predicate;
> > + unsigned long fixup;
> > + unsigned int id = BUGFRAME_NR, lineno;
> > +
> > + region = find_text_region(pc);
> > + if ( region )
>
> NIT: If you invert the condition here, then you can reduce the
> indention
> by one below.
Thanks. i'll added in the next patch version.
>
> > + {
> > + for ( id = 0; id < BUGFRAME_NR; id++ )
> > + {
> > + const struct bug_frame *b;
> > + unsigned int i;
>
> You compare this against n_bugs which is a size_t. So, this wants to
> be
> a size_t.
This one will be updated too. Thanks.
>
> > +
> > + for ( i = 0, b = region->frame[id].bugs;
> > + i < region->frame[id].n_bugs; b++, i++ )
> > + {
> > + if ( bug_loc(b) == pc )
> > + {
> > + bug = b;
> > + goto found;
> > + }
> > + }
> > + }
> > + }
> > +
> > + found:
> > + if ( !bug )
> > + return -EINVAL;
> > +
> > + if ( id == BUGFRAME_run_fn )
> > + {
> > +#ifdef BUG_FN_REG
> > + void (*fn)(const struct cpu_user_regs *) = (void *)regs-
> > >BUG_FN_REG;
>
> AFAIU, this is necessary so Arm can use the generic do_bug_frame().
>
> I was under the impression that RISC-V and Arm had the similar issue
> with %c. It seems like you managed to resolve it on RISC-V, so can we
> fully switch Arm to the generic implementation of bug?
I tried to switch ARM to generic implementation.
Here is the patch: [1]
diff --git a/xen/arch/arm/include/asm/bug.h
b/xen/arch/arm/include/asm/bug.h
index e6cc37e1d6..ffb0f569fc 100644
--- a/xen/arch/arm/include/asm/bug.h
+++ b/xen/arch/arm/include/asm/bug.h
@@ -1,8 +1,6 @@
#ifndef __ARM_BUG_H__
#define __ARM_BUG_H__
-#include <xen/types.h>
-
#if defined(CONFIG_ARM_32)
# include <asm/arm32/bug.h>
#elif defined(CONFIG_ARM_64)
@@ -11,63 +9,7 @@
# error "unknown ARM variant"
#endif
-#define BUG_FRAME_STRUCT
-
-struct bug_frame {
- signed int loc_disp; /* Relative address to the bug address */
- signed int file_disp; /* Relative address to the filename */
- signed int msg_disp; /* Relative address to the predicate (for
ASSERT) */
- uint16_t line; /* Line number */
- uint32_t pad0:16; /* Padding for 8-bytes align */
-};
-
-#define bug_ptr(b) ((const void *)(b) + (b)->file_disp)
-#define bug_line(b) ((b)->line)
-#define bug_msg(b) ((const char *)(b) + (b)->msg_disp)
-
-/* Many versions of GCC doesn't support the asm %c parameter which
would
- * be preferable to this unpleasantness. We use mergeable string
- * sections to avoid multiple copies of the string appearing in the
- * Xen image. BUGFRAME_run_fn needs to be handled separately.
- */
-#define BUG_FRAME(type, line, file, has_msg, msg) do {
\
- BUILD_BUG_ON((line) >> 16);
\
- BUILD_BUG_ON((type) >= BUGFRAME_NR);
\
- asm ("1:"BUG_INSTR"\n"
\
- ".pushsection .rodata.str, \"aMS\", %progbits, 1\n"
\
- "2:\t.asciz " __stringify(file) "\n"
\
- "3:\n"
\
- ".if " #has_msg "\n"
\
- "\t.asciz " #msg "\n"
\
- ".endif\n"
\
- ".popsection\n"
\
- ".pushsection .bug_frames." __stringify(type) ", \"a\",
%progbits\n"\
- "4:\n"
\
- ".p2align 2\n"
\
- ".long (1b - 4b)\n"
\
- ".long (2b - 4b)\n"
\
- ".long (3b - 4b)\n"
\
- ".hword " __stringify(line) ", 0\n"
\
- ".popsection");
\
-} while (0)
-
-/*
- * GCC will not allow to use "i" when PIE is enabled (Xen doesn't set
the
- * flag but instead rely on the default value from the compiler). So
the
- * easiest way to implement run_in_exception_handler() is to pass the
to
- * be called function in a fixed register.
