gcov: clang: fix the buffer overflow issue

Currently, in clang version of gcov code when module is getting removed
gcov_info_add() incorrectly adds the sfn_ptr->counter to all the
dst->functions and it result in the kernel panic in below crash report.
Fix this by properly handling it.

[ 8.899094][ T599] Unable to handle kernel write to read-only memory at virtual address ffffff80461cc000
[ 8.899100][ T599] Mem abort info:
[ 8.899102][ T599] ESR = 0x9600004f
[ 8.899103][ T599] EC = 0x25: DABT (current EL), IL = 32 bits
[ 8.899105][ T599] SET = 0, FnV = 0
[ 8.899107][ T599] EA = 0, S1PTW = 0
[ 8.899108][ T599] FSC = 0x0f: level 3 permission fault
[ 8.899110][ T599] Data abort info:
[ 8.899111][ T599] ISV = 0, ISS = 0x0000004f
[ 8.899113][ T599] CM = 0, WnR = 1
[ 8.899114][ T599] swapper pgtable: 4k pages, 39-bit VAs, pgdp=00000000ab8de000
[ 8.899116][ T599] [ffffff80461cc000] pgd=18000009ffcde003, p4d=18000009ffcde003, pud=18000009ffcde003, pmd=18000009ffcad003, pte=00600000c61cc787
[ 8.899124][ T599] Internal error: Oops: 9600004f [#1] PREEMPT SMP
[ 8.899265][ T599] Skip md ftrace buffer dump for: 0x1609e0
....
..,
[ 8.899544][ T599] CPU: 7 PID: 599 Comm: modprobe Tainted: G S OE 5.15.41-android13-8-g38e9b1af6bce #1
[ 8.899547][ T599] Hardware name: XXX (DT)
[ 8.899549][ T599] pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
[ 8.899551][ T599] pc : gcov_info_add+0x9c/0xb8
[ 8.899557][ T599] lr : gcov_event+0x28c/0x6b8
[ 8.899559][ T599] sp : ffffffc00e733b00
[ 8.899560][ T599] x29: ffffffc00e733b00 x28: ffffffc00e733d30 x27: ffffffe8dc297470
[ 8.899563][ T599] x26: ffffffe8dc297000 x25: ffffffe8dc297000 x24: ffffffe8dc297000
[ 8.899566][ T599] x23: ffffffe8dc0a6200 x22: ffffff880f68bf20 x21: 0000000000000000
[ 8.899569][ T599] x20: ffffff880f68bf00 x19: ffffff8801babc00 x18: ffffffc00d7f9058
[ 8.899572][ T599] x17: 0000000000088793 x16: ffffff80461cbe00 x15: 9100052952800785
[ 8.899575][ T599] x14: 0000000000000200 x13: 0000000000000041 x12: 9100052952800785
[ 8.899577][ T599] x11: ffffffe8dc297000 x10: ffffffe8dc297000 x9 : ffffff80461cbc80
[ 8.899580][ T599] x8 : ffffff8801babe80 x7 : ffffffe8dc2ec000 x6 : ffffffe8dc2ed000
[ 8.899583][ T599] x5 : 000000008020001f x4 : fffffffe2006eae0 x3 : 000000008020001f
[ 8.899586][ T599] x2 : ffffff8027c49200 x1 : ffffff8801babc20 x0 : ffffff80461cb3a0
[ 8.899589][ T599] Call trace:
[ 8.899590][ T599] gcov_info_add+0x9c/0xb8
[ 8.899592][ T599] gcov_module_notifier+0xbc/0x120
[ 8.899595][ T599] blocking_notifier_call_chain+0xa0/0x11c
[ 8.899598][ T599] do_init_module+0x2a8/0x33c
[ 8.899600][ T599] load_module+0x23cc/0x261c
[ 8.899602][ T599] __arm64_sys_finit_module+0x158/0x194
[ 8.899604][ T599] invoke_syscall+0x94/0x2bc
[ 8.899607][ T599] el0_svc_common+0x1d8/0x34c
[ 8.899609][ T599] do_el0_svc+0x40/0x54
[ 8.899611][ T599] el0_svc+0x94/0x2f0
[ 8.899613][ T599] el0t_64_sync_handler+0x88/0xec
[ 8.899615][ T599] el0t_64_sync+0x1b4/0x1b8
[ 8.899618][ T599] Code: f905f56c f86e69ec f86e6a0f 8b0c01ec (f82e6a0c)
[ 8.899620][ T599] ---[ end trace ed5218e9e5b6e2e6 ]---

Link: https://lkml.kernel.org/r/1668020497-13142-1-git-send-email-quic_mojha@quicinc.com
Fixes: e178a5beb369 ("gcov: clang support")
Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Tested-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tom Rix <trix@redhat.com>
Cc: <stable@vger.kernel.org> [5.2+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

gcov: clang: drop support for clang-10 and older

LLVM changed the expected function signatures for llvm_gcda_start_file()
and llvm_gcda_emit_function() in the clang-11 release. Drop the older
implementations and require folks to upgrade their compiler if they're
interested in GCOV support.

Link: https://reviews.llvm.org/rGcdd683b516d147925212724b09ec6fb792a40041
Link: https://reviews.llvm.org/rG13a633b438b6500ecad9e4f936ebadf3411d0f44
Link: https://lkml.kernel.org/r/20210312224132.3413602-3-ndesaulniers@google.com
Link: https://lkml.kernel.org/r/20210413183113.2977432-1-ndesaulniers@google.com
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Cc: Prasad Sodagudi <psodagud@quicinc.com>
Cc: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

gcov: use kvmalloc()

Using vmalloc() in gcov is really quite wasteful, many of the objects
allocated are really small (e.g. I've seen 24 bytes.) Use kvmalloc() to
automatically pick the better of kmalloc() or vmalloc() depending on the
size.

