[lkml]   [2018]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH] x86/fault: Print "SUPERVISOR" and "READ" when decoding #PF oops
...instead of manually handling the case where error_code=0, e.g. to
display "[SUPERVISOR] [READ]" instead of "normal kernel read fault".

This makes the zero case consistent with all other messages and also
provides additional information for other error code combinations,
e.g. error_code==1 will display "[PROT] [SUPERVISOR] [READ]" instead
of simply "[PROT]".

Print unique names for the negative cases as opposed to e.g. "[!USER]"
to avoid mixups due to users missing a single "!" character, and to be
more concise for the !INSTR && !WRITE case.

Print "SUPERVISOR" in favor of "KERNEL" to reduce the likelihood that
the message is misinterpreted as a generic kernel/software error and
to be consistent with the SDM's nomenclature.

An alternative to passing a negated error code to err_str_append() would
be to expand err_str_append() to take a second string for the negative
test, but that approach complicates handling the "[READ]" case, which
looks for !INSTR && !WRITE, e.g. it would require an extra call to
err_str_append() and logic in err_str_append() to allow null messages
for both the positive and negative tests. Printing "[INSTR] [READ]"
wouldn't be the end of the world, but a little bit of trickery in the
kernel is a relatively small price to pay in exchange for the ability
to unequivocally know the access type by reading a single word.

Now that all components of the message use the [<code>] format,
explicitly state that it's the error *code* that's being printed and
group the err_str_append() calls by type so that the resulting print
messages are consistent, e.g. the deciphered codes will always be:


Cc: Andy Lutomirski <>
Cc: Borislav Petkov <>
Cc: Dave Hansen <>
Cc: H. Peter Anvin <>
Cc: Linus Torvalds <>
Cc: Peter Zijlstra <>
Cc: Rik van Riel <>
Cc: Thomas Gleixner <>
Cc: Yu-cheng Yu <>
Cc: Ingo Molnar <>
Signed-off-by: Sean Christopherson <>
arch/x86/mm/fault.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 2ff25ad33233..0b4ce5d2b461 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -609,7 +609,7 @@ static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index)
static void err_str_append(unsigned long error_code, char *buf, unsigned long mask, const char *txt)
- if (error_code & mask) {
+ if ((error_code & mask) == mask) {
if (buf[0])
strcat(buf, " ");
strcat(buf, txt);
@@ -655,13 +655,16 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
* zero delimiter must fit into err_txt[].
err_str_append(error_code, err_txt, X86_PF_PROT, "[PROT]" );
- err_str_append(error_code, err_txt, X86_PF_WRITE, "[WRITE]");
err_str_append(error_code, err_txt, X86_PF_USER, "[USER]" );
- err_str_append(error_code, err_txt, X86_PF_RSVD, "[RSVD]" );
+ err_str_append(~error_code, err_txt, X86_PF_USER, "[SUPERVISOR]");
+ err_str_append(error_code, err_txt, X86_PF_WRITE, "[WRITE]");
err_str_append(error_code, err_txt, X86_PF_INSTR, "[INSTR]");
+ err_str_append(~error_code, err_txt, X86_PF_WRITE | X86_PF_INSTR,
+ "[READ]");
+ err_str_append(error_code, err_txt, X86_PF_RSVD, "[RSVD]" );
err_str_append(error_code, err_txt, X86_PF_PK, "[PK]" );

- pr_alert("#PF error: %s\n", error_code ? err_txt : "[normal kernel read fault]");
+ pr_alert("#PF error code: %s\n", err_txt);

if (!(error_code & X86_PF_USER) && user_mode(regs)) {
struct desc_ptr idt, gdt;
 \ /
  Last update: 2018-12-05 17:37    [W:0.119 / U:2.260 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site