- */
-#define run_in_exception_handler(fn) do {
\
- asm ("mov " __stringify(BUG_FN_REG) ", %0\n"
\
- "1:"BUG_INSTR"\n"
\
- ".pushsection .bug_frames." __stringify(BUGFRAME_run_fn) ","
\
- " \"a\", %%progbits\n"
\
- "2:\n"
\
- ".p2align 2\n"
\
- ".long (1b - 2b)\n"
\
- ".long 0, 0, 0\n"
\
- ".popsection" :: "r" (fn) : __stringify(BUG_FN_REG) );
\
-} while (0)
+#define BUG_ASM_CONST "c"
#endif /* __ARM_BUG_H__ */
...
(it will be merged with patch 3 if it is OK )
And looks like we can switch ARM to generic implementation as all tests
passed:
https://gitlab.com/xen-project/people/olkur/xen/-/pipelines/791549396
The only issue is with yocto-arm:
https://gitlab.com/xen-project/people/olkur/xen/-/pipelines/791549396/failures
But I am not sure that it is because of my patch
Is this enough from a verification point of view?
[1]
https://gitlab.com/xen-project/people/olkur/xen/-/commit/5ff7a06e1d354e1e42bde1c203f3cf05a3653ad6https://gitlab.com/xen-project/people/olkur/xen/-/commit/5ff7a06e1d354e1e42bde1c203f3cf05a3653ad6
>
> > +#else
> > + void (*fn)(const struct cpu_user_regs *) = bug_ptr(bug);
> > +#endif
> > +
> > + fn(regs);
> > +
> > + return id;
> > + }
> > +
> > + /* WARN, BUG or ASSERT: decode the filename pointer and line
> > number. */
> > + filename = bug_ptr(bug);
> > + if ( !is_kernel(filename) && !is_patch(filename) )
> > + return -EINVAL;
> > + fixup = strlen(filename);
> > + if ( fixup > 50 )
> > + {
> > + filename += fixup - 47;
> > + prefix = "...";
> > + }
> > + lineno = bug_line(bug);
> > +
> > + switch ( id )
> > + {
> > + case BUGFRAME_warn:
> > + printk("Xen WARN at %s%s:%d\n", prefix, filename, lineno);
> > + show_execution_state(regs);
> > +
> > + return id;
> > +
> > + case BUGFRAME_bug:
> > + printk("Xen BUG at %s%s:%d\n", prefix, filename, lineno);
> > +
> > + if ( debugger_trap_fatal(TRAP_invalid_op, regs) )
> > + return id;
> > +
> > + show_execution_state(regs);
> > + panic("Xen BUG at %s%s:%d\n", prefix, filename, lineno);
> > +
> > + case BUGFRAME_assert:
> > + /* ASSERT: decode the predicate string pointer. */
> > + predicate = bug_msg(bug);
> > + if ( !is_kernel(predicate) && !is_patch(predicate) )
> > + predicate = "<unknown>";
> > +
> > + printk("Assertion '%s' failed at %s%s:%d\n",
> > + predicate, prefix, filename, lineno);
> > +
> > + if ( debugger_trap_fatal(TRAP_invalid_op, regs) )
> > + return id;
> > +
> > + show_execution_state(regs);
> > + panic("Assertion '%s' failed at %s%s:%d\n",
> > + predicate, prefix, filename, lineno);
> > + }
> > +
> > + return id;
> > +}
> > diff --git a/xen/include/xen/bug.h b/xen/include/xen/bug.h
> > new file mode 100644
> > index 0000000000..4b18cfa69c
> > --- /dev/null
> > +++ b/xen/include/xen/bug.h
> > @@ -0,0 +1,150 @@
> > +#ifndef __XEN_BUG_H__
> > +#define __XEN_BUG_H__
> > +
> > +#define BUG_DISP_WIDTH 24
> > +#define BUG_LINE_LO_WIDTH (31 - BUG_DISP_WIDTH)
> > +#define BUG_LINE_HI_WIDTH (31 - BUG_DISP_WIDTH)
> > +
> > +#define BUGFRAME_run_fn 0
> > +#define BUGFRAME_warn 1
> > +#define BUGFRAME_bug 2
> > +#define BUGFRAME_assert 3
> > +
> > +#define BUGFRAME_NR 4
> > +
> > +#include <asm/bug.h>
> > +
> > +#ifndef __ASSEMBLY__
> > +
> > +#include <xen/errno.h>
>
> errno.h doesn't look to be used within this here. So is it necessary
> to
> import it?
>
> > +#include <xen/lib.h>
>
> Why is this necessary to include in the header?
>
> > +#include <xen/stringify.h>
>
> You don't seem to use __stringify in this header. So is this
> necessary?
The mentioned headers will be removed. They was needed when I tried to
use ARM implementation as generic one.