[johannes.berg@intel.com: fix clang-11+ build]
Link: https://lkml.kernel.org/r/20210412214210.6e1ecca9cdc5.I24459763acf0591d5e6b31c7e3a59890d802f79c@changeid

Link: https://lkml.kernel.org/r/20210315235453.799e7a9d627d.I741d0db096c6f312910f7f1bcdfde0fda20801a4@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

gcov: combine common code

There's a lot of duplicated code between gcc and clang implementations,
move it over to fs.c to simplify the code, there's no reason to believe
that for small data like this one would not just implement the simple
convert_to_gcda() function.

Link: https://lkml.kernel.org/r/20210315235453.e3fbb86e99a0.I08a3ee6dbe47ea3e8024956083f162884a958e40@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Revert "gcov: clang: fix clang-11+ build"

This reverts commit 04c53de57cb6435738961dace8b1b71d3ecd3c39.

Nathan Chancellor points out that it should not have been merged into
mainline by itself. It was a fix for "gcov: use kvmalloc()", which is
still in -mm/-next. Merging it alone has broken the build.

Link: https://github.com/ClangBuiltLinux/continuous-integration2/runs/2384465683?check_suite_focus=true
Reported-by: Nathan Chancellor <nathan@kernel.org>
Cc: Johannes Berg <johannes.berg@intel.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

gcov: clang: fix clang-11+ build

With clang-11+, the code is broken due to my kvmalloc() conversion
(which predated the clang-11 support code) leaving one vmalloc() in
place. Fix that.

Link: https://lkml.kernel.org/r/20210412214210.6e1ecca9cdc5.I24459763acf0591d5e6b31c7e3a59890d802f79c@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

gcov: re-fix clang-11+ support

LLVM changed the expected function signature for llvm_gcda_emit_function()
in the clang-11 release. Users of clang-11 or newer may have noticed
their kernels producing invalid coverage information:

$ llvm-cov gcov -a -c -u -f -b <input>.gcda -- gcno=<input>.gcno
1 <func>: checksum mismatch, \
(<lineno chksum A>, <cfg chksum B>) != (<lineno chksum A>, <cfg chksum C>)
2 Invalid .gcda File!
...

Fix up the function signatures so calling this function interprets its
parameters correctly and computes the correct cfg checksum. In
particular, in clang-11, the additional checksum is no longer optional.

Link: https://reviews.llvm.org/rG25544ce2df0daa4304c07e64b9c8b0f7df60c11d
Link: https://lkml.kernel.org/r/20210408184631.1156669-1-ndesaulniers@google.com
Reported-by: Prasad Sodagudi <psodagud@quicinc.com>
Tested-by: Prasad Sodagudi <psodagud@quicinc.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Cc: <stable@vger.kernel.org> [5.4+]

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

gcov: fix clang-11+ support

LLVM changed the expected function signatures for llvm_gcda_start_file()
and llvm_gcda_emit_function() in the clang-11 release. Users of
clang-11 or newer may have noticed their kernels failing to boot due to
a panic when enabling CONFIG_GCOV_KERNEL=y +CONFIG_GCOV_PROFILE_ALL=y.
Fix up the function signatures so calling these functions doesn't panic
the kernel.

Link: https://reviews.llvm.org/rGcdd683b516d147925212724b09ec6fb792a40041
Link: https://reviews.llvm.org/rG13a633b438b6500ecad9e4f936ebadf3411d0f44
Link: https://lkml.kernel.org/r/20210312224132.3413602-2-ndesaulniers@google.com
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reported-by: Prasad Sodagudi <psodagud@quicinc.com>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Cc: <stable@vger.kernel.org> [5.4+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

gcov: clang support

LLVM uses profiling data that's deliberately similar to GCC, but has a
very different way of exporting that data. LLVM calls llvm_gcov_init()
once per module, and provides a couple of callbacks that we can use to
ask for more data.

We care about the "writeout" callback, which in turn calls back into
compiler-rt/this module to dump all the gathered coverage data to disk:

llvm_gcda_start_file()
llvm_gcda_emit_function()
llvm_gcda_emit_arcs()
llvm_gcda_emit_function()
llvm_gcda_emit_arcs()
[... repeats for each function ...]
llvm_gcda_summary_info()
llvm_gcda_end_file()

This design is much more stateless and unstructured than gcc's, and is
intended to run at process exit. This forces us to keep some local
state about which module we're dealing with at the moment. On the other
hand, it also means we don't depend as much on how LLVM represents
profiling data internally.

See LLVM's lib/Transforms/Instrumentation/GCOVProfiling.cpp for more
details on how this works, particularly GCOVProfiler::emitProfileArcs(),
GCOVProfiler::insertCounterWriteout(), and GCOVProfiler::insertFlush().

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20190417225328.208129-1-trong@android.com
Signed-off-by: Greg Hackmann <ghackmann@android.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Tri Vo <trong@android.com>
Co-developed-by: Nick Desaulniers <ndesaulniers@google.com>
Co-developed-by: Tri Vo <trong@android.com>
Tested-by: Trilok Soni <tsoni@quicinc.com>
Tested-by: Prasad Sodagudi <psodagud@quicinc.com>
Tested-by: Tri Vo <trong@android.com>
Tested-by: Daniel Mentz <danielmentz@google.com>
Tested-by: Petri Gynther <pgynther@google.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>