>
> > +
> > +#ifndef BUG_FRAME_STRUCT
> > +
> > +struct bug_frame {
> > + signed int loc_disp:BUG_DISP_WIDTH;
> > + unsigned int line_hi:BUG_LINE_HI_WIDTH;
> > + signed int ptr_disp:BUG_DISP_WIDTH;
> > + unsigned int line_lo:BUG_LINE_LO_WIDTH;
> > + signed int msg_disp[];
> > +};
> > +
> > +#endif /* BUG_FRAME_STRUCT */
> > +
> > +#ifndef bug_loc
> > +#define bug_loc(b) ((unsigned long)(b) + (b)->loc_disp)
> > +#endif
> > +
> > +#ifndef bug_ptr
> > +#define bug_ptr(b) ((const void *)(b) + (b)->ptr_disp)
> > +#endif
> > +
> > +#ifndef bug_line
> > +#define bug_line(b) (((((b)->line_hi + ((b)->loc_disp < 0))
> > & \
> > + ((1 << BUG_LINE_HI_WIDTH) - 1))
> > << \
> > + BUG_LINE_LO_WIDTH)
> > + \
> > + (((b)->line_lo + ((b)->ptr_disp < 0))
> > & \
> > + ((1 << BUG_LINE_LO_WIDTH) - 1)))
> > +#endif
> > +
> > +#ifndef bug_msg
> > +#define bug_msg(b) ((const char *)(b) + (b)->msg_disp[1])
> > +#endif
>
> For all the macro above, it feels wrong to me to allow an
> architecture
> to override them if the default BUG_FRAME_STRUCT.
>
> It would also feels wrong to me that if the default BUG_FRAME_STRUCT
> is
> not used to still partially rely on the generic version of the
> helper.\
>
> So I would suggest to move them in the #ifndef BUG_FRAME_STRUCT and
> drop
> the #ifndef <helper>.
Agree. I'll do that in the next version of the patch. Thanks.
>
> > +
> > +#ifndef BUG_ASM_CONST
> > +#define BUG_ASM_CONST ""
> > +#endif
>
> This line is a bit misterious to me. Would you be able to outline why
> an
> architecture would override this?
It is needed in case if compiler for an architecture doesn't have
proper support of '%c' ( it is so for ARM & RISC-V )
>
> > +
> > +#if !defined(_ASM_BUGFRAME_TEXT) || !defined(_ASM_BUGFRAME_INFO)
> > +
> > +#define
> > _ASM_BUGFRAME_TEXT(second_frame)
> > \
> > +
> > ".Lbug%=:"BUG_INSTR"\n"
> > \
> > + " .pushsection .bug_frames.%"BUG_ASM_CONST"[bf_type], \"a\",
> > %%progbits\n" \
> > + " .p2align
> > 2\n"
> > \
> > +
> > ".Lfrm%=:\n"
> > \
> > + " .long (.Lbug%= - .Lfrm%=) +
> > %"BUG_ASM_CONST"[bf_line_hi]\n" \
> > + " .long (%"BUG_ASM_CONST"[bf_ptr] - .Lfrm%=) +
> > %"BUG_ASM_CONST"[bf_line_lo]\n"\
> > + " .if " #second_frame
> > "\n" \
> > + " .long 0, %"BUG_ASM_CONST"[bf_msg] -
> > .Lfrm%=\n" \
> > + "
> > .endif\n"
> > \
> > + " .popsection\n"
> > +
> > +#define _ASM_BUGFRAME_INFO(type, line, ptr,
> > msg) \
> > + [bf_type] "i"
> > (type), \
> > + [bf_ptr] "i"
> > (ptr), \
> > + [bf_msg] "i"
> > (msg), \
> > + [bf_line_lo] "i" ((line & ((1 << BUG_LINE_LO_WIDTH) -
> > 1)) \
> > + <<
> > BUG_DISP_WIDTH), \
> > + [bf_line_hi] "i" (((line) >> BUG_LINE_LO_WIDTH) <<
> > BUG_DISP_WIDTH)
> > +
> > +#endif /* _ASM_BUGFRAME_TEXT || _ASM_BUGFRAME_INFO */
> > +
> > +#ifndef BUG_FRAME
> > +
> > +#define BUG_FRAME(type, line, ptr, second_frame, msg) do
> > { \
> > + BUILD_BUG_ON((line) >> (BUG_LINE_LO_WIDTH +
> > BUG_LINE_HI_WIDTH)); \
> > + BUILD_BUG_ON((type) >=
> > BUGFRAME_NR); \
> > + asm volatile (
> > _ASM_BUGFRAME_TEXT(second_frame) \
> > + :: _ASM_BUGFRAME_INFO(type, line, ptr, msg)
> > ); \
> > +} while (0)
> > +
> > +#endif
> > +
> > +#ifndef run_in_exception_handler
> > +
> > +/*
> > + * TODO: untangle header dependences, break BUILD_BUG_ON() out of
> > xen/lib.h,
> > + * and use a real static inline here to get proper type checking
> > of fn().
> > + */
> > +#define run_in_exception_handler(fn) \
> > + do { \
> > + (void)((fn) == (void (*)(struct cpu_user_regs *))NULL); \
> > + BUG_FRAME(BUGFRAME_run_fn, 0, fn, 0, NULL); \
> > + } while ( 0 )
> > +
> > +#endif /* run_in_exception_handler */
> > +
> > +#ifndef WARN
> > +#define WARN() BUG_FRAME(BUGFRAME_warn, __LINE__, __FILE__, 0,
> > NULL)
> > +#endif
> > +
> > +#ifndef BUG
> > +#define BUG() do { \
> > + BUG_FRAME(BUGFRAME_bug, __LINE__, __FILE__, 0, NULL); \
> > + unreachable(); \
> > +} while (0)
> > +#endif
> > +
> > +#ifndef assert_failed
> > +#define assert_failed(msg) do { \
> > + BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, msg); \
> > + unreachable(); \
> > +} while (0)
> > +#endif
> > +
> > +#ifdef CONFIG_GENERIC_BUG_FRAME
> > +
> > +struct cpu_user_regs;
> > +
> > +int do_bug_frame(const struct cpu_user_regs *regs, unsigned long
> > pc);
> > +
> > +#endif /* CONFIG_GENERIC_BUG_FRAME */
> > +
> > +extern const struct bug_frame __start_bug_frames[],
> > + __stop_bug_frames_0[],
> > + __stop_bug_frames_1[],
> > + __stop_bug_frames_2[],
> > + __stop_bug_frames_3[];
> > +
> > +#endif /* !__ASSEMBLY__ */
> > +
> > +#endif /* __XEN_BUG_H__ */
> > +/*
> > + * Local variables:
> > + * mode: C
> > + * c-file-style: "BSD"
> > + * c-basic-offset: 4
> > + * indent-tabs-mode: nil
> > + * End:
> > + */
>
> Cheers,
>
~ Oleksii
next prev parent reply other threads:[~2023-02-28 17:22 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-24 11:31 [PATCH v3 0/4] introduce generic implementation of macros from bug.h Oleksii Kurochko
2023-02-24 11:31 ` [PATCH v3 1/4] xen: introduce CONFIG_GENERIC_BUG_FRAME Oleksii Kurochko
2023-02-25 16:42 ` Julien Grall
2023-02-27 9:48 ` Jan Beulich
2023-02-28 17:21 ` Oleksii [this message]
2023-02-28 18:01 ` Julien Grall
2023-02-28 20:24 ` Oleksii
2023-02-27 14:23 ` Jan Beulich
2023-02-28 10:30 ` Oleksii
2023-02-28 10:42 ` Jan Beulich
2023-02-24 11:31 ` [PATCH v3 2/4] xen: change <asm/bug.h> to <xen/bug.h> Oleksii Kurochko
2023-02-25 16:47 ` Julien Grall
2023-02-28 12:38 ` Oleksii
2023-02-28 14:04 ` Julien Grall
2023-02-28 13:07 ` Oleksii
2023-02-28 13:30 ` Jan Beulich
2023-02-28 16:00 ` Oleksii
2023-02-27 14:29 ` Jan Beulich
2023-02-28 13:14 ` Oleksii
2023-02-24 11:31 ` [PATCH v3 3/4] xen/arm: switch ARM to use generic implementation of bug.h Oleksii Kurochko
2023-02-25 16:49 ` Julien Grall
2023-02-25 17:05 ` Julien Grall
2023-02-28 17:21 ` Oleksii
2023-02-28 17:57 ` Julien Grall
2023-03-01 12:31 ` Oleksii
2023-03-01 13:58 ` Julien Grall
2023-03-01 15:16 ` Oleksii
2023-03-01 15:21 ` Julien Grall
2023-03-01 15:28 ` Oleksii
2023-03-01 15:58 ` Oleksii
2023-02-28 15:09 ` Oleksii
2023-02-28 17:48 ` Julien Grall
2023-03-01 8:58 ` Oleksii
2023-03-01 9:31 ` Julien Grall
2023-03-01 12:33 ` Oleksii
2023-02-24 11:31 ` [PATCH v3 4/4] xen/x86: switch x86 to use generic implemetation " Oleksii Kurochko
2023-02-27 14:46 ` Jan Beulich
2023-02-28 16:28 ` Oleksii
2023-02-28 16:36 ` Jan Beulich